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inflationary scenario : the rapid expansion of the universe by an incredible factor of 10â50for the brief time from 10â35to about 10â32s | https://openstax.org/books/college-physics-2e/pages/34-glossary |
MACHOs : massive compact halo objects; microlensing objects of huge mass | https://openstax.org/books/college-physics-2e/pages/34-glossary |
microlensing : a process in which light from a distant star is focused and the star appears to brighten in a characteristic manner, when a small body (smaller than about 1/1000 the mass of the Sun) passes between us and the star | https://openstax.org/books/college-physics-2e/pages/34-glossary |
negatively curved : an open universe that expands forever | https://openstax.org/books/college-physics-2e/pages/34-glossary |
neutralinos : a type of WIMPs having masses several orders of magnitude greater than nucleon masses | https://openstax.org/books/college-physics-2e/pages/34-glossary |
neutrino oscillations : a process in which any type of neutrino could change spontaneously into any other | https://openstax.org/books/college-physics-2e/pages/34-glossary |
neutron stars : literally a star composed of neutrons | https://openstax.org/books/college-physics-2e/pages/34-glossary |
positively curved : a universe that is closed and eventually contracts | https://openstax.org/books/college-physics-2e/pages/34-glossary |
Quantum gravity : the theory that deals with particle exchange of gravitons as the mechanism for the force | https://openstax.org/books/college-physics-2e/pages/34-glossary |
quasars : the moderately distant galaxies that emit as much or more energy than a normal galaxy | https://openstax.org/books/college-physics-2e/pages/34-glossary |
Schwarzschild radius : the radius of the event horizon | https://openstax.org/books/college-physics-2e/pages/34-glossary |
spontaneous symmetry breaking : the transition from GUT to electroweak where the forces were no longer unified | https://openstax.org/books/college-physics-2e/pages/34-glossary |
Superconductors : materials with resistivity of zero | https://openstax.org/books/college-physics-2e/pages/34-glossary |
superforce : hypothetical unified force in TOE epoch | https://openstax.org/books/college-physics-2e/pages/34-glossary |
Superstring theory : a theory to unify gravity with the other three forces in which the fundamental particles are considered to act like one-dimensional vibrating strings | https://openstax.org/books/college-physics-2e/pages/34-glossary |
thought experiment : mental analysis of certain carefully and clearly defined situations to develop an idea | https://openstax.org/books/college-physics-2e/pages/34-glossary |
TOE epoch : before 10â43after the Big Bang | https://openstax.org/books/college-physics-2e/pages/34-glossary |
WIMPs : weakly interacting massive particles; chargeless leptons (non-baryonic matter) interacting negligibly with normal matter | https://openstax.org/books/college-physics-2e/pages/34-glossary |
Cosmology is the study of the character and evolution of the universe. | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
The two most important features of the universe are the cosmological red shifts of its galaxies being proportional to distance and its cosmic microwave background (CMBR). Both support the notion that there was a gigantic explosion, known as the Big Bang that created the universe. | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
Galaxies farther away than our local group have, on an average, a recessional velocity given byv=H0d,v=H0d,whereddis the distance to the galaxy andH0H0is the Hubble constant, taken to have the average valueH0=20 km/sâMly.H0=20 km/sâMly. | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
whereddis the distance to the galaxy andH0H0is the Hubble constant, taken to have the average valueH0=20 km/sâMly.H0=20 km/sâMly. | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
Explanations of the large-scale characteristics of the universe are intimately tied to particle physics. | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
The dominance of matter over antimatter and the smoothness of the CMBR are two characteristics that are tied to particle physics. | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
The epochs of the universe are known back to very shortly after the Big Bang, based on known laws of physics. | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
The earliest epochs are tied to the unification of forces, with the electroweak epoch being partially understood, the GUT epoch being speculative, and the TOE epoch being highly speculative since it involves an unknown single superforce. | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
The transition from GUT to electroweak is called spontaneous symmetry breaking. It released energy that caused the inflationary scenario, which in turn explains the smoothness of the CMBR. | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
