nov. 27, 2009 physicists from the japanese - led multi - national t2k neutrino collaboration have just announced that over the weekend they detected the first neutrino events generated by their newly built neutrino beam at the j - parc ( japan proton accelerator research complex ) accelerator laboratory in tokai, japan. protons from the 30 - gev main ring synchrotron were directed onto a carbon target, where their collisions produced charged particles called pions. these pions travelled through a helium - filled volume where they decayed to produce a beam of the elusive particles called neutrinos. these neutrinos then flew 200 metres through the earth to a sophisticated detector system capable of making detailed measurements of their energy, direction, and type. the data from the complex detector system is still being analysed, but the physicists have seen at least 3 neutrino events, in line with the expectation based on the current beam and detector performance. this detection therefore marks the beginning of the operational phase of the t2k experiment, a 474 - physicist, 13 - nation collaboration to measure new properties of the ghostly neutrino. neutrinos interact only weakly with matter, and thus pass effortlessly through the earth ( and mostly through the detectors! ). neutrinos exist in three types, called electron, muon, and tau ; linked by particle interactions to their more familiar charged cousins like the electron. measurements over the last few decades, notably by the super kamiokande and kamland neutrino experiments in western japan, have shown that neutrinos possess the strange property of neutrino oscillations, whereby one type of neutrino will turn into another as they propagate through space. neutrino oscillations, which require neutrinos to have mass and therefore were not allowed in our previous theoretical understanding of particle physics, probe new physical laws and are thus of great interest in the study of the fundamental constituents of matter. they may even be related to the mystery of why there is more matter than anti - matter in the universe, and thus are the focus of intense study worldwide. precision measurements of neutrino oscillations can be made using artificial neutrino beams, as pioneered by the k2k neutrino experiment where neutrinos from the kek laboratory were detected using the vast super kamiokande neutrino detector near toyama. t2k is a more powerful and sophisticated version of


by i. peterson unlike an ordinary, incandescent bulb, a laser produces light of a single wavelength. moreover, the emitted light waves are coherent, meaning that all of the energy peaks and troughs are precisely in step. now, a team at the massachusetts institute of technology has demonstrated experimentally that a cloud consisting of millions of atoms can also be made coherent. instead of flying about and colliding randomly, the atoms display coordinated behavior, acting as if the entire assemblage were a single entity. according to quantum mechanics, atoms can behave like waves. thus, two overlapping clouds made up of atoms in coherent states should produce a zebra - striped interference pattern of dark and light fringes, just like those generated when two beams of ordinary laser light overlap. by detecting such a pattern, the researchers proved that the clouds ' atoms are coherent and constitute an " atom laser, " says physicist wolfgang ketterle, who heads the mit group. these matter waves, in principle, can be focused just like light. ketterle and his coworkers describe their observations in the jan. 31 science. the demonstration of coherence involving large numbers of atoms is the latest step in a series of studies of a remarkable state of matter called a bose - einstein condensate. chilled to temperatures barely above absolute zero, theory predicted, the atoms would collectively enter the same quantum state and behave like a single unit, or superparticle, with a specific wavelength. first created in the laboratory in 1995 by eric a. cornell and his collaborators at the university of colorado and the national institute of standards and technology, both in boulder, bose - einstein condensates have been the subject of intense investigation ever since ( sn : 7 / 15 / 95, p. 36 ; 5 / 25 / 96, p. 327 ). at mit, ketterle and his colleagues cool sodium atoms to temperatures below 2 microkelvins. the frigid atoms are then confined in a special magnetic trap inside a vacuum chamber. to determine whether the atoms in the resulting condensate are indeed as coherent as photons in a laser beam, the researchers developed a novel method of extracting a clump of atoms from the trap. in effect, they manipulate the magnetic states of the atoms to expel an adjustable fraction of the original cloud ; under the influence of gravity, the released clump falls. the method can produce a sequence of descending clumps, with each containing 100, 000 to several million coherent atoms. the apparatus acts like


expel an adjustable fraction of the original cloud ; under the influence of gravity, the released clump falls. the method can produce a sequence of descending clumps, with each containing 100, 000 to several million coherent atoms. the apparatus acts like a dripping faucet, ketterle says. he and his colleagues describe the technique in the jan. 27 physical review letters. to demonstrate interference, the mit group created a double magnetic trap so that two pulses of coherent atoms could be released at the same time. as the two clumps fell, they started to spread and overlap. the researchers could then observe interference between the atomic waves of the droplets. " the signal was almost too good to be true, " ketterle says. " we saw a high - contrast, very regular pattern. " " it ' s a beautiful result, " cornell remarks. " this work really shows that bose - einstein condensation is an atom laser. " from the pattern, the mit researchers deduced that the condensate of sodium atoms has a wavelength of about 30 micrometers, considerably longer than the 0. 04 - nanometer wavelength typical of individual atoms at room temperature. ketterle and his colleagues are already planning several improvements to their primitive atom laser, including getting more atoms into the emitted pulses and going from pulses to a continuous beam. practical use of an atom laser for improving the precision of atomic clocks and for manipulating atoms is still distant, however, cornell notes.


a b c d e f g h i j k l m n o p q r s t u v w x y z a modem self - test in which data from the keyboard or an internal test pattern is sent to the modem ' s transmitter, turned into analog form, looped back to the receiver, and converted back into digital form. a variety of signals and wavelengths that can be transmitted over communications lines such as the sound of a voice over the phone line. the mode used by your modem when answering an incoming call from an originating modem. the transmit / receive frequencies are the reverse of the originating modem, which is in originate mode. a computer program designed to perform a specific task or set of tasks. examples include word processing and spreadsheet applications. automatic repeat request. a function that allows your modem to detect flawed data and request that it be retransmitted. see mnp and v. 42. american standard code for information interchange. a code used to represent letters, numbers, and special characters such as $,!, and /. data transmission in which the length of time between transmitted characters may vary. because characters may not be transmitted at set intervals, start / stop bits are used to mark the beginning and end of each character. sets the modem to pick up the phone line when it detects a certain number of rings. see s - register s0 in the technical reference section of this guide. a process where your modem dials a call for you. the dialing process is initiated by sending an atdt ( dial tone ) or atdp ( dial pulse ) command followed by the telephone number. auto - dial is used to dial voice numbers. see basic data command dn in the technical reference section of this guide. a term used to measure the speed of an analog transmission from one point to another. although not technically accurate, baud rate is commonly used to mean bit rate. a 0 or 1, reflecting the use of the binary numbering system. used because the computer recognizes either of two states, off or on. shortened form of binary digit is bit. also referred to as transmission rate. the number of binary digits, or bits, transmitted per second ( bps ). communications channels using analog modems are established at set bit rates, commonly 2400, 4800, 9600, 14, 400, 28, 800, 33, 600, and higher. bits per second ( bps ) the bits ( binary digits ) per second rate. thousands


are established at set bit rates, commonly 2400, 4800, 9600, 14, 400, 28, 800, 33, 600, and higher. bits per second ( bps ) the bits ( binary digits ) per second rate. thousands of bits per second are expressed as kilobits per second ( kbps ). a temporary memory area used as storage during input and output operations. an example is the modem ' s command buffer. a group of binary digits stored and operated upon as a unit. most often the term refers to 8 - bit units or characters. one kilobyte ( kb ) is equal to 1, 024 bytes or characters ; 640 kb is equal to 655, 360 bytes or characters. the basic signal altered or modulated by the modem in order to carry information. a representation, coded in binary digits, of a letter, number, or other symbol. characters per second ( cps ) a data transfer rate generally estimated from the bit rate and the character length. for example, at 2400 bps, 8 - bit characters with start / stop bits ( for a total of ten bits per character ) will be transmitted at a rate of approximately 240 characters per second ( cps ). some protocols, such as error - control protocols, employ advanced techniques such as longer transmission frames and data compression to increase cps. class 1 and 2. 0 international standards used by fax application programs and faxmodems for sending and receiving faxes. cyclic redundancy checking ( crc ) an error - detection technique consisting of a test performed on each block or frame of data by both sending and receiving modems. the sending modem inserts the results of its tests in each data block in the form of a crc code. the receiving modem compares its results with the received crc code and responds with either a positive or negative acknowledgment. the transmission or sharing of data between computers via an electronic medium. data compression table a table containing values assigned for each character during a call under mnp5 data compression. default values in the table are continually altered and built during each call : the longer the table, the more efficient throughput gained. mode used by a modem when sending and receiving data files. data communications ( or circuit - terminating ) equipment, such as dial - up modems that establish and control the data link via the telephone network. any setting assumed, at startup or reset, by the computer ' s software and attached devices.


