{"text": "the national science foundation available languages : english, spanish this classroom - tested learning module gives a condensed, easily - understood view of the development of atomic theory from the late 19th through early 20th century. the key idea was the discovery that the atom is not an \" indivisible \" particle, but consists of smaller constituents : the proton, neutron, and electron. it discusses the contributions of john dalton, j. j. thomson, ernest rutherford, and james chadwick, whose experiments revolutionized the world view of atomic structure. see related materials for a link to part 2 of this series. atomic structure, cathode ray experiment, electron, helium atom, history of atom, history of the atom, hydrogen atom, neutron, proton metadata instance created july 12, 2011 by caroline hall october 10, 2012 by caroline hall last update when cataloged : january 1, 2006 aaas benchmark alignments ( 2008 version ) 4. the physical setting 4d. the structure of matter 6 - 8 : 4d / m1a. all matter is made up of atoms, which are far too small to see directly through a microscope. 9 - 12 : 4d / h1. atoms are made of a positively charged nucleus surrounded by negatively charged electrons. the nucleus is a tiny fraction of the volume of an atom but makes up almost all of its mass. the nucleus is composed of protons and neutrons which have roughly the same mass but differ in that protons are positively charged while neutrons have no electric charge. 9 - 12 : 4d / h2. the number of protons in the nucleus determines what an atom ' s electron configuration can be and so defines the element. an atom ' s electron configuration, particularly the outermost electrons, determines how the atom can interact with other atoms. atoms form bonds to other atoms by transferring or sharing electrons. 10. historical perspectives 10f. understanding fire 9 - 12 : 10f / h1. in the late 1700s and early 1800s, the idea of atoms reemerged in response to questions about the structure of matter, the nature of fire, and the basis of chemical phenomena. 9 - 12 : 10f / h3. in the early 1800s, british chemist and physicist john dalton united the concepts of atoms and elements. he proposed two ideas that laid the groundwork for modern chemistry : first, that elements are formed from small, indivisible particles called atoms, which are identical for a given element but different from any other element ; and second, that chemical compounds are", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6774994993901745, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:01:59.564756"} {"text": "proposed two ideas that laid the groundwork for modern chemistry : first, that elements are formed from small, indivisible particles called atoms, which are identical for a given element but different from any other element ; and second, that chemical compounds are formed from atoms by combining a definite number of each type of atom to form one molecule of the compound. 9 - 12 : 10f / h4. dalton figured out how the relative weights of the atoms could be determined experimentally. his idea that every substance had a unique atomic composition provided an explanation for why substances were made up of elements in specific proportions. this resource is part of a physics front topical unit. topic : particles and interactions and the standard model unit title : history and discovery this classroom - tested learning module gives a condensed, easily - understood view of the development of atomic theory from the late 19th through early 20th century. the key idea was the discovery that the atom is not an \" indivisible \" particle, but consists of smaller constituents : the proton, neutron, and electron. it discusses the contributions of john dalton, j. j. thomson, ernest rutherford, and james chadwick, whose experiments revolutionized the world view of atomic structure. % 0 electronic source % a carpi, anthony % d january 1, 2006 % t visionlearning : atomic theory i % i visionlearning % v 2013 % n 21 may 2013 % 8 january 1, 2006 % 9 text / html % u http : / / www. visionlearning. com / library / module _ viewer. php? mid = 50 & l = disclaimer : compadre offers citation styles as a guide only. we cannot offer interpretations about citations as this is an automated procedure. please refer to the style manuals in the citation source information area for clarifications.", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.656568539898098, "token_count": 371, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 1, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:01:59.565435"} {"text": "an electron is a subatomic particles of spin 1 / 2. it couples with photons and, thus, is electrically charged. it is a lepton with a rest mass of 9. 109 * 10 \u2212 31kg and an electric charge of \u2212 1. 602 * 10 \u2212 19 c, which is the smallest known charge possible for an isolated particle ( confined quarks have fractional charge ). the electric charge of the electron e is used as a unit of charge in much of physics. electron pairs within an orbital system have opposite spins due to the pauli exclusion principle ; this characteristic spin pairing allows electrons to exist in the same quantum orbital, as the opposing magnetic dipole moments induced by each of the electrons ensures that they are attracted together. current theories consider the electron as a point particle, as no evidence for internal structure has been observed. as a theoretical construct, electrons have been able to explain other observed phenomena, such as the shell - like structure of an atom, energy distribution around an atom, and energy beams ( electron and positron beams ). - \u2191 massimi, m. ( 2005 ). pauli ' s exclusion principle, the origin and validation of a scientific principle. cambridge university press. pp. 7 \u2013 8 - \u2191 mauritsson, j.. \" electron filmed for the first time ever \". lunds universitet. retrieved 2008 - 09 - 17. http : / / www. atomic. physics. lu. se / research / attosecond _ physics - \u2191 chao, a. w. ; tigner, m. ( 1999 ). handbook of accelerator physics and engineering. world scientific. pp. 155, 188. isbn 981 - 02 - 3500 - 3.", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.7203689697977753, "token_count": 354, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:01:59.566990"} {"text": "heat is a sad fact of life for current generation electronics. any android, iphone, or blackberry user can tell you that smartphones tend to get pretty hot at times. and by today ' s standards a balmy 85 degrees celsius, while hot enough to cook an egg, is a pretty \" good \" operating temperature for a high - powered pc graphics processing unit. but that could all soon change, according to the results of a new study by researchers at the university of illinois. examining graphene transistors, a team led by mechanical science and engineering professor william king [ profile ] and electrical and computer engineering professor eric pop [ profile ] made a remarkable discovery - - graphene appears to self - cool. i. what is graphene? graphene is somewhat like a miniature \" fence \" of carbon. the material consists of a single - atom thick layer composed of hexagonal units. at each point of the hexagon sits a carbon atom that is bonded to its three close neighbors. the material behaves like a semiconductor, despite being made of organic atoms. it offers remarkable performance at an incredibly small scale, thus the electronics industry views it as a potential material to power electronic devices of the future. a variety of methods exist for producing graphene. the earliest method was an exfoliation technique that involved stripping individual graphene layers off a layer of graphite ( the material found in pencil lead ) - - this technique ( as of 2008 ) cost as much as $ 100m usd to produce a single cubic centimeter of material. however, rapid advances in production have allowed manufacturers to begin scaling up production to the point where tons of exfoliated graphene can now be produced. techniques promise to drop the price even further. one method, epitaxial growth on silicon cost $ 100 per cubic centimeter in 2009. its limitation is that, obviously, it requires silicon ( eliminating some desirable properties like flexibility ). south korean researchers have tested another promising method, nickel metal transfer. graphene is fascinating from a physics perspective. in 2005 physicists at the university of manchester and the philip kim group from columbia university demonstrated that quasiparticles inside graphene were massless dirac fermions. these unusual particles help give rise to the material ' s unique characteristics. ii. graphene as a self - cooling device despite the extreme interest in the material, deal of mystery still surrounds graphene. because it is so extremely thin, it is difficult to test and measure accurately certain properties of the material. overcoming technical challenges,", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6531761394557124, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:01:59.601499"} {"text": ". graphene as a self - cooling device despite the extreme interest in the material, deal of mystery still surrounds graphene. because it is so extremely thin, it is difficult to test and measure accurately certain properties of the material. overcoming technical challenges, the university of illinois team used an atomic force microscope tip as a temperature probe to make the first nanometer - scale temperature measurements of a working graphene what they found was that the resistive heating ( \" waste heat \" ) effect in graphene was weaker than its thermo - electric cooling effect at times. this is certainly not the case in silicon or other semiconductors where resistive heating far surpasses cooling effects. what this means is that graphene circuits may not get hot like traditional silicon - based ones. this could open the door to dense 3d chips and more. further, as the heat is converted back into electricity by the device, graphene transistors may have a two - fold power efficiency gain, both in ditching energetically expensive fans and by recycling heat losses into usable electricity. professor king describes, \" in silicon and most materials, the electronic heating is much larger than the self - cooling. however, we found that in these graphene transistors, there are regions where the thermoelectric cooling can be larger than the resistive heating, which allows these devices to cool themselves. this self - cooling has not previously been seen for graphene devices. \" professor pop adds, \" graphene electronics are still in their infancy ; however, our measurements and simulations project that thermoelectric effects will become enhanced as graphene transistor technology and contacts improve. \" a paper has been published [ full text ] in nanotechnology ' s most prestigious peer - reviewed journal, nature nanoscience. university of illinois graduate student kyle undergraduate feifei lian and postdoctoral researcher myung - ho bae [ profile ] are listed as co - authors on the paper. iii. what ' s next? the study should provide even more motivation for semiconductor manufacturing companies like intel, globalfoundries, and tmsc to lay down the process work necessary to mass - produce circuits based on graphene transistors, capacitors, etc. as for the university of illinois team, they plan to next use their new measurement technique to analyze carbon nanotubes and other novel structures that are of interest to future electronics applications. their work is funded via a grant from the air force office of scientific research and the office of naval research.", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6459845621119397, "token_count": 509, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 1, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:01:59.602466"} {"text": "researchers at new jersey institute of technology ( njit ) have developed an inexpensive solar cell that can be painted or printed on flexible plastic sheets. \u201c someday, homeowners will even be able to print sheets of these solar cells with inexpensive home - based inkjet printers. consumers can then slap the finished product on a wall, roof or billboard to create their own power stations, \u201d said somenath mitra, ph. d., lead researcher, professor and acting chair of njit \u2019 s department of chemistry and environmental sciences. harvesting energy directly from abundant solar radiation using solar cells is increasingly emerging as a major component of future global energy strategy, mitra said. yet, when it comes to harnessing renewable energy, challenges remain. expensive, large - scale infrastructures, such as windmills or dams, are necessary to drive renewable energy sources, such as wind or hydroelectric power plants. purified silicon, also used for making computer chips, which continue to rise in demand, is a core material for fabricating conventional solar cells. however, the processing of a material such as purified silicon is beyond the reach of most consumers. \u201c developing organic solar cells from polymers, however, is a cheap and potentially simpler alternative, \u201d mitra said. \u201c we foresee a great deal of interest in our work because solar cells can be inexpensively printed or simply painted on exterior building walls and / or rooftops. imagine some day driving in your hybrid car with a solar panel painted on the roof, which is producing electricity to drive the engine. the opportunities are endless. \u201d the solar cell developed at njit uses a carbon nanotubes complex, which is a molecular configuration of carbon in a cylindrical shape. although estimated to be 50, 000 times smaller than a human hair, just one nanotube can conduct current better than any conventional electrical wire. mitra and his research team took the carbon nanotubes and combined them with tiny carbon fullerenes ( sometimes known as buckyballs ) to form snake - like structures. buckyballs trap electrons, although they can \u2019 t make electrons flow. add sunlight to excite the polymers, and the buckyballs will grab the electrons. nanotubes, behaving like copper wires, then will be able to make the electrons or current flow. \u201c someday, i hope to see this process become an inexpensive energy alternative for households around the world, \u201d mitra said. ec", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6007537755385658, "token_count": 488, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:01:59.667095"} {"text": "breakthroughs bring the next two major leaps in computing power into sight breakthroughs might make quantum computing, replacement for silicon practical within a decade one of the best things about covering technology is that you ' re always on the edge of a completely new generation of stuff that will make everything completely different than it ever was before, even before the last generation made everything different. \" completely different \" always seems pretty much the same, with a few more complications, higher costs and a couple of cool new capabilities, of course. unless you look back a decade or two and see that everything is completely different from the way it was then \u2026 must be some conceptual myopia that keeps us in happy suspense over the future, nostalgic wonder at the past and bored annoyance with the present. the next future to get excited about is going to be really cool, though. you know how long scientists have been working on quantum computers that will be incomparably more powerful than the ones we have now because don ' t have to be built on a \" bit \" that ' s either a 1 or a zero? they would use a piece of quantum data called a qubit ( or qbit, consistent with everything in the quantum world, the spelling wants to be two things at once ), that can exist in several states at the same time. that would turn the most basic function in computing from a toggle switch to a dial with many settings. multiply the number of pieces of data in the lowest - level function of the computer and you increase its power logarithmically. making it happen has been a trick ; they ' ve been under development for 20 years and probably won ' t show up for another 10. teams of austrian scientists may cut that time down a bit with a system they developed they say can create digital models of quantum - computing systems to make testing and development of both theory and manufacturing issues quicker and easier. they did it the same way lord of the rings brought gollum to life : putting a living example in front of cameras and taking detailed pictures they could use to recreate the image in any other digital environment. rather than an actor, the photo subject was a calcium atom, drastically cooled to slow its motion, then manipulated it using lasers, putting it through a set of paces predicted by quantum - mechanical theory, and recorded the results. abstracting those results lets the computer model predict the behavior of almost any other quantum particle or environment, making it possible to use the quantum version of a cad / cam system to develop and test new", "subdomain_id": "subdomain_quantum_computing", "similarity_score": 0.6501102775386948, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:00.172564"} {"text": "by quantum - mechanical theory, and recorded the results. abstracting those results lets the computer model predict the behavior of almost any other quantum particle or environment, making it possible to use the quantum version of a cad / cam system to develop and test new approaches to the systems that will actually become quantum computers, according to a paper published in the journal science by researchers from the university of innsbruck and the institute for quantum optics and quantum information ( iqoqi ). far sooner than quantum computers will blow our digitized minds, transistors made from grapheme rather than chunkier materials will allow designers to create processors far more dense \u2013 and therefore more potentially powerful \u2013 than anything theoretically possible using silicon and metallic alloys we rely on now. graphene is a one - atom - thick layer of carbon that offers almost no resistance to electricity flowing through it, but doesn ' t naturally contain electrons at two energy levels, as silicon does. silicon transistors flip on or off by shifting electrons from one energy level to another. even silicon doesn ' t work that way naturally. it has to be \" doped \" with impurities to change its properties as a semiconductor. for graphene to work the same way, researchers have to add inverters that that mimic the dual energy levels of silicon. so far they only work at 320 degrees below zero fahrenheit ( 77 degrees kelvin ). researchers at purdue ' s birck nanotechnology center built a version that operates at room temperature, removing the main barrier to graphene as a practical option for computer systems design the researchers, led by doctoral candidate hong - yan chen presented their paper at the device research conference in santa barbara. calif. in june to publicize their results with the inverter. real application will have to wait for chen or others to integrate the design into a working circuit based on graphene rather than silicon. systems built on graphene have the potential to boost the computing power of current processors by orders of magnitude while reducing their size and energy use, but only if they operate in offices not cooled to 77 degrees kelvin. it will still be a few years before graphene starts showing up in airline magazines, let alone in it budgets. we ' ll probably be tired of them, too, by the time quantum computers show up, but there ' s just no satisfying some people. read more of kevin fogarty ' s coreit blog and follow the latest it news at itworld. follow kevin on twitter at @ kevinfogarty. for the latest it news, analysis", "subdomain_id": "subdomain_quantum_computing", "similarity_score": 0.679936233973469, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 1, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:00.173729"} {"text": "in this study, ni and cu nanowire arrays and ni / cu superlattice nanowire arrays are fabricated using standard techniques such as electrochemical deposition of metals into porous anodic alumina oxide templates having pore diameters of about 50 nm. we perform optical measurements on these nanowire array structures. optical reflectance ( or ) of the as - prepared samples is recorded using an imaging spectrometer in the wavelength range from 400 to 2, 000 nm ( i. e., from visible to near - infrared bandwidth ). the measurements are carried out at temperatures set to be 4. 2, 70, 150, and 200 k and at room temperature. we find that the intensity of the or spectrum for nanowire arrays depends strongly on the temperature. the strongest or can be observed at about t = 200 k for all samples in visible regime. the or spectra for these samples show different features in the visible and near - infrared bandwidths. we discuss the physical mechanisms responsible for these interesting experimental findings. this study is relevant to the application of metal nanowire arrays as optical and optoelectronic devices. keywords : nanowire array ; optical properties ; visible and near - infrared ; temperature dependence in recent years, quasi one - dimensional ( 1d ) nanostructured materials have received much attention attributed to their interesting physical properties in sharp contrast to the bulk ones and to the potential applications as electronic, magnetic, photonic, and optoelectronic devices [ 1 - 4 ]. from a viewpoint of physics, the basic physical properties of nanostructured materials differ significantly from those of bulk materials with the same chemical components. in particular, quantum confinement effects can be observed in the dimensionally reduced nanomaterial systems. therefore, nanowires have been a major focus of research on nanoscaled materials which can be taken as a fundamental building block of nanotechnology and practical nanodevices. it should be noticed that metal nanowires have displayed unique optical and optoelectronic properties due to surface plasmon resonance ( spr ) which is a resonant oscillation of the conducting electrons within the metallic nanostructures. the spr effect in nanowire structures can cause a tremendous enhancement of the electromagnetic near - field in the immediate vicinity of the particles and can give rise to enhanced scattering and absorption of light radiation. the spr in metal nanowires and related phenomena ( such as the surface - enhanced raman spectroscopy, nonlinear optic response, plas", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6539668844714464, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:00.506551"} {"text": "- field in the immediate vicinity of the particles and can give rise to enhanced scattering and absorption of light radiation. the spr in metal nanowires and related phenomena ( such as the surface - enhanced raman spectroscopy, nonlinear optic response, plasmonic excitation, to mention but a few ) contributes greatly to their promising applications in biosensors, optical devices, and photonic and plasmonic devices [ 5 - 8 ]. moreover, metal nanowire wave guides can excite and emit terahertz ( 1012 hz or thz ) surface plasmon polaritons, which can fill the gap of terahertz electronics and optoelectronics. on the other hand, superlattice nanowires have even richer physical properties owing to further quantum confinement of electron motion along the wire direction. they have been proposed as advanced electronic device systems to observe novel effects such as giant magnetoresistance and even high thermoelectric figure of merit [ 10, 11 ]. furthermore, with the rapid development of nanotechnology, it is now possible to fabricate nanowire arrays and superlattice nanowire arrays [ 12, 13 ]. one of the major advantages to apply nanowire arrays and superlattice nanowire arrays as optic and optoelectronic devices is that the optical response of the array structures can be tuned and modulated via varying sample parameters such as the diameter of the wire and the pattern of the array structure. due to potential applications of the nanowire arrays and superlattice nanowire arrays as optical devices, it is of importance and significance to examine their basic optical properties. in this article, we present a detailed experimental study on the optical properties of three kinds of nanowire array structures such as ni and cu nanowire arrays and ni / cu superlattice nanowire arrays. we would like to examine how these advanced nanostructured material systems can respond to light radiation, how their optical properties depend on temperature and radiation wavelength, and why the optical properties of the nanowire arrays differ from those observed in bulk materials. samples and measurements in this study, three kinds of nanowire array structures are fabricated, including ni arrays, cu arrays, and ni / cu superlattice arrays. samples are prepared by direct current electrodeposition [ 14 - 16 ] of metal into the holes of porous anodic alumina membrane ( paam ) with the pore size of about 50 nm. noteworthy is the diameter", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6345971095236509, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 1, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:00.507680"} {"text": "is used for the detection of 400 - to 800 - nm wavelength regime, and the ingaas photodetector is employed for the measurement of 1 - to 2 - \u03bcm wavelength regime. for measurements in the visible regime, the temperatures are set at 4. 2, 70, 150, and 200 k and at room temperature. the change of temperature is achieved in an oxford cooling system. the measurements in the near - infrared regime are undertaken at room temperature. results and discussion the or spectra for ni and cu nanowire arrays and ni / cu superlattice nanowire arrays are shown in figure 2 in visible bandwidth for different temperatures at 4. 2, 70, 150, 200, and 297 k, respectively. as can be seen, the intensity of or in nanowire array structures depends strongly on temperature. when temperature ( t ) < 200 k, the intensity of or for a ni nanowire array sample increases with temperature. when t > 200 k, the or intensity decreases with increasing temperature. the strongest or can be observed at about 200 k. a similar phenomenon can be found for a ni / cu superlattice nanowire array sample. in contrast, the or spectra for cu nanowire arrays ( see figure 2c ) show different temperature dependence. with increasing temperature, the intensity of or for a cu nanowire array first decreases in the 4. 2 - to 70 - k regime, then increases in the 70 - to 200 - k regime, and decreases again when t > 200 k. again, the strongest or for cu nanowire arrays can be observed at about t = 200 k. these experimental findings suggest that 200 k is an appropriate temperature for the enhancement of optical reflection from cu, ni, and ni / cu superlattice nanowire array structures. this can provide a basis for further investigation into other optical properties such as optical absorption and emission from metal nanowire arrays in visible regime. we find that when t > 200 k, the or spectrum for ni / cu superlattice nanowire array lies between those for cu and ni nanowire arrays. however, at lower temperatures ( e. g., at 150 k ), the intensity of the or spectrum for ni / cu superlattice nanowire array is lower than those for cu and ni nanowire arrays. figure 2. the spectra of optical reflection for nanowire arrays measured at different temperatures of 4. 2, 70, 150, 200, and 297 k as indicated. the results for a ni nanowire array ( a ), a", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6418822065466325, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 3, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:00.510003"} {"text": "nanowire arrays. figure 2. the spectra of optical reflection for nanowire arrays measured at different temperatures of 4. 