Einsteinâs theory of general relativityincludes accelerated frames and, thus, encompasses special relativity and gravity. Created by use of careful thought experiments, it has been repeatedly verified by real experiments. | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
One direct result of this behavior of nature is the gravitational lensingof light by massive objects, such as galaxies, also seen in the microlensingof light by smaller bodies in our galaxy. | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
Another prediction is the existence of black holes, objects for which the escape velocity is greater than the speed of light and from which nothing can escape. | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
The event horizonis the distance from the object at which the escape velocity equals the speed of lightcc. It is called the Schwarzschild radiusRSRSand is given byRS=2GMc2,RS=2GMc2,whereGGis the universal gravitational constant, andMMis the mass of the body. | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
whereGGis the universal gravitational constant, andMMis the mass of the body. | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
Physics is unknown inside the event horizon, and the possibility of wormholes and time travel are being studied. | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
Candidates for black holes may power the extremely energetic emissions of quasars, distant objects that seem to be early stages of galactic evolution. | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
Neutron starsare stellar remnants, having the density of a nucleus, that hint that black holes could form from supernovas, too. | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
Gravitational waves are wrinkles in space, predicted by general relativity but not yet observed, caused by changes in very massive objects. | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
Quantum gravityis an incompletely developed theory that strives to include general relativity, quantum mechanics, and unification of forces (thus, a TOE). | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
One unconfirmed connection between general relativity and quantum mechanics is the prediction of characteristic radiation from just outside black holes. | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
Superstring theory holds that fundamental particles are one-dimensional vibrations analogous to those on strings and is an attempt at a theory of quantum gravity. | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
Dark matteris non-luminous matter detected in and around galaxies and galactic clusters. | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
It may be 10 times the mass of the luminous matter in the universe, and its amount may determine whether the universe is open or closed (expands forever or eventually stops). | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
The determining factor is the critical densityof the universe and the cosmological constant, a theoretical construct intimately related to the expansion and closure of the universe. | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
The critical densityÏcis the density needed to just halt universal expansion. It is estimated to be approximately 10â26kg/m3. | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
An open universe is negatively curved, a closed universe is positively curved, whereas a universe with exactly the critical density is flat. | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
Dark matterâs composition is a major mystery, but it may be due to the suspected mass of neutrinos or a completely unknown type of leptonic matter. | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
If neutrinos have mass, they will change families, a process known as neutrino oscillations, for which there is growing evidence. | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
Complexity is an emerging field, rooted primarily in physics, that considers complex adaptive systems and their evolution, including self-organization. | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
Complexity has applications in physics and many other disciplines, such as biological evolution. | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
Chaos is a field that studies systems whose properties depend extremely sensitively on some variables and whose evolution is impossible to predict. | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
Chaotic systems may be simple or complex. | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
Studies of chaos have led to methods for understanding and predicting certain chaotic behaviors. | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
High-temperature superconductors are materials that become superconducting at temperatures well above a few kelvin. | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
The critical temperatureTcTcis the temperature below which a material is superconducting. | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