files. data communications ( or circuit - terminating ) equipment, such as dial - up modems that establish and control the data link via the telephone network. any setting assumed, at startup or reset, by the computer ' s software and attached devices. the computer or software will use these settings until changed by the user or other software. a test that checks the modem ' s rs - 232 interface and the cable that connects the terminal or computer and the modem. the modem receives data ( in the form of digital signals ) from the computer or terminal and immediately returns the data to the screen for verification. discrete, uniform signals. in this guide, the term refers to the binary digits 0 and 1. data terminal ( or terminating ) equipment. a computer that generates or is the final destination of data. indicates a communications channel capable of carrying signals in both directions. see half - duplex, full - duplex. electronic industries association ( eia ) group which defines electronic standards in the u. s. various techniques that check the reliability of characters ( parity ) or blocks of data. v. 42 and mnp error - control protocols use error detection ( crc ) and retransmission of flawed frames ( arq ). a method for transmitting the image on a page from one point to another. commonly referred to as fax. the mode used by a modem to send and receive data in facsimile format. see definitions for v. 17, v. 27 ter, v. 29. a mechanism that compensates for differences in the flow of data into and out of a modem or other device. see extended data commands & hn, & in, & rn in the technical reference section of this guide. a data communications term for a block of data with header and trailer information attached. the added information usually includes a frame number, block size data, error - check codes, and start / end indicators. signals can flow in both directions at the same time over one line. in microcomputer communications, this may refer to the suppression of the online local echo. signals can flow in both directions, but only one way at a time. in microcomputer communications, may refer to activation of the online local echo, which causes the modem to send a copy of the transmitted data to the screen of the sending computer. hertz, a frequency measurement unit used internationally to indicate cycles per second. an electronic communications network that connects computer networks and organizational computer facilities around the world. internet service


next higher speed. the mode used by your modem when initiating an outgoing call to a destination modem. the transmit / receive frequencies are the reverse of the called modem, which is in answer mode. a simple error - detection method that checks the validity of a transmitted character. character checking has been surpassed by more reliable and efficient forms of error checking, including v. 42 and mnp 2 - 4 protocols. either the same type of parity must be used by two communicating computers, or both may omit parity. a system of rules and procedures governing communications between two or more devices. protocols vary, but communicating devices must follow the same protocol in order to exchange data. the format of the data, readiness to receive or send, error detection and error correction are some of the operations that may be defined in protocols. random access memory. memory that is available for use when the modem is turned on, but that clears of all information when the power is turned off. the modem ' s ram holds the current operational settings, a flow control buffer, and a command buffer. remote digital loopback a test that checks the phone link and a remote modem ' s transmitter and receiver. a copy of the data received by the remote system, returned to the sending system, and displayed on the screen. remote echoing is a function of the remote system. read only memory. permanent memory, not user - programmable. the consecutive flow of data in a single channel. compare to parallel transmissions where data flows simultaneously in multiple channels. the signaling bits attached to a character before and after the character is transmitted during asynchronous transmission. a device whose keyboard and display are used for sending and receiving data over a communications link. differs from a microcomputer or a mainframe in that it has little or no internal processing capabilities. software mode that allows direct communication with the modem. also known as command mode. the amount of actual user data transmitted per second without the overhead of protocol information such as start / stop bits or frame headers and trailers. compare with characters per second. the itu - t standard specification that covers the initial handshaking process. an itu - t standard for making facsimile connections at 14, 400 bps, 12, 000 bps, 9, 600 bps, and 7, 200 bps. an itu - t standard for modems operating in asynchronous mode at speeds up to 300 bps, full - duplex, on public switched telephone


robb godshaw, from syynlabs, has created a haptic cube that gives you an impression of what the temperature will be like tomorrow. the cube, which godshaw has named the cryoscope, consists of an aluminium shell surrounding a peltier element, heatsink, cooling fan and an led, all controlled by an arduino. the cube is heated to a " neutral " state of 30c, and then adjusted by the number of degrees that the next day ' s forecast differs from room temperature ( 23c ). it takes into account wind chill and humidity to give an idea what the following day will " feel " like, rather than merely reflecting air temperature. so, for example, if the forecast for the next day is for 18c, once those factors are all taken into account, the cube ' s temperature will decrease five degrees from 30c to 25c, resulting in it being slightly cool to the touch. godshaw describes it in the video above as a " haptic weathervane ", adding : " users enter their location into a web app. the cube then automatically adjusts to the forecasted temperature. by touching the cryoscope, the user is able to feel tomorrow ' s air you can see the cryoscope in action over on godshaw ' s website. updated 08 : 29 09 / 05 / 2012 : godshaw has redesigned the cryoscope and is raising money for full production over on kickstarter.


first mechanical calculator. this machine is considered to be the forerunner of the modern computer though none of them were built in his lifetime. study of the molecules and proteins that are the basis of biological functions has led to the concept of a molecular machine. for example, current models of the operation of the kinesin molecule that transports vesicles inside the cell as well as the myocin molecule that operates against actin to cause muscle contraction ; these molecules control movement in response to chemical stimuli. researchers in nano - technology are working to construct molecules that perform movement in response to a specific stimulus. in contrast to molecules such as kinesin and myosin, these nano - machines or molecular machines are constructions like traditional machines that are designed to perform in a task. machines are assembled from standardized types of components. these elements consist of mechanisms that control movement in various ways such as gear trains, transistor switches, belt or chain drives, linkages, cam and follower systems, brakes and clutches, and structural components such as frame members and fasteners. modern machines include sensors, actuators and computer controllers. the shape, texture and color of covers provide a styling and operational interface between the mechanical components of a machine and its users. assemblies within a machine that control movement are often called " mechanisms. " mechanisms are generally classified as gears and gear trains, cam and follower mechanisms, and linkages, though there are other special mechanisms such as clamping linkages, indexing mechanisms and friction devices such as brakes and clutches. controllers combine sensors, logic, and actuators to maintain the performance of components of a machine. perhaps the best known is the flyball governor for a steam engine. examples of these devices range from a thermostat that as temperature rises opens a valve to cooling water to speed controllers such the cruise control system in an automobile. the programmable logic controller replaced relays and specialized control mechanisms with a programmable computer. servomotors that accurately position a shaft in response to an electrical command are the actuators that make robotic systems possible. design plays an important role in all three of the major phases of a product lifecycle : the industrial revolution was a period from 1750 to 1850 where changes in agriculture, manufacturing, mining, transportation, and technology had a profound effect on the social, economic and cultural conditions of the times. it began in the united kingdom, then subsequently spread throughout western europe, north america, japan, and eventually the rest of the world. starting in the later part of


date : december 2004 creator : habel, agnieszka description : this problem in lieu of thesis is a discussion of two topics : brownian movement and quantum computers. brownian movement is a physical phenomenon in which the particle velocity is constantly undergoing random fluctuations. chapters 2, 3 and 4, describe brownian motion from three different perspectives. the next four chapters are devoted to the subject of quantum computers, which are the signal of a new era of technology and science combined together. in the first chapter i present to a reader the two topics of my problem in lieu of thesis. in the second chapter i explain the idea of brownian motion, its interpretation as a stochastic process and i find its distribution function. the next chapter illustrates the probabilistic picture of brownian motion, where the statistical averages over trajectories are related to the probability distribution function. chapter 4 shows how to derive the langevin equation, introduced in chapter 1, using a hamiltonian picture of a bath with infinite number of harmonic oscillators. the chapter 5 explains how the idea of quantum computers was developed and how step - by - step all the puzzles for the field of quantum computers were created. the next chapter, chapter 6, discus the basic quantum unit of information... contributing partner : unt libraries


real form ( lie theory ) in mathematics, the notion of a real form relates objects defined over the field of real and complex numbers. a real lie algebra g0 is called a real form of a complex lie algebra g if g is the complexification of g0 : real forms for lie groups and algebraic groups using the lie correspondence between lie groups and lie algebras, the notion of a real form can be defined for lie groups. in the case of linear algebraic groups, the notions of complexification and real form have a natural description in the language of algebraic geometry. just as complex semisimple lie algebras are classified by dynkin diagrams, the real forms of a semisimple lie algebra are classified by satake diagrams, which are obtained from the dynkin diagram of the complex form by labeling some vertices black ( filled ), and connecting some other vertices in pairs by arrows, according to certain rules. it is a basic fact in the structure theory of complex semisimple lie algebras that every such algebra has two special real forms : one is the compact real form and corresponds to a compact lie group under the lie correspondence ( its satake diagram has all vertices blackened ), and the other is the split real form and corresponds to a lie group that is as far as possible from being compact ( its satake diagram has no vertices blackened and no arrows ). in the case of the complex special linear group sl ( n, c ), the compact real form is the special unitary group su ( n ) and the split real form is the real special linear group sl ( n, r ). the classification of real forms of semisimple lie algebras was accomplished by elie cartan in the context of riemannian symmetric spaces. in general, there may be more than two real forms. suppose that g0 is a semisimple lie algebra over the field of real numbers. by cartan ' s criterion, the killing form is nondegenerate, and can be diagonalized in a suitable basis with the diagonal entries + 1 or - 1. by sylvester ' s law of inertia, the number of positive entries, or the positive index of intertia, is an invariant of the bilinear form, i. e. it does not depend on the choice of the diagonalizing basis. this is a number between 0 and the dimension of g which is an important invariant of the real lie algebra, called its index. split real form a real form g0 of a complex semisimple lie algebra g