2, 70, 150, 200, and 297 k as indicated. the results for a ni nanowire array ( a ), a ni / cu superlattice nanowire array ( b ), and a cu nanowire array ( c ) are shown. in figure 3, the or spectra are shown at room temperature for three metal nanowire array samples in visible and near - infrared bandwidths. in the visible regime ( see figure 3a ), two relatively wide reflection peaks can be observed for all samples at about 500 to 650 nm and 650 to 700 nm, respectively. the 650 - to 700 - nm peaks for the three samples appear at almost the same position ( at about 667 nm ), while the 500 - to 650 - nm ones redshift slightly with respect to that of the incident light source. the peak position of the light source is at about 554 nm, whereas the peaks for cu and ni / cu superlattice nanowire arrays are at about 585 nm and that for ni nanowire arrays is at about 600 nm. it should be noted that the visible light source provided by the tungsten halogen lamp has two main peaks in the 400 - to 800 - nm wavelength regime. the intensity of infrared light source given by the si carbide rod decreases when the radiation wavelength approaches 2 \u03bcm. the variation of the intensity of the light sources is enhanced via measurement systems. we notice that ni nanowire arrays reflect more strongly the visible light ; cu nanowire arrays reflect relatively weakly, and the or spectrum for ni / cu superlattice nanowire arrays is just in between them. in the near - infrared range of 1, 000 to 2, 000 nm ( see figure 3b ), the peaks of or spectra for cu nanowire arrays and ni / cu superlattice nanowire arrays are at about 1, 808 nm, and ni nanowire arrays and light source are at about 1, 727 nm. the or spectra for nanowire arrays redshift slightly with respect to the spectrum of the light source. in contrast to the visible regime, the cu nanowire array reflects more strongly the infrared radiation than ni nanowire array. interestingly, the or spectrum for ni / cu superlattice nanowire array is below that for ni nanowire array when radiation wavelength is less than 1, 730 nm, and it is located in between the or spectra for ni", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6379449692274421, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 4, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:00.510874"} {"text": "arrays do. because the quantum confinement effect affects mainly the electronic states in different bands in the array structure, the main features of or due to interband electronic transition does not change very significantly. this is why ni nanowire arrays can reflect more strongly the visible radiation than cu arrays can, as shown in figure 3a and similar to the case for bulk materials. moreover, our results show that in the visible regime and when t > 200 k, the or spectrum for ni / cu superlattice nanowire arrays lies between those for cu and ni nanowire arrays. however, at relatively lower temperatures ( e. g., at 150 k ), the intensity of the or spectrum for ni / cu superlattice nanowire array is lower than those for cu and ni nanowire arrays. we believe that this may have resulted from different features of the phonon modes and electron - phonon scattering in nanowire and superlattice nanowire structures. in superlattice nanowire systems formed by different host materials, the phonon modes can be quantized and the conducting electrons are confined along the wire direction. the quantized phonon modes can weaken the electron - phonon scattering because a scattering event requires momentum and energy conservation. on the other hand, the localized electrons can interact more strongly with phonons. our results suggest that when t > 200 k, the former case is dominant, and when t 150 k, the latter effect is stronger. in this study, cu, ni, and ni / cu nanowire arrays have been fabricated using state - of - the - art nanotechnology. the optical measurements on these nanowire arrays have been carried out in visible and near - infrared bandwidths for different temperatures. we have found that the optical reflection spectra of these samples depend strongly on temperature and on radiation wavelength. in particular, ( 1 ) the strongest or in the visible regime can be observed at about 200 k for all samples, and ( 2 ) the or for cu nanowire arrays show a different dependence on temperature and radiation wavelength from that for ni nanowire arrays. these results indicate that the surface plasmon resonances induced by inter - and intraband electronic transitions, the electron - phonon interaction, and the quantum confinement effect can play important roles in affecting optical properties of the metal nanowire array structure. we hope that the interesting experimental findings from this study can provide an in - depth understanding of optical properties of cu and ni nanowire arrays and cu / ni superlattice nano", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6750823262737514, "token_count": 511, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 7, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:00.515502"} {"text": "important roles in affecting optical properties of the metal nanowire array structure. we hope that the interesting experimental findings from this study can provide an in - depth understanding of optical properties of cu and ni nanowire arrays and cu / ni superlattice nanowire arrays and can provide a physical base for the application of metal nanowire arrays as advanced optical and optoelectronic devices. the authors declare that they have no competing interests. wx proposed the research work, coordinated the collaboration, and carried out the analyses of experimental results. yyz designed the experiment and experimental setup, carried out the measurements, and drafted the manuscript. shx and gtf fabricated the nanowire and superlattice nanowire array samples. ymx and jgh participated in experimental measurements, results and discussion, and analyses. all authors read and approved the final manuscript. this work was supported by the national natural science foundation of china ( grant no. 10974206 ), department of science and technology of yunnan province, and by the chinese academy of sciences. j crystal growth 2003, 254 : 14. publisher full text j appl phys 2002, 91 : 4590 - 4594. publisher full text appl surf sci 2008, 255 : 1901. publisher full text surf coat technol 2010, 205 : 2432 - 2437. publisher full text c r physique 2008, 9 : 215 - 231. publisher full text appl phys lett 1994, 65 : 2484. publisher full text appl phys lett 1994, 65 : 3019. publisher full text nano lett 2002, 2 : 83. publisher full text", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6365773265464079, "token_count": 334, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 8, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:00.517700"} {"text": "is light made of waves, or particles? this fundamental question has dogged scientists for decades, because light seems to be both. however, until now, experiments have revealed light to act either like a particle, or a wave, but never the two at once. now, for the first time, a new type of experiment has shown light behaving like both a particle and a wave simultaneously, providing a new dimension to the quandary that could help reveal the true nature of light, and of the whole quantum world. the debate goes back at least as far as isaac newton, who advocated that light was made of particles, and james clerk maxwell, whose successful theory of electromagnetism, unifying the forces of electricity and magnetism into one, relied on a model of light as a wave. then in 1905, albert einstein explained a phenomenon called the photoelectric effect using the idea that light was made of particles called photons ( this discovery won him the nobel prize in physics ). [ what ' s that? your physics questions answered ] ultimately, there ' s good reason to think that light is both a particle and a wave. in fact, the same seems to be true of all subatomic particles, including electrons and quarks and even the recently discovered higgs boson - like particle. the idea is called wave - particle duality, and is a fundamental tenet of the theory of quantum mechanics. depending on which type of experiment is used, light, or any other type of particle, will behave like a particle or like a wave. so far, both aspects of light ' s nature haven ' t been observed at the same time. but still, scientists have wondered, does light switch from being a particle to being a wave depending on the circumstance? or is light always both a particle and a wave simultaneously? now, for the first time, researchers have devised a new type of measurement apparatus that can detect both particle and wave - like behavior at the same time. the device relies on a strange quantum effect called quantum nonlocality, a counter - intuitive notion that boils down to the idea that the same particle can exist in two locations at once. \" the measurement apparatus detected strong nonlocality, which certified that the photon behaved simultaneously as a wave and a particle in our experiment, \" physicist alberto peruzzo of england ' s university of bristol said in a statement. \" this represents a strong refutation of models in which the photon is either a wave or a particle. \" peruzzo", "subdomain_id": "subdomain_quantum_optics", "similarity_score": 0.6903532918704651, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:00.538143"} {"text": "a wave and a particle in our experiment, \" physicist alberto peruzzo of england ' s university of bristol said in a statement. \" this represents a strong refutation of models in which the photon is either a wave or a particle. \" peruzzo is lead author of a paper describing the experiment published in the nov. 2 issue of the journal science. the experiment further relies on another weird aspect of quantum mechanics \u2014 the idea of quantum entanglement. two particles can become entangled so that actions performed on one particle affect the other. in this way, the researchers were able to allow the photons in the experiment to delay the choice of whether to be particles or waves. mit physicist seth lloyd, who was not involved in the project, called the experiment \" audacious \" in a related essay in science, and said that while it allowed the photons to delay the choice of being particles or waves for only a few nanoseconds, \" if one has access to quantum memory in which to store the entanglement, the decision could be put off until tomorrow ( or for as long as the memory works reliably ). so why decide now? just let those quanta slide! \" - twisted physics : 7 mind - blowing findings - quantum weirdness goes big \u2013 molecules act like waves | video - wacky physics : the coolest little particles in nature \u00a9 2012 livescience. com. all rights reserved.", "subdomain_id": "subdomain_quantum_optics", "similarity_score": 0.6947035332384561, "token_count": 289, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 1, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:00.538724"} {"text": "pppl scientists propose a solution to a critical barrier to producing fusion posted april 23, 2012 ; 05 : 00 p. m. physicists from the u. s. department of energy ' s princeton plasma physics laboratory ( pppl ) have discovered a possible solution to a mystery that has long baffled researchers working to harness fusion. if confirmed by experiment, the finding could help scientists eliminate a major impediment to the development of fusion as a clean and abundant source of energy for producing electric power. an in - depth analysis by pppl scientists zeroed in on tiny, bubble - like islands that appear in the hot, charged gases \u2014 or plasmas \u2014 during experiments. these minute islands collect impurities that cool the plasma. and these islands, the scientists report in the april 20 issue of the journal physical review letters, are at the root of a longstanding problem known as the \" density limit \" that can prevent fusion reactors from operating at maximum efficiency. fusion occurs when plasmas become hot and dense enough for the atomic nuclei contained within the hot gas to combine and release energy. but when the plasmas in experimental reactors called tokamaks reach the mysterious density limit, they can spiral apart into a flash of light. \" the big mystery is why adding more heating power to the plasma doesn ' t get you to higher density, \" said david gates, a principal research physicist at pppl and co - author of the proposed solution with luis delgado - aparicio, a postdoctoral fellow at pppl and a visiting scientist at the massachusetts institute of technology ' s plasma science fusion center. \" this is critical because density is the key parameter in reaching fusion and people have been puzzling about this for more than 30 years. \" a discovery by princeton plasma physics laboratory physicists luis delgado - aparicio ( left ) and david gates could help scientists eliminate a major impediment to the development of fusion as a clean and abundant source of energy for producing electric power. listen to a podcast with the scientists discussing their discovery. ( photo by elle starkman ) the scientists hit upon their theory in what gates called \" a 10 - minute ' aha! ' moment. \" working out equations on a whiteboard in gates ' office, the physicists focused on the islands and the impurities that drive away energy. the impurities stem from particles that the plasma kicks up from the tokamak wall. \" when you hit this magical density limit, the islands grow and coalesce and the plasma ends up in a disruption, \" said delgado - ap", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6227632358062047, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:00.839749"} {"text": "energy. the impurities stem from particles that the plasma kicks up from the tokamak wall. \" when you hit this magical density limit, the islands grow and coalesce and the plasma ends up in a disruption, \" said delgado - aparicio. these islands actually inflict double damage, the scientists said. besides cooling the plasma, the islands act as shields that block out added power. the balance tips when more power escapes from the islands than researchers can pump into the plasma through a process called ohmic heating \u2014 the same process that heats a toaster when electricity passes through it. when the islands grow large enough, the electric current that helps to heat and confine the plasma collapses, allowing the plasma to fly apart. gates and delgado - aparicio now hope to test their theory with experiments on a tokamak called alcator c - mod at mit, and on the diii - d tokamak at general atomics in san diego. among other things, they intend to see if injecting power directly into the islands will lead to higher density. if so, that could help future tokamaks reach the extreme density and 100 - million - degree temperatures that fusion requires. the scientists ' theory represents a fresh approach to the density limit, which also is known as the \" greenwald limit \" after mit physicist martin greenwald, who has derived an equation that describes it. greenwald has another potential explanation for the source of the limit. he thinks it may occur when turbulence creates fluctuations that cool the edge of the plasma and squeeze too much current into too little space in the core of the plasma, causing the current to become unstable and crash. \" there is a fair amount of evidence for this, \" greenwald said. however, he added, \" we don ' t have a nice story with a beginning and end and we should always be open to new ideas. \" gates and delgado - aparicio pieced together their model from a variety of clues that have developed in recent decades. gates first heard of the density limit while working as a postdoctoral fellow at the culham centre for fusion energy in abingdon, england, in 1993. the limit had previously been named for culham scientist jan hugill, who described it to gates in detail. separately, papers on plasma islands were beginning to surface in scientific circles. french physicist paul - henri rebut described radiation - driven islands in a mid - 1980s conference paper, but not in a periodical. german physicist wolfgang suttrop speculated a decade later that", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6193701266488554, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 1, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:00.840960"} {"text": "science, students are learning to isolate important characteristics, enumerate characteristics, use appropriate terminology, and use synonyms which are important reading skills ( carter & simpson, 1978 ). when students have used the process skills of observing, identifying, and classifying, they are better able to discriminate between vowels and consonants and to learn the sounds represented by letters, letter blends, and syllables ( murray & pikul ski, 1978 ). science instruction provides an alternative teaching strategy that motivates students who may have reading difficulties ( wellman, 1978 ). children ' s involvement with process skills enables them to recognize more easily the contextual and structural clues in attacking new words and better equips them to interpret data in a paragraph. science process skills are essential to logical thinking, as well as to forming the basic skills for learning to read ( barufaldi & swift, 1977 ). guszak defines reading readiness as a skill - complex. of the three areas within the skill - complex, two can be directly enhanced by science process skills : ( 1 ) physical factors ( health, auditory, visual, speech, and motor ) ; and ( 2 ) understanding factors ( concepts, processes ). when students see, hear, and talk about science experiences, their understanding, perception, and comprehension of concepts and processes may improve ( barufaldi & swift, 1977 and bethel, 1974 ). the hands - on manipulative experiences science provides are the key to the relationship between process skills in both science and reading ( lucas & burlando, 1975 ). science activities provide opportunities for manipulating large quantities of multi - sensory materials which promote perceptual skills, i. e., tactile, kinesthetic, auditory, and visual ( neuman, 1969 ). these skills then contribute to the development of the concepts, vocabulary, and oral language skills ( listening and speaking ) necessary for learning to read ( wellman, 1978 ). studies viewed cumulatively suggest that science instruction at the intermediate and upper elementary grades does improve the attainment of reading skills. the findings reveal that students have derived benefits in the areas of vocabulary enrichment, increased verbal fluency, enhanced ability to think logically, and improved concept formation and communication skills ( campbell, 1972 ; kraft, 1961 ; olson, 1971 ; quinn & kessler, 1976 ).", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6053057124582927, "token_count": 473, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 1, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:00.900297"} {"text": "please read how you can help keep the encyclopedia free absolute and relational theories of space and motion since antiquity, natural philosophers have struggled to comprehend the nature of three tightly interconnected concepts : space, time, and motion. a proper understanding of motion, in particular, has been seen to be crucial for deciding questions about the natures of space and time, and their interconnections. since the time of newton and leibniz, philosophers \u2019 struggles to comprehend these concepts have often appeared to take the form of a dispute between absolute conceptions of space, time and motion, and relational conceptions. this article guides the reader through some of the history of these philosophical struggles. rather than taking sides in the ( alleged ) ongoing debates, or reproducing the standard dialectic recounted in most introductory texts, we have chosen to scrutinize carefully the history of the thinking of the canonical participants in these debates \u2014 principally descartes, newton, leibniz, mach and einstein. readers interested in following up either the historical questions or current debates about the natures of space, time and motion will find ample links and references scattered through the discussion and in the other internet resources section below. - 1. introduction - 2. aristotle - 3. descartes - 4. newton - 5. absolute space in the twentieth century - 6. leibniz - 7. \u2018 not - newton \u2019 versus \u2018 be - leibniz \u2019 - 8. mach and later machians - 9. relativity and motion - 10. conclusion - other internet resources - related entries things change. a platitude perhaps, but still a crucial feature of the world, and one which causes many philosophical perplexities \u2014 see for instance the entry on zeno ' s paradoxes. for aristotle, motion ( he would have called it \u2018 locomotion \u2019 ) was just one kind of change, like generation, growth, decay, fabrication and so on. the atomists held on the contrary that all change was in reality the motion of atoms into new configurations, an idea that was not to begin to realize its full potential until the seventeenth century, particularly in the work of descartes. ( of course, modern physics seems to show that the physical state of a system goes well beyond the geometrical configuration of bodies. fields, while determined by the states of bodies, are not themselves configurations of bodies if interpreted literally, and in quantum mechanics bodies have \u2018 internal states ' such as particle spin. ) while not all changes seem to be merely the ( loco )", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6430417505675261, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.056980"} {"text": "bodies. fields, while determined by the states of bodies, are not themselves configurations of bodies if interpreted literally, and in quantum mechanics bodies have \u2018 internal states ' such as particle spin. ) while not all changes seem to be merely the ( loco ) motions of bodies in physical space. yet since antiquity, in the western tradition, this kind of motion has been absolutely central to the understanding of change. and since motion is a crucial concept in physical theories, one is forced to address the question of what exactly it is. the question might seem trivial, for surely what is usually meant by saying that something is moving is to say that it is moving relative to something, often tacitly understood between speakers. for instance : the car is moving at 60mph ( relative to the road and things along it ), the plane is flying ( relative ) to london, the rocket is lifting off ( the ground ), or the passenger is moving ( to the front of the speeding train ). typically the relative reference body is either the surroundings of the speakers, or the earth, but this is not always the case. for instance, it seems to make sense to ask whether the earth rotates about its axis west - east diurnally or whether it is instead the heavens that rotate east - west ; but if all motions are to be reckoned relative to the earth, then its rotation seems impossible. but if the earth does not offer a unique frame of reference for the description of motion, then we may wonder whether any arbitrary object can be used for the definition of motions : are all such motions on a par, none privileged over any other? it is unclear whether anyone has really, consistently espoused this view : aristotle, perhaps, in the metaphysics ; descartes and leibniz are often thought to have but, as we ' ll see, those claims are suspect ; possibly huygens, though his remarks remain cryptic ; mach at some moments perhaps. if this view were correct, then the question of whether the earth or heavens rotate would be meaningless, merely different but equivalent expressions of the facts. but suppose, like aristotle, you take ordinary language accurately to reflect the structure of the world, then you could recognize systematic everyday uses of \u2018 up \u2019 and \u2018 down \u2019 that require some privileged standards \u2014 uses that treat things closer to a point at the center of the earth as more \u2018 down \u2019 and motions towards that point as \u2018 downwards '. of course we would likely explain this usage in terms of the fact that we and our language evolved", "subdomain_id": "subdomain_quantum_mechanics", "similarity_score": 0.6562939292678346, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 1, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.058304"} {"text": "standards \u2014 uses that treat things closer to a point at the center of the earth as more \u2018 down \u2019 and motions towards that point as \u2018 downwards '. of course we would likely explain this usage in terms of the fact that we and our language evolved in a very noticeable gravitational field directed towards the center of the earth, but for aristotle, as we shall see, this usage helped identify an important structural feature of the universe, which itself was required for the explanation of weight. now a further question arises : how should a structure, such as a preferred point in the universe, which privileges certain motions, be understood? what makes that point privileged? one might expect that aristotle simply identified it with the center of the earth, and so relative to that particular body ; but in fact he did not adopt that tacit convention as fundamental, for he thought it possible for the earth to move from the \u2018 down \u2019 point. thus the question arises ( although aristotle does not address it explicitly ) of whether the preferred point is somewhere picked out in some other way by the bodies in the universe \u2014 the center of the heavens perhaps? or is it picked out quite independently of the arrangements of matter? the issues that arise in this simple theory help frame the debates between later physicists and philosophers concerning the nature of motion ; in particular, we will focus on the theories of descartes, newton, leibniz, mach and einstein, and their interpretations. but similar issues circulate through the different contexts : is there any kind of privileged sense of motion, a sense in which things can be said to move or not, not just relative to this or that reference body, but \u2018 truly \u2019? if so, can this true motion be analyzed in terms of motions relative to other bodies \u2014 to some special body, or to the entire universe perhaps? ( and in relativity, in which distances, times and measures of relative motion are frame - dependent, what relations are relevant? ) if not, then how is the privileged kind of motion to be understood, as relative to space itself \u2014 something physical but non - material \u2014 perhaps? or can some kinds of motion be best understood as not being spatial changes \u2014 changes of relative location or of place \u2014 at all? to see that the problem of the interpretation of spatiotemporal quantities as absolute or relative is endemic to almost any kind of mechanics one can imagine, we can look to one of the simplest theories \u2014 aristotle ' s account of natural motion ( e. g., on the heavens i. 2 ). according", "subdomain_id": "subdomain_quantum_metrology", "similarity_score": 0.6307767156505324, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 2, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.059319"} {"text": "the space that it occupies. thus it doesn ' t change place, which is should be to say that it doesn ' t move after all! descartes resolved this difficulty by taking all motion to be the motion of bodies relative to one another, not a literal change of space. now, a body has as many relative motions as there are bodies but it does not follow that all are equally significant. indeed, descartes uses several different concepts of relational motion. first there is \u2018 change of place \u2019, which is nothing but motion relative to this or that arbitrary reference body ( ii. 13 ). in this sense no motion of a body is privileged, since the speed, direction, and even curve of a trajectory depends on the reference body, and none is singled out. next, he discusses motion in \u2018 the ordinary sense \u2019 ( ii. 24 ). this is often conflated with mere change of arbitrary place, but it in fact differs because according to the rules of ordinary speech one properly attributes motion only to bodies whose motion is caused by some action, not to any relative motion. ( for instance, a person sitting on a speeding boat is ordinarily said to be at rest, since \u2018 he feels no action in himself \u2019. ) finally, he defined motion \u2018 properly speaking \u2019 ( ii. 25 ) to be a body ' s motion relative to the matter contiguously surrounding it, which the impossibility of a vacuum guarantees to exist. ( descartes \u2019 definition is complicated by the fact that he modifies this technical concept to make it conform more closely to the pre - theoretical sense of \u2018 motion \u2019 ; however, in our discussion transference is all that matters, so we will ignore those complications. ) since a body can only be touching one set of surroundings, descartes ( dubiously ) argued that this standard of motion was unique. what we see here is that descartes, despite holding motion to be the motion of bodies relative to one another, also held there to be a privileged sense of motion ; in a terminology sometimes employed by writers of the period, he held there to be a sense of \u2018 true motion \u2019, over and above the merely relative motions. equivalently, we can say that descartes took motion ( \u2018 properly speaking \u2019 ) to be a complete predicate : that is, moves - properly - speaking is a one - place predicate. ( in contrast, moves - relative - to is a two - place predicate. ) and note that the predicate is complete", "subdomain_id": "subdomain_quantum_mechanics", "similarity_score": 0.6116289904038381, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 5, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.062422"} {"text": ") to be a complete predicate : that is, moves - properly - speaking is a one - place predicate. ( in contrast, moves - relative - to is a two - place predicate. ) and note that the predicate is complete despite the fact that it is analyzed in terms of relative motion. ( formally, let contiguous - surroundings be a function from bodies to their contiguous surroundings, then x moves - properly - speaking is analyzed as x moves - relative - to contiguous - surroundings ( x ). ) this example illustrates why it is crucial to keep two questions distinct : on the one hand, is motion to be understood in terms of relations between bodies or by invoking something additional, something absolute ; on the other hand, are all relative motions equally significant, or is there some \u2018 true \u2019, privileged notion of motion? descartes ' views show that eschewing absolute motion is logically compatible with accepting true motion ; which is of course not to say that his definitions of motion are themselves tenable. there is an interpretational tradition which holds that descartes only took the first, \u2018 ordinary \u2019 sense of motion seriously, and introduced the second notion to avoid conflict with the catholic church. such conflict was a real concern, since the censure of galileo ' s copernicanism took place only 11 years before publication of the principles, and had in fact dissuaded descartes from publishing an earlier work, the world. indeed, in the principles ( iii. 28 ) he is at pains to explain how \u2018 properly speaking \u2019 the earth does not move, because it is swept around the sun in a giant vortex of matter \u2014 the earth does not move relative to its surroundings in the vortex. the difficulty with the reading, aside from the imputation of cowardice to the old soldier, is that it makes nonsense of descartes ' mechanics, a theory of collisions. for instance, according to his laws of collision if two equal bodies strike each other at equal and opposite velocities then they will bounce off at equal and opposite velocities ( rule i ). on the other hand, if the very same bodies approach each other with the very same relative speed, but at different speeds then they will move off together in the direction of the faster one ( rule iii ). but if the operative meaning of motion in the rules is the ordinary sense, then these two situations are just the same situation, differing only in the choice of reference frame, and so could not have different outcomes \u2014 bouncing", "subdomain_id": "subdomain_quantum_mechanics", "similarity_score": 0.6094777294144809, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 6, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.063423"} {"text": "faster one ( rule iii ). but if the operative meaning of motion in the rules is the ordinary sense, then these two situations are just the same situation, differing only in the choice of reference frame, and so could not have different outcomes \u2014 bouncing apart versus moving off together. it seems inconceivable that descartes could have been confused in such a trivial way. ( additionally, as pooley 2002 points out, just after he claims that the earth is at rest \u2018 properly speaking \u2019, descartes argues that the earth is stationary in the ordinary sense, because common practice is to determine the positions of the stars relative to the earth. descartes simply didn ' t need motion properly speaking to avoid religious conflict, which again suggests that it has some other significance in his system of thought. ) thus garber ( 1992, chapter 6 - 8 ) proposes that descartes actually took the unequivocal notion of motion properly speaking to be the correct sense of motion in mechanics. then rule i covers the case in which the two bodies have equal and