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Stoney Units
In physics, the Stoney units form a system of units named after the Irish physicist George Johnstone Stoney, who first proposed them in 1874 (but published only in 1881). They are the earliest example of natural units, i.e., a coherent set of units of measurement designed so that chosen physical constants fully define and are included in the set. Units The constants that Stoney used to define his set of units is the following: * , the speed of light in vacuum, * , the gravitational constant, * , the Coulomb constant, * , the charge of the electron. Later authors typically replace the Coulomb constant with . This means that the numerical values of all these constants, when expressed in coherent Stoney units, is equal to one: \begin c &= 1\ l_\text \cdot t_\text^ \\ G &= 1\ l_\text^3 \cdot t_\text^ \cdot m_\text^ \\ k_\text &= 1\ l_\text^3 \cdot t_\text^ \cdot m_\text \cdot q_\text^\\ e &= 1\ q_\text \end In Stoney units, the numerical value of the reduced Planck constant is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Physics
Physics is the scientific study of matter, its Elementary particle, fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which relates to the order of nature, or, in other words, to the regular succession of events." It is one of the most fundamental scientific disciplines. "Physics is one of the most fundamental of the sciences. Scientists of all disciplines use the ideas of physics, including chemists who study the structure of molecules, paleontologists who try to reconstruct how dinosaurs walked, and climatologists who study how human activities affect the atmosphere and oceans. Physics is also the foundation of all engineering and technology. No engineer could design a flat-screen TV, an interplanetary spacecraft, or even a better mousetrap without first understanding the basic laws of physics. (...) You will come to see physics as a towering achievement of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Standard Temperature And Pressure
Standard temperature and pressure (STP) or standard conditions for temperature and pressure are various standard sets of conditions for experimental measurements used to allow comparisons to be made between different sets of data. The most used standards are those of the International Union of Pure and Applied Chemistry (IUPAC) and the National Institute of Standards and Technology (NIST), although these are not universally accepted. Other organizations have established a variety of other definitions. In industry and commerce, the standard conditions for temperature and pressure are often necessary for expressing the volumes of gases and liquids and related quantities such as the rate of volumetric flow (the volumes of gases vary significantly with temperature and pressure): standard cubic meters per second (Sm3/s), and normal cubic meters per second (Nm3/s). Many technical publications (books, journals, advertisements for equipment and machinery) simply state "standard cond ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Natural Units
In physics, natural unit systems are measurement systems for which selected physical constants have been set to 1 through nondimensionalization of physical units. For example, the speed of light may be set to 1, and it may then be omitted, equating mass and energy directly rather than using as a conversion factor in the typical mass–energy equivalence equation . A purely natural system of units has all of its dimensions collapsed, such that the physical constants completely define the system of units and the relevant physical laws contain no conversion constants. While natural unit systems simplify the form of each equation, it is still necessary to keep track of the non-collapsed dimensions of each quantity or expression in order to reinsert physical constants (such dimensions uniquely determine the full formula). Systems of natural units Summary table where: * is the fine-structure constant ( ≈ 0.007297) * ≈ * ≈ * A dash (—) indicates where the system ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dirac Large Numbers Hypothesis
The Dirac large numbers hypothesis (LNH) is an observation made by Paul Dirac in 1937 relating ratios of size scales in the Universe to that of force scales. The ratios constitute very large, dimensionless numbers: some Orders of magnitude (numbers)#1039, 40 orders of magnitude in the present cosmological epoch. According to Dirac's hypothesis, the apparent similarity of these ratios might not be a mere coincidence but instead could imply a physical cosmology, cosmology with these unusual features: *The strength of gravity, as represented by the gravitational constant, is inversely proportional to the age of the universe: G \propto 1/t\, *The mass of the universe is proportional to the square of the universe's age: M \propto t^2. *Physical constants are actually not constant. Their values depend on the age of the Universe. Stated in another way, the hypothesis states that all very large dimensionless quantities occurring in fundamental physics should be simply related to a single v ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hermann Weyl
Hermann Klaus Hugo Weyl (; ; 9 November 1885 – 8 December 1955) was a German mathematician, theoretical physicist, logician and philosopher. Although much of his working life was spent in Zürich, Switzerland, and then Princeton, New Jersey, he is associated with the University of Göttingen tradition of mathematics, represented by Carl Friedrich Gauss, David Hilbert and Hermann Minkowski. His research has had major significance for theoretical physics as well as purely mathematical disciplines such as number theory. He was one of the most influential mathematicians of the twentieth century, and an important member of the Institute for Advanced Study during its early years. Weyl contributed to an exceptionally wide range of fields, including works on space, time, matter, philosophy, logic, symmetry and the history of mathematics. He was one of the first to conceive of combining general relativity with the laws of electromagnetism. Freeman Dyson wrote that Weyl alone bore comp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Unified Theory