choice of the diagonalizing basis. this is a number between 0 and the dimension of g which is an important invariant of the real lie algebra, called its index. split real form a real form g0 of a complex semisimple lie algebra g is said to be split, or normal, if in each cartan decomposition g0 = k0 ⊕ p0, the space p0 contains a maximal abelian subalgebra of g0, i. e. its cartan subalgebra. elie cartan proved that every complex semisimple lie algebra g has a split real form, which is unique up to isomorphism. it has maximal index among all real forms. the split form corresponds to the satake diagram with no vertices blackened and no arrows. compact real form a real lie algebra g0 is called compact if the killing form is negative definite, i. e. the index of g0 is zero. in this case g0 = k0 is a compact lie algebra. it is known that under the lie correspondence, compact lie algebras correspond to compact lie groups. the compact form corresponds to the satake diagram with all vertices blackened. construction of the compact real form in general, the construction of the compact real form uses structure theory of semisimple lie algebras. for classical lie algebras there is a more explicit construction. let g0 be a real lie algebra of matrices over r that is closed under the transpose map, the complexification g of g0 decomposes into the direct sum of g0 and ig0. the real vector space of matrices is a subspace of the complex lie algebra g that is closed under the commutators and consists of skew - hermitian matrices. it follows that u0 is a real lie subalgebra of g, that its killing form is negative definite ( making it a compact lie algebra ), and that the complexification of u0 is g. therefore, u0 is a compact form of g. see also - helgason 1978, p. 426


hypothesis 1, 2, 3, 4, 5, 6 and 7 will be rejected. in variance analysis, at the significance 0. 05 is with n = 30. - ii. literature review the use of brainstorming brainstorming is a group creativity technique designed to generate a large number of ideas for the solution of a problem. in 1953 the method was popularized by alex faickney osborn in a book called applied imagination. osborn proposed that groups could double their creative output with brainstorming. oxford defined that brainstorming is a way of making a group of people all think about something at the same time, often in order to solve a problem or to create good ideas. brainstorming is the name given to a situation when a group of people meet to generate new ideas around a specific area of interest. using rules which remove inhibitions, people are able to think more freely and move into new areas of thought and so create numerous new ideas and solutions. the participants shout out ideas as they occur to them and then build on the ideas raised by others. all the ideas are noted down and are not criticized. only when the brainstorming session is over are the ideas evaluated. the other meaning of brainstorming is to brainstorm is to use a set of specific rules and techniques which encourage and spark off new ideas which would never have happened under normal circumstances. so there you have it : brainstorming will help you come up with new ideas. and not only will you come up with new ideas but you will do so with surprisingly little effort. brainstorming makes the generation of new ideas easy and is a tried - and - tested process. exactly what you apply brainstorming techniques to depends on what you want to achieve. you can apply them to develop new products, services and processes in your job, or you can apply them to develop your personal life. there are two models of brainstorming - traditional brainstorming the normal view of brainstorming is where a group of people sit in a room and shout out ideas as they occur to them. they are told to lose their inhibitions and that no ideas will be judged so that people are free to shout out any ideas at all without feeling uncomfortable. people should build on the ideas called out by other participants. the purpose of this is to gain as many ideas as possible for later analysis. out of the many ideas suggested there will be some of great value. because of the free - thinking environment, the session will help promote radical new ideas which break free from


decoupled mar 27, 2013 | 4. 9 / 5 ( 8 ) | 0 - sizing things up : the evolutionary neurobiology of scale invariance feb 28, 2013 | 4. 8 / 5 ( 10 ) | 14 classical and quantum mechanics via lie algebras apr 15, 2011 i ' d like to open a discussion thread for version 2 of the draft of my book ' ' classical and quantum mechanics via lie algebras ' ', available online at http : / / lanl. arxiv. org / abs / 0810. 1019, and for the... - more from physics forums - independent research more news stories no new human cases of the h7n9 virus have been recorded in china for a week, national health authorities said, for the first time since the outbreak began in march. diseases, conditions, syndromes 33 minutes ago | not rated yet | 0 a nobel prize - winning scientist tuesday played down " shock - horror scenarios " that a new virus strain will emerge with the potential to kill millions of people. diseases, conditions, syndromes 51 minutes ago | 5 / 5 ( 1 ) | 0 bacteria resistant to the antibiotic colistin are also commonly resistant to antimicrobial substances made by the human body, according to a study in mbio, the online open - access journal of the american society for microb... diseases, conditions, syndromes 5 hours ago | 5 / 5 ( 1 ) | 0 ( ap ) — federal investigators probing the hantavirus outbreak blamed for three deaths at yosemite national park recommend that design changes to tent cabins and other lodging run by private concessionaires first be reviewed... diseases, conditions, syndromes 11 hours ago | not rated yet | 0 a new diagnostic test for a worm infection that can lead to severe enlargement and deformities of the legs and genitals is far more sensitive than the currently used test, according to results of a field... diseases, conditions, syndromes 12 hours ago | not rated yet | 0 | ( medical xpress ) — a three - year multinational study has tracked and detailed the progression of huntington ' s disease ( hd ), predicting clinical decline in people carrying the hd gene more than 10 years before... 44 seconds ago | not rated yet | 0 1 hour ago | not rated yet | 0 | ( medical xpress ) — a research team, led by jeremy barr, a biology post - doctoral fellow, unveils a new


and applications, nasa / marshall space flight center, huntsville, alabama 35812 ; # department of chemical engineering, university of alabama in huntsville, huntsville, alabama 35899 ; § biochemistry department, michigan state university, east lansing, michigan 48825 ; and ¶ biophysics sd48, nasa / marshall space flight center, huntsville, alabama 35812 usa part of the challenge of macromolecular crystal growth for structure determination is obtaining crystals with a volume suitable for x - ray analysis. in this respect an understanding of the effect of solution conditions on macromolecule nucleation rates is advantageous. this study investigated the effects of supersaturation, temperature, and ph on the nucleation rate of tetragonal lysozyme crystals. batch crystallization plates were prepared at given solution concentrations and incubated at set temperatures over 1 week. the number of crystals per well with their size and axial ratios were recorded and correlated with solution conditions. crystal numbers were found to increase with increasing supersaturation and temperature. the most significant variable, however, was ph ; crystal numbers changed by two orders of magnitude over the ph range 4. 0 - 5. 2. crystal size also varied with solution conditions, with the largest crystals obtained at ph 5. 2. having optimized the crystallization conditions, we prepared a batch of crystals under the same initial conditions, and 50 of these crystals were analyzed by x - ray diffraction techniques. the results indicate that even under the same crystallization conditions, a marked variation in crystal properties exists. more space science headlines - nasa research on the web life and microgravity sciences and applications information from nasa hq on science in space microgravity research programs office headquartered at marshall space flight center microgravity news online version of nasa ' s latest in microgravity advancements, published quarterly. join our growing list of subscribers - sign up for our express news delivery and you will receive a mail message every time we post a new story!!! for more information, please contact : | dr. john m. horack, director of science communications curator : linda porter nasa official : m. frank rose


elements | blogs wednesday, september 7, 2011 is there oxygen in space? yes, this summer astronomers using the herschel telescope identified oxygen molecules in space. they found these molecules in the orion nebula, 1, 344 light years away. oxygen is the third most abundant element in the universe. until now, scientists have only seen individual oxygen atoms in space. we do not breathe individual oxygen atoms, but rather oxygen molecules. ( a molecule is a group of atoms banded together and it is the smallest unit of chemical compound that can take part in a chemical reaction. ) oxygen molecules make up 20 % of the air we breathe. scientists theorize that the oxygen molecules were locked up in water ice that... thursday, march 10, 2011 i ' m atoms ( scientific cover of jason mraz ' s i ' m yours ) here in chicago it has been gray for the last three weeks – no sun, just melting snow and rain. this song made our day. it has sunshine, great music and atoms! the lyrics include fabulous lines such as : “ atoms bond together to form molecules most of what ’ s surrounding me and you … ” this science verse has been set to the music of jason mraz ’ s “ i ’ m yours ”. this is a must watch! saturday, february 26, 2011 the deep carbon observatory here at supersmart carbon, we love learning about carbon. apparently, we are not alone. there is a project being launched called the deep carbon observatory that is being funded by the alfred p. sloan foundation. the purpose of this group is to study carbon deep inside the earth. carbon makes up somewhere from 0. 7 % to 3. 2 % of the earth ’ s elements. we know that there is carbon trapped under the earth ’ s crust, but we don ’ t know how much. the deep carbon observatory is going to study how much carbon there is in the earth and what happens to it. another question is what form is the... friday, february 25, 2011 where does gas come from? carbon! ( we always love it when the answer is carbon. ) the gas we use to power our cars comes from decomposing organic matter. what does that mean? all life has carbon in it - - this includes everything living from you and me to zebras, tapeworms, tulips and seaweed. since all living things have carbon in them, they are referred to as organic matter. non - organic matter includes things like rocks, water and metals. when something organic dies