opposite motions relative to their contiguous surroundings, while rule vi covers the case in which the bodies have different motions relative to those surroundings \u2014 one is perhaps at rest in its surroundings. that is, exactly what is needed to make the rules consistent is the kind of privileged, true, sense of motion provided by descartes ' second definition. insurmountable problems with the rules remain, but rejecting the traditional interpretation and taking motion properly speaking seriously in descartes ' philosophy clearly gives a more charitable reading. in an unpublished essay \u2014 de gravitatione ( newton, 2004 ) \u2014 and in a scholium to the definitions given in his 1687 mathematical principles of natural philosophy ( see newton, 1999 for an up - to - date translation ), newton attacked both of descartes ' notions of motion as candidates for the operative notion in mechanics. ( see stein 1967and rynasiewicz 1995 for important, and differing, views on the issue. ) ( this critique is studied in more detail in the entry newton ' s views on space, time, and motion. ) the most famous argument invokes the so - called \u2018 newton ' s bucket \u2019 experiment. stripped to its basic elements one compares : - a bucket of water hanging from a cord as the bucket is set spinning about the cord ' s axis, with - the same bucket and water when they are rotating at the same rate about the cord ' s axis. as is familiar from any rotating system,", "subdomain_id": "subdomain_quantum_mechanics", "similarity_score": 0.6080937527110188, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 7, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.064481"} {"text": "the sense of motion relative to an arbitrary reference body, is not the mechanical sense, since that kind of rotation is not unique at all, but depends on the motion of the reference body. and so descartes \u2019 change of place ( and for similar reasons, motion in the ordinary sense ) is not the mechanically significant sense of motion. in our discussion of descartes we called the sense of motion operative in the science of mechanics \u2018 true motion \u2019, and the phrase is used in this way by newton in the scholium. thus newton ' s bucket shows that true ( rotational ) motion is anti - correlated with, and so not identical with, proper motion ( as descartes proposed according to the garber reading ) ; and newton further argues that the rate of true ( rotational ) motion is unique, and so not identical with change of place, which is multiple. newton proposed instead that true motion is motion relative to a temporally enduring, rigid, 3 - dimensional euclidean space, which he dubbed \u2018 absolute space \u2019. of course, descartes also defined motion as relative to an enduring 3 - dimensional euclidean space ; the difference is that descartes space was divided into parts ( his space was identical with a plenum of corpuscles ) in motion, not a rigid structure in which ( mobile ) material bodies are embedded. so according to newton, the rate of true rotation of the bucket ( and water ) is the rate at which it rotates relative to absolute space. or put another way, newton effectively defines the complete predicate x moves - absolutely as x moves - relative - to absolute space ; both newton and descartes offer the competing complete predicates as analyses of x moves - truly. newton ' s proposal for understanding motion solves the problems that he posed for descartes, and provides an interpretation of the concepts of constant motion and acceleration that appear in his laws of motion. however, it suffers from two notable interpretational problems, both of which were pressed forcefully by leibniz ( in the leibniz - clarke correspondence, 1715 \u2013 1716 ) \u2014 which is not to say that leibniz himself offered a superior account of motion ( see below ). ( of course, there are other features of newton ' s proposal that turned out to be empirically inadequate, and are rejected by relativity : newton ' s account violates the relativity of simultaneity and postulates a non - dynamical spacetime structure. ) first, according to this account, absolute velocity is a well - defined", "subdomain_id": "subdomain_quantum_mechanics", "similarity_score": 0.6116910677975018, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 9, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.067783"} {"text": "hand, presumably it is supposed to be part of the physical, not mental, realm. in de gravitatione, newton rejected both the standard philosophical categories of substance and attribute as suitable characterizations. absolute space is not a substance for it lacks causal powers and does not have a fully independent existence, and yet not an attribute since it would exist even in a vacuum, which by definition is a place where there are no bodies in which it might inhere. newton proposes that space is what we might call a \u2018 pseudo - substance \u2019, more like a substance than property, yet not quite a substance. ( note that samuel clarke, in his correspondence with leibniz, which newton had some role in composing, advocates the property view, and note further that when leibniz objects because of the vacuum problem, clarke suggests that there might be non - material beings in the vacuum in which space might inhere. ) in fact, newton accepted the principle that everything that exists, exists somewhere \u2014 i. e., in absolute space. thus he viewed absolute space as a necessary consequence of the existence of anything, and of god ' s existence in particular \u2014 hence space ' s ontological dependence. leibniz was presumably unaware of the unpublished de gravitatione in which these particular ideas were developed, but as we shall see, his later works are characterized by a robust rejection of any notion of space as a real thing rather than an ideal, purely mental entity. this is a view that attracts even fewer contemporary adherents, but there is something deeply peculiar about a non - material but physical entity, a worry that has influenced many philosophical opponents of absolute space. after the development of relativity ( which we will take up below ), and its interpretation as a spacetime theory, it was realized that the notion of spacetime had applicability to a range of theories of mechanics, classical as well as relativistic. in particular, there is a spacetime geometry \u2014 \u2018 galilean \u2019 or \u2018 neo - newtonian \u2019 spacetime \u2014 for newtonian mechanics that solves the problem of absolute velocity ; an idea exploited by a number of philosophers from the late 1960s ( e. g., earman 1970, friedman 1983, sklar 1974 and stein 1968 ). for details the reader is referred to the entry on spacetime : inertial frames, but the general idea is that although a spatial distance is well - defined between any two simultaneous points of this spacetime, only the temporal interval is well - defined between non", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6503981176526774, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 11, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.069983"} {"text": "the reader is referred to the entry on spacetime : inertial frames, but the general idea is that although a spatial distance is well - defined between any two simultaneous points of this spacetime, only the temporal interval is well - defined between non - simultaneous points. thus things are rather unlike newton ' s absolute space, whose points persist through time and maintain their distances ; in absolute space the distance between p - now and q - then ( where p and q are points ) is just the distance between p - now and q - now. however, galilean spacetime has an \u2018 affine connection \u2019 which effectively specifies for every point of every continuous curve, the rate at which the curve is changing from straightness at that point ; for instance, the straight lines are picked out as those curves whose rate of change from straightness is zero at every point. ( another way of thinking about this space is as possessing \u2014 in addition to a distance between any two simultaneous points and a temporal interval between any points \u2014 a three - place relation of colinearity, satisfied by three points just in case they lie on a straight line. ) since the trajectories of bodies are curves in spacetime the affine connection determines the rate of change from straightness at every point of every possible trajectory. the straight trajectories thus defined can be interpreted as the trajectories of bodies moving inertially, and the rate of change from straightness of any trajectory can be interpreted as the acceleration of a body following that trajectory. that is, newton ' s second law can be given a geometric formulation as \u2018 the rate of change from straightness of a body ' s trajectory is equal to the forces acting on the body divided by its mass \u2019. the significance of this geometry is that while acceleration is well - defined, velocity is not \u2014 in accord with empirically determinability of acceleration but not velocity according to newtonian mechanics. ( a simple analogy helps see how such a thing is possible : betweenness but not \u2018 up \u2019 is a well - defined concept in euclidean space. ) thus galilean spacetime gives a very nice interpretation of the choice that nature makes when it decides that the laws of mechanics should be formulated in terms of accelerations not velocities ( as aristotle and descartes proposed ). put another way, we can define the complete predicate x accelerates as trajectory ( x ) has - non - zero - rate - of - change - from - straightness, where trajectory maps bodies onto", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.640816088232705, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 12, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.070967"} {"text": "as aristotle and descartes proposed ). put another way, we can define the complete predicate x accelerates as trajectory ( x ) has - non - zero - rate - of - change - from - straightness, where trajectory maps bodies onto their trajectories in galilean spacetime. and this predicate, defined this way, applies to the water in the bucket if and only if it is rotating, according to newtonian mechanics formulated in terms of the geometry of galilean spacetime ; it is the mechanically relevant sense of the word in this theory. but all of this formulation and definition has been given in terms of the geometry of spacetime, not relations between bodies ; acceleration is \u2018 absolute \u2019 in the sense that there is a preferred ( true ) sense of acceleration in mechanics and which is not defined in terms of the motions of bodies relative to one another. ( note that this sense of \u2018 absolute \u2019 is broader than that of motion relative to absolute space, which we defined earlier. in the remainder of this article we will use it in the broader sense. the reader should be aware that the term is used in many ways in the literature, and such equivocation often leads to massive misunderstandings. ) thus if any of this analysis of motion is taken literally then one arrives at a position regarding the ontology of spacetime rather like that of newton ' s regarding space : it is some kind of \u2018 substantial \u2019 ( or maybe pseudo - substantial ) thing with the geometry of galilean spacetime, just as absolute space possessed euclidean geometry. this view regarding the ontology of spacetime is usually called \u2018 substantivalism \u2019 ( sklar, 1974 ). the galilean substantivalist usually sees himself as adopting a more sophisticated geometry than newton but sharing his substantivalism ( though there is room for debate on newton ' s exact ontological views, see disalle, 2002 ). the advantage of the more sophisticated geometry is that although it allows the absolute sense of acceleration apparently required by newtonian mechanics to be defined, it does not allow one to define a similar absolute speed or velocity \u2014 x accelerates can be defined as a complete predicate in terms of the geometry of galilean spacetime but not x moves in general \u2014 and so the first of leibniz ' s problem is resolved. of course we see that the solution depends on a crucial shift from speed and velocity to acceleration as the relevant senses of \u2018 motion \u2019 : from the rate of change of", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6560256103405397, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 13, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.071970"} {"text": "in general \u2014 and so the first of leibniz ' s problem is resolved. of course we see that the solution depends on a crucial shift from speed and velocity to acceleration as the relevant senses of \u2018 motion \u2019 : from the rate of change of position to the rate of rate of change. while this proposal solves the first kind of problem posed by leibniz, it seems just as vulnerable to the second. while it is true that it involves the rejection of absolute space as newton conceived it, and with it the need to explicate the nature of an enduring space, the postulation of galilean spacetime poses the parallel question of the nature of spacetime. again, it is a physical but non - material something, the points of which may be coincident with material bodies. what kind of thing is it? could we do without it? as we shall see below, some contemporary philosophers believe so. there is a \u2018 folk - reading \u2019 of leibniz that one finds either explicitly or implicitly in the philosophy of physics literature which takes account of only some of his remarks on space and motion. the reading underlies vast swathes of the literature : for instance, the quantities captured by earman ' s ( 1999 ) \u2018 leibnizian spacetime \u2019, do not do justice to leibniz ' s view of motion ( as earman acknowledges ). but it is perhaps most obvious in introductory texts ( e. g., ray 1991, huggett 2000 to mention a couple ). according to this view, the only quantities of motion are relative quantities, relative velocity, acceleration and so on, and all relative motions are equal, so there is no true sense of motion. however, leibniz is explicit that other quantities are also \u2018 real \u2019, and his mechanics implicitly \u2014 but obviously \u2014 depends on yet others. the length of this section is a measure, not so much the importance of leibniz ' s actual views, but the importance of showing what the prevalent folk view leaves out regarding leibniz ' s views on the metaphysics of motion and interpretation of mechanics. that said, we shall also see that no one has yet discovered a fully satisfactory way of reconciling the numerous conflicting things that leibniz says about motion. some of these tensions can be put down simply to his changing his mind ( see cover and hartz 1988 for an explication of how leibniz ' s views on space developed ). however, we will concentrate on the fairly short period in", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6132106901656396, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 14, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.072893"} {"text": ". some of these tensions can be put down simply to his changing his mind ( see cover and hartz 1988 for an explication of how leibniz ' s views on space developed ). however, we will concentrate on the fairly short period in the mid 1680 - 90s during which leibniz developed his theory of mechanics, and was most concerned with their interpretation. we will supplement this discussion with the important remarks that he made in his correspondence with samuel clarke around 30 years later ( 1715 \u2013 1716 ) ; this discussion is broadly in line with the earlier period, and the intervening period is one in which he turned to other matters, rather than one in which his views on space were dramatically evolving. arguably, leibniz ' s views concerning space and motion do not have a completely linear logic, starting from some logically sufficient basic premises, but instead form a collection of mutually supporting doctrines if one starts questioning why leibniz held certain views \u2014 concerning the ideality of space, for instance \u2014 one is apt to be led in a circle. still, exposition requires starting somewhere, and leibniz ' s argument for the ideality of space in the correspondence with clarke is a good place to begin. but bear in mind the caveats made here \u2014 this argument was made later than a number of other relevant writings, and its logical relation to leibniz ' s views on motion is complex. leibniz ( lv. 47 \u2014 this notation means leibniz ' s fifth letter, section 47, and so on ) says that ( i ) a body comes to have the \u2018 same place \u2019 as another once did, when it comes to stand in the same relations to bodies we \u2018 suppose \u2019 to be unchanged ( more on this later ). ( ii ) that we can define \u2018 a place \u2019 to be that which any such two bodies have in common ( here he claims an analogy with the euclidean / eudoxan definition of a rational number in terms of an identity relation between ratios ). and finally that ( iii ) space is all such places taken together. however, he also holds that properties are particular, incapable of being instantiated by more than one individual, even at different times ; hence it is impossible for the two bodies to be in literally the same relations to the unchanged bodies. thus the thing that we take to be the same for the two bodies \u2014 the place \u2014 is something added by our minds to the situation, and only ideal. as a result, space, which is after all constructed from these ideal places,", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6094895094674775, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 15, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.073871"} {"text": "bodies. thus the thing that we take to be the same for the two bodies \u2014 the place \u2014 is something added by our minds to the situation, and only ideal. as a result, space, which is after all constructed from these ideal places, is itself ideal : \u2018 a certain order, wherein the mind conceives the application of relations \u2019. it ' s worth pausing briefly to contrast this view of space with those of descartes and of newton. both descartes and newton claim that space is a real, mind - independent entity ; for descartes it is matter, and for newton a \u2018 pseudo - substance \u2019, distinct from matter. and of course for both, these views are intimately tied up with their accounts of motion. leibniz simply denies the mind - independent reality of space, and this too is bound up with his views concerning motion. ( note that fundamentally, in the metaphysics of monads that leibniz was developing contemporaneously with his mechanics, everything is in the mind of the monads ; but the point that leibniz is making here is that even within the world that is logically constructed from the contents of the minds of monads, space is ideal. ) so far ( apart from that remark about \u2018 unchanged \u2019 bodies ) we have not seen leibniz introduce anything more than relations of distance between bodies, which is certainly consistent with the folk view of his philosophy. however, leibniz sought to provide a foundation for the cartesian / mechanical philosophy in terms of the aristotelian / scholastic metaphysics of substantial forms ( here we discuss the views laid out in sections 17 - 22 of the 1686 discourse on metaphysics and the 1695 specimen of dynamics, both in garber and ariew 1989 ). in particular, he identifies primary matter with what he calls its \u2018 primitive passive force \u2019 of resistance to changes in motion and to penetration, and the substantial form of a body with its \u2018 primitive active force \u2019. it is important to realize that these forces are not mere properties of matter, but actually constitute it in some sense, and further that they are not themselves quantifiable. however because of the collisions of bodies with one another, these forces \u2018 suffer limitation \u2019, and \u2018 derivative \u2019 passive and active forces result. ( there ' s a real puzzle here. collision presupposes space, but primitive forces constitute matter prior to any spatial concepts \u2014 the primitive active and passive forces ground motion and extension respectively. see garber and rauzy", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6148762738036647, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 16, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.074991"} {"text": "active forces result. ( there ' s a real puzzle here. collision presupposes space, but primitive forces constitute matter prior to any spatial concepts \u2014 the primitive active and passive forces ground motion and extension respectively. see garber and rauzy, 2004. ) derivative passive force shows up in the different degrees of resistance to change of different kinds of matter ( of \u2018 secondary matter \u2019 in scholastic terms ), and apparently is measurable. derivative active force however, is considerably more problematic for leibniz. on the one hand, it is fundamental to his account of motion and theory of mechanics \u2014 motion fundamentally is possession of force. but on the other hand, leibniz endorses the mechanical philosophy, which precisely sought to abolish aristotelian substantial form, which is what force represents. leibniz ' s goal was to reconcile the two philosophies, by providing an aristotelian metaphysical foundation for modern mechanical science ; as we shall see, it is ultimately an open question exactly how leibniz intended to deal with the inherent tensions in such a view. the texts are sufficiently ambiguous to permit dissent, but arguably leibniz intends that one manifestation of derivative active force is what he calls vis viva \u2014 \u2018 living force \u2019. leibniz had a famous argument with the cartesians over the correct definition of this quantity. descartes defined it as size times speed \u2014 effectively as the magnitude of the momentum of a body. leibniz gave a brilliant argument ( repeated in a number of places, for instance section 17 of the discourse on metaphysics ) that it was size times speed2 \u2014 so ( proportional to ) kinetic energy. if the proposed identification is correct then kinetic energy quantifies derivative active force according to leibniz ; or looked at the other way, the quantity of virtus ( another term used by leibniz for active force ) associated with a body determines its kinetic energy and hence its speed. as far as the authors know, leibniz never explicitly says anything conclusive about the relativity of virtus, but it is certainly consistent to read him ( as roberts 2003 does ) to claim that there is a unique quantity of virtus and hence \u2018 true \u2019 ( as we have been using the term ) speed associated with each body. at the very least, leibniz does say that there is a real difference between possession and non - possession of vis viva ( e. g., in section 18 of the discourse ) and it is a small step", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6134837607912337, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 17, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.075990"} {"text": "speed associated with each body. at the very least, leibniz does say that there is a real difference between possession and non - possession of vis viva ( e. g., in section 18 of the discourse ) and it is a small step from there to true, privileged speed. indeed, for leibniz, mere change of relative position is not \u2018 entirely real \u2019 ( as we saw for instance in the correspondence ) and only when it has vis viva as its immediate cause is there some reality to it. ( however, just to muddy the waters, leibniz also claims that as a matter of fact, no body ever has zero force, which on the reading proposed means no body is ever at rest, which would be surprising given all the collisions bodies undergo. ) an alternative interpretation to the one suggested here might say that leibniz intends that while there is a difference between motion / virtus and no motion / virtus, there is somehow no difference between any strictly positive values of those quantities. it is important to emphasize two points about the preceding account of motion in leibniz ' s philosophy. first, motion in the everyday sense \u2014 motion relative to something else \u2014 is not really real. fundamentally motion is possession of virtus, something that is ultimately non - spatial ( modulo its interpretation as primitive force limited by collision ). if this reading is right \u2014 and something along these lines seems necessary if we aren ' t simply to ignore important statements by leibniz on motion \u2014 then leibniz is offering an interpretation of motion that is radically different from the obvious understanding. one might even say that for leibniz motion is not movement at all! ( we will leave to one side the question of whether his account is ultimately coherent. ) the second point is that however we should understand leibniz, the folk reading simply does not and cannot take account of his clearly and repeatedly stated view that what is real in motion is force not relative motion, for the folk reading allows leibniz only relative motion ( and of course additionally, motion in the sense of force is a variety of true motion, again contrary to the folk reading ). however, from what has been said so far it is still possible that the folk reading is accurate when it comes to leibniz ' s views on the phenomena of motion, the subject of his theory of mechanics. the case for the folk reading is in fact supported by leibniz ' s resolution of the tension that we mentioned earlier, between the fundamental role of force", "subdomain_id": "subdomain_quantum_mechanics", "similarity_score": 0.6093383524713754, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 18, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.076965"} {"text": "an order of successions \u201d ( liii. 4 ), which is naturally taken to mean that space is at base nothing but the distance and temporal relations between bodies. ( though even this passage has its subtleties, because of the ideality of space discussed above, and because in leibniz ' s conception space determines what sets of relations are possible. ) and if relative distances and times exhaust the spatiotemporal in this way, then shouldn ' t all quantities of motion be defined in terms of those relations? we have seen two ways in which this would be the wrong conclusion to draw : force seems to involve a notion of speed that is not identified with any relative speed, and ( unless the equivalence of hypotheses is after all a principle of general relativity ) the laws pick out a standard of constant motion that need not be any constant relative motion. of course, it is hard to reconcile these quantities with the view of space and time that leibniz proposes \u2014 what is speed in size times speed2 or constant speed if not speed relative to some body or to absolute space? given leibniz ' s view that space is literally ideal ( and indeed that even relative motion is not \u2018 entirely real \u2019 ) perhaps the best answer is that he took force and hence motion in its real sense not to be determined by motion in a relative sense at all, but to be primitive monadic quantities. that is, he took x moves to be a complete predicate, but he believed that it could be fully analyzed in terms of strictly monadic predicates : x moves iff x possesses - non - zero - derivative - active - force. and this reading explains just what leibniz took us to be supposing when we \u2018 supposed certain bodies to be unchanged \u2019 in the construction of the idea of space : that they had no force, nothing causing, or making real any motion. it ' s again helpful to compare leibniz with descartes and newton, this time regarding motion. commentators often express frustration at leibniz ' s response to newton ' s arguments for absolute space : \u201c i find nothing \u2026 in the scholium that proves or can prove the reality of space in itself. however, i grant that there is a difference between an absolute true motion of a body and a mere relative change \u2026 \u201d ( lv. 53 ). not only does leibniz apparently fail to take the argument seriously, he then goes on to concede the step in the argument that seems to require absolute space", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6046256969212522, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 21, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.079979"} {"text": "the kind of folk - reading of newton that underlies much of the contemporary literature replaces mach ' s interpretation with a more charitable one. according to this reading, newton ' s point is that his mechanics \u2014 unlike descartes ' \u2014 could explain why the surface of the rotating water is curved, that his explanation involves a privileged sense of rotation, and that absent an alternative hypothesis about its relative nature, we should accept absolute space. but our discussion of newton ' s argument showed that it simply does not have an \u2018 abductive \u2019, \u2018 best explanation \u2019 form, but shows deductively, from cartesian premises, that rotation is neither proper nor ordinary motion. that is not to say that newton had no understanding of how such effects would be explained in his mechanics. for instance, in corollaries 5 and 6 to the definitions of the principles he states in general terms the conditions under which different states of motion are not \u2014 and so by implication are \u2014 discernible according to his laws of mechanics. nor is it to say that newton ' s contemporaries weren ' t seriously concerned with explaining inertial effects. leibniz, for instance, analyzed a rotating body ( in the specimen ). in short, parts of a rotating system collide with the surrounding matter and are continuously deflected, into a series of linear motions that form a curved path. but the system as leibniz envisions it \u2014 comprised of a plenum of elastic particles of matter \u2014 is far too complex for him to offer any quantitative model based on this qualitative picture. ( in the context of the proposed \u2018 abductive \u2019 reading of newton, note that this point is telling against a rejection of intrinsic rigidity or forces acting at a distance, not narrow relationism ; it is the complexity of collisions in a plenum that stymies analysis. and since leibniz ' s collision theory requires a standard of inertial motion, even if he had explained inertial effects, he would not have thereby shown that all motions are relative, much less that all are equal. ) although the argument is then not newton ' s, it is still an important response to the kind of relationism proposed by the folk - leibniz, especially when it is extended by bringing in a further example