Some high-temperature superconductors have verifiedTcTcs above 125 K, and there are reports ofTcTcs as high as 250 K. | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
On the largest scale, the questions which can be asked may be about dark matter, dark energy, black holes, quasars, and other aspects of the universe. | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
On the intermediate scale, we can query about gravity, phase transitions, nonlinear phenomena, high-TcTcsuperconductors, and magnetic effects on materials. | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
On the smallest scale, questions may be about quarks and leptons, fundamental forces, stability of protons, and existence of monopoles. | https://openstax.org/books/college-physics-2e/pages/34-section-summary |
Percent uncertainty = δ A A à 100 % Percent uncertainty = δ A A à 100 % | https://openstax.org/books/university-physics-volume-1/pages/1-key-equations |
accuracy : the degree to which a measured value agrees with an accepted reference value for that measurement | https://openstax.org/books/university-physics-volume-1/pages/1-key-terms |
base quantity : physical quantity chosen by convention and practical considerations such that all other physical quantities can be expressed as algebraic combinations of them | https://openstax.org/books/university-physics-volume-1/pages/1-key-terms |
base unit : standard for expressing the measurement of a base quantity within a particular system of units; defined by a particular procedure used to measure the corresponding base quantity | https://openstax.org/books/university-physics-volume-1/pages/1-key-terms |
conversion factor : a ratio that expresses how many of one unit are equal to another unit | https://openstax.org/books/university-physics-volume-1/pages/1-key-terms |
derived quantity : physical quantity defined using algebraic combinations of base quantities | https://openstax.org/books/university-physics-volume-1/pages/1-key-terms |
derived units : units that can be calculated using algebraic combinations of the fundamental units | https://openstax.org/books/university-physics-volume-1/pages/1-key-terms |
dimension : expression of the dependence of a physical quantity on the base quantities as a product of powers of symbols representing the base quantities; in general, the dimension of a quantity has the formLaMbTcIdÎeNfJgLaMbTcIdÎeNfJgfor some powers a, b, c, d, e, f, and g. | https://openstax.org/books/university-physics-volume-1/pages/1-key-terms |
dimensionally consistent : equation in which every term has the same dimensions and the arguments of any mathematical functions appearing in the equation are dimensionless | https://openstax.org/books/university-physics-volume-1/pages/1-key-terms |
dimensionless : quantity with a dimension ofL0M0T0I0Î0N0J0=1;L0M0T0I0Î0N0J0=1;also called quantity of dimension 1 or a pure number | https://openstax.org/books/university-physics-volume-1/pages/1-key-terms |
discrepancy : the difference between the measured value and a given standard or expected value | https://openstax.org/books/university-physics-volume-1/pages/1-key-terms |
English units : system of measurement used in the United States; includes units of measure such as feet, gallons, and pounds | https://openstax.org/books/university-physics-volume-1/pages/1-key-terms |
estimation : using prior experience and sound physical reasoning to arrive at a rough idea of a quantityâs value; sometimes called an âorder-of-magnitude approximation,â a âguesstimate,â a âback-of-the-envelope calculationâ, or a âFermi calculationâ | https://openstax.org/books/university-physics-volume-1/pages/1-key-terms |
kilogram : SI unit for mass, abbreviated kg | https://openstax.org/books/university-physics-volume-1/pages/1-key-terms |
law : description, using concise language or a mathematical formula, of a generalized pattern in nature supported by scientific evidence and repeated experiments | https://openstax.org/books/university-physics-volume-1/pages/1-key-terms |
meter : SI unit for length, abbreviated m | https://openstax.org/books/university-physics-volume-1/pages/1-key-terms |
method of adding percents : the percent uncertainty in a quantity calculated by multiplication or division is the sum of the percent uncertainties in the items used to make the calculation. | https://openstax.org/books/university-physics-volume-1/pages/1-key-terms |
metric system : system in which values can be calculated in factors of 10 | https://openstax.org/books/university-physics-volume-1/pages/1-key-terms |
model : representation of something often too difficult (or impossible) to display directly | https://openstax.org/books/university-physics-volume-1/pages/1-key-terms |
order of magnitude : the size of a quantity as it relates to a power of 10 | https://openstax.org/books/university-physics-volume-1/pages/1-key-terms |
percent uncertainty : the ratio of the uncertainty of a measurement to the measured value, expressed as a percentage | https://openstax.org/books/university-physics-volume-1/pages/1-key-terms |