so write it offline in an editor ( e. g., notepad ) and paste it in your little post box, viz. : from wikipedia, the free encyclopedia this article is about the general notion of determinism in philosophy. for other uses, see determinism ( disambiguation ). not to be confused with fatalism, predeterminism, or predictability. determinism is a metaphysical philosophical position stating that for everything that happens there are conditions such that, given those conditions, nothing else could happen. " there are many determinisms, depending upon what pre - conditions are considered to be determinative of an event. " determinism throughout the history of philosophy has sprung from diverse considerations, some of which overlap. some forms of determinism can be tested empirically with ideas stemming from physics and the philosophy of physics. the opposite of determinism is some kind of indeterminism ( otherwise called nondeterminism ). determinism is often contrasted with free will. determinism often is taken to mean simply causal determinism, that is, basing determinism upon the idea of cause - and - effect. it is the concept that events within a given paradigm are bound by causality in such a way that any state ( of an object or event ) is completely determined by prior states. this meaning can be distinguished from other varieties of determinism mentioned below. the introduction of " cause - and - effect " introduces unnecessary complications related to what is meant by a ' cause ' and how the presence of a ' cause ' might be established, the interpretation of which varies from one physical theory to another. these complications are avoided by a more general formulation based upon connections between ' events ' supplied by a theory : " a theory is deterministic if, and only if, given its state variables for some initial period, the theory logically determines a unique set of values for those variables for any other period. " — ernest nagel, alternative descriptions of physical state p. 292 this quote replaces the idea of ' cause - and - effect ' with that of ' logical implication ' according to one or another theory that connects events. in addition, an ' event ' is related by the theory itself to formalized states described using the parameters defined by that theory. thus, the details of interpretation are placed where they belong, fitted to the context in which the chosen theory applies. other debates often concern the scope of determined systems, with some maintaining that


to formalized states described using the parameters defined by that theory. thus, the details of interpretation are placed where they belong, fitted to the context in which the chosen theory applies. other debates often concern the scope of determined systems, with some maintaining that the entire universe ( or multiverse ) is a single determinate system and others identifying other more limited determinate systems. for example, using the definition of physical determinism above, the limitations of a theory to some particular domain of experience also limits the associated definition of ' determinism ' to that same domain. there are numerous historical debates involving many philosophical positions and varieties of determinism. they include debates concerning determinism and free will, technically denoted as compatibilistic ( allowing the two to coexist ) and incompatibilistic ( denying their coexistence is a possibility ). determinism should not be confused with self - determination of human actions by reasons, motives, and desires. determinism rarely requires that perfect prediction be practically possible – merely predictable in theory. many philosophical theories of determinism frame themselves with the idea that reality follows a sort of predetermined path causal determinism is " the idea that every event is necessitated by antecedent events and conditions together with the laws of nature ". however, causal determinism is a broad enough term to consider that " one ' s deliberations, choices, and actions will often be necessary links in the causal chain that brings something about. in other words, even though our deliberations, choices, and actions are themselves determined like everything else, it is still the case, according to causal determinism, that the occurrence or existence of yet other things depends upon our deliberating, choosing and acting in a certain way ". causal determinism proposes that there is an unbroken chain of prior occurrences stretching back to the origin of the universe. the relation between events may not be specified, nor the origin of that universe. causal determinists believe that there is nothing uncaused or self - caused. historical determinism ( a sort of path dependence ) can also be synonymous with causal determinism. nomological determinism ( sometimes called ' scientific ' determinism, although that is a misnomer ) is the most common form of causal determinism. it is the notion that the past and the present dictate the future entirely and necessarily by rigid natural laws, that every occurrence results inevitably from prior events. quantum mechanics and


misnomer ) is the most common form of causal determinism. it is the notion that the past and the present dictate the future entirely and necessarily by rigid natural laws, that every occurrence results inevitably from prior events. quantum mechanics and various interpretations thereof pose a serious challenge to this view. nomological determinism is sometimes illustrated by the thought experiment of laplace ' s demon. physical determinism holds holds that all physical events occur as described by physical laws. depending upon definitions, there is some room here for the view that not everything in the universe must be tied to some physical state, but that view is not usually emphasized by adherents of physical determinism because of the widely accepted scientific view that the operation of all physical systems ( often unnecessarily taken to mean everything ) can be explained entirely in physical terms, the assumed causal closure of physics. necessitarianism is very related to the causal determinism described above. it is a metaphysical principle that denies all mere possibility ; there is exactly one way for the world to be. leucippus claimed there were no uncaused events, and that everything occurs for a reason and by necessity. predeterminism is the idea that all events are determined in advance. the concept of predeterminism is often argued by invoking causal determinism, implying that there is an unbroken chain of prior occurrences stretching back to the origin of the universe. in the case of predeterminism, this chain of events has been pre - established, and human actions cannot interfere with the outcomes of this pre - established chain. predeterminism can be used to mean such pre - established causal determinism, in which case it is categorised as a specific type of determinism. it can also be used interchangeably with causal determinism - in the context of its capacity to determine future events. despite this, predeterminism is often considered as independent of causal determinism. the term predeterminism is also frequently used in the context of biology and hereditary, in which case it represents a form of biological determinism. fatalism is normally distinguished from " determinism ". fatalism is the idea that everything is fated to happen, so that humans have no control over their future. fate has arbitrary power, and need not follow any causal or otherwise deterministic laws. types of fatalism include hard theological determinism and the idea of predestination


the past, present, or future, are either true or false. note that one can support causal determinism without necessarily supporting logical determinism and vice versa ( depending on one ' s views on the nature of time, but also randomness ). the problem of free will is especially salient now with logical determinism : how can choices be free, given that propositions about the future already have a truth value in the present ( i. e. it is already determined as either true or false )? this is referred to as the problem of future contingents. adequate determinism focuses on the fact that, even without a full understanding of microscopic physics, we can predict the distribution of 1000 coin tosses often synonymous with logical determinism are the ideas behind spatio - temporal determinism or eternalism : the view of special relativity. j. j. c. smart, a proponent of this view, uses the term " tenselessness " to describe the simultaneous existence of past, present, and future. in physics, the " block universe " of hermann minkowski and albert einstein assumes that time is a fourth dimension ( like the three spatial dimensions ). in other words, all the other parts of time are real, like the city blocks up and down a street, although the order in which they appear depends on the driver ( see rietdijk – putnam argument ). adequate determinism is the idea that quantum indeterminacy can be ignored for most macroscopic events. this is because of quantum decoherence. random quantum events " average out " in the limit of large numbers of particles ( where the laws of quantum mechanics asymptotically approach the laws of classical mechanics ). stephen hawking explains a similar idea : he says that the microscopic world of quantum mechanics is one of determined probabilities. that is, quantum effects rarely alter the predictions of classical mechanics, which are quite accurate ( albeit still not perfectly certain ) at larger scales. something as large as an animal cell, then, would be " adequately determined " ( even in light of quantum indeterminacy ). nature and nurture interact in humans. a scientist looking at a sculpture after some time does not ask whether we are seeing the effects of the starting materials or environmental influences. although some of the above forms of determinism concern human behaviors and cognition, others frame themselves as an answer to the nature or nurture debate. they will suggest that one factor will entirely determine behavior. as scientific understanding has grown, however


science fair project encyclopedia the sampling frequency or sampling rate defines the number of samples per second taken from a continuous signal to make a discrete signal. the inverse of the sampling frequency is the sampling period or sampling time, which is the time between samples. the sampling frequency can only be applied to samplers in which each sample is periodically taken. there is no rule that limits a sampler from taking a sample at a non - periodic rate. if a signal has a bandwidth of 100 hz then to avoid aliasing the sampling frequency must be greater than 200 hz. in some cases, it is desirable to have a sampling frequency more than twice the bandwidth so that a digital filter can be used in exchange for a weaker analog anti - aliasing filter. this process is known as oversampling. in digital audio, common sampling rates are : - 8, 000 hz - telephone, adequate for human speech - 11, 025 hz - 22, 050 hz - radio - 44, 100 hz - compact disc - 48, 000 hz - digital sound used for films and professional audio - 96, 000 or 192, 400 hz - dvd - audio, some lpcm dvd audio tracks, bd - rom ( blu - ray disc ) audio tracks, and hd - dvd ( high - definition dvd ) audio tracks in digital video, which uses a ccd as the sensor, the sampling rate is defined the frame / field rate, rather than the notional pixel clock. all modern tv cameras use ccds, and the image sampling frequency is the repetition rate of the ccd integration period. - 13. 5 mhz - ccir 601, d1 video - continuous signal vs. discrete signal - digital control - sample and hold - sample ( signal ) - sampling ( information theory ) - signal ( information theory ) the contents of this article is licensed from www. wikipedia. org under the gnu free documentation license. click here to see the transparent copy and copyright details


the life - giving ideas of chemistry are not reducible to physics. or, if one tries to reduce them, they wilt at the edges, lose not only much of their meaning, but interest too. and, most importantly, they lose their chemical utility — their ability to relate seemingly disparate compounds to each other, their fecundity in inspiring new experiments. i ' m thinking of concepts such as the chemical bond, a functional group and the logic of substitution, aromaticity, steric effects, acidity and basicity, electronegativity and oxidation - reduction. as well as some theoretical ideas i ' ve been involved in personally — through - bond coupling, orbital symmetry control, the isolobal analogy. consider the notion of oxidation state. if you had to choose two words to epitomize the same - and - not - the - same nature of chemistry, would you not pick ferrous and ferric? the concept evolved at the end of the 19th century ( not without confusion with " valency " ), when the reality of ions in solution was established. as did a multiplicity of notations — ferrous iron is iron in an oxidation state of + 2 ( or is it 2 +? ) or fe ( ii ). schemes for assigning oxidation states ( sometimes called oxidation numbers ) adorn every introductory chemistry text. they begin with the indisputable : in compounds, the oxidation states of the most electronegative elements ( those that hold on most tightly to their valence electrons ), oxygen and fluorine for example, are – 2 and – 1, respectively. after that the rules grow ornate, desperately struggling to balance wide applicability with simplicity. the oxidation - state scheme had tremendous classificatory power ( for inorganic compounds, not organic ones ) from the beginning. think of the sky blue color of chromium ( ii ) versus the violet or green of chromium ( iii ) salts, the four distinctly colored oxidation states of vanadium. oliver sacks writes beautifully of the attraction of these colors for a boy starting out in chemistry. and not only boys. but there was more to oxidation states than just describing color. or balancing equations. chemistry is transformation. the utility of oxidation states dovetailed with the logic of oxidizing and reducing agents — molecules and ions that with ease removed or added electrons to other molecules. between electron transfer and proton transfer you have much of reaction chemistry. i want to tell you how this logic leads to quite