from newton ' s scholium. newton considered a pair of identical spheres, connected by a cord, too far from any bodies to observe any relative motions ; he pointed out that their rate and direction of rotation could still be experimental", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6284933631608285, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 24, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.084198"} {"text": "in a further example from newton ' s scholium. newton considered a pair of identical spheres, connected by a cord, too far from any bodies to observe any relative motions ; he pointed out that their rate and direction of rotation could still be experimentally determined by measuring the tension in the rod, and by pushing on opposite faces of the two globes to see whether the tension increased or decreased. he intended this simple example to demonstrate that the project he intended in the principia, of determining the absolute accelerations and hence gravitational forces on the planets from their relative motions, was possible. however, if we further specify that the spheres and cord are rigid and that they are the only things in their universe, then the example can be used to point out that there are infinitely many different rates of rotation all of which agree on the relations between bodies. since there are no differences in the relations between bodies in the different situations, it follows that the observable differences between the states of rotation cannot be explained in terms of the relations between bodies. therefore, a theory of the kind attributed to the folk ' s leibniz cannot explain all the phenomena of newtonian mechanics, and again we can argue abductively for absolute space. ( of course, the argument works by showing that, granted the different states of rotation, there are states of rotation that cannot merely be relative rotations of any kind ; for the differences cannot be traced to any relational differences. that is, granted the assumptions of the argument, rotation is not true relative motion of any kind. ) this argument ( neither the premises nor conclusion ) is not newton ' s, and must not be taken as a historically accurate reading, however, that is not to say that the argument is fallacious, and indeed many have found it attractive, particularly as a defense not of newton ' s absolute space, but of galilean spacetime. that is, newtonian mechanics with galilean spacetime can explain the phenomena associated with rotation, while theories of the kind proposed by mach cannot explain the differences between situations allowed by newtonian mechanics, but these explanations rely on the geometric structure of galilean spacetime \u2014 particularly its connection, to interpret acceleration. and thus \u2014 the argument goes \u2014 those explanations commit us to the reality of spacetime \u2014 a manifold of points \u2014 whose properties include the appropriate geometric ones. this final doctrine, of the reality of spacetime with its component points or regions, distinct from matter, with geometric properties, is what we earlier identified as \u2018 substantiv", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6262314292350222, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 25, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.085604"} {"text": "deny any relations between bodies and spacetime itself. like the actual leibniz, they allow absolute quantities of motion, but claim that space and time themselves are nothing but the relations between bodies. of course, such views raise the question of how a motion can be not relative to anything at all, and how we are to understand the privileging of frames ; huggett ( 2006 ) contains a proposal for addressing these problems. ( note that sklar and van fraassen are committed to the idea that in some sense newton ' s laws are capable of explaining all the phenomena without recourse to spacetime geometry ; that the connection and the metrical properties are explanatorily redundant. a similar view is defended in the context of relativity in brown 2005. ) between the time of newton and leibniz and the 20th century, newton ' s mechanics and gravitation theory reigned essentially unchallenged, and with that long period of dominance, absolute space came to be widely accepted. at least, no natural philosopher or physicist offered a serious challenge to newton ' s absolute space, in the sense of offering a rival theory that dispenses with it. but like the action at a distance in newtonian gravity, absolute space continued to provoke metaphysical unease. seeking a replacement for the unobservable newtonian space, neumann ( 1870 ) and lange ( 1885 ) developed more concrete definitions of the reference frames in which newton ' s laws hold. in these and a few other works, the concept of the set of inertial frames was first clearly expressed, though it was implicit in both remarks and procedures to be found in the principia. ( see the entries on space and time : inertial frames and newton ' s views on space, time, and motion ) the most sustained, comprehensive, and influential attack on absolute space was made by ernst mach in his science of mechanics ( 1883 ). in a lengthy discussion of newton ' s scholium on absolute space, mach accuses newton of violating his own methodological precepts by going well beyond what the observational facts teach us concerning motion and acceleration. mach at least partly misinterpreted newton ' s aims in the scholium, and inaugurated a reading of the bucket argument ( and by extension the globes argument ) that has largely persisted in the literature since. mach viewed the argument as directed against a \u2018 strict \u2019 or \u2018 general - relativity \u2019 form of relationism, and as an attempt to establish the existence of absolute", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6204168911572865, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 27, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.087770"} {"text": "( and by extension the globes argument ) that has largely persisted in the literature since. mach viewed the argument as directed against a \u2018 strict \u2019 or \u2018 general - relativity \u2019 form of relationism, and as an attempt to establish the existence of absolute space. mach points out the obvious gap in the argument when so construed : the experiment only establishes that acceleration ( rotation ) of the water with respect to the earth, or the frame of the fixed stars, produces the tendency to recede from the center ; it does not prove that a strict relationist theory cannot account for the bucket phenomena, much less the existence of absolute space. ( the reader will recall that newton ' s actual aim was simply to show that descartes ' two kinds of motion are not adequate to accounting for rotational phenomena. ) although mach does not mention the globes thought experiment specifically, it is easy to read an implicit response to it in the things he does say : nobody is competent to say what would happen, or what would be possible, in a universe devoid of matter other than two globes. so neither the bucket nor the globes can establish the existence of absolute space. both in mach ' s interpretations of newton ' s arguments and in his replies, one can already see two anti - absolute space viewpoints emerge, though mach himself never fully kept them apart. the first strain, which we may call \u2018 mach - lite \u2019, criticizes newton ' s postulation of absolute space as a metaphysical leap that is neither justified by actual experiments, nor methodologically sound. the remedy offered by mach - lite is simple : we should retain newton ' s mechanics and use it just as we already do, but eliminate the unnecessary posit of absolute space. in its place we need only substitute the frame of the fixed stars, as is the practice in astronomy in any case. if we find the incorporation of a reference to contingent circumstances ( the existence of a single reference frame in which the stars are more or less stationary ) in the fundamental laws of nature problematic ( which mach need not, given his official positivist account of scientific laws ), then mach suggests that we replace the 1st law with an empirically equivalent mathematical rival : mach ' s equation ( 1960, 287 ) the sums in this equation are to be taken over all massive bodies in the universe. since the top sum is weighted by distance, distant masses count much more than near ones. in a world with a ( reasonably ) static distribution of heavy distant bodies, such as we appear to live", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6247717054319598, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 28, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.088799"} {"text": "to be taken over all massive bodies in the universe. since the top sum is weighted by distance, distant masses count much more than near ones. in a world with a ( reasonably ) static distribution of heavy distant bodies, such as we appear to live in, the equation entails local conservation of linear momentum in \u2018 inertial \u2019 frames. the upshot of this equation is that the frame of the fixed stars plays exactly the role of absolute space in the statement of the 1st law. ( notice that this equation, unlike newton ' s first law, is not vectorial. ) this proposal does not, by itself, offer an alternative to newtonian mechanics, and as mach himself pointed out, the law is not well - behaved in an infinite universe filled with stars ; but the same can perhaps be said of newton ' s law of gravitation ( see malament 1995, and norton 1993 ). but mach did not offer this equation as a proposed law valid in any circumstances ; he avers, \u201c it is impossible to say whether the new expression would still represent the true condition of things if the stars were to perform rapid movements among one another. \u201d ( p. 289 ) it is not clear whether mach offered this revised first law as a first step toward a theory that would replace newton ' s mechanics, deriving inertial effects from only relative motions, as leibniz desired. but many other remarks made by mach in his chapter criticizing absolute space point in this direction, and they have given birth to the mach - heavy view, later to be christened \u201c mach ' s principle \u201d by albert einstein. the mach - heavy viewpoint calls for a new mechanics that invokes only relative distances and ( perhaps ) their 1st and 2nd time derivatives, and thus \u2018 generally relativistic \u2019 in the sense sometimes read into leibniz ' s remarks about motion. mach wished to eliminate absolute time from physics too, so he would have wanted a proper relationist reduction of these derivatives also. the barbour - bertotti theories, discussed below, provide this. mach - heavy apparently involves the prediction of novel effects due to \u2018 merely \u2019 relative accelerations. mach hints at such effects in his criticism of newton ' s bucket : newton ' s experiment with the rotating vessel of water simply informs us that the relative rotation of the water with respect to the sides of the vessel produces no noticeable centrifugal forces, but that such forces are produced by its relative rotation with respect to the mass of the earth and the other celestial bodies. no", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6083564460708635, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 29, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.089815"} {"text": "us that the relative rotation of the water with respect to the sides of the vessel produces no noticeable centrifugal forces, but that such forces are produced by its relative rotation with respect to the mass of the earth and the other celestial bodies. no one is competent to say how the experiment would turn out if the sides of the vessel [ were ] increased until they were ultimately several leagues thick. ( 1883, 284. ) the suggestion here seems to be that the relative rotation in stage ( i ) of the experiment might immediately generate an outward force ( before any rotation is communicated to the water ), if the sides of the bucket were massive enough. more generally, mach - heavy involves the view that all inertial effects should be derived from the motions of the body in question relative to all other massive bodies in the universe. the water in newton ' s bucket feels an outward pull due ( mainly ) to the relative rotation of all the fixed stars around it. mach - heavy is a speculation that an effect something like electromagnetic induction should be built into gravity theory. ( such an effect does exist according to the general theory of relativity, and is called \u2018 gravitomagnetic induction \u2019. the recently finished gravity probe b mission was designed to measure the gravitomagnetic induction effect due to the earth ' s rotation. ) its specific form must fall off with distance much more slowly than 1 / r2, if it is to be empirically similar to newtonian physics ; but it will certainly predict experimentally testable novel behaviors. a theory that satisfies all the goals of mach - heavy would appear to be ideal for the vindication of strict relationism and the elimination of absolute quantities of motion from mechanics. direct assault on the problem of satisfying mach - heavy in a classical framework proved unsuccessful, despite the efforts of others besides mach ( e. g., friedlander 1896, fopl 1904, reissner 1914, 1915 ), until the work of barbour and bertotti in the 1970s and 80s. ( between the late 19th century and the 1970s, there was of course one extremely important attempt to satisfy mach - heavy : the work of einstein that led to the general theory of relativity. since einstein ' s efforts took place in a non - classical ( lorentz / einstein / minkowski ) spacetime setting, we discuss them in the next section. ) rather than formulating a revised law of gravity / inertia using relative quantities, barbour and bertotti attacked the problem using the framework of lagrangian", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6188728167661921, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 30, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.090931"} {"text": "/ minkowski ) spacetime setting, we discuss them in the next section. ) rather than formulating a revised law of gravity / inertia using relative quantities, barbour and bertotti attacked the problem using the framework of lagrangian mechanics, replacing the elements of the action that involve absolute quantities of motion with new terms invoking only relative distances, velocities etc. their first ( 1977 ) theory uses a very simple and elegant action, and satisfies everything one could wish for from a mach - heavy theory : it is relationally pure ( even with respect to time : while simultaneity is absolute, the temporal metric is derived from the field equations ) ; it is nearly empirically equivalent to newton ' s theory in a world such as ours ( with a large - scale uniform, near - stationary matter distribution ) ; yet it does predict novel effects such as the ones mach posited with his thick bucket. among these is an \u2018 anisotropy of inertia \u2019 effect \u2014 accelerating a body away from the galactic center requires more force than accelerating it perpendicular to the galactic plane \u2014 large enough to be ruled out empirically. barbour and bertotti ' s second attempt ( 1982 ) at a relational lagrangian mechanics was arguably less machian, but more empirically adequate. in it, solutions are sought beginning with two temporally - nearby, instantaneous relational configurations of the bodies in the universe. barbour and bertotti define an \u2018 intrinsic difference \u2019 parameter that measures how different the two configurations are. in the solutions of the theory, this intrinsic difference quantity gets minimized, as well as the ordinary action, and in this way full solutions are derived despite not starting from a privileged inertial - frame description. the theory they end up with turns out to be, in effect, a fragment of newtonian theory : the set of models of newtonian mechanics and gravitation in which there is zero net angular momentum. this result makes perfect sense in terms of strict relationist aims. in a newtonian world in which there is a nonzero net angular momentum ( e. g., a lone rotating island galaxy ), this fact reveals itself in the classic \u201c tendency to recede from the center \u201d. since a strict relationist demands that bodies obey the same mechanical laws even in \u2018 rotating \u2019 coordinate systems, there cannot be any such tendency to recede from the center ( other than in a local subsystem ), in any of the relational theory ' s models", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6386380863196413, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 31, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.091865"} {"text": "a temptation to think of at least acceleration as \u2018 true \u2019 or \u2018 absolute \u2019. if such a realist believes motion to be by nature a relation rather than a property ( and as we saw in the introduction, not all philosophers accept this ) then she will feel obliged to accord some sort of existence or reality to the structure \u2014 e. g., the structure of galilean spacetime \u2014 in relation to which these motions are defined. for philosophers with such realist inclinations, the ideal relational account of motion would therefore be some version of mach - heavy. the special theory of relativity ( str ) is notionally based on a principle of relativity of motion ; but that principle is \u2018 special \u2019 \u2014 meaning, restricted. the relativity principle built into str is in fact nothing other than the galilean principle of relativity, which is built into newtonian physics. in other words, while there is no privileged standard of velocity, there is nevertheless a determinate fact of the matter about whether a body has accelerated or non - accelerated ( i. e., inertial ) motion. in this regard, the spacetime of str is exactly like galilean spacetime ( defined in section 5 above ). in terms of the question of whether all motion can be considered purely relative, one could argue that there is nothing new brought to the table by the introduction of einstein ' s str \u2014 at least, as far as mechanics is concerned. as dorling ( 1978 ) first pointed out, however, there is a sense in which the standard absolutist arguments against \u2018 strict \u2019 relationism using rotating objects ( buckets or globes ) fail in the context of str. maudlin ( 1993 ) used the same considerations to show that there is a way of recasting relationism in str that appears to be very successful. str incorporates certain novelties concerning the nature of time and space, and how they mesh together ; perhaps the best - known examples are the phenomena of \u2018 length contraction \u2019, \u2018 time dilation \u2019, and the \u2018 relativity of simultaneity. \u2019 since in str both spatial distances and time intervals \u2014 when measured in the standard ways \u2014 are observer - relative ( observers in different states of motion \u2018 disagreeing \u2019 about their sizes ), it is arguably most natural to restrict oneself to the invariant spacetime separation given by the interval between two points : [ dx2 + dy2 + dz2 \u2014 dt2 ] \u2014 the four - dimensional analog of the p", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6395687675540962, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 33, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.094444"} {"text": "sizes ), it is arguably most natural to restrict oneself to the invariant spacetime separation given by the interval between two points : [ dx2 + dy2 + dz2 \u2014 dt2 ] \u2014 the four - dimensional analog of the pythagorean theorem, for spacetime distances. if one regards the spacetime interval relations between masses - at - times as one ' s basis on which space - time is built up as an ideal entity, then with only mild caveats relationism works : the \u2018 relationally pure \u2019 facts suffice to uniquely fix how the material systems are embeddable ( up to isomorphism ) in the \u2018 minkowski \u2019 spacetime of str. the modern variants of newton ' s bucket and globes arguments no longer stymie the relationist because ( for example ) the spacetime interval relations among bits of matter in newton ' s bucket at rest are quite different from the spacetime interval relations found among those same bits of matter after the bucket is rotating. for example, the spacetime interval relation between a bit of water near the side of the bucket, at one time, and itself ( say ) a second later is smaller than the interval relation between a center - bucket bit of water and itself one second later ( times referred to inertial - frame clocks ). the upshot is that, unlike the situation in classical physics, a body at rest cannot have all the same spatial relations among its parts as a similar body in rotation. we cannot put a body or system into a state of rotation ( or other acceleration ) without thereby changing the spacetime interval relations between the various bits of matter at different moments of time. rotation and acceleration supervene on spacetime interval relations. it is worth pausing to consider to what extent this victory for ( some form of ) relationism satisfies the classical \u2018 strict \u2019 relationism traditionally ascribed to mach and leibniz. the spatiotemporal relations that save the day against the bucket and globes are, so to speak, mixed spatial and temporal distances. they are thus quite different from the spatial - distances - at - a - time presupposed by classical relationists ; moreover they do not correspond to relative velocities ( - at - a - time ) either. their oddity is forcefully captured by noticing that if we choose appropriate bits of matter at \u2018 times \u2019 eight minutes apart, i - now am at zero distance from the surface of the sun ( of eight minutes \u2018 past \u2019, since it took", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6413390962034573, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 34, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.095384"} {"text": "either. their oddity is forcefully captured by noticing that if we choose appropriate bits of matter at \u2018 times \u2019 eight minutes apart, i - now am at zero distance from the surface of the sun ( of eight minutes \u2018 past \u2019, since it took 8 minutes for light from the sun to reach me - now ). so we are by no means dealing here with an innocuous, \u2018 natural \u2019 translation of classical relationist quantities into the str setting. on the other hand, in light of the relativity of simultaneity ( see note ), it can be argued that the absolute simultaneity presupposed by classical relationists and absolutists alike was, in fact, something that relationists should always have regarded with misgivings. from this perspective, instantaneous relational configurations \u2014 precisely what one starts with in the theories of barbour and bertotti \u2014 would be the things that should be treated with suspicion. if we now return to our questions about motions \u2014 about the nature of velocities and accelerations \u2014 we find, as noted above, that matters in the interval - relational interpretation of str are much the same as in newtonian mechanics in galilean spacetime. there are no well - defined absolute velocities, but there are indeed well - defined absolute accelerations and rotations. in fact, the difference between an accelerating body ( e. g., a rocket ) and an inertially moving body is codified directly in the cross - temporal interval relations of the body with itself. so we are very far from being able to conclude that all motion is relative motion of a body with respect to other bodies. it is true that the absolute motions are in 1 - 1 correlation with patterns of spacetime interval relations, but it is not at all correct to say that they are, for that reason, eliminable in favor of merely relative motions. rather we should simply say that no absolute acceleration can fail to have an effect on the material body or bodies accelerated. but this was already true in classical physics if matter is modeled realistically : the cord connecting the globes does not merely tense, but also stretches ; and so does the bucket, even if imperceptibly, i. e., the spatial relations change. maudlin does not claim this version of relationism to be victorious over an absolutist or substantivalist conception of minkowski spacetime, when it comes time to make judgments about the theory ' s ontology", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6159763653969308, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 35, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.096307"} {"text": "spatial relations change. maudlin does not claim this version of relationism to be victorious over an absolutist or substantivalist conception of minkowski spacetime, when it comes time to make judgments about the theory ' s ontology. there may be more to vindicating relationism than merely establishing a 1 - 1 correlation between absolute motions and patterns of spatiotemporal relations. the simple comparison made above between str and newtonian physics in galilean spacetime is somewhat deceptive. for one thing, galilean spacetime is a mathematical innovation posterior to einstein ' s 1905 theory ; before then, galilean spacetime had not been conceived, and full acceptance of newtonian mechanics implied accepting absolute velocities and, arguably, absolute positions, just as laid down in the scholium. so einstein ' s elimination of absolute velocity was a genuine conceptual advance. moreover, the scholium was not the only reason for supposing that there existed a privileged reference frame of \u2018 rest \u2019 : the working assumption of almost all physicists in the latter half of the 19th century was that, in order to understand the wave theory of light, one had to postulate an aetherial medium filling all space, wave - like disturbances in which constituted electromagnetic radiation. it was assumed that the aether rest frame would be an inertial reference frame ; and physicists felt some temptation to equate its frame with the absolute rest frame, though this was not necessary. regardless of this equation of the aether with absolute space, it was assumed by all 19th century physicists that the equations of electrodynamic theory would have to look different in a reference frame moving with respect to the aether than they did in the aether ' s rest frame ( where they presumably take their canonical form, i. e., maxwell ' s equations and the lorentz force law. ) so while theoreticians labored to find plausible transformation rules for the electrodynamics of moving bodies, experimentalists tried to detect the earth ' s motion in the aether. experiment and theory played collaborative roles, with experimental results ruling out certain theoretical moves and suggesting new ones, while theoretical advances called for new experimental tests for their confirmation or \u2014 as it happened \u2014 disconfirmation. as is well known, attempts to detect the earth ' s velocity in the aether were unsuccessful. on the theory side, attempts to formulate the transformation laws for electrodynamics in moving frames \u2014 in such", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6276288009075288, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 36, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.097256"} {"text": "happened \u2014 disconfirmation. as is well known, attempts to detect the earth ' s velocity in the aether were unsuccessful. on the theory side, attempts to formulate the transformation laws for electrodynamics in moving frames \u2014 in such a way as to be compatible with experimental results \u2014 were complicated and inelegant. a simplified way of seeing how einstein swept away a host of problems at a stroke is this : he proposed that the galilean principle of relativity holds for maxwell ' s theory, not just for mechanics. the canonical ( \u2018 rest - frame \u2019 ) form of maxwell ' s equations should be their form in any inertial reference frame. since the maxwell equations dictate the velocity c of electromagnetic radiation ( light ), this entails that any inertial observer, no matter how fast she is moving, will measure the velocity of a light ray as c \u2014 no matter what the relative velocity of its emitter. einstein worked out logically the consequences of this application of the special relativity principle, and discovered that space and time must be rather different from how newton described them. str undermined newton ' s absolute time just as decisively as it undermined his absolute space ( see note ). einstein ' s str was the first clear and empirically successful physical theory to overtly eliminate the concepts of absolute rest and absolute velocity while recovering most of the successes of classical mechanics and 19th century electrodynamics. it therefore deserves to be considered the first highly successful theory to explicitly relativize motion, albeit only partially. but str only recovered most of the successes of classical physics : crucially, it left out gravity. and there was certainly reason to be concerned that newtonian gravity and str would prove incompatible : classical gravity acted instantaneously at a distance, while str eliminated the privileged absolute simultaneity that this instantaneous action presupposes. several ways of modifying newtonian gravity to make it compatible with the spacetime structure of str suggested themselves to physicists in the years 1905 - 1912, and a number of interesting lorentz - covariant theories were proposed ( set in the minkowski spacetime of str ). einstein rejected these efforts one and all, for violating either empirical facts or theoretical desiderata. but einstein ' s chief reason for not pursuing the reconciliation of gravitation with str ' s spacetime appears to have been his desire, beginning in 1907, to replace str with a theory in which not only velocity could", "subdomain_id": "subdomain_quantum_optics", "similarity_score": 0.6152108732487237, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 37, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.098339"} {"text": "desiderata. but einstein ' s chief reason for not pursuing the reconciliation of gravitation with str ' s spacetime appears to have been his desire, beginning in 1907, to replace str with a theory in which not only velocity could be considered merely relative, but also acceleration. that is to say, einstein wanted if possible to completely eliminate all absolute quantities of motion from physics, thus realizing a theory that satisfies at least one kind of \u2018 strict \u2019 relationism. ( regarding einstein ' s rejection of lorentz - covariant gravity theories, see norton 1992 ; regarding einstein ' s quest to fully relativize motion, see hoefer 1994. ) einstein began to see this complete relativization as possible in 1907, thanks to his discovery of the equivalence principle. imagine we are far out in space, in a rocket ship accelerating at a constant rate g = 9. 