physical quantity : characteristic or property of an object that can be measured or calculated from other measurements | https://openstax.org/books/university-physics-volume-1/pages/1-key-terms |
physics : science concerned with describing the interactions of energy, matter, space, and time; especially interested in what fundamental mechanisms underlie every phenomenon | https://openstax.org/books/university-physics-volume-1/pages/1-key-terms |
precision : the degree to which repeated measurements agree with each other | https://openstax.org/books/university-physics-volume-1/pages/1-key-terms |
second : the SI unit for time, abbreviated s | https://openstax.org/books/university-physics-volume-1/pages/1-key-terms |
SI units : the international system of units that scientists in most countries have agreed to use; includes units such as meters, liters, and grams | https://openstax.org/books/university-physics-volume-1/pages/1-key-terms |
significant figures : used to express the precision of a measuring tool used to measure a value | https://openstax.org/books/university-physics-volume-1/pages/1-key-terms |
theory : testable explanation for patterns in nature supported by scientific evidence and verified multiple times by various groups of researchers | https://openstax.org/books/university-physics-volume-1/pages/1-key-terms |
uncertainty : a quantitative measure of how much measured values deviate from one another | https://openstax.org/books/university-physics-volume-1/pages/1-key-terms |
units : standards used for expressing and comparing measurements | https://openstax.org/books/university-physics-volume-1/pages/1-key-terms |
Physics is about trying to find the simple laws that describe all natural phenomena. | https://openstax.org/books/university-physics-volume-1/pages/1-summary |
Physics operates on a vast range of scales of length, mass, and time. Scientists use the concept of the order of magnitude of a number to track which phenomena occur on which scales. They also use orders of magnitude to compare the various scales. | https://openstax.org/books/university-physics-volume-1/pages/1-summary |
Scientists attempt to describe the world by formulating models, theories, and laws. | https://openstax.org/books/university-physics-volume-1/pages/1-summary |
Systems of units are built up from a small number of base units, which are defined by accurate and precise measurements of conventionally chosen base quantities. Other units are then derived as algebraic combinations of the base units. | https://openstax.org/books/university-physics-volume-1/pages/1-summary |
Two commonly used systems of units are English units and SI units. All scientists and most of the other people in the world use SI, whereas nonscientists in the United States still tend to use English units. | https://openstax.org/books/university-physics-volume-1/pages/1-summary |
The SI base units of length, mass, and time are the meter (m), kilogram (kg), and second (s), respectively. | https://openstax.org/books/university-physics-volume-1/pages/1-summary |
SI units are a metric system of units, meaning values can be calculated by factors of 10. Metric prefixes may be used with metric units to scale the base units to sizes appropriate for almost any application. | https://openstax.org/books/university-physics-volume-1/pages/1-summary |
To convert a quantity from one unit to another, multiply by conversion factors in such a way that you cancel the units you want to get rid of and introduce the units you want to end up with. | https://openstax.org/books/university-physics-volume-1/pages/1-summary |
Be careful with areas and volumes. Units obey the rules of algebra so, for example, if a unit is squared we need two factors to cancel it. | https://openstax.org/books/university-physics-volume-1/pages/1-summary |
The dimension of a physical quantity is just an expression of the base quantities from which it is derived. | https://openstax.org/books/university-physics-volume-1/pages/1-summary |
All equations expressing physical laws or principles must be dimensionally consistent. This fact can be used as an aid in remembering physical laws, as a way to check whether claimed relationships between physical quantities are possible, and even to derive new physical laws. | https://openstax.org/books/university-physics-volume-1/pages/1-summary |
An estimate is a rough educated guess at the value of a physical quantity based on prior experience and sound physical reasoning. Some strategies that may help when making an estimate are as follows:Get big lengths from smaller lengths.Get areas and volumes from lengths.Get masses from volumes and densities.If all else... | https://openstax.org/books/university-physics-volume-1/pages/1-summary |
Get big lengths from smaller lengths. | https://openstax.org/books/university-physics-volume-1/pages/1-summary |
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