. people in the trade will recognize that i ' m talking about " mulliken population analysis " or " natural bond analysis " or richard bader ' s beautifully worked out scheme for dividing up space in a molecule. what about experiment? is there an observable that might gauge a charge on an atom? i think photoelectron spectroscopies ( esca or auger ) come the closest. here one measures the energy necessary to promote an inner - core electron to a higher level or to ionize it. atoms in different oxidation states do tend to group themselves at certain energies. but the theoretical framework that relates these spectra to charges depends on the same assumptions that bedevil the definition of a charge on an atom. an oxidation state bears little relation to the actual charge on the atom ( except in the interior of the sun, where ligands are gone, there is plenty of energy, and you can have iron in oxidation states up to + 26 ). this doesn ' t stop the occasional theoretician today from making a heap of a story when the copper in a formal cu ( iii ) complex comes out of a calculation bearing a charge of, say, + 0. 51. nor does it stop oxidation states from being just plain useful. many chemical reactions involve electron transfer, with an attendant complex of changes in chemical, physical and biological properties. oxidation state, a formalism and not a representation of the actual electron density at a metal center, is a wonderful way to " bookkeep " electrons in the course of a reaction. even if that electron, whether added or removed, spends a good part of its time on the ligands. but enough theory, or, as some of my colleagues would sigh, anthropomorphic platitudes. let ' s look at some beautiful chemistry of extreme oxidation states. incredible, but true recently, a young polish postdoctoral associate, wojciech grochala, led me to look with him at the chemical and theoretical design of novel high - temperature superconductors. we focused on silver ( ag ) fluorides ( f ) with silver in oxidation states ii and iii. the reasoning that led us there is described in our forthcoming paper. for now let me tell you about some chemistry that i learned in the process. i can only characterize this chemistry as incredible but true. ( some will say that i should have known about it, since it was hardly hidden, but the fact is i didn ' t. ) here is what ag ( ii


as teflon and kel - f, synthetic sapphire and platinum, manipulation of and physicochemical investigation of hf solutions in closed systems is now reasonably straightforward. " for this we must thank the pioneers in the field — generations of fluorine chemists, but especially bartlett and boris zemva of the university of ljubljana. bartlett reports the oxidation of agf2 to agf4 – ( as kagf4 ) using photochemical irradiation of f2 in anhydrous hf ( made less acidic by adding kf to the hf ). and zemva used kr2 + ( in krf2 ) to react with agf2 in anhydrous hf in the presence of xef6 to make xef5 + agf4 –. what a startling list of reagents! to appreciate the difficulty and the inspiration of this chemistry, one must look at the original papers, or at the informal letters of the few who have tried it. you can find some of neil bartlett ' s commentary in the article that wojciech and i wrote, and in an interview with him. charge it, please chemists are always changing things. how to tune the propensity of a given oxidation state to oxidize or reduce? one way to do it is by changing the charge on the molecule that contains the oxidizing or reducing center. the syntheses of the silver fluorides cited above contain some splendid examples of this strategy. let me use bartlett ' s words again, just explaining that " electronegativity " gauges in some rough way the tendency of an atom to hold on to electrons. ( high electronegativity means the electron is strongly held, low electronegativity that it is weakly held. ) it ' s easy to make a high oxidation state in an anion because an anion is electron - rich. the electronegativity is lower for a given oxidation state in an anion than it is in a neutral molecule. that in turn, is lower than it is in a cation. if i take silver and i expose it to fluorine in the presence of fluoride ion, in hf, and expose it to light to break of f2 to atoms, i convert the silver to silver ( iii ), agf4 -. this is easy because the ag ( iii ) is in an anion. i can then pass in boron trifluoride and precipitate silver


to atoms, i convert the silver to silver ( iii ), agf4 -. this is easy because the ag ( iii ) is in an anion. i can then pass in boron trifluoride and precipitate silver trifluoride, which is now a much more potent oxidizer than agf4 - because the electronegativity in the neutral agf3 is much higher than it is in the anion. if i can now take away a fluoride ion, and make a cation, i drive the electronegativity even further up. with such a cation, for example, agf2 +, i can steal the electron from ptf6 - and make ptf6.... this is an oxidation that even kr ( ii ) is unable to bring about. simple, but powerful reasoning. and it works. a world record? finally, a recent oxidation - state curiosity : what is the highest oxidation state one could get in a neutral molecule? pekka pyykko and coworkers suggest cautiously, but i think believably, that octahedral uo6, that is u ( xii ), may exist. there is evidence from other molecules that uranium 6p orbitals can get involved in bonding, which is what they would have to do in uo6. what wonderful chemistry has come — and still promises to come — from the imperfect logic of oxidation states! © roald hoffmann i am grateful to wojciech grochala, robert fay and debra rolison for corrections and comments. thanks to stan marcus for suggesting the title of this column.


quantum time waits for no quantum theory, also quantum mechanics, in physics, a theory based on using the concept of the quantum unit to describe the dynamic properties of subatomic particles and the interactions of matter and radiation. the foundation was laid by the german physicist max planck, who postulated in 1900 that energy can be emitted or absorbed by matter only in small, discrete units called quanta. fundamental to the development of quantum mechanics was the uncertainty principle, formulated by the german physicist werner heisenberg in 1927, which states that the position and momentum of a subatomic particle cannot be specified simultaneously. spectral lines of atomic hydrogen : when an electron makes a transition from one energy level to another, the electron emits a photon with a particular energy. these photons are then observed as emission lines using a spectroscope. the lyman series involves transitions to the lowest or ground state energy level. to the second energy level are called the balmer series. these transitions involve frequencies in the visible part of the spectrum. in this frequency range each transition is characterized by a in the 18th and 19th centuries, newtonian, or classical, mechanics appeared to provide a wholly accurate description of the motions of bodies — for example, planetary motion. in the late 19th and early 20th centuries, however, experimental findings raised doubts about the completeness of newtonian theory. among the newer observations were the lines that appear in the spectra of light emitted by heated gases, or gases in which electric discharges take place. model of the atom developed in the early 20th century by the english physicist ernest rutherford, in which negatively charged electrons circle a positive nucleus in orbits prescribed by newton ’ s laws of motion, scientists had also expected that the electrons would emit light over a broad frequency range, rather than in the narrow frequency ranges that form the lines in a spectrum. another puzzle for physicists was the coexistence of two theories of light : the corpuscular theory, which explains light as a stream of particles, and the wave theory, which views light as electromagnetic waves. a third problem was the absence of a molecular basis for in his book elementary principles in statistical mechanics ( 1902 ), the american mathematical physicist j. willard gibbs conceded the impossibility of framing a theory of molecular action that reconciled thermodynamics, radiation, and electrical phenomena as they were then understood. at the turn of the century, physicists did not yet clearly recognize that these and other difficulties in physics were in any way related. the first development that led to the solution of these difficulties


, radiation, and electrical phenomena as they were then understood. at the turn of the century, physicists did not yet clearly recognize that these and other difficulties in physics were in any way related. the first development that led to the solution of these difficulties was planck ’ s introduction of the concept of the quantum, as a result of physicists ’ studies of blackbody radiation during the closing years of the 19th century. ( the term blackbody refers to an ideal body or surface that absorbs all radiant energy without any reflection. ) a body at a moderately high temperature — a " red heat " — gives off most of its radiation in the low frequency ( red and infrared ) regions ; a body at a higher temperature — " white heat " — gives off comparatively more radiation in higher frequencies ( yellow, green, or blue ). during the 1890s physicists conducted detailed quantitative studies of these phenomena and expressed their results in a series of curves or graphs. the classical, or prequantum, theory predicted an altogether different set of curves from those actually observed. what planck did was to devise a mathematical formula that described the curves exactly ; he then deduced a physical hypothesis that could explain the formula. his hypothesis was that energy is radiated only in quanta of energy hu, where u is the frequency and h is the quantum action, now known as the next important developments in quantum mechanics were the work of german - born american physicist and nobel laureate albert einstein. he used planck ’ s concept of the quantum to explain certain properties of the photoelectric effect — an experimentally observed phenomenon in which electrons are emitted from metal surfaces when radiation falls on these surfaces. according to classical theory, the energy, as measured by the voltage of the emitted electrons, should be proportional to the intensity of the radiation. the energy of the electrons, however, was found to be independent of the intensity of radiation — which determined only the number of electrons emitted — and to depend solely on the frequency of the radiation. the higher the frequency of the incident radiation, the greater is the electron energy ; below a certain critical frequency no electrons are emitted. these facts were explained by einstein by assuming that a single quantum of radiant energy ejects a single electron from the metal. of the quantum is proportional to the frequency, and so the energy of the electron depends on the frequency. in 1911 rutherford established the existence of the atomic nucleus. he assumed, on the basis of experimental evidence obtained from the scattering of alpha particles by the nuclei of gold atoms, that every atom consists of a