98 m / s2. things will feel just like they do on the surface of the earth ; we will feel a clear up - down direction, bodies will fall to the floor when released, etc. indeed, due to the well - known empirical fact that gravity affects all bodies by imparting a force proportional to their matter ( and energy ) content, independent of their internal constitution, we know that any experiment performed on this rocket will give the same results that the same experiment would give if performed on the earth. now, newtonian theory teaches us to consider the apparent downward, gravity - like forces in the rocket ship as \u2018 pseudo - forces \u2019 or \u2018 inertial forces \u2019, and insists that they are to be explained by the fact that the ship is accelerating in absolute space. but einstein asked : \u201c is there any way for the person in the rocket to regard him / herself as being \u2018 at rest \u2019 rather than in absolute ( accelerated ) motion? \u201d and the answer he gave is : yes. the rocket traveler may regard him / herself as being \u2018 at rest \u2019 in a homogeneous and uniform gravitational field. this will explain all the observational facts just as well as the supposition that he / she is accelerating relative to absolute space ( or, absolutely accelerating in minkowski spacetime ). but is it not clear that the latter is the truth, while the former is a fiction? by no means ; if there were a uniform gravitational field filling all space, then it would affect all the other bodies in the world \u2014 the earth, the stars, etc, imparting to them a downward acceleration away from", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6168432963822829, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 38, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.100152"} {"text": "gtr ). there is one key element left out of this success story, however, and it is crucial to understanding why most physicists reject einstein ' s claim to have eliminated absolute states of motion in gtr. going back to our accelerating rocket, we accepted einstein ' s claim that we could regard the ship as hovering at rest in a universe - filling gravitational field. but a gravitational field, we usually suppose, is generated by matter. how is this universe - filling field linked to generating matter? the answer may be supplied by mach - heavy. regarding the \u2018 accelerating \u2019 rocket which we decide to regard as \u2018 at rest \u2019 in a gravitational field, the machian says : all those stars and galaxies, etc., jointly accelerating downward ( relative to the rocket ), \u2018 produce \u2019 that gravitational field. the mathematical specifics of how this field is generated will have to be different from newton ' s law of gravity, of course ; but it should give essentially the same results when applied to low - mass, slow - moving problems such as the orbits of the planets, so as to capture the empirical successes of newtonian gravity. einstein thought, in 1916 at least, that the field equations of gtr are precisely this mathematical replacement for newton ' s law of gravity, and that they fully satisfied the desiderata of mach - heavy relationism. but it was not so. ( see the entry on early philosophical interpretations of general relativity. ) in gtr, spacetime is locally very much like flat minkowski spacetime. there is no absolute velocity locally, but there are clear local standards of accelerated vs non - accelerated motion, i. e., local inertial frames. in these \u2018 freely falling \u2019 frames bodies obey the usual rules for non - gravitational physics familiar from str, albeit only approximately. but overall spacetime is curved, and local inertial frames may tip, bend and twist as we move from one region to another. the structure of curved spacetime is encoded in the metric field tensor gab, with the curvature encoding gravity at the same time : gravitational forces are so to speak \u2018 built into \u2019 the metric field, geometrized away. since the spacetime structure encodes gravity and inertia, and in a mach - heavy theory these phenomena should be completely determined by the relational distribution of matter ( and relative motions ), einstein wished to see the metric as entirely determined by the distribution of matter and energy. but what the gtr field equations entail is, in general, only a partial -", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6038560160334725, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 40, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.102686"} {"text": "be completely determined by the relational distribution of matter ( and relative motions ), einstein wished to see the metric as entirely determined by the distribution of matter and energy. but what the gtr field equations entail is, in general, only a partial - determination relation. we cannot go into the mathematical details necessary for a full discussion of the successes and failures of mach - heavy in the gtr context. but one can see why the machian interpretation einstein hoped he could give to the curved spacetimes of his theory fails to be plausible, by considering a few simple \u2018 worlds \u2019 permitted by gtr. in the first place, for our hovering rocket ship, if we are to attribute the gravity field it feels to matter, there has got to be all this other matter in the universe. but if we regard the rocket as a mere \u2018 test body \u2019 ( not itself substantially affecting the gravity present or absent in the universe ), then we can note that according to gtr, if we remove all the stars, galaxies, planets etc. from the world, the gravitational field does not disappear. on the contrary, it stays basically the same locally, and globally it takes the form of empty minkowski spacetime, precisely the quasi - absolute structure einstein was hoping to eliminate. solutions of the gtr field equations for arbitrary realistic configurations of matter ( e. g., a rocket ship ejecting a stream of particles to push itself forward ) are hard to come by, and in fact a realistic two - body exact solution has yet to be discovered. but numerical methods can be applied for many purposes, and physicists do not doubt that something like our accelerating rocket \u2014 in otherwise empty space \u2014 is possible according to the theory. we see clearly, then, that gtr fails to satisfy einstein ' s own understanding of mach ' s principle, according to which, in the absence of matter, space itself should not be able to exist. a second example : gtr allows us to model a single rotating object in an otherwise empty universe ( e. g., a neutron star ). relationism of the machian variety says that such rotation is impossible, since it can only be understood as rotation relative to some sort of absolute space. in the case of gtr, this is basically right : the rotation is best understood as rotation relative to a \u2018 background \u2019 spacetime that is identical to the minkowski spacetime of str, only \u2018 curved \u2019 by the presence of matter in the region of the star. on the other hand, there is one", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6235657658011506, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 41, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.103655"} {"text": "is best understood as rotation relative to a \u2018 background \u2019 spacetime that is identical to the minkowski spacetime of str, only \u2018 curved \u2019 by the presence of matter in the region of the star. on the other hand, there is one charge of failure - to - relativize - motion sometimes leveled at gtr that is unfair. it is sometimes asserted that the simple fact that the metric field ( or the connection it determines ) distinguishes, at every location, motions that are \u2018 absolutely \u2019 accelerated and / or \u2018 absolutely rotating \u2019 from those that are not, by itself entails that gtr fails to embody a folk - leibniz style general relativity of motion ( e. g. earman ( 1989 ), ch. 5 ). we think this is incorrect, and leads to unfairly harsh judgments about confusion on einstein ' s part. the local inertial structure encoded in the metric would not be \u2018 absolute \u2019 in any meaningful sense, if that structure were in some clear sense fully determined by the relationally specified matter - energy distribution. einstein was not simply confused when he named his gravity theory. ( just what is to be understood by \u201c the relationally specified matter - energy distribution \u201d is a further, thorny issue, which we cannot enter into here. ) gtr does not fulfill all the goals of mach - heavy, at least as understood by einstein, and he recognized this fact by 1918 ( einstein 1918 ). and yet \u2026 gtr comes tantalizingly close to achieving those goals, in certain striking ways. for one thing, gtr does predict mach - heavy effects, known as \u2018 frame - dragging \u2019 : if we could model mach ' s thick - walled bucket in gtr, it seems clear that it would pull the water slightly outward, and give it a slight tendency to begin rotating in the same sense as the bucket ( even if the big bucket ' s walls were not actually touching the water. while gtr does permit us to model a lone rotating object, if we model the object as a shell of mass ( instead of a solid sphere ) and let the size of the shell increase ( to model the \u2018 sphere of the fixed stars \u2019 we see around us ), then as brill & cohen ( 1966 ) showed, the frame - dragging becomes complete inside the shell. in other words : our original minkowski background structure effectively disappears, and inertia becomes wholly determined by the shell of matter, just as mach posited was the case. this complete determination of in", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.611793431522214, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 42, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.104624"} {"text": "frame - dragging becomes complete inside the shell. in other words : our original minkowski background structure effectively disappears, and inertia becomes wholly determined by the shell of matter, just as mach posited was the case. this complete determination of inertia by the global matter distribution appears to be a feature of other models, including the friedman - robertson - walker - lemaitre big bang models that best match observations of our universe. finally, it is important to recognize that gtr is generally covariant in a very special sense : unlike all other prior theories ( and unlike many subsequent quantum theories ), it postulates no fixed \u2018 prior \u2019 or \u2018 background \u2019 spacetime structure. as mathematicians and physicists realized early on, other theories, e. g., newtonian mechanics and str, can be put into a generally covariant form. but when this is done, there are inevitably mathematical objects postulated as part of the formalism, whose role is to represent absolute elements of spacetime structure. what is unique about gtr is that it was the first, and is still the only \u2018 core \u2019 physical theory, to have no such absolute elements in its covariant equations. the spacetime structure in gtr, represented by the metric field ( which determines the connection ), is at least partly \u2018 shaped \u2019 by the distribution of matter and energy. and in certain models of the theory, such as the big bang cosmological models, some authors have claimed that the local standards of inertial motion \u2014 the local \u2018 gravitational field \u2019 of einstein ' s equivalence principle \u2014 are entirely fixed by the matter distribution throughout space and time, just as mach - heavy requires ( see, for example, wheeler and cuifollini 1995 ). absolutists and relationists are thus left in a frustrating and perplexing quandary by gtr. considering its anti - machian models, we are inclined to say that motions such as rotation and acceleration remain absolute, or nearly - totally - absolute, according to the theory. on the other hand, considering its most mach - friendly models, which include all the models taken to be good candidates for representing the actual universe, we may be inclined to say : motion in our world is entirely relative ; the inertial effects normally used to argue for absolute motion are all understandable as effects of rotations and accelerations relative to the cosmic matter, just as mach hoped. but even if we agree that motions in our world are in fact all", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6441469182264572, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 43, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.105657"} {"text": "; the inertial effects normally used to argue for absolute motion are all understandable as effects of rotations and accelerations relative to the cosmic matter, just as mach hoped. but even if we agree that motions in our world are in fact all relative in this sense, this does not automatically settle the traditional relationist / absolutist debate, much less the relationist / substantivalist debate. many philosophers ( including, we suspect, nerlich 1994 and earman 1989 ) would be happy to acknowledge the mach - friendly status of our spacetime, and argue nevertheless that we should understand that spacetime as a real thing, more like a substance than a mere ideal construct of the mind as leibniz insisted. ( nerlich ( 1994 ) and earman ( 1989 ), we suspect, would take this stance. ) some, though not all, attempts to convert gtr into a quantum theory would accord spacetime this same sort of substantiality that other quantum fields possess. this article has been concerned with tracing the history and philosophy of \u2018 absolute \u2019 and \u2018 relative \u2019 theories of space and motion. along the way we have been at pains to introduce some clear terminology for various different concepts ( e. g., \u2018 true \u2019 motion, \u2018 substantivalism \u2019, \u2018 absolute space \u2019 ), but what we have not really done is say what the difference between absolute and relative space and motion is : just what is at stake? recently rynasiewicz ( 2000 ) has argued that there simply are no constant issues running through the history that we have discussed here ; that there is no stable meaning for either \u2018 absolute motion \u2019 or \u2018 relative motion \u2019 ( or \u2018 substantival space \u2019 vs \u2018 relational space \u2019 ). while we agree to a certain extent, we think that nevertheless there are a series of issues that have motivated thinkers again and again ; indeed, those that we identified in the introduction. ( one quick remark : rynasiewicz is probably right that the issues cannot be expressed in formally precise terms, but that does not mean that there are no looser philosophical affinities that shed useful light on the history. ) our discussion has revealed several different issues, of which we will highlight three as components of the \u2018 absolute - relative debate \u2019. ( i ) there is the question of whether all motions and all possible descriptions of motions are equal, or whether some are \u2018 real \u2019 \u2014 what we have called, in seventeenth century parlance, \u2018 true \u2019. there is a natural", "subdomain_id": "subdomain_quantum_mechanics", "similarity_score": 0.6636796645993395, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 44, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.107003"} {"text": "debate \u2019. ( i ) there is the question of whether all motions and all possible descriptions of motions are equal, or whether some are \u2018 real \u2019 \u2014 what we have called, in seventeenth century parlance, \u2018 true \u2019. there is a natural temptation for those who hold that there is \u2018 nothing but the relative positions and motions between bodies ' ( and more so for their readers ) to add \u2018 and all such motions are equal \u2019, thus denying the existence of true motion. however, arguably \u2014 perhaps surprisingly \u2014 no one we have discussed has unreservedly held this view ( at least not consistently ) : descartes considered motion \u2018 properly speaking \u2019 to be privileged, leibniz introduced \u2018 active force \u2019 to ground motion ( arguably in his mechanics as well as metaphysically ), and mach ' s view seems to be that the distribution of matter in the universe determines a preferred standard of inertial motion. ( again, in general relativity, there is a distinction between inertial and accelerated motion. ) that is, relationists can allow true motions if they offer an analysis of them in terms of the relations between bodies. given this logical point, and given the historical ways thinkers have understood themselves, it seems unhelpful to characterize the issues in ( i ) as constituting an absolute - relative debate, hence our use of the term \u2018 true \u2019 instead of \u2018 absolute \u2019. so we are led to the second question : ( ii ) is true motion definable in terms of relations or not? ( of course the answer depends on what kind of definitions will count, and absent an explicit definition \u2014 descartes ' proper motion for example \u2014 the issue is often taken to be that of whether true motions supervene on relations, as newton ' s globes are often supposed to refute. ) it seems reasonable to call this issue that of whether motion is absolute or relative. descartes and mach are relationists about motion in this sense, while newton is an absolutist. leibniz is also an absolutist about motion in his metaphysics, and if our reading is correct, also about the interpretation of motion in the laws of collision. this classification of leibniz ' s views runs contrary to his customary identification as relationist - in - chief, but we will clarify his relationist credentials below. finally, we have discussed ( ii ) in the context of relativity, first examining maudlin ' s proposal that the embedding of a relationally - specified system in min", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6266272414168814, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 45, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.108049"} {"text": "- in - chief, but we will clarify his relationist credentials below. finally, we have discussed ( ii ) in the context of relativity, first examining maudlin ' s proposal that the embedding of a relationally - specified system in minkowski spacetime is in general unique once all the spacetime interval - distance relations are given. this proposal may or may not be held to satisfy the relational - definability question of ( ii ), but in any case it cannot be carried over to the context of general relativity theory. in the case of gtr we linked relational motion to the satisfaction of mach ' s principle, just as einstein did in the early years of the theory. despite some promising features displayed by gtr, and certain of its models, we saw that mach ' s principle is not fully satisfied in gtr as a whole. we also noted that in the absence of absolute simultaneity, it becomes an open question what relations are to be permitted in the definition ( or supervience base ) \u2014 spacetime interval relations? instantaneous spatial distances and velocities on a 3 - d hypersurface? ( in recent works, barbour has argued that gtr is fully machian, using a 3 - d relational - configuration approach. see barbour, foster and murchadha 2002. ) the final issue is that of ( iii ) whether absolute motion is motion with respect to substantival space or not. of course this is how newton understood acceleration \u2014 as acceleration relative to absolute space. more recent newtonians share this view, although motion for them is with respect to substantival galilean spacetime ( or rather, since they know newtonian mechanics is false, they hold that this is the best interpretation of that theory ). leibniz denied that motion was relative to space itself, since he denied the reality of space ; for him true motion was the possession of active force. so despite his \u2018 absolutism \u2019 ( our adjective not his ) about motion he was simultaneously a relationist about space : \u2018 space is merely relative \u2019. following leibniz ' s lead we can call this debate the question of whether space is absolute or relative. the drawback of this name is that it suggests a separation between motion and space, which exists in leibniz ' s views, but which is otherwise problematic ; still, no better description presents itself. others who are absolutists about motion but relationists about space include sklar ( 1974 ) and van", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6402585037289191, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 46, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.109083"} {"text": "motion and space, which exists in leibniz ' s views, but which is otherwise problematic ; still, no better description presents itself. others who are absolutists about motion but relationists about space include sklar ( 1974 ) and van fraassen ( 1985 ) ; sklar introduced a primitive quantity of acceleration, not supervenient on motions relative to anything at all, while van fraassen let the laws themselves pick out the inertial frames. it is of course arguable whether any of these three proposals are successful ; ( even ) stripped of leibniz ' s aristotelian packaging, can absolute quantities of motion \u2018 stand on their own feet \u2019? and under what understanding of laws can they ground a standard of inertial motion? huggett ( 2006 ) defends a similar position of absolutism about motion, but relationism about space ; he argues \u2014 in the case of newtonian physics \u2014 that fundamentally there is nothing to space but relations between bodies, but that absolute motions supervene \u2014 not on the relations at any one time \u2014 but on the entire history of relations. works cited in text - aristotle, 1984, the complete works of aristotle : the revised oxford translation, j. barnes ( ed. ), princeton : princeton university press. - barbour, j. and bertotti, b., 1982, \u201c mach ' s principle and the structure of dynamical theories, \u201d proceedings of the royal society ( london ), 382 : 295 - 306. - \u2013 \u2013 \u2013, 1977, \u201c gravity and inertia in a machian framework, \u201d nuovo cimento, 38b : 1 - 27. - brill, d. r. and cohen, j., 1966, \u201c rotating masses and their effects on inertial frames, \u201d physical review 143 : 1011 - 1015. - brown, h. r., 2005, physical relativity : space - time structure from a dynamical perspective, oxford : oxford university press. - descartes, r., 1983, principles of philosophy, r. p. miller and v. r. miller ( trans. ), dordrecht, london : reidel. - dorling, j., 1978, \u201c did einstein need general relativity to solve the problem of space? or had the problem already been solved by special relativity?, \u201d british journal for the philosophy of science, 29 : 311 - 323. - earman, j., 1989, world enough and spacetime :", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6108576894493661, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 47, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.110027"} {"text": "c., 1994, \u201c einstein ' s struggle for a machian gravitation theory, \u201d studies in history and philosophy of science, 25 : 287 - 336. - huggett, n., 2006, \u201c the regularity account of relational spacetime, \u201d mind, 115 : 41 - 74. - \u2013 \u2013 \u2013, 2000, \u201c space from zeno to einstein : classic readings with a contemporary commentary, \u201d international studies in the philosophy of science, 14 : 327 - 329. - lange, l., 1885, \u201c ueber das beharrungsgesetz, \u201d berichte der koniglichen sachsischen gesellschaft der wissenschaften zu leipzig, mathematisch - physische classe 37 ( 1885 ) : 333 - 51. - leibniz, g. w., 1989, philosophical essays, r. ariew and d. garber ( trans. ), indianapolis : hackett pub. co. - leibniz, g. w., and samuel clarke, 1715 \u2013 1716, \u201c correspondence \u201d, in the leibniz - clarke correspondence, together with extracts from newton ' s \u201c principia \u201d and \u201c opticks \u201d, h. g. alexander ( ed. ), manchester : manchester university press, 1956. - lodge, p., 2003, \u201c leibniz on relativity and the motion of bodies, \u201d philosophical topics, 31 : 277 - 308. - mach, e., 1883, die mechanik in ihrer entwickelung, historisch - kritisch dargestellt. 2nd edition. leipzig : brockhaus. english translation ( 6th edition, 1960 ) : the science of mechanics, la salle, illinois : open court press. - malament, d., 1995, \u201c is newtonian cosmology really inconsistent?, \u201d philosophy of science 62, no. 4. - maudlin, t., 1993, \u201c buckets of water and waves of space : why space - time is probably a substance, \u201d philosophy of science, 60 : 183 - 203. - minkowski, h. ( 1908 ). \u201c space and time, \u201d in einstein, et al. ( 1952 ), pp. 75 - 91. - nerlich, graham, 1994, the shape of space ( 2nd edition ), cambridge : cambridge university press. - neumann, c., 1870, ueber die principien der galilei - newton ' schen theorie. leipzig : b.", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6356925955393196, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 49, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.111656"} {"text": "graham, 1994, the shape of space ( 2nd edition ), cambridge : cambridge university press. - neumann, c., 1870, ueber die principien der galilei - newton ' schen theorie. leipzig : b. g. teubner, 1870. - newton, i., 2004, newton : philosophical writings, a. janiak ( ed. ), cambridge : cambridge university press. - newton, i. and i. b. cohen, 1999, the principia : mathematical principles of natural philosophy, i. b. cohen and a. m. whitman ( trans. ), berkeley ; london : university of california press. - norton, j., 1995, \u201c mach ' s principle before einstein, \u201d in j. barbour and h. pfister ( eds. ) mach ' s principle : from newton ' s bucket to quantum gravity : einstein studies, vol. 6. boston : birkhauser, pp. 9 - 57. - norton, j., 1993, \u201c a paradox in newtonian cosmology, \u201d in m. forbes, d. hull and k. okruhlik ( eds. ) psa 1992 : proceedings of the 1992 biennial meeting of the philosophy of science association. vol. 2. east lansing, mi : philosophy of science association, pp. 412 - 20. - \u2013 \u2013 \u2013, 1992, \u201c einstein, nordstrom and the early demise of scalar, lorentz - covariant theories of gravitation, \u201d archive for history of exact sciences, 45 : 17 - 94. - pooley, o., 2002, the reality of spacetime, d. phil thesis, oxford university. - ray, c., 1991, time, space and philosophy, new york : routledge. - roberts, j. t., 2003, \u201c leibniz on force and absolute motion, \u201d philosophy of science, 70 : 553 - 573. - rynasiewicz, r., 1995, \u201c by their properties, causes, and effects : newton ' s scholium on time, space, place, and motion \u2014 i. the text, \u201d studies in history and philosophy of science, 26 : 133 - 153. - sklar, l., 1974, space, time and spacetime, berkeley : university of california press. - stein, h., 1977, \u201c some philosophical prehistory of general relativity, \u201d in minnesota studies in the philosophy of science 8 : foundations of", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6461768259430711, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 50, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.112528"} {"text": "l., 1974, space, time and spacetime, berkeley : university of california press. - stein, h., 1977, \u201c some philosophical prehistory of general relativity, \u201d in minnesota studies in the philosophy of science 8 : foundations of space - time theories :, j. earman, c. glymour and j. stachel ( eds. ), minneapolis : university of minnesota press. - \u2013 \u2013 \u2013, 1967, \u201c newtonian space - time, \u201d texas quarterly, 10 : 174 - 200. - wheeler, j. a. and ciufolini, i., 1995, gravitation and inertia, princeton, n. j. : princeton u. press. notable philosophical discussions of the absolute - relative debates - barbour, j. b., 1982, \u201c relational concepts of space and time, \u201d british journal for the philosophy of science, 33 : 251 - 274. - belot, g., 2000, \u201c geometry and motion, \u201d british journal for the philosophy of science, 51 : 561 - 595. - butterfield, j., 1984, \u201c relationism and possible worlds, \u201d british journal for the philosophy of science, 35 : 101 - 112. - callender, c., 2002, \u201c philosophy of space - time physics, \u201d in the blackwell guide to the philosophy of science, p. machamer ( ed. ), cambridge : blackwell. 