Unified Theory, previously Luma, were an American rock band from Seattle, Washington, formed in 1998. The lineup consisted of Chris Shinn (lead vocals, rhythm guitar), formerly of Celia Green, former Blind Melon members Christopher Thorn (lead guitar) and Brad Smith (bass) as well as Dave Krusen (drums) formerly of Pearl Jam. Following the death of singer Shannon Hoon in 1995, former Blind Melon members Christopher Thorn and Brad Smith moved to Seattle and began working on a new project. This project was put on hold following Thorn's move to Los Angeles. However, after meeting former Celia Green singer Chris Shinn, they regrouped with Smith in Seattle and, with the addition of former Pearl Jam drummer Dave Krusen, formed Luma in 1998. The following year, they released a self-titled EP before renaming themselves Unified Theory, after Albert Einstein's unified field theory, releasing their self-titled debut album in 2000. Unified Theory toured in support of their album and beg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Planck Scale
In particle physics and physical cosmology, Planck units are a system of units of measurement defined exclusively in terms of four universal physical constants: '' c'', '' G'', '' ħ'', and ''k''B (described further below). Expressing one of these physical constants in terms of Planck units yields a numerical value of 1. They are a system of natural units, defined using fundamental properties of nature (specifically, properties of free space) rather than properties of a chosen prototype object. Originally proposed in 1899 by German physicist Max Planck, they are relevant in research on unified theories such as quantum gravity. The term Planck scale refers to quantities of space, time, energy and other units that are similar in magnitude to corresponding Planck units. This region may be characterized by particle energies of around or , time intervals of around and lengths of around (approximately the energy-equivalent of the Planck mass, the Planck time and the Planck len ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
String Theory
In physics, string theory is a theoretical framework in which the point-like particles of particle physics are replaced by one-dimensional objects called strings. String theory describes how these strings propagate through space and interact with each other. On distance scales larger than the string scale, a string acts like a particle, with its mass, charge, and other properties determined by the vibrational state of the string. In string theory, one of the many vibrational states of the string corresponds to the graviton, a quantum mechanical particle that carries the gravitational force. Thus, string theory is a theory of quantum gravity. String theory is a broad and varied subject that attempts to address a number of deep questions of fundamental physics. String theory has contributed a number of advances to mathematical physics, which have been applied to a variety of problems in black hole physics, early universe cosmology, nuclear physics, and condensed matter ph ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quantum Gravity
Quantum gravity (QG) is a field of theoretical physics that seeks to describe gravity according to the principles of quantum mechanics. It deals with environments in which neither gravitational nor quantum effects can be ignored, such as in the vicinity of black holes or similar compact astrophysical objects, as well as in the early stages of the universe moments after the Big Bang. Three of the four fundamental forces of nature are described within the framework of quantum mechanics and quantum field theory: the Electromagnetism, electromagnetic interaction, the Strong interaction, strong force, and the Weak interaction, weak force; this leaves gravity as the only interaction that has not been fully accommodated. The current understanding of gravity is based on Albert Einstein's general theory of relativity, which incorporates his theory of special relativity and deeply modifies the understanding of concepts like time and space. Although general relativity is highly regarded for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Planck Constant
The Planck constant, or Planck's constant, denoted by h, is a fundamental physical constant of foundational importance in quantum mechanics: a photon's energy is equal to its frequency multiplied by the Planck constant, and the wavelength of a matter wave equals the Planck constant divided by the associated particle momentum. The constant was postulated by Max Planck in 1900 as a proportionality constant needed to explain experimental black-body radiation. Planck later referred to the constant as the "quantum of Action (physics), action". In 1905, Albert Einstein associated the "quantum" or minimal element of the energy to the electromagnetic wave itself. Max Planck received the 1918 Nobel Prize in Physics "in recognition of the services he rendered to the advancement of Physics by his discovery of energy quanta". In metrology, the Planck constant is used, together with other constants, to define the kilogram, the SI unit of mass. The SI units are defined in such a way that, w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Planck Units
In particle physics and physical cosmology, Planck units are a system of units of measurement defined exclusively in terms of four universal physical constants: ''Speed of light, c'', ''Gravitational constant, G'', ''Reduced Planck constant, ħ'', and Boltzmann constant, ''k''B (described further below). Expressing one of these physical constants in terms of Planck units yields a numerical value of 1 (number), 1. They are a system of natural units, defined using fundamental properties of Nature#Matter and energy, nature (specifically, properties of vacuum, free space) rather than properties of a chosen Prototype (metrology), prototype object. Originally proposed in 1899 by German physicist Max Planck, they are relevant in research on unified theories such as quantum gravity. The term Planck scale refers to quantities of space, time, energy and other units that are similar in magnitude to corresponding Planck units. This region may be characterized by particle energy, energies of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