the energy of the electron depends on the frequency. in 1911 rutherford established the existence of the atomic nucleus. he assumed, on the basis of experimental evidence obtained from the scattering of alpha particles by the nuclei of gold atoms, that every atom consists of a dense, positively charged nucleus, surrounded by negatively charged electrons revolving around the nucleus as planets revolve around the sun. electromagnetic theory developed by the british physicist james clerk maxwell unequivocally predicted that an electron revolving around a nucleus will continuously radiate electromagnetic energy until it has lost all its energy, and eventually will fall into the nucleus. thus, according to classical theory, an atom, as described by rutherford, is unstable. this difficulty led the danish physicist niels bohr, in 1913, to postulate that in an atom the classical theory does not hold, and that electrons move in fixed orbits. every change in orbit by the electron corresponds to the absorption or emission of a quantum of radiation. the application of bohr ’ s theory to atoms with more than one electron proved difficult. the mathematical equations for the next simplest atom, the helium atom, were solved during the 1910s and 1920s, but the results were not entirely in accordance with for more complex atoms, only approximate solutions of the equations are possible, and these are only partly concordant the french physicist louis victor de broglie suggested in 1924 that because electromagnetic waves show particle characteristics, particles should, in some cases, also exhibit wave properties. this prediction was verified experimentally within a few years by the american physicists clinton joseph davisson and lester halbert germer and the british physicist george paget thomson. that a beam of electrons scattered by a crystal produces a diffraction pattern characteristic of a wave ( see diffraction ). the wave concept of a particle led the austrian physicist erwin schrodinger to develop a so - called wave equation to describe the wave properties of a particle and, more specifically, the wave behavior of the electron in the hydrogen atom. although this differential equation was continuous and gave solutions for all points in space, the permissible solutions of the equation were restricted by certain conditions expressed by mathematical equations called eigenfunctions ( german eigen, " own " ). the schrodinger wave equation thus had only certain discrete solutions ; these solutions were mathematical expressions in which quantum numbers appeared as parameters. ( quantum numbers are integers developed in particle physics to give the magnitudes of certain characteristic quantities of particles or systems. ) schrodinger equation was solved for the hydrogen atom and


; these solutions were mathematical expressions in which quantum numbers appeared as parameters. ( quantum numbers are integers developed in particle physics to give the magnitudes of certain characteristic quantities of particles or systems. ) schrodinger equation was solved for the hydrogen atom and gave conclusions in substantial agreement with earlier quantum theory. moreover, it was solvable for the helium atom, which earlier theory had failed to explain adequately, and here also it was in agreement with experimental evidence. the solutions of the schrodinger equation also indicated that no two electrons could have the same four quantum numbers — that is, be in the same energy state. rule, which had already been established empirically by austro - american physicist and nobel laureate wolfgang pauli in 1925, is called the exclusion principle. what is matter in the 20th century, physicists discovered that matter behaved as both a wave and a particle. austrian physicist and nobel prize winner erwin schrodinger discussed this apparent paradox in a lecture in geneva, switzerland, in 1952. a condensed and translated version of his lecture appeared in scientific american the following what is matter? the wave - particle dualism afflicting modern physics is best resolved in favor of waves, believes the author, but there is no clear picture of matter on which physicists can agree fifty years ago science seemed on the road to a clear - cut answer to the ancient question which is the title of this article. it looked as if matter would be reduced at last to its ultimate building blocks — to certain submicroscopic but nevertheless tangible and measurable particles. but it proved to be less simple than that. today a physicist no longer can distinguish significantly between matter and something else. we no longer contrast matter with forces or fields of force as different entities ; we know now that these concepts must be merged. it is true that we speak of " empty " space ( i. e., space free of matter ), but space is never really empty, because even in the remotest voids of the universe there is always starlight — and that is matter. besides, space is filled with gravitational fields, and according to einstein gravity and inertia cannot very well be separated. thus the subject of this article is in fact the total picture of space - time reality as envisaged by physics. we have to admit that our conception of material reality today is more wavering and uncertain than it has been for a long time. we know a great many interesting details, learn new ones every week. but to construct a clear, easily comprehensible


have to admit that our conception of material reality today is more wavering and uncertain than it has been for a long time. we know a great many interesting details, learn new ones every week. but to construct a clear, easily comprehensible picture on which all physicists would agree — that is simply impossible. physics stands at a grave crisis of ideas. in the face of this crisis, many maintain that no objective picture of reality is possible. however, the optimists among us ( of whom i consider myself one ) look upon this view as a philosophical extravagance born of despair. we hope that the present fluctuations of thinking are only indications of an upheaval of old beliefs which in the end will lead to something better than the mess of formulas which today surrounds our subject. since the picture of matter that i am supposed to draw does not yet exist, since only fragments of it are visible, some parts of this narrative may be inconsistent with others. like cervantes ’ tale of sancho panza, who loses his donkey in one chapter but a few chapters later, thanks to the forgetfulness of the author, is riding the dear little animal again, our story has contradictions. we must start with the well - established concept that matter is composed of corpuscles or atoms, whose existence has been quite " tangibly " demonstrated by many beautiful experiments, and with max planck ’ s discovery that energy also comes in indivisible units, called quanta, which are supposed to be transferred abruptly from one carrier to another. but then sancho panza ’ s donkey will return. for i shall have to ask you to believe neither in corpuscles as permanent individuals nor in the suddenness of the transfer of an energy quantum. discreteness is present, but not in the traditional sense of discrete single particles, let alone in the sense of abrupt processes. discreteness arises merely as a structure from the laws governing the phenomena. these laws are by no means fully understood ; a probably correct analogue from the physics of palpable bodies is the way various partial tones of a bell derive from its shape and from the laws of elasticity to which, of themselves, nothing discontinuous adheres. the idea that matter is made up of ultimate particles was advanced as early as the fifth century b. c. by leucippus and democritus, who called these particles atoms. the corpuscular theory of matter was lifted to physical reality in the theory of gases developed during the 19th century by james clerk maxwell


as the fifth century b. c. by leucippus and democritus, who called these particles atoms. the corpuscular theory of matter was lifted to physical reality in the theory of gases developed during the 19th century by james clerk maxwell and ludwig boltzmann. the concept of atoms and molecules in violent motion, colliding and rebounding again and again, led to full comprehension of all the properties of gases : their elastic and thermal properties, their viscosity, heat conductivity and diffusion. at the same time it led to a firm foundation of the mechanical theory of heat, namely, that heat is the motion of these ultimate particles, which becomes increasingly violent with rising temperature. within one tremendously fertile decade at the turn of the century came the discoveries of x - rays, of electrons, of the emission of streams of particles and other forms of energy from the atomic nucleus by radioactive decay, of the electric charges on the various particles. the masses of these particles, and of the atoms themselves, were later measured very precisely, and from this was discovered the mass defect of the atomic nucleus as a whole. mass of a nucleus is less than the sum of the masses of its component particles ; the lost mass becomes the binding energy holding the nucleus firmly together. this is called the packing effect. the nuclear forces of course are not electrical forces — those are repellent — but are much stronger and act only within very short distances, about 10 - 13 centimeter. here i am already caught in a contradiction. didn ’ t i say at the beginning that we no longer assume the existence of force fields apart from matter? i could easily talk myself out of it by saying : well, the force field of a particle is simply considered a part of it. but that is not the fact. the established view today is rather that everything is at the same time both particle and field. everything has the continuous structure with which we are familiar in fields, as well as the discrete structure with which we are equally familiar in particles. this concept is supported by innumerable experimental facts and is accepted in general, though opinions differ on details, as we shall see. in the particular case of the field of nuclear forces, the particle structure is more or less known. most likely the continuous force field is represented by the so - called pi mesons. on the other hand, the protons and neutrons, which we think of as discrete particles, indisputably also have a continuous wave structure, as is shown by the interference patterns