173 - 198. - carrier, m., 1992, \u201c kant ' s relational theory of absolute space, \u201d kant studien, 83 : 399 - 416. - dieks, d., 2001, \u201c space - time relationism in newtonian and relativistic physics, \u201d international studies in the philosophy of science, 15 : 5 - 17. - disalle, r., 1995, \u201c spacetime theory as physical geometry, \u201d erkenntnis, 42 : 317 - 337. - earman, j., 1986, \u201c why space is not a substance ( at least not to first degree ), \u201d pacific philosophical quarterly, 67 : 225 - 244. - \u2013 \u2013 \u2013, 1970, \u201c who ' s afraid of absolute space?, \u201d australasian journal of philosophy, 48 : 287 - 319. - earman, j. and j. norton, 1987, \u201c what price spacetime substantivalism : the hole story, \u201d british journal for the philosophy of science, 38 : 515 - 525. - ho", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6466938916257496, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 51, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.113367"} {"text": "287 - 319. - earman, j. and j. norton, 1987, \u201c what price spacetime substantivalism : the hole story, \u201d british journal for the philosophy of science, 38 : 515 - 525. - hoefer, c., 2000, \u201c kant ' s hands and earman ' s pions : chirality arguments for substantival space, \u201d international studies in the philosophy of science, 14 : 237 - 256. - \u2013 \u2013 \u2013, 1998, \u201c absolute versus relational spacetime : for better or worse, the debate goes on, \u201d british journal for the philosophy of science, 49 : 451 - 467. - \u2013 \u2013 \u2013, 1996, \u201c the metaphysics of space - time substantialism, \u201d journal of philosophy, 93 : 5 - 27. - huggett, n., 2000, \u201c reflections on parity nonconservation, \u201d philosophy of science, 67 : 219 - 241. - le poidevin, r., 2004, \u201c space, supervenience and substantivalism, \u201d analysis, 64 : 191 - 198. - malament, d., 1985, \u201c discussion : a modest remark about reichenbach, rotation, and general relativity, \u201d philosophy of science, 52 : 615 - 620. - maudlin, t., 1993, \u201c buckets of water and waves of space : why space - time is probably a substance, \u201d philosophy of science, 60 : 183 - 203. - \u2013 \u2013 \u2013, 1990, \u201c substances and space - time : what aristotle would have said to einstein, \u201d studies in history and philosophy of science, 531 - 561. - mundy, b., 1992, \u201c space - time and isomorphism, \u201d proceedings of the biennial meetings of the philosophy of science association, 1 : 515 - 527. - \u2013 \u2013 \u2013, 1983, \u201c relational theories of euclidean space and minkowski space - time, \u201d philosophy of science, 50 : 205 - 226. - nerlich, g., 2003, \u201c space - time substantivalism, \u201d in the oxford handbook of metaphysics, m. j. loux ( ed. ), oxford : oxford univ pr. 281 - 314. - \u2013 \u2013 \u2013, 1996, \u201c what spacetime explains, \u201d philosophical quarterly, 46 : 127 - 131. - \u2013 \u2013 \u2013, 1994, what spacetime explains : metaphysical essays on space and time, new york : cambridge univ", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6454471911322122, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 52, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.114200"} {"text": "314. - \u2013 \u2013 \u2013, 1996, \u201c what spacetime explains, \u201d philosophical quarterly, 46 : 127 - 131. - \u2013 \u2013 \u2013, 1994, what spacetime explains : metaphysical essays on space and time, new york : cambridge univ pr. - \u2013 \u2013 \u2013, 1973, \u201c hands, knees, and absolute space, \u201d journal of philosophy, 70 : 337 - 351. - rynasiewicz, r., 2000, \u201c on the distinction between absolute and relative motion, \u201d philosophy of science, 67 : 70 - 93. - \u2013 \u2013 \u2013, 1996, \u201c absolute versus relational space - time : an outmoded debate?, \u201d journal of philosophy, 93 : 279 - 306. - teller, p., 1991, \u201c substance, relations, and arguments about the nature of space - time, \u201d philosophical review, 363 - 397. - torretti, r., 2000, \u201c spacetime models for the world, \u201d studies in history and philosophy of modern physics, 31b : 171 - 186. - st. andrews school of mathematics and statistics index of biographies - the pittsburgh phil - sci archive of pre - publication articles in philosophy of science - ned wright ' s special relativity tutorial - andrew hamilton ' s special relativity pages descartes, rene : physics | general relativity : early philosophical interpretations of | newton, isaac : views on space, time, and motion | space and time : inertial frames | space and time : the hole argument | zeno of elea : zeno ' s paradoxes", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6096642699258253, "token_count": 314, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 53, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.115167"} {"text": "by staff writers chicago il ( spx ) jan 11, 2013 technologically valuable ultrastable glasses can be produced in days or hours with properties corresponding to those that have been aged for thousands of years, computational and laboratory studies have confirmed. aging makes for higher quality glassy materials because they have slowly evolved toward a more stable molecular condition. this evolution can take thousands or millions of years, but manufacturers must work faster. armed with a better understanding of how glasses age and evolve, researchers at the universities of chicago and wisconsin - madison raise the possibility of designing a new class of materials at the molecular level via a vapor - deposition process. \" in attempts to work with aged glasses, for example, people have examined amber, \" said juan de pablo, uchicago ' s liew family professor in molecular theory and simulations. \" amber is a glass that has been aged millions of years, but you cannot engineer that material. you get what you get. \" de pablo and wisconsin co - authors sadanand singh and mark ediger report their findings in the latest issue of nature materials. ultrastable glasses could find potential applications in the production of stronger metals and in faster - acting pharmaceuticals. the latter may sound surprising, but drugs with the amorphous molecular structure of ultrastable glass could avoid crystallization during storage and be delivered more rapidly in the bloodstream than pharmaceuticals with a semi - crystalline structure. amorphous metals, likewise, are better for high - impact applications than crystalline metals because of their greater strength. the nature materials paper describes computer simulations that singh, a doctoral student in chemical engineering at uw - madison, carried out with de pablo to follow - up some intriguing results from ediger ' s laboratory. growing stable glasses several years ago, he discovered that glasses grown this way on a specially prepared surface that is kept within a certain temperature range exhibit far more stability than ordinary glasses. previous researchers must have grown this material under the same temperature conditions, but failed to recognize the significance of what they had done, ediger said. ediger speculated that growing glasses under these conditions, which he compares to the tetris video game, gives molecules extra room to arrange themselves into a more stable configuration. but he needed singh and de pablo ' s computer simulations to confirm his suspicions that he had actually produced a highly evolved, ordinary glass rather than an entirely new material. \" there ' s interest in making these materials on the computer because you have direct access to the structure, and you can therefore determine the relationship between the arrangement of the molecules", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6053736167486063, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.155985"} {"text": "had actually produced a highly evolved, ordinary glass rather than an entirely new material. \" there ' s interest in making these materials on the computer because you have direct access to the structure, and you can therefore determine the relationship between the arrangement of the molecules and the physical properties that you measure, \" said de pablo, a former uw - madison faculty member who joined uchicago ' s new institute for molecular engineering earlier this year. there are challenges, though, to simulating the evolution of glasses on a computer. scientists can cool a glassy material at the rate of one degree per second in the laboratory, but the slowest computational studies can only simulate cooling at a rate of 100 million degrees per second. \" we cannot cool it any slower because the calculations would take forever, \" de pablo said. \" it had been believed until now that there is no correlation between the mechanical properties of a glass and the molecular structure ; that somehow the properties of a glass are \" hidden \" somewhere and that there are no obvious structural signatures, \" de pablo said. creating better materials ultrastable glasses achieve their stability in a manner analogous to the most efficiently packed, multishaped objects in tetris, each consisting of four squares in various configurations that rain from the top of the screen. \" this is a little bit like the molecules in my deposition apparatus raining down onto this surface, and the goal is to perfectly pack a film, not to have any voids left, \" ediger said. the object of tetris is to manipulate the objects so that they pack into a perfectly tight pattern at the bottom of the screen. \" the difference is, when you play the game, you have to actively manipulate the pieces in order to build a well - packed solid, \" ediger said. \" in the vapor deposition, nature does it for us. \" but in tetris and experiments alike, when the objects or molecules descend too quickly, the result is a poorly packed, void - riddled pattern. \" in the experiment, if you either rain the molecules too fast or choose a low temperature at which there ' s no mobility at the surface, then this trick doesn ' t work, \" ediger said. then it would be like taking a bucket of odd - shaped pieces and just dumping them on the floor. there are all sorts of voids and gaps because the molecules didn ' t have any opportunity to find a good way of packing. \" \" ultrastable glasses from in silico vapor deposition, \" by sadamand", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6190680655273035, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 1, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.156955"} {"text": "in the star wars : where science meets imagination exhibit, luke skywalker ' s landspeeder is on display for the first time. click on image for full size courtesy of landspeeder image \u00a9 2006 lucasfilm ltd. & tm photo : dom miguel photography star wars exhibition brings reality to fantasy news story originally written on april 16, 2008 a new museum exhibit shows that some of the robots, vehicles and devices from the star wars films are close to the types of things scientists have developed to use in space. the exhibition - - at the science museum of minnesota in st. paul, minn., from june 13 until august 24 - - showcases landspeeders, r2d2 and other items from the star wars films. visitors will learn how researchers today are pursuing similar technologies. the exhibit developers were surprised and excited to learn that many of today ' s scientists were inspired by the fantasy technologies they saw in the star wars movies. one of the goals of the exhibit is to be an inspiration for the kids will be the next set of future scientists. the exhibit contains film clips, props, models and costumes. visitors are encouraged to participate in hands - on exhibits and activities. shop windows to the universe science store! our online store includes fun classroom activities for you and your students. issues of nesta ' s quarterly journal, the earth scientist are also full of classroom activities on different topics in earth and space science! you might also be interested in : scientists have learned that mount hood, oregon ' s tallest mountain, has erupted in the past due to the mixing of two different types of magma. \" the data will help give us a better road map to what a future... more the earth ' s mantle is a rocky, solid shell that is between the earth ' s crust and the outer core, and makes up about 84 percent of the earth ' s volume. the mantle is made up of many distinct portions or... more some geologic faults that appear strong and stable, slip and slide like weak faults, causing earthquakes. scientists have been looking at one of these faults in a new way to figure out why. in theory,... more the sun goes through cycles that last approximately 11 years. these solar cycle include phases with more magnetic activity, sunspots, and solar flares. they also include phases with less activity. the... more studying tree rings doesn ' t only tell us the age of that tree. tree rings also show what climate was like for each year of a tree ' s life,", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6042653232751081, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.429180"} {"text": "learn something new every day more info... by email a block diagram is a graphical method used to explain the concept of a system without the need to understand the individual components within that system. this type of diagram might be used in a variety of industries to illustrate and educate individuals about how a system operates, either in part or in its entirety. block diagrams usually will have a logical, methodical flow from beginning to end. engineers and software programmers are examples of individuals who might be familiar with block diagrams. block diagrams essentially are synonymous with flow charts, but a block diagram is generalized in nature. sometimes block diagrams are used to conceal specific information or processes that might prove to be advantageous or detrimental, whichever the case might be. people who are being presented with a block diagram should be able to develop an understanding of what that block represents. to assist in understanding the block itself, lines should be drawn to the block representing various inputs, outputs or alternative choices. depending on the type of process being illustrated, blocks might serve in any capacity that is needed to adequately describe the process or parts of the process. for instance, a manufacturing cell of machine tools might include a drill press, a milling machine and a sanding machine. to illustrate a process within that cell, each machine tool might be represented by its own block. when the manufacturing process is illustrated in its entirety, a single block might be used to represent all of the components within that cell. a block diagram also can be used to illustrate how a computer program works or how parts of a program work. if, for instance, a program is needed to calculate four different methods of interest rates, a block might represent each of these lines of code for one of these methods. in this way, a supervisor does not need to understand the code itself, as it is written, as long as the purpose of that block is communicated effectively. some block diagrams can be used as a way to map out a process as a top - down diagram. for instance, a person who has an inspired project might use a block diagram as a way to convey the idea as a series of individual blocks, each of which helps support the main topic. later, these individual blocks might then be analyzed and further developed into additional block diagrams as needed. this method can be repeated until the process is mapped out to the satisfaction of all those involved with the project. if compiled and mapped out completely, the block diagram might resemble a pine tree type of structure of the entire project, which is typical for a top - down diagram.", "subdomain_id": "subdomain_quantum_computing", "similarity_score": 0.6135658768906974, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.467918"} {"text": "p ] ( x ) to be the result of running p with input x. now we define p ( x ) to be the program p modified so that it no longer takes an argument or input but instead substitutes the ' hard - coded ' value of x instead. in other words [ p ( x ) ] = [ p ] ( x ). p ( x ) is, of course, another program. there are also many ways of implementing p ( x ). we could simply evaluate [ p ] ( x ) and write a program to simply print this out or return it. on the other hand, we could do the absolute minimum and write a new piece of code that simply calls p and supplies it with a hard - coded argument. whatever we choose is irrelevant to the following discussion. so here ' s the demand that we make of our programming language : that it ' s powerful enough for us to write a program that can compute p ( x ) from inputs p and x. this might not be a trivial program to write, but it ' s not conceptually hard either. it doesn ' t have gotchas like the quotation mark issue above. typically we can compute p ( x ) by some kind of textual substitution on p. with that assumption in mind, here ' s a theorem : any program p that takes one argument or input has a fixed point, x, in the sense that running p with input x gives the same result as just running x. given an input x, p acts just like an interpreter for the programming language as it outputs the same thing as an interpreter would given input x. so here ' s a proof : define the function f ( q ) = [ p ] ( q ( q ) ). we ' ve assumed that we can write a program that computes p ( x ) from p and x so we know we can write a program to compute q ( q ) for any q. we can then feed this as an input to [ p ]. so f is obviously computable by some program which we call q0. so [ q0 ] ( q ) = [ p ] ( q ( q ) ). now the fun starts : [ p ] ( q0 ( q0 ) ) = [ q0 ] ( q0 ) ( by definition of q0 ) = [ q0 ( q0 ) ] ( by definition of p ( x ) ) in other words q0 ( q0 ) is our fixed point. so now take p to compute the identity function.", "subdomain_id": "subdomain_quantum_computing", "similarity_score": 0.630228536453438, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 1, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.725466"} {"text": ") ( by definition of q0 ) = [ q0 ( q0 ) ] ( by definition of p ( x ) ) in other words q0 ( q0 ) is our fixed point. so now take p to compute the identity function. then [ q0 ( q0 ) ] = [ p ] ( q0 ( q0 ) ) = q0 ( q0 ). so q0 ( q0 ) outputs itself when run! what ' s more, this also tells us how to do other fun stuff like write a program to print itself out backwards. and it tells us how to do this in any reasonably powerful programming language. we don ' t need to worry about having to work around problems like ' escaping ' quotation marks - we can always find a way to replicate the escape mechanism too. so does it work in practice? well it does for haskell - i derived the haskell fragment above by applying this theorem directly, and then simplifying a bit. for c + +, however, it might give you a piece of code that is longer than you want. in fact, you can go one step further and write a program that automatically generates a self - replicator. check out samuel moelius ' s kpp. it is a preprocessor that converts an ordinary c + + program into one that can access its own source code by including the code to generate its own source within it. another example of an application of these methods is futamura ' s theorem which states that there exists a program that can take as input an interpreter for a language and output a compiler. i personally think this is a little bogus.", "subdomain_id": "subdomain_quantum_cryptography", "similarity_score": 0.6320003078242767, "token_count": 337, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 2, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.726202"} {"text": "principles of design balance in design is similar to balance in physics. a large shape close to the center can be balanced by a small shape close to the edge. a large light toned shape will be balanced by a small dark toned shape ( the darker the shape the heavier it appears to be ) graduation of size and direction produce linear perspective. graduation of colour from warm to cool and tone from dark to light produce aerial perspective. graduation can add interest and movement to a shape. a graduation from dark to light will cause the eye to move along a shape. repetition with variation is interesting, without variation repetition can become monotonous. if you wish to create interest, any repeating element should include a degree of variation. contrast is the juxtaposition of opposing elements eg. opposite colours on the colour wheel \u2013 red / green, blue / orange etc. contrast in tone or value \u2013 light / dark. contrast in direction \u2013 horizontal / vertical. the major contrast in a painting should be located at the center of interest. too much contrast scattered throughout a painting can destroy unity and make a work difficult to look at. unless a feeling of chaos and confusion are what you are seeking, it is a good idea to carefully consider where to place your areas of maximum contrast. harmony in painting is the visually satisfying effect of combining similar, related elements. eg. adjacent colurs on the colour wheel, similar shapes etc. dominance gives a painting interest, counteracting confusion and monotony. dominance can be applied to one or more of the elements to give emphasis. relating the design elements to the idea being expressed in a painting reinforces the principal of unity. eg. a painting with an active aggressive subject would work better with a dominant oblique direction, course, rough texture, angular lines etc. whereas a quiet passive subject would benefit from horizontal lines, soft texture and less tonal contrast. unity in a painting also refers to the visual linking of various elements of the work.", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.608988247405515, "token_count": 396, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.728275"} {"text": "what is fluorescence? fluorescence is the ability of certain chemicals to give off visible light after absorbing radiation which is not normally visible, such as ultraviolet light. this property has led to a variety of uses. let \u2019 s shed some further light on this topic ; consider the omnipresent \u201c fluorescent \u201d lights. just how do they work? fluorescent tubes contain a small amount of mercury vapor. the application of an electric current causes a stream of electrons to traverse the tube. these collide with the mercury atoms which become energized and consequently emit ultraviolet light. the inside of the tube is coated with a fluorescent material, such as calcium chlorophosphate, which converts the invisible ultraviolet light into visible light. the same idea is used to produce color television pictures. the screen is coated with tiny dots of substances which fluoresce in different colours when they are excited by a beam of electrons which is used to scan the picture. but fluorescent materials had practical uses even before we dreamed of color television. one of the most amazing of all fluorescent materials is a synthetic compound, appropriately called fluorescein. under ultraviolet light it produces an intense yellow - green fluorescence which during world war ii was responsible for saving the lives of many downed flyers. over a million pounds of the stuff were manufactured in 1943 and distributed to airmen in little packets to use as a sea marker. since the fluorescence is so potent that it can be seen when the concentration of fluorescein is as little as 25 parts per billion, rescue planes easily spotted the men in the ocean. aircraft carriers also made extensive use of fluorescein. the signal men on deck wore clothes and waved flags treated with the compound which was then made to glow by illumination with ultraviolet light. the incoming pilots could clearly see the deck and the need to use runway lights which would have drawn the attention of enemy aircraft was eliminated. certain natural substances also fluoresce under ultraviolet light. urine and moose fur are interesting examples. prisoners have actually made use of this property of urine and have used it as a secret ink. what about the moose fur? well, in canada and sweden there are hundreds of accidents each year involving the collision of automobiles with moose. some of these result in fatalities. some car manufacturers are now considering fitting their vehicles with uv emitting headlights to reduce moose collisions! how \u2019 s that for putting the right chemistry to work.", "subdomain_id": "subdomain_quantum_optics", "similarity_score": 0.6446777803728252, "token_count": 486, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.730836"} {"text": "one of my favorite science fiction ideas is in a short story called light of other days about something called \u201c slow glass. \u201d light took decades to pass through. in this story, the idea was that people could buy glass windows that took so long for the light to pass through, that they could nostalgically watch long gone scenes, such as their children playing outside as toddlers long after they had gone off to college, or green fields with horses where now ugly cities grew. it was about the speed of light. here is a concept that is similar. instead of slow windows, it is slow walls. ravenbrick has made a nanotech wall that can slow down the day \u2019 s heat coming into a building. using phase - changing material at the molecular level, you get to transfer the warmth of the sun \u2019 s heat from the afternoon well into the night. ravenbrick makes several clean tech materials for building that greatly reduce energy needs, most notably windows that turn off the sun, like sage electrochromics windows do. the one that is new to me is this \u201c slow wall \u201d. they claim that their glass - clad smart wall : ravenskin could literally reduce your heating bill to zero! ( coupled with good building design, of course, you can \u2019 t expect a zero bill if you put leaky windows in their wall! ) their wall can delay solar heat gain from hot afternoons, to later that night, when you need it more. this helps regulate the internal temperatures of buildings. it has excellent r - values to begin with ( r - 11 or more ) so it insulates like a normal wall limiting the conduction and convection of heat. the magic \u2013 or science fiction \u2013 part is achieved by converting incoming sunlight to infrared, and then directing the flow of energy inward only when you want it to come through the walls. the problem with super well - insulated buildings is that sometimes you do want the suns heat getting in, and regular insulated walls are dumb walls that don \u2019 t know when to send the heat in and when to shut it out. the smart wall knows because you can tell it. susan kraemer writes at cleantechnica, csp - today, pv - insider, smartgridupdate and greenprophet and has been published at ecoseed, nrdc onearth, matternetwork, celsius, energynow and scientific american. as a former serial entrepreneur in product design she brings an innovator ' s perspective on inventing a carbon - constrained civilization :", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6198525126203026, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:01.768494"} {"text": "textbooks. discussions of textbooks have been included on creation and evolution in the public education debate. the smith v. board of school commissioners of mobile county case brought forward a debate about scientific fact being presented in textbooks. in his book, surely you ' re joking, mr. feynman!, the late physics nobel prize laureate richard p. feynman described his experiences as a member of a committee that evaluated science textbooks. at some instances, there were nonsensical examples to illustrate physical phenomena ; then a company sent \u2014 for reasons of timing \u2014 a textbook that contained blank pages, which even got good critiques. feynman himself experienced attempts at bribery. largely in the us, but increasingly in other nations, k - 12 mathematics textbooks have reflected the controversies of new math and reform mathematics which have sought to replace traditional mathematics in what have been called the math wars. traditional texts, still favored in asia and other areas, merely taught the same time - tested mathematics that most adults have learned. by contrast \" progressive \" approaches seek to address problems in social inequity with approaches that often incorporate principles of constructivism and discovery. texts such as terc and cmp discourage or omit standard mathematics methods and concepts such as long division and lowest common denominators. for example an index entry to multiply fractions would lead to \" devise your own method to multiply fractions which work on these examples \", and the formula for the area of a circle would be an exercise for a student to derive rather than including it in the student text. by the 2000s, while some districts were still adopting the more novel methods, others had abandoned them as unworkable. higher education in the u. s., college and university textbooks are chosen by the professor teaching the course, or by the department as a whole. students are typically responsible for obtaining their own copies of the books used in their courses, although alternatives to owning textbooks, such as textbook rental services and library reserve copies of texts, are available in some instances. in some european countries, such as sweden or spain, students attending institutions of higher education pay for textbooks themselves, although higher education is free of charge otherwise. with higher education costs on the rise, many students are becoming sensitive to every aspect of college pricing, including textbooks, and in many cases amount to one tenth of tuition costs. the 2005 government accountability office report on college textbooks said that since the 1980s, textbook and supply prices have risen twice the rate of inflation in the past two decades. a 2005 pi", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.601351817838259, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 12, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:02.010975"} {"text": "phosphorescence is a specific type of photoluminescence related to fluorescence. unlike fluorescence, a phosphorescent material does not immediately re - emit the radiation it absorbs. the slower time scales of the re - emission are associated with \" forbidden \" energy state transitions in quantum mechanics. as these transitions occur very slowly in certain materials, absorbed radiation may be re - emitted at a lower intensity for up to several hours after the original excitation. commonly seen examples of phosphorescent materials are the glow - in - the - dark toys, paint, and clock dials that glow for some time after being charged with a bright light such as in any normal reading or room light. typically the glowing then slowly fades out within minutes ( or up to a few hours ) in a dark room. the study of phosphorescent materials led to the discovery of radioactivity in 1896. in simple terms, phosphorescence is a process in which energy absorbed by a substance is released relatively slowly in the form of light. this is in some cases the mechanism used for \" glow - in - the - dark \" materials which are \" charged \" by exposure to light. unlike the relatively swift reactions in a common fluorescent tube, phosphorescent materials used for these materials absorb the energy and \" store \" it for a longer time as the processes required to re - emit the light occur less often. quantum mechanical most photoluminescent events, in which a chemical substrate absorbs and then re - emits a photon of light, are fast, on the order of 10 nanoseconds. light is absorbed and emitted at these fast time scales in cases where the energy of the photons involved matches the available energy states and allowed transitions of the substrate. in the special case of phosphorescence, the absorbed photon energy undergoes an unusual intersystem crossing into an energy state of higher spin multiplicity ( see term symbol ), usually a triplet state. as a result, the energy can become trapped in the triplet state with only classically \" forbidden \" transitions available to return to the lower energy state. these transitions, although \" forbidden \", will still occur in quantum mechanics but are kinetically unfavored and thus progress at significantly slower time scales. most phosphorescent compounds are still relatively fast emitters, with triplet lifetimes on the order of milliseconds. however, some compounds have triplet lifetimes up to minutes or even", "subdomain_id": "subdomain_quantum_optics", "similarity_score": 0.6805941039802765, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:02.117018"} {"text": "thus progress at significantly slower time scales. most phosphorescent compounds are still relatively fast emitters, with triplet lifetimes on the order of milliseconds. however, some compounds have triplet lifetimes up to minutes or even hours, allowing these substances to effectively store light energy in the form of very slowly degrading excited electron states. if the phosphorescent quantum yield is high, these substances will release significant amounts of light over long time scales, creating so - called \" glow - in - the - dark \" materials. where s is a singlet and t a triplet whose subscripts denote states ( 0 is the ground state, and 1 the excited state ). transitions can also occur to higher energy levels, but the first excited state is denoted for simplicity. some examples of \" glow - in - the - dark \" materials do not glow by phosphorescence. for example, \" glow sticks \" glow due to a chemiluminescent process which is commonly mistaken for phosphorescence. in chemiluminescence, an excited state is created via a chemical reaction. the light emission tracks the kinetic progress of the underlying chemical reaction. the excited state will then transfer to a \" dye \" molecule, also known as a sensitizer or fluorophor, and subsequently fluoresce back to the ground state common pigments used in phosphorescent materials include zinc sulfide and strontium aluminate. use of zinc sulfide for safety related products dates back to the 1930s. however, the development of strontium aluminate, with a luminance approximately 10 times greater than zinc sulfide, has relegated most zinc sulfide based products to the novelty category. strontium aluminate based pigments are now used in exit signs, pathway marking, and other safety related signage. | this section requires expansion. ( october 2008 ) | see also - karl a. franz, wolfgang g. kehr, alfred siggel, jurgen wieczoreck, and waldemar adam \" luminescent materials \" in ullmann ' s encyclopedia of industrial chemistry 2002, wiley - vch, weinheim. doi : 10. 