field is represented by the so - called pi mesons. on the other hand, the protons and neutrons, which we think of as discrete particles, indisputably also have a continuous wave structure, as is shown by the interference patterns they form when diffracted by a crystal. the difficulty of combining these two so very different character traits in one mental picture is the main stumbling - block that causes our conception of matter to be so uncertain. neither the particle concept nor the wave concept is hypothetical. the tracks in a photographic emulsion or in a wilson cloud chamber leave no doubt of the behavior of particles as discrete units. the artificial production of nuclear particles is being attempted right now with terrific expenditure, defrayed in the main by the various state ministries of defense. it is true that one cannot kill anybody with one such racing particle, or else we should all be dead by now. but their study promises, indirectly, a hastened realization of the plan for the annihilation of mankind which is so close to all our you can easily observe particles yourself by looking at a luminous numeral of your wrist watch in the dark with a magnifying glass. the luminosity surges and undulates, just as a lake sometimes twinkles in the sun. the light consists of sparklets, each produced by a so - called alpha particle ( helium nucleus ) expelled by a radioactive atom which in this process is transformed into a different atom. a specific device for detecting and recording single particles is the geiger - muller counter. in this short resume i cannot possibly exhaust the many ways in which we can observe single particles. now to the continuous field or wave character of matter. wave structure is studied mainly by means of diffraction and interference — phenomena which occur when wave trains cross each other. for the analysis and measurement of light waves the principal device is the ruled grating, which consists of a great many fine, parallel, equidistant lines, closely engraved on a specular metallic light impinging from one direction is scattered by them and collected in different directions depending on its wavelength. but even the finest ruled gratings we can produce are too coarse to scatter the very much shorter waves associated with matter. the fine lattices of crystals, however, which max von laue first used as gratings to analyze the very short x - rays, will do the same for " matter waves. " directed at the surface of a crystal, high - velocity streams of particles manifest their wave nature. with crystal


max von laue first used as gratings to analyze the very short x - rays, will do the same for " matter waves. " directed at the surface of a crystal, high - velocity streams of particles manifest their wave nature. with crystal gratings physicists have diffracted and measured the wavelengths of electrons, neutrons and protons. what does planck ’ s quantum theory have to do with all this? planck told us in 1900 that he could comprehend the radiation from red - hot iron, or from an incandescent star such as the sun, only if this radiation was produced in discrete portions and transferred in such discrete quantities from one carrier to another ( e. g., from atom to this was extremely startling, because up to that time energy had been a highly abstract concept. five years later einstein told us that energy has mass and mass is energy ; in other words, that they are one and the same. now the scales begin to fall from our eyes : our dear old atoms, corpuscles, particles are planck ’ s energy quanta. the carriers of those quanta are themselves quanta. one gets dizzy. something quite fundamental must lie at the bottom of this, but it is not surprising that the secret is not yet understood. after all, the scales did not fall suddenly. it took 20 or 30 years. and perhaps they still have not fallen completely. the next step was not quite so far reaching, but important enough. by an ingenious and appropriate generalization of planck ’ s hypothesis niels bohr taught us to understand the line spectra of atoms and molecules and how atoms were composed of heavy, positively charged nuclei with light, negatively charged electrons revolving each small system — atom or molecule — can harbor only definite discrete energy quantities, corresponding to its nature or its constitution. in transition from a higher to a lower " energy level " it emits the excess energy as a radiation quantum of definite wavelength, inversely proportional to the quantum given off. this means that a quantum of given magnitude manifests itself in a periodic process of definite frequency which is directly proportional to the quantum ; the frequency equals the energy quantum divided by the famous planck ’ s constant, h. according to einstein a particle has the energy mc2, m being the mass of the particle and c the velocity of light. in 1925 louis de broglie drew the inference, which rather suggests itself, that a particle might have associated with it a wave process of frequency mc2 divided by h. the particle for which he postulated


particle and c the velocity of light. in 1925 louis de broglie drew the inference, which rather suggests itself, that a particle might have associated with it a wave process of frequency mc2 divided by h. the particle for which he postulated such a wave was the electron. within two years the " electron waves " required by his theory were demonstrated by the famous electron diffraction experiment of c. j. davisson and l. h. germer. this was the starting point for the cognition that everything — anything at all — is simultaneously particle and wave field. thus de broglie ’ s dissertation initiated our uncertainty about the nature of matter. both the particle picture and the wave picture have truth value, and we cannot give up either one or the other. but we do not know how to that the two pictures are connected is known in full generality with great precision and down to amazing details. but concerning the unification to a single, concrete, palpable picture opinions are so strongly divided that a great many deem it altogether impossible. i shall briefly sketch the connection. but do not expect that a uniform, concrete picture will emerge before you ; and do not blame the lack of success either on my ineptness in exposition or your own denseness — nobody has yet succeeded. one distinguishes two things in a wave. first of all, a wave has a front, and a succession of wave fronts forms a system of surfaces like the layers of an onion. you are familiar with the two - dimensional analogue of the beautiful wave circles that form on the smooth surface of a pond when a stone is thrown in. the second characteristic of a wave, less intuitive, is the path along which it travels — a system of imagined lines perpendicular to the wave fronts. these lines are known as the wave " normals " or " rays. " we can make the provisional assertion that these rays correspond to the trajectories of particles. indeed, if you cut a small piece out of a wave, approximately 10 or 20 wavelengths along the direction of propagation and about as much across, such a " wave packet " would actually move along a ray with exactly the same velocity and change of velocity as we might expect from a particle of this particular kind at this particular place, taking into account any force fields acting on the particle. here i falter. for what i must say now, though correct, almost contradicts this provisional assertion. although the behavior of the wave packet gives us a more or less intuitive picture of a particle,


any force fields acting on the particle. here i falter. for what i must say now, though correct, almost contradicts this provisional assertion. although the behavior of the wave packet gives us a more or less intuitive picture of a particle, which can be worked out in detail ( e. g., the momentum of a particle increases as the wavelength decreases ; the two are inversely proportional ), yet for many reasons we cannot take this intuitive picture quite seriously. for one thing, it is, after all, somewhat vague, the more so the greater the wavelength. for another, quite often we are dealing not with a small packet but with an extended wave. for still another, we must also deal with the important special case of very small " packelets " which form a kind of " standing wave " which can have no wave fronts or wave normals. one interpretation of wave phenomena which is extensively supported by experiments is this : at each position of a uniformly propagating wave train there is a twofold structural connection of interactions, which may be distinguished as " longitudinal " and " transversal. " the transversal structure is that of the wave fronts and manifests itself in diffraction and interference experiments ; the longitudinal structure is that of the wave normals and manifests itself in the observation of single particles. however, these concepts of longitudinal and transversal structures are not sharply defined and absolute, since the concepts of wave front and wave normal are not, the interpretation breaks down completely in the special case of the standing waves mentioned above. here the whole wave phenomenon is reduced to a small region of the dimensions of a single or very few wavelengths. you can produce standing water waves of a similar nature in a small basin if you dabble with your finger rather uniformly in its center, or else just give it a little push so that the water surface undulates. in this situation we are not dealing with uniform wave propagation ; what catches the interest are the normal frequencies of these standing waves. the water waves in the basin are an analogue of a wave phenomenon associated with electrons, which occurs in a region just about the size of the atom. the normal frequencies of the wave group washing around the atomic nucleus are universally found to be exactly equal to bohr ’ s atomic " energy levels " divided by planck ’ s constant h. thus the ingenious yet somewhat artificial assumptions of bohr ’ s model of the atom, as well as of the older quantum theory in general, are superseded by the far more natural idea of


energy levels " divided by planck ’ s constant h. thus the ingenious yet somewhat artificial assumptions of bohr ’ s model of the atom, as well as of the older quantum theory in general, are superseded by the far more natural idea of de broglie ’ s wave phenomenon. phenomenon forms the " body " proper of the atom. it takes the place of the individual pointlike electrons which in bohr ’ s model are supposed to swarm around the nucleus. such pointlike single particles are completely out of the question within the atom, and if one still thinks of the nucleus itself in this way one does so quite consciously for reasons of expediency. what seems to me particularly important about the discovery that " energy levels " are virtually nothing but the frequencies of normal modes of vibration is that now one can do without the assumption of sudden transitions, or quantum jumps, since two or more normal modes may very well be excited simultaneously. the discreteness of the normal frequencies fully suffices — so i believe — to support the considerations from which planck started and many similar and just as important ones — i mean, in short, to support all of quantum the theory of quantum jumps is becoming more and more unacceptable, at least to me personally, as the years go on. its abandonment has, however, far - reaching consequences. it means that one must give up entirely the idea of the exchange of energy in well - defined quanta and replace it with the concept of resonance between vibrational frequencies. yet we have seen that because of the identity of mass and energy, we must consider the particles themselves as planck ’ s energy quanta. this is at first frightening. for the substituted theory implies that we can no longer consider the individual particle as a well - defined permanent entity. that it is, in fact, no such thing can be reasoned in other ways. for one thing, there is werner heisenberg ’ s famous uncertainty principle, according to which a particle cannot simultaneously have a well - defined position and a sharply defined velocity. this uncertainty implies that we cannot be sure that the same particle could ever be observed twice. another conclusive reason for not attributing identifiable sameness to individual particles is that we must obliterate their individualities whenever we consider two or more interacting particles of the same kind, e. g., the two electrons of a helium atom. two situations which are distinguished only by the interchange of the two electrons must be counted as one and the same ; if they are counted as two equal situations,