1002 / 14356007. a15 _ 519 - zitoun, d. ; bernaud, l. ; manteghetti, a. microwave synthesis of a long - lasting phosphor. j. chem. ed. 2009, 86, 72 -", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6256019458107305, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 1, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:02.118206"} {"text": "| quantum field theory | | | it has been suggested that this article be merged with zero - point energy. ( discuss ) proposed since june 2012. | in quantum field theory, the vacuum state ( also called the vacuum ) is the quantum state with the lowest possible energy. generally, it contains no physical particles. zero - point field is sometimes used [ by whom? ] as a synonym for the vacuum state of an individual quantized field. according to present - day understanding of what is called the vacuum state or the quantum vacuum, it is \" by no means a simple empty space \", and again : \" it is a mistake to think of any physical vacuum as some absolutely empty void. \" according to quantum mechanics, the vacuum state is not truly empty but instead contains fleeting electromagnetic waves and particles that pop into and out of existence. the qed vacuum of quantum electrodynamics ( or qed ) was the first vacuum of quantum field theory to be developed. qed originated in the 1930s, and in the late 1940s and early 1950s it was reformulated by feynman, tomonaga and schwinger, who jointly received the nobel prize for this work in 1965. today the electromagnetic interactions and the weak interactions are unified in the theory of the electroweak interaction. the standard model is a generalization of the qed work to include all the known elementary particles and their interactions ( except gravity ). quantum chromodynamics is the portion of the standard model that deals with strong interactions, and qcd vacuum is the vacuum of quantum chromodynamics. it is the object of study in the large hadron collider and the relativistic heavy ion collider, and is related to the so - called vacuum structure of strong interactions. non - zero expectation value if the quantum field theory can be accurately described through perturbation theory, then the properties of the vacuum are analogous to the properties of the ground state of a quantum mechanical harmonic oscillator ( or more accurately, the ground state of a qm problem ). in this case the vacuum expectation value ( vev ) of any field operator vanishes. for quantum field theories in which perturbation theory breaks down at low energies ( for example, quantum chromodynamics or the bcs theory of superconductivity ) field operators may have non - vanishing vacuum expectation values called condensates. in the standard model, the non - zero vacuum expectation value of the higgs field, arising from spontaneous symmetry", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.7290323946032521, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:02.186493"} {"text": "a field \u03c6, which should be written as, is usually condensed to. virtual particles the presence of virtual particles can be rigorously based upon the non - commutation of the quantized electromagnetic fields. non - commutation means that although the average values of the fields vanish in a quantum vacuum, their variances do not. the term \" vacuum fluctuations \" refers to the variance of the field strength in the minimal energy state, and is described picturesquely as evidence of \" virtual particles \". it is sometimes attempted to provide an intuitive picture of virtual particles based upon the heisenberg energy - time uncertainty principle : ( with \u03b4e and \u03b4t being the energy and time variations respectively ; \u03b4e is the accuracy in the measurement of energy and \u03b4t is the time taken in the measurement, and \u0127 is the planck constant divided by 2\u03c0 ) arguing along the lines that the short lifetime of virtual particles allows the \" borrowing \" of large energies from the vacuum and thus permits particle generation for short times. although the phenomenon of virtual particles is accepted, this interpretation of the energy - time uncertainty relation is not universal. one issue is the use of an uncertainty relation limiting measurement accuracy as though a time uncertainty \u03b4t determines a \" budget \" for borrowing energy \u03b4e. another issue is the meaning of \" time \" in this relation, because energy and time ( unlike position q and momentum p, for example ) do not satisfy a canonical commutation relation ( such as [ q, p ] = i \u0127 ). various schemes have been advanced to construct an observable that has some kind of time interpretation, and yet does satisfy a canonical commutation relation with energy. the very many approaches to the energy - time uncertainty principle are a long and continuing subject. physical nature of the quantum vacuum according to astrid lambrecht ( 2002 ) : \" when one empties out a space of all matter and lowers the temperature to absolute zero, one produces in a gedankenexperiment the quantum vacuum state. \" photon - photon interaction can occur only through interaction with the vacuum state of some other field, for example through the dirac electron - positron vacuum field ; this is associated with the concept of vacuum polarization. according to milonni ( 1994 ) : \"... all quantum fields have zero - point energies and vacuum fluctuations. \" this means that there is a component of the quantum vacuum respectively for each component field ( considered in the conceptual absence of the other fields ), such as the electromagnetic field, the dirac electron", "subdomain_id": "subdomain_quantum_thermodynamics", "similarity_score": 0.7088683234462585, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 2, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:02.188738"} {"text": "quantum fields have zero - point energies and vacuum fluctuations. \" this means that there is a component of the quantum vacuum respectively for each component field ( considered in the conceptual absence of the other fields ), such as the electromagnetic field, the dirac electron - positron field, and so on. according to milonni ( 1994 ), some of the effects attributed to the vacuum electromagnetic field can have several physical interpretations, some more conventional than others. the casimir attraction between uncharged conductive plates is often proposed as an example of an effect of the vacuum electromagnetic field. schwinger, deraad, and milton ( 1978 ) are cited by milonni ( 1994 ) as validly, though unconventionally, explaining the casimir effect with a model in which \" the vacuum is regarded as truly a state with all physical properties equal to zero. \" in this model, the observed phenomena are explained as the effects of the electron motions on the electromagnetic field, called the source field effect. milonni writes : \" the basic idea here will be that the casimir force may be derived from the source fields alone even in completely conventional qed,... \" milonni provides detailed argument that the measurable physical effects usually attributed to the vacuum electromagnetic field cannot be explained by that field alone, but require in addition a contribution from the self - energy of the electrons, or their radiation reaction. he writes : \" the radiation reaction and the vacuum fields are two aspects of the same thing when it comes to physical interpretations of various qed processes including the lamb shift, van der waals forces, and casimir effects. \" this point of view is also stated by jaffe ( 2005 ) : \" the casimir force can be calculated without reference to vacuum fluctuations, and like all other observable effects in qed, it vanishes as the fine structure constant, \u03b1, goes to zero. \" see also references and notes - astrid lambrecht ( hartmut figger, dieter meschede, claus zimmermann eds. ) ( 2002 ). observing mechanical dissipation in the quantum vacuum : an experimental challenge ; in laser physics at the limits. berlin / new york : springer. p. 197. isbn 3 - 540 - 42418 - 0. - christopher ray ( 1991 ). time, space and philosophy. london / new york : routledge. chapter 10, p. 205. isbn 0 - 415 - 03221 - 0. - aip physics news update, 1996 - physical review focus dec. 1998 - walter dittrich & gi", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.675242959454109, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 3, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:02.189715"} {"text": "and philosophy. london / new york : routledge. chapter 10, p. 205. isbn 0 - 415 - 03221 - 0. - aip physics news update, 1996 - physical review focus dec. 1998 - walter dittrich & gies h ( 2000 ). probing the quantum vacuum : perturbative effective action approach. berlin : springer. isbn 3 - 540 - 67428 - 4. - for an historical discussion, see for example ari ben - menahem, ed. ( 2009 ). \" quantum electrodynamics ( qed ) \". historical encyclopedia of natural and mathematical sciences, volume 1 ( 5th ed. ). springer. pp. 4892 ff. isbn 3 - 540 - 68831 - 5. for the nobel prize details and the nobel lectures by these authors see \" the nobel prize in physics 1965 \". nobelprize. org. retrieved 2012 - 02 - 06. - jean letessier, johann rafelski ( 2002 ). hadrons and quark - gluon plasma. cambridge university press. p. 37 ff. isbn 0 - 521 - 38536 - 9. - sean carroll, sr research associate - physics, california institute of technology, june 22, 2006 c - span broadcast of cosmology at yearly kos science panel, part 1 - david delphenich ( 2006 ). \" nonlinear electrodynamics and qed \". arxiv : hep - th / 0610088 [ hep - th ]. - klein, james j. and b. p. nigam, birefringence of the vacuum, physical review vol. 135, p. b1279 - b1280 ( 1964 ). - mourou, g. a., t. tajima, and s. v. bulanov, optics in the relativistic regime ; \u00a7 xi nonlinear qed, reviews of modern physics vol. 78 ( no. 2 ), 309 - 371 ( 2006 ) pdf file. - holger gies ; joerg jaeckel ; andreas ringwald ( 2006 ). \" polarized light propagating in a magnetic field as a probe of millicharged fermions \". physical review letters 97 ( 14 ). arxiv : hep - ph / 0607118. bibcode : 2006phrvl.. 97n0402g. doi : 10. 1103 / physrevlett.", "subdomain_id": "subdomain_quantum_optics", "similarity_score": 0.7105397537603355, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 4, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:02.190479"} {"text": "( 14 ). arxiv : hep - ph / 0607118. bibcode : 2006phrvl.. 97n0402g. doi : 10. 1103 / physrevlett. 97. 140402. - davis ; joseph harris ; gammon ; smolyaninov ; kyuman cho ( 2007 ). \" experimental challenges involved in searches for axion - like particles and nonlinear quantum electrodynamic effects by sensitive optical techniques \". arxiv : 0704. 0748 [ hep - th ]. - myron wyn evans, stanis\u0142aw kielich ( 1994 ). modern nonlinear optics, volume 85, part 3. john wiley & sons. p. 462. isbn 0 - 471 - 57548 - 8. \" for all field states that have classical analog the field quadrature variances are also greater than or equal to this commutator. \" - david nikolaevich klyshko ( 1988 ). photons and nonlinear optics. taylor & francis. p. 126. isbn 2 - 88124 - 669 - 9. - milton k. munitz ( 1990 ). cosmic understanding : philosophy and science of the universe. princeton university press. p. 132. isbn 0 - 691 - 02059 - 0. \" the spontaneous, temporary emergence of particles from vacuum is called a \" vacuum fluctuation \". \" - for an example, see p. c. w. davies ( 1982 ). the accidental universe. cambridge university press. p. 106. isbn 0 - 521 - 28692 - 1. - a vaguer description is provided by jonathan allday ( 2002 ). quarks, leptons and the big bang ( 2nd ed ed. ). crc press. pp. 224 ff. isbn 0 - 7503 - 0806 - 0. \" the interaction will last for a certain duration \u03b4t. this implies that the amplitude for the total energy involved in the interaction is spread over a range of energies \u03b4e. \" - this \" borrowing \" idea has led to proposals for using the zero - point energy of vacuum as an infinite reservoir and a variety of \" camps \" about this interpretation. see, for example, moray b. king ( 2001 ). quest for zero point energy : engineering principles for ' free energy ' inventions. adventures unlimited press. pp. 124 ff. isbn 0 - 932813 - 94 - 1. - quantities satisfying a", "subdomain_id": "subdomain_quantum_optics", "similarity_score": 0.7440256790172282, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 5, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:02.191342"} {"text": "example, moray b. king ( 2001 ). quest for zero point energy : engineering principles for ' free energy ' inventions. adventures unlimited press. pp. 124 ff. isbn 0 - 932813 - 94 - 1. - quantities satisfying a canonical commutation rule are said to be noncompatible observables, by which is meant that they can both be measured simultaneously only with limited precision. see kiyosi ito ( 1993 ). \" \u00a7 351 ( xx. 23 ) c : canonical commutation relations \". encyclopedic dictionary of mathematics ( 2nd ed ed. ). mit press. p. 1303. isbn 0 - 262 - 59020 - 4. - paul busch, marian grabowski, pekka j. lahti ( 1995 ). \" \u00a7 iii. 4 : energy and time \". operational quantum physics. springer. pp. 77 ff. isbn 3 - 540 - 59358 - 6. - for a review, see paul busch ( 2008 ). \" chapter 3 : the time \u2013 energy uncertainty relation \". in j. g. muga, r. sala mayato and i. l. egusquiza, editors. time in quantum mechanics ( 2nd ed ed. ). springer. pp. 73 ff. isbn 3 - 540 - 73472 - 4. - fowler, r., guggenheim, e. a. ( 1965 ). statistical thermodynamics. a version of statistical mechanics for students of physics and chemistry, reprinted with corrections, cambridge university press, london, page 224. - partington, j. r. ( 1949 ). an advanced treatise on physical chemistry, volume 1, fundamental principles. the properties of gases, longmans, green and co., london, page 220. - wilks, j. ( 1971 ). the third law of thermodynamics, chapter 6 in thermodynamics, volume 1, ed. w. jost, of h. eyring, d. henderson, w. jost, physical chemistry. an advanced treatise, academic press, new york, page 477. - bailyn, m. ( 1994 ). a survey of thermodynamics, american institute of physics, new york, isbn 0 \u2013 88318 \u2013 797 \u2013 3, page 342. - jauch, j. m., rohrlich, f. ( 1955 / 1980 ). the theory of photons and electrons. the relat", "subdomain_id": "subdomain_quantum_thermodynamics", "similarity_score": 0.7292263381752636, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 6, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:02.192395"} {"text": "york, isbn 0 \u2013 88318 \u2013 797 \u2013 3, page 342. - jauch, j. m., rohrlich, f. ( 1955 / 1980 ). the theory of photons and electrons. the relativistic quantum field theory of charged particles with spin one - half, second expanded edition, springer - verlag, new york, isbn 0 \u2013 387 \u2013 07295 \u2013 0, pages 287 \u2013 288. - milonni, p. w. ( 1994 ). the quantum vacuum. an introduction to quantum electrodynamics, academic press, inc., boston, isbn 0 \u2013 12 \u2013 498080 \u2013 5, page xv. - milonni, p. w. ( 1994 ). the quantum vacuum. an introduction to quantum electrodynamics, academic press, inc., boston, isbn 0 \u2013 12 \u2013 498080 \u2013 5, page 239. - schwinger, j., deraad, l. l., milton, k. a. ( 1978 ). casimir effect in dielectrics, annals of physics, 115 : 1 \u2013 23. - milonni, p. w. ( 1994 ). the quantum vacuum. an introduction to quantum electrodynamics, academic press, inc., boston, isbn 0 \u2013 12 \u2013 498080 \u2013 5, page 418. - jaffe, r. l. ( 2005 ). casimir effect and the quantum vacuum, phys. rev. d 72 : 021301 ( r ), http : / / 1 \u2013 5. cua. mit. edu / 8. 422 _ s07 / jaffe2005 _ casimir. pdf further reading - free pdf copy of the structured vacuum - thinking about nothing by johann rafelski and berndt muller ( 1985 ) isbn 3 - 87144 - 889 - 3. - m. e. peskin and d. v. schroeder, an introduction to quantum field theory. - h. genz, nothingness : the science of empty space - maybe this should discuss star trek and / or star gate : engineering the zero - point field and polarizable vacuum for interstellar flight - e. w. davis, v. l. teofilo, b. haisch, h. e. puthoff, l. j. nickisch, a. rueda and d. c. cole ( 2006 ) \" review of experimental concepts for studying the quantum vacuum field \"", "subdomain_id": "subdomain_quantum_optics", "similarity_score": 0.6822181922870342, "token_count": 509, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 7, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:02.193180"} {"text": "by the temperature factors. high values, indicating lots of motion, are in red and yellow, and low values are in blue. notice that the interior of the protein has low b - values and the amino acids on the surface have higher values. you can click on the picture for an interactive jmol view. tip : temperature factors are a measure of our confidence in the location of each atom. if you find an atom on the surface of a protein with a high temperature factor, keep in mind that this atom is probably moving a lot, and that the coordinates specified in the pdb file are only one possible snapshot of its location. occupancy and multiple conformations macromolecular crystals are composed of many individual molecules packed into a symmetrical arrangement. in some crystals, there are slight differences between each of these molecules. for instance, a sidechain on the surface may wag back and forth between several conformations, or a substrate may bind in two orientations in an active site, or a metal ion may be bound to only a few of the molecules. when researchers build the atomic model of these portions, they can use the occupancy to estimate the amount of each conformation that is observed in the crystal. for most atoms, the occupancy is given a value of 1, indicating that the atom is found in all of the molecules in the same place in the crystal. however, if a metal ion binds to only half of the molecules in the crystal, the researcher will see a weak image of the ion in the electron density map, and can assign an occupancy of 0. 5 in the pdb structure file for this atom. occupancies are also commonly used to identify sidechains or ligands that are observed in multiple conformations. the occupancy value is used to indicate the fraction of molecules that have each of the conformations. two ( or more ) atom records are included for each atom, with occupancies like 0. 5 and 0. 5, or 0. 4 and 0. 6, or other fractional occupancies that sum to a total of 1. the two images shown are taken from the high - resolution structure of myoglobin in entry 1a6m : glutamine 8 is on the left, and tyrosine 151 on the right. in both cases, the depositors interpreted the experimental data as showing two conformations of the amino acid, with occupancies of", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6175302138992194, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 3, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:02.669440"} {"text": "it ' s entertaining, the same way you or i would enjoy a video game in a completely sandboxed environment. they, however, are doing things in the real world. same layer of digital separation between you and the consequences of your actions, with the added thrill of knowing it ' s real. - does computer insecurity exist because of the nature of computers? to a point, yes. computers are powerful, but they are extremely dumb. they require humans to do their thinking for them, to design them in a way that is difficult to subvert, to program them in a way that is difficult to subvert, and to use them in a way that is difficult to subvert. the inherent difficulty of this is similar to the inherent difficulty ( maybe the impossibility ) of designing a \" completely foolproof system \" : a common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools. - douglas adams in both cases, you ' re very simply trying to pre - emptively outsmart someone willing to spend a lot of time and effort finding a way to misuse what you ' re designing once the finished product has left your hands. you effectively have to come up with the same ideas that the other person would have, and incorporate mechanisms to defeat that line of thinking. the more complex the system is internally, the more of those ideas become possible, and the less likely you are to have thought of everything. the more you put in place to prevent misuse, the more complexity you add. it ' s a vicious cycle.", "subdomain_id": "subdomain_quantum_cryptography", "similarity_score": 0.6002074051061214, "token_count": 326, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 1, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:02.809371"} {"text": "mit professor \u2019 s book digs into the eclectic, textually linked reading choices of people in medieval london. cambridge, mass. - - following the 1997 creation of the first laser to emit pulsed beams of atoms, mit researchers report in the may 16 online version of science that they have now made a continuous source of coherent atoms. this work paves the way for a laser that emits a continuous stream of atoms. mit physicists led by physics professor wolfgang ketterle ( who shared the 2001 nobel prize in physics ) created the first atom laser. a long - sought goal in physics, the atom laser emitted atoms, similar in concept to the way an optical laser emits light. \" i am amazed at the rapid progress in the field, \" ketterle said. \" a continuous source of bose - einstein condensate is just one of many recent advances. \" because the atom laser operates in an ultra - high vacuum, it may never be as ubiquitous as optical lasers. but, like its predecessor, the pulsed atom laser, a continuous - stream atom laser may someday be used for a variety of applications in fundamental physics. it could be used to directly deposit atoms onto computer chips, and improve the precision and accuracy of atomic clocks and gyroscopes. it could aid in precision measurements of fundamental constants, atom optics and interferometry. a continuous stream laser could do all of these things better than a pulsed atomic laser, said co - author ananth p. chikkatur, a physics graduate student at mit. \" similar to the optical laser revolution, a continuous stream atom laser might be useful for more things than a pulsed laser, \" he said. in addition to ketterle and chikkatur, authors include mit graduate students yong - il shin and aaron e. leanhardt ; david f. kielpinski, postdoctoral fellow in the mit research laboratory of electronics ( rle ) ; physics senior edem tsikata ; mit affiliate todd l. gustavson ; and david e. pritchard, cecil and ida green professor of physics and a member of the mit - harvard center for ultracold atoms and the rle. a new form of matter an important step toward the first atom laser was the creation of a new form of matter - the bose - einstein condensate ( bec ). bec forms at temperatures around one millionth of a degree kelvin, a million times colder than interstellar space. ketterle ' s group had developed novel cooling techniques that were key to", "subdomain_id": "subdomain_quantum_metrology", "similarity_score": 0.6408125626313932, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:03.087622"} {"text": "the bose - einstein condensate ( bec ). bec forms at temperatures around one millionth of a degree kelvin, a million times colder than interstellar space. ketterle ' s group had developed novel cooling techniques that were key to the observation of bec in 1995, first by a group at the university of colorado at boulder, then a few months later by ketterle at mit. it was for this achievement that researchers from both institutions were honored with the nobel prize last year. ketterle and his research team managed to merge a bunch of atoms into what he calls a single matter - wave, and then used fluctuating magnetic fields to shape the matter - wave into a beam much like a laser. to test the coherence of a bec, the researchers generated two separate matter - waves, made them overlap and photographed a so - called \" interference pattern \" that only can be created by coherent waves. the researchers then had proof that they had created the first atom laser. since 1995, all atom lasers and bec have been produced in a pulsed manner, emitting individual pulses of atoms several times per minute. until now, little progress has been made toward a continuous bec source. while it took about six months to create a continuous optical laser after the first pulsed optical laser was produced in 1960, the much more technically challenging continuous source of coherent atoms has taken seven years since ketterle and colleagues first observed bec in 1995. a new challenge creating a continuous bec source involved three steps : building a chamber where the condensate could be stored in an optical trap, moving the fresh condensate and merging the new condensate with the existing condensate stored in the optical trap. ( the same researchers first developed an optical trap for becs in 1998. ) the researchers built an apparatus containing two vacuum chambers : a production chamber where the condensate is produced and a \" science chamber \" around 30 centimeters away, where the condensate is stored. the condensate in the science chamber had to be protected from laser light, which was necessary to produce a fresh condensate, and also from hot atoms. this required great precision, because a single laser - cooled atom has enough energy to knock thousands of atoms out of the condensate. in addition, they used an optical trap as the reservoir trap, which is insensitive to the magnetic fields used for cooling atoms into a bec. the researchers also needed to figure out how to move the fresh condensate -", "subdomain_id": "subdomain_quantum_optics", "similarity_score": 0.6512381115578469, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 1, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:03.090172"} {"text": "##nsate. in addition, they used an optical trap as the reservoir trap, which is insensitive to the magnetic fields used for cooling atoms into a bec. the researchers also needed to figure out how to move the fresh condensate - chilled to astronomically low temperatures - from the production chamber to the science chamber without heating them up. this was accomplished using optical tweezers - a focused laser light beam that traps the condensate. finally, to merge the new condensate with the existing condensate in the science chamber, they moved the new condensate in the tweezers into the science chamber by merging the condensates together. a bucket of atoms if the pulsed atom laser is like a faucet that drips, chikkatur says the new innovations create a sort of bucket that collects the drips without wasting or changing the condensate too dramatically by heating it. this way, a reservoir of condensate is always on hand to replenish an atom laser. the condensate pulses are like a dripping faucet, where the drops are analogous to the pulsed bec production. \" we have now implemented a bucket ( our reservoir trap ), where we collect these drips to have continuous source of water ( bec ), \" chikkatur said. \" although we did not demonstrate this, if we poke a hole in this bucket, we will have a steady stream of water. this hole would be an outcoupling technique from which we can produce a continuous atom laser output. \" the big achievement here is that we have invented the bucket, which can store atoms continuously and also makes sure that the drips of water do not cause a lot of splashing ( heating of becs ), \" he said. the next step would be to improve the number of atoms in the source, perhaps by implementing a large - volume optical trap. another important step would be to demonstrate a phase - coherent condensate merger using a matter wave amplification technique pioneered by the mit group and a group in japan, he said. this work is funded by the national science foundation, the office of naval research, the army research office, the packard foundation and nasa.", "subdomain_id": "subdomain_quantum_metrology", "similarity_score": 0.6432099348719158, "token_count": 452, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 2, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:03.092088"} {"text": "reactions, with the result being a massive release of energy in the form of heat. in every way, this technology matches what i had hoped for throughout my childhood and later on in my life : in addition, the millions of jobs created around the world by a cold - fusion revolution would galvanize the global economy and end the current global recession - and do it all safely, without fukushima - like events. to be blunt, cold - fusion technology holds the potential to transform our world from a planet of poverty, war and self - destruction into a place of enlightened prosperity. on the other hand, the existence of the higgs boson offers no near - term benefits to humanity. it may give us a bit more knowledge about