particles of the same kind, e. g., the two electrons of a helium atom. two situations which are distinguished only by the interchange of the two electrons must be counted as one and the same ; if they are counted as two equal situations, nonsense obtains. this circumstance holds for any kind of particle in arbitrary numbers without exception. most theoreticians will probably accept the foregoing reasoning and admit that the individual particle is not a well - defined permanent entity of detectable identity or sameness. nevertheless this inadmissible concept of the individual particle continues to play a large role in their ideas and discussions. even deeper rooted is the belief in " quantum jumps, " which is now surrounded with a highly abstruse terminology whose common - sense meaning is often difficult for instance, an important word in the standing vocabulary of quantum theory is " probability, " referring to transition from one level to another. but, after all, one can speak of the probability of an event only assuming that, occasionally, it actually occurs. if it does occur, the transition must indeed be sudden, since intermediate stages are disclaimed. moreover, if it takes time, it might conceivably be interrupted halfway by an unforeseen disturbance. this possibility leaves one completely at sea. the wave v. corpuscle dilemma is supposed to be resolved by asserting that the wave field merely serves for the computation of the probability of finding a particle of given properties at a given position if one looks for it there. but once one deprives the waves of reality and assigns them only a kind of informative role, it becomes very difficult to understand the phenomena of interference and diffraction on the basis of the combined action of discrete single particles. it certainly seems easier to explain particle tracks in terms of waves than to explain the wave phenomenon in terms of corpuscles. " real existence " is, to be sure, an expression which has been virtually chased to death by many philosophical hounds. its simple, naive meaning has almost become lost to us. therefore i want to recall something else. i spoke of a corpuscle ’ s not being an individual. properly speaking, one never observes the same particle a second time — very much as heraclitus says of the river. you cannot mark an electron, you cannot paint it red. indeed, you must not even think of it as marked ; if you do, your " counting " will be false and you will get wrong results at every step — for the structure of line spectra, in thermod


you cannot paint it red. indeed, you must not even think of it as marked ; if you do, your " counting " will be false and you will get wrong results at every step — for the structure of line spectra, in thermodynamics and elsewhere. a wave, on the other hand, can easily be imprinted with an individual structure by which it can be recognized beyond doubt. think of the beacon fires that guide ships at sea. the light shines according to a definite code ; for example : three seconds light, five seconds dark, one second light, another pause of five seconds, and again light for three seconds — the skipper knows that is san sebastian. or you talk by wireless telephone with a friend across the atlantic ; as soon as he says, " hello there, edward meier speaking, " you know that his voice has imprinted on the radio wave a structure which can be distinguished from any other. but one does not have to go that far. if your wife calls, " francis! " from the garden, it is exactly the same thing, except that the structure is printed on sound waves and the trip is shorter ( though it takes somewhat longer than the journey of radio waves across the atlantic ). all our verbal communication is based on imprinted individual wave structures. and, according to the same principle, what a wealth of details is transmitted to us in rapid succession by the movie or the television picture! this characteristic, the individuality of the wave phenomenon, has already been found to a remarkable extent in the very much finer waves of particles. one example must suffice. a limited volume of gas, say helium, can be thought of either as a collection of many helium atoms or as a superposition of elementary wave trains of matter waves. both views lead to the same theoretical results as to the behavior of the gas upon heating, compression, and so on. when you attempt to apply certain somewhat involved enumerations to the gas, you must carry them out in different ways according to the mental picture with which you approach it. if you treat the gas as consisting of particles, then no individuality must be ascribed to them, as i said. if, however, you concentrate on the matter wave trains instead of on the particles, every one of the wave trains has a well - defined structure which is different from that of any other. it is true that there are many pairs of waves which are so similar to each other that they could change roles without any noticeable effect on the gas. but if


the wave trains has a well - defined structure which is different from that of any other. it is true that there are many pairs of waves which are so similar to each other that they could change roles without any noticeable effect on the gas. but if you should count the very many similar states formed in this way as merely a single one, the result would be quite wrong. in spite of everything we cannot completely banish the concepts of quantum jump and individual corpuscle from the vocabulary of physics. we still require them to describe many details of the structure of matter. how can one ever determine the weight of a carbon nucleus and of a hydrogen nucleus, each to the precision of several decimals, and detect that the former is somewhat lighter than the 12 hydrogen nuclei combined in it, without accepting for the time being the view that these particles are something quite concrete and real? this view is so much more convenient than the roundabout consideration of wave trains that we cannot do without it, just as the chemist does not discard his valence - bond formulas, although he fully realizes that they represent a drastic simplification of a rather involved wave - mechanical situation. if you finally ask me : " well, what are these corpuscles, really? " i ought to confess honestly that i am almost as little prepared to answer that as to tell where sancho panza ’ s second donkey came from. at the most, it may be permissible to say that one can think of particles as more or less temporary entities within the wave field whose form and general behavior are nevertheless so clearly and sharply determined by the laws of waves that many processes take place as if these temporary entities were substantial permanent beings. the mass and the charge of particles, defined with such precision, must then be counted among the structural elements determined by the wave laws. the conservation of charge and mass in the large must be considered as a statistical effect, based on the " law of large numbers. " simultaneously with the development of wave mechanics, heisenberg evolved a different mathematical analysis known as matrix mechanics. according to heisenberg ’ s theory, which was developed in collaboration with the german physicists max born and ernst pascual jordan, the formula was not a differential equation but a matrix : an array consisting of an infinite number of rows, each row consisting of an infinite number of quantities. matrix mechanics introduced infinite matrices to represent the position and momentum of an electron inside an atom. also, different matrices exist, one for each observable physical property associated with the motion of an electron,


each row consisting of an infinite number of quantities. matrix mechanics introduced infinite matrices to represent the position and momentum of an electron inside an atom. also, different matrices exist, one for each observable physical property associated with the motion of an electron, such as energy, position, momentum, and angular momentum. these matrices, like schrodinger ’ s differential equations, could be solved ; in other words, they could be manipulated to produce predictions as to the frequencies of the lines in the hydrogen spectrum and other observable quantities. like wave mechanics, matrix mechanics was in agreement with the earlier quantum theory for processes in which the earlier quantum theory agreed with experiment ; it was also useful in explaining phenomena that earlier quantum theory could not explain. schrodinger subsequently succeeded in showing that wave mechanics and matrix mechanics are different mathematical versions of the same theory, now called quantum mechanics. even for the simple hydrogen atom, which consists of two particles, both mathematical interpretations are extremely complex. the next simplest atom, helium, has three particles, and even in the relatively simple mathematics of classical dynamics, the three - body problem ( that of describing the mutual interactions of three separate bodies ) is not the energy levels can be calculated accurately, however, even if not exactly. in applying quantum - mechanics mathematics to relatively complex situations, a physicist can use one of a number of mathematical formulations. the choice depends on the convenience of the formulation for obtaining suitable although quantum mechanics describes the atom purely in terms of mathematical interpretations of observed phenomena, a rough verbal description can be given of what the atom is now thought to be like. surrounding the nucleus is a series of stationary waves ; these waves have crests at certain points, each complete standing wave representing an orbit. the absolute square of the amplitude of the wave at any point is a measure of the probability that an electron will be found at that point at any given time. thus, an electron can no longer be said to be at any precise point at any given time. the impossibility of pinpointing an electron at any precise time was analyzed by heisenberg, who in 1927 formulated the uncertainty principle. this principle states the impossibility of simultaneously specifying the precise position and momentum of any particle. in other words, the more accurately a particle ’ s momentum is measured and known, the less accuracy there can be in the measurement and knowledge of its position. this principle is also fundamental to the understanding of quantum mechanics as it is generally accepted today : the wave and particle character of electromagnetic radiation can be understood


momentum is measured and known, the less accuracy there can be in the measurement and knowledge of its position. this principle is also fundamental to the understanding of quantum mechanics as it is generally accepted today : the wave and particle character of electromagnetic radiation can be understood as two complementary properties of radiation. another way of expressing the uncertainty principle is that the wavelength of a quantum mechanical principle is inversely proportional to its momentum. as atoms are cooled they slow down and their corresponding wavelength grows larger. at a low enough temperature this wavelength is predicted to exceed the spacing between particles, causing atoms to overlap, becoming indistinguishable, and melding into a single quantum state. in 1995 a team of colorado scientists, led by national institutes of standards and technology physicist eric cornell and university of colorado physicist carl weiman, cooled rubidium atoms to a temperature so low that the particles entered this merged state, known as a bose - einstein condensate. the condensate essentially behaves like one atom even though it is made up of thousands. - physicists condense supercooled atoms, forming new state of matter a team of colorado physicists has cooled atoms of gas to a temperature so low that the particles entered a merged state, known as a " bose - einstein condensate. " this phenomenon was first predicted about 70 years ago by the theories of german - born american physicist albert einstein and indian physicist satyendra nath bose. the condensed particles are considered a new state of matter, different from the common states of matter — gas, liquid, and solid — and from plasma, a high temperature, ionized form of matter that is found in the sun and other stars. physicists have great expectations for the application of this discovery. because the condensate essentially behaves like one atom even though it is made up of thousands, investigators should be able to measure interactions at the atomic and subatomic level that were previously extremely difficult, if not impossible, to study the condensate was detected june 5 by a colorado team led by national institutes of standards and technology physicist eric cornell and university of colorado physicist carl wieman. their discovery was reported in the journal science on july 14. cornell and wieman formed their condensate from rubidium gas. several groups of physicists, including the teams in texas and colorado and a group at the massachusetts institute of technology, have been working to form pure condensate in recent years. the goal of the investigations has been to create a pure chunk of condensate out of atoms in