the universe, but no one claims that even one single technology that could be immediately developed using this knowledge. if the existence of the higgs boson could yield a warp drive, free - energy device, gravity - modifying device, or other breakthrough in a reasonable period of time, perhaps the billions of dollars spent would be worth it. but the truth is that just like hot fusion research, the search for the higgs boson is a boondoggle. due to the lack of any near - term benefits, the funds could be better spent elsewhere. if a fraction of the money spent on the search for the higgs boson had been put into cold fusion research 20 years ago, there would be no energy crisis today. instead, cold fusion devices that could produce kilowatts of power and very high temperatures - like the e - cat - would have been quickly developed and commercialized. instead of putting money into practical technologies that could benefit all mankind in the near term, the career scientists naysayed exotic technologies like cold fusion, and lobbied for billions of dollars in additional funding for giant hot fusion reactors and particle colliders. all these years later, we have seen little or no return on the investment in the form of technological advancement. we are still stuck with rockets for propulsion and burning fossil fuels for energy. literally, we are still in a technological dark age when it comes to the most fundamental of technologies - energy and propulsion. ( if you don ' t count the \" black, \" off - budget projects that use taxpayer money with no taxpayer benefit, and actually have the agenda of making us all slaves. ) i do not want to call the search for the higgs field or the higgs boson totally meaningless. however, i think nicola tesla ' s work ( although still ignored by", "subdomain_id": "subdomain_quantum_thermodynamics", "similarity_score": 0.6027013979321785, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 1, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:03.273345"} {"text": "a substantial threat to human health and the environment. mine : an underground opening or open pit used for the purpose of extracting minerals. mines commonly include features, such as shafts, adits, pits, trenches, tunnels, waste rock dumps, tailings, and structures including, but not limited to, mills, buildings, head frames, hoists, and loading chutes. potentially responsible party ( prp ) : any individual or entity, including current and past owners, operators, transporters, arrangers, or generators who may be liable for clean - up costs for hazardous substances under cercla section 107 ( a ) or for injuries to natural resources on public lands from hazardous substance releases under section 311 ( f ) of the cwa and cercla section 107 ( f ). project : the investigation, cleanup of safety risks, stabilization, or reclamation of an abandoned mine land site or sites. a project may include one or more individual abandoned mines. the project area may be based on geologic, geographic, hydrologic, watershed, ownership, or other legal boundaries, or based on practical or logistical convenience, and is often contiguous. remedial action : permanent remedy taken to prevent or minimize the release of hazardous substances into the environment. long - term actions ( 5 - 8 years ) are necessary to return a site to its original conditions. removal action : short - term actions necessary to remove or mitigate a release or threat of release of hazardous substances. site : the area identified as being impacted by physical safety and / or environmental hazards. this can include any area where hazardous substances have been released or have migrated. the area size is influenced by the extent of the investigation, migration, evaluation, and past, current, and future clean - up activities. special status species : includes proposed species, listed species, and candidate species under the esa ; state - listed species ; and the blm state director - designated sensitive species ( see blm manual 6840 - special status species management strategic plan : a plan that establishes the overall direction for the blm. this plan is guided by the requirements of gpra, covers a 5 - year period, and is updated every 3 years. it is consistent with flpma and other laws affecting the public lands. total maximum daily load ( tmdl ) : pursuant to the clean water act, an estimate of the total quantity of pollutants ( from all sources : point, nonpoint, and natural ) that may be allowed into waters without exceeding applicable water quality criteria. watershed : this term", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6127342859650826, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 2, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:03.351158"} {"text": "an earthquake is a sudden vibration or trembling in the earth. more than 150, 000 tremors strong enough to be felt by humans occur each year worldwide ( see chance of an earthquake ). earthquake motion is caused by the quick release of stored potential energy into the kinetic energy of motion. most earthquakes are produced along faults, tectonic plate boundary zones, or along the mid - oceanic ridges ( figures 1 and 2 ). figure 1 : distribution of earthquake epicenters from 1975 to 1995. depth of the earthquake focus is indicated by color. deep earthquakes occur in areas where oceanic crust is being actively subducted. about 90 % of all earthquakes occur at a depth between 0 and 100 kilometers. ( source : u. s. geologic survey, national earthquake information center ) figure 2 : distribution of earthquakes with a magnitude less than 5. 0 relative to the various tectonic plates found on the earth ' s surface. each tectonic plate has been given a unique color. this illustration indicates that the majority of small earthquakes occur along plate boundaries. ( source : physicalgeography. net ) at these areas, large masses of rock that are moving past each other can become locked due to friction. friction is overcome when the accumulating stress has enough force to cause a sudden slippage of the rock masses. the magnitude of the shock wave released into the surrounding rocks is controlled by the quantity of stress built up because of friction, the distance the rock moved when the slippage occurred, and ability of the rock to transmit the energy contained in the seismic waves. the san francisco earthquake of 1906 involved a six meter horizontal displacement of bedrock. sometime after the main shock wave, aftershocks can occur because of the continued release of frictional stress. most aftershocks are smaller than the main earthquake, but they can still cause considerable damage to already weakened natural and human - constructed features. earthquakes that occur under or near bodies of water can give rise to tsunamis, which in cases like the december 26, 2004 sumatra - andaman island earthquake reult in far greater distruction and loss of life that the initial earthquake. earthquakes are a form of wave energy that is transferred through bedrock. motion is transmitted from the point of sudden energy release, the earthquake focus ( hypocenter ), as spherical seismic waves that travel in all directions outward ( figure 3 ). the point on the earth ' s surface directly above the focus is termed the epicenter. two different types of seismic waves have been described by geologists : body waves and surface waves", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6027498401087821, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:04.105469"} {"text": "the ilc promises extraordinary power in the study of the terascale. the annihilation of an electron and its antiparticle, the positron, allows the understanding of collisions to an unparalleled level of detail and precision. as others have comprehensively documented, the ilc view of the terascale, complementary to the lhc ' s perspective, makes the ilc an essential tool for unraveling new phenomena discovered at these extreme energies. it makes the ilc the top priority at fermilab for a future global facility. a superconducting ilc cavity credit : fermilab visual media services the ilc ' s opportunities for discovery have motivated the global particle physics community to come together in an effort to design the accelerator and its experimental program. the completion of the reference design report in early 2007 and the structuring of a collaborative worldwide r & d program represent successful community efforts. fermilab has contributed strongly to this effort : the design of the accelerator ; the development of superconducting radio - frequency, or scrf, technology in the u. s. ; the design of the physics and experimental program ; the site studies necessary for hosting the ilc at or near fermilab ; and the establishment of a test - beam facility for the development of ilc detectors. the ilc and related scrf efforts at fermilab make up by far the laboratory ' s largest future program. in the next phase of the ilc effort, fermilab ' s aim is to be a leader in the global engineering design and in the development of the scrf technology, steps necessary to reach a decision early in the next decade to build the ilc. fermilab is building the required infrastructure and test facilities and is coordinating the national efforts in the development of scrf technology, in collaboration with national and international partners in europe, asia and the u. s. to these efforts fermilab brings strong engineering capability, accelerator physics expertise and technology development skills. innovative detectors will be key to exploiting the ilc physics opportunities. in general, an improvement in resolution of both tracking and calorimetric detectors over the present state - of - the - art detectors will allow experimenters to distinguish the signals of new physics from backgrounds much more efficiently. fermilab has a strong instrumentation development effort in collaboration with laboratories and universities across the world. just as important for the global ilc effort, fermilab has developed and will operate a flexible high - energy test beam to provide", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6046122363379414, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:04.224268"} {"text": "until the page is filled ( although, over time, they should be able to condense all the essential material from one entire lecture on the top half of one sheet ). next, students fold the earlier columns behind and engage in repeated sketching and writing of these concepts in columns three and four. the recopying and rethinking of these concepts engages a student \u2019 s motor memory and visual cortex. dr. heideman says that his method forces students to extract the essentials from a large amount of material and learn the key concepts as sequential events. it is an active - learning method that engages students \u2019 attention and allows them to review material quickly and to assess how much they have accomplished within a given time. dr. heideman says the method can be applied to other study techniques, such as concept mapping. program director : margaret somosi saha, ph. d. award years : 1989, 1998, 2002, 2006 summary : the college of william and mary is a public research university in williamsburg, virginia. its hhmi - funded educational initiatives emphasize the importance of interdisciplinary and integrative approaches to education and research. they include : - the development of a biological mathematics program ( which includes substantial curricular changes and the addition of new faculty positions ), the strengthening of the interdisciplinary neuroscience major, and the establishment of a new undergraduate applied science minor. - the enhancement of both introductory biology and chemistry and upper - level immunology, molecular genetics, physiology, and neurophysiology laboratories through new equipment and expanded laboratory exercises. - the hhmi freshman research program in biology and chemistry and related sciences, which allows participating students to conduct independent research with a faculty mentor very early in their college careers \u2014 as freshmen. many of these students have the opportunity to continue their research during the following summer and throughout the next three years. - student participation in the national genomics research initiative ( ngri ), a national experiment in both research and education sponsored by hhmi \u2019 s science education alliance. through this initiative, groups of freshmen at selected colleges participate in an authentic research experience \u2014 integrated into an introductory laboratory course \u2014 on the genetics of phages or bacteriophages ( viruses that infect bacteria ). freshmen in the college of william and mary \u2019 s program discovered a new life form, a bacteriophage they named crimd. - the expansion of a summer fellowship program to include students at thomas nelson community college and three neighboring hbcu \u2014 hampton university, norfolk state university, and virginia state", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6015000885217323, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 1, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:04.640406"} {"text": "at the heart of materials science is an understanding of the microstructure of solids. \" microstructure \" is used broadly in reference to solids viewed at the subatomic ( electronic ) and atomic levels, and the nature of the defects at these levels. the microstructures of solids at various levels, especially the defects, profoundly influence the mechanical, electronic, chemical, and biological properties of solids. the phenomenological and mechanistic relationships between the microstructure and the macroscopic properties of solids are, in essence, what the materials science is all about. this is best represented by the \" materials science triangle \" : synthesis - microstructure - properties. materials engineering, on the other hand, is concerned with the design, fabrication, and testing of engineering materials. such materials must fulfill simultaneously the dimensional properties, quality control, and economic requirements. several manufacturing steps may be involved : ( 1 ) primary fabrication, such as solidification or vapor deposition of homogeneous or composite materials ; ( 2 ) secondary fabrication, including shaping and microstructural control by operations such as mechanical working, machining, sintering, joining and heat treatment and ( 3 ) testing, which measures the degree of reliability of a processed part, destructively or non - destructively. because the science of materials branches into other fields of study, the department offers joint fields of study in collaboration with other departments. a degree specializing in electronic materials is offered which provides a broad - based background in materials science, with the opportunity to specialize in semiconducting materials used in electronic and optoelectronic devices. the program incorporates several courses in electrical engineering in addition to those in the materials science curriculum. a joint major field, chemistry / materials science, is offered to students enrolled in the department of chemistry and biochemistry ( college of letters and science ). several courses in the undergraduate curriculum also play an important role in the manufacturing engineering program. the graduate program allows for specialization in one of the following fields : ceramics and ceramic processing, electronic and optical materials, and structural materials.", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6986775206041498, "token_count": 423, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:05.158506"} {"text": "the most romantic way i have ever heard chaos theory described is, \u201c there are patterns, and even great beauty, in seemingly chaotic events. \u201d formally, chaos theory is defined as a sub - discipline of mathematics that studies complex, or dynamic, systems. these complex systems contain so many moving parts that it takes computers to calculate and model all of the movements of the system. in fact, it has been said that the emergence of this theory could not have happened without the invention and proliferation of the computer. up until what is called the quantum mechanical revolution, \u201c people believed that things were directly caused by other things. \u201d in latin it is referred to as post hoc ergo propter hoc, or after, therefore, because of it. in essence, if one thing follows another, it must have been caused by it. it is the basis of freudian psychoanalysis, \u201c a belief that malfunctions in the mind are the results of traumas suffered in the past \u201d and that regression therapy \u2014 pinpointing when and how these traumas occurred \u2014 would allow us to heal. it is called linear cause and effect. chaos theory, however, tells us that it is less about linear effect and more the existence and production of patterns caused by many different forces, the most important of which are initial conditions, popularly referred to as the butterfly effect. the butterfly effect posits that the flapping of a butterfly \u2019 s wings in south america could affect the weather in texas, meaning that the smallest, seemingly inconsequential part of a system can have a huge effect on all the other parts. simply said, \u201c unless all factors can be accounted for, large systems would be impossible to predict with total accuracy because there are too many unknown variables to track. \u201d the study of chaos theory has helped us understand simple, or everyday, phenomena such as water boiling on a stove and complex events such as how birds migrate, how vegetation spreads and the structure of stars in the night sky, but its origins stem from the study of weather systems. it all started in 1960 when edward lorentz created a weather - model on his computer at the massachusetts institute of technology. lorentz \u2019 s weather model consisted of an extensive array of complex formulas that successfully modeled, and later helped predict, the weather and turned a large, unpredictable system into one of those everyday phenomena, the daily weather forecast. this month \u2019 s quality continues in the tradition of mr. lorentz with michelle bangert \u2019 s analysis of our annual spending study, \u201c quality spending stays strong", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6173109565125521, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:05.596898"} {"text": "mar. 4, 2013 behind locked doors, in a lab built like a bomb shelter, perry gerakines makes something ordinary yet truly alien : ice. this isn ' t the ice of snowflakes or ice cubes. no, this ice needs such intense cold and low pressure to form that the right conditions rarely, if ever, occur naturally on earth. and when gerakines makes the ice, he must keep the layer so microscopically thin it is dwarfed by a grain of pollen. these ultrathin layers turn out to be perfect for recreating some of the key chemistry that takes place in space. in these tiny test tubes, gerakines and his colleagues in the cosmic ice lab at nasa ' s goddard space flight center in greenbelt, md., can reproduce reactions in ice from almost any time and place in the history of the solar system, including some that might help explain the origin of life. \" this is not the chemistry people remember from high school, \" says reggie hudson, who heads the cosmic ice lab. \" this is chemistry in the extreme : bitter cold, harsh radiation and nearly non - existent pressure. and it ' s usually taking place in gases or solids, because generally speaking, there aren ' t liquids in interstellar space. \" the cosmic ice lab is one of a few laboratories worldwide where researchers have been studying the ultracool chemistry of cosmic ice. with its powerful particle accelerator, the goddard lab has the special ability to mimic almost any kind of solar or cosmic radiation to drive these reactions. and that lets them dig deep to study the chemistry of ice below the surface of planets and moons as well as ice in space. recipe for disorder in a vacuum chamber about the size of a lunchbox, gerakines recreates a little patch of deep space, in all its extremes. he pumps out air until the pressure inside drops to a level a billion times lower than normal for earth, then chills the chamber to minus 433 degrees fahrenheit ( 15 kelvins ). to get ice, all that remains is to open a valve and let in water vapor. the instant the sprightly vapor molecules enter the chamber they are literally frozen in their tracks. still pointing every which way, the molecules are transformed immediately from their gaseous state into the disorderly solid called amorphous ice. amorphous ice is exactly the opposite of the typical ice on earth, which forms perfect crystals like those that make up snowflakes or frost needles. these crystals are so orderly", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6039506455639456, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:05.735807"} {"text": "gaseous state into the disorderly solid called amorphous ice. amorphous ice is exactly the opposite of the typical ice on earth, which forms perfect crystals like those that make up snowflakes or frost needles. these crystals are so orderly and predictable that this ice is considered a mineral, complete with a rating of 2. 5 on the mohs scale of hardness - - the same rating as a fingernail. though almost unheard of on earth, amorphous ice is so widespread in interstellar space that it could be the most common form of water in the universe. left over from the age when the solar system was born, it is scattered across vast distances, often as particles no bigger than grains of dust. it ' s also been spotted in comets and icy moons. the secret to making amorphous ice in the lab, gerakines finds, is to limit the layer to a depth of about half a micrometer - - thinner than a strand of spider ' s silk. \" water is such a good insulator that if the ice gets too thick, only the bottom of the sample, closer to the cooling source, will stay sufficiently cold, \" says gerakines. \" the ice on top will get warm enough to crystallize. \" the superthin ice can be spiked with all kinds of interesting chemicals found in space. one set of chemicals that gerakines works with is amino acids, which are key players in the chemistry of life on earth. researchers have spent decades identifying a whole smorgasbord of amino acids in meteorites ( including some involved in life ), as well as one found in a sample taken from a comet. \" and because water is the dominant form of frozen material in the interstellar medium and outer solar system, \" says gerakines, \" any amino acids out there are probably in contact with water at some point. \" for his current set of experiments, gerakines makes three kinds of ice, each spiked with an amorphous form of an amino acid ( either glycine, alanine or phenylalanine ) that is found in proteins. the real action begins when gerakines hits the ice with radiation. earlier studies by other researchers have looked at ice chemistry using ultraviolet light. gerakines opts instead to look at cosmic radiation, which can reach ice hidden below the surface of a planet or moon. to mimic this radiation, he uses a proton beam from the high - voltage particle accelerator, which resides in an underground room lined", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6441095976272215, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 1, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:05.737011"} {"text": "quantum teleportation leaps to new distance record a new record of roughly 60 miles has been set in the field of qubit transmission. \" this is just a transmission method, so it could have wide utility, though i expect the cost will initially make it best for huge data streams, \" said analyst rob enderle. \" something like this could turn us into a saas world. \" scientists in china have transmitted quantum bits, or qubits, over a record distance of 97 km, or roughly 60 miles. this is more than six times the distance of the previous record of 16 km, set by another team of chinese researchers in may of 2010, as reported in nature. com. the results represent a step toward the establishment of a global quantum network, and the methods used in the experiment could be utilized for satellite - based quantum communications, the scientists said. \" this is just a transmission method, so it could have wide utility, though i expect the cost will initially make it best for huge data streams, \" rob enderle, principal analyst at the enderle group, told technewsworld. this technology \" could end up changing much of the world \" because it ' s both potentially higher bandwidth and lower latency, approaching zero, and these factors \" could drive massive computer centralization on a world scale and force a massive shakeout of security, networking and computer companies, \" enderle continued. \" something like this could turn us into a saas ( software as a service ) world. \" the theory behind the experiment the latest experiment demonstrated quantum teleportation of an independent unknown state between two optical free - space links 97 km apart with multi - photon entanglement. quantum teleportation is a process for transmitting information using quantum physics to, in effect, encrypt the data transmitted. it ' s also known as entanglement - assisted teleportation. in quantum teleportation experiments, beams of lights are used to encode qubits. the encoded beam of light, which is described as quantum entangled, is split into two and transmitted. when a qubit at one receiver is observed and take a defined form, the other half of the qubit at the other receiver takes the same defined form. quantum entanglement results when particles such as photons or electrons interact physically and then become separated but remain in the same quantum state. a quantum state is a set of mathematical variables, including position, momentum and spin, that fully describes a quantum system", "subdomain_id": "subdomain_quantum_information_theory", "similarity_score": 0.719282089234476, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:05.877064"} {"text": "its electrons orbit the atomic nucleus like the planets orbit the sun. exactly 112 electrons circle the atomic nucleus in an atom of the new element \" copernicium \". element 112 is the heaviest element in the periodic table, 277 times heavier than hydrogen. it is produced by a nuclear fusion, when bombarding zinc ions onto a lead target. as the element already decays after a split second, its existence can only be proved with the help of extremely fast and sensitive analysis methods. twenty - one scientists from germany, finland, russia and slovakia have been involved in the experiments that led to the discovery of element 112. since 1981, gsi accelerator experiments have yielded the discovery of six chemical elements, which carry the atomic numbers 107 to 112. the discovering teams at gsi already named five of them : element 107 is called bohrium, element 108 hassium, element 109 meitnerium, element 110 darmstadtium, and element 111 is named roentgenium. the new element 112 discovered by gsi has been officially recognized and will be named by the darmstadt group in due course. their suggestion should be made public over this summer. the element 112, discovered at the gsi helmholtzzentrum fur schwerionenforschung ( centre for heavy ion research ) in darmstadt, has been officially recognized as a new element by the international union of pure and applied chemistry ( iupac ). iupac confirmed the recognition of element 112 in an official letter to the head of the discovering team, professor sigurd hofmann. the letter furthermore asks the discoverers to propose a name for the new element. their suggestion will be submitted within the next weeks. in about 6 months, after the proposed name has been thoroughly assessed by iupac, the element will receive its official name. the new element is approximately 277 times heavier than hydrogen, making it the heaviest element in the periodic table. \u201c we are delighted that now the sixth element \u2013 and thus all of the elements discovered at gsi during the past 30 years \u2013 has been officially recognized. during the next few weeks, the scientists of the discovering team will deliberate on a name for the new element \u201d, says sigurd hofmann. 21 scientists from germany, finland, russia and slovakia were involved in the experiments around the discovery of the new element 112. since 1981, gsi accelerator experiments have yielded the discovery of six chemical elements, which carry the atomic numbers 107 to 112. gsi has already named their officially recognized elements 107 to 111 :", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6272619061946121, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 1, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:06.126026"} {"text": "atommate is a chemistry card game that consists of a deck of 49 playing cards with the names, symbols and facts about the elements of the periodic table. it is used to play games that involve making chemical compounds. designed for students aged 10 and up, it is a grow - with - me game. beginning students learn the names and symbols of the elements. intermediate students learn to combine the elements to form molecules and compounds. more advanced students can use the cards to enhance their understanding of simple reactions. instructions for eight easy games, which range in difficulty from easy to complex, are included. there are several games that may be played with these cards. all games are designed for 2 to 4 players. the deck contains a sub - set of the elements in the periodic table, with repetitions of some elements. some of the elements have the word toxic on them - this gives the card special powers in some of the games. there are 8 non - element cards : 4 reduce and 4 oxidize. these allow the player to make additional moves in some of the games. the following information on the cards may be used to play the games : atommate is a game developed by dr. carol brevett who has taught chemistry at iowa state university and has been working in industry, including at the dupont company of delaware, as a research scientist for over 13 years. she has developed and tested the atommate games over many years. a must for the chemistry enthusiast, the science scholar, the science - oriented pupil or anyone who wants to play an unusual and novel card game. with each order we ' ll send you a free silky periodic table bookmark and a free glossy laminated postcard sized periodic table for your noticeboard! delivery and shipping | terms and conditions | about us |", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6156049100028853, "token_count": 358, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-25T19:02:06.127992"}