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Zero-energy Universe
The zero-energy universe hypothesis proposes that the total amount of energy in the universe is exactly zero: its amount of positive energy in the form of matter is exactly canceled out by its negative energy in the form of gravity. Some physicists, such as Lawrence Krauss, Stephen Hawking or Alexander Vilenkin, call or called this state "a universe from nothingness", although the zero-energy universe model requires both a matter field with positive energy and a gravitational field with negative energy to exist. The hypothesis is broadly discussed in popular sources. Edward P. Tryon, "Is the Universe a Vacuum Fluctuation?", ''Nature'', vol. 246, p.396–397, 1973. Other cancellation examples include the expected symmetric prevalence of right- and left-handed angular momenta of objects ("spin" in the common sense), the observed flatness of the universe, the equal prevalence of positive and negative charges, opposing particle spin in quantum mechanics, as well as the crests and tro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Energy
In physics, energy (from Ancient Greek: ἐνέργεια, ''enérgeia'', “activity”) is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of heat and light. Energy is a conserved quantity—the law of conservation of energy states that energy can be converted in form, but not created or destroyed. The unit of measurement for energy in the International System of Units (SI) is the joule (J). Common forms of energy include the kinetic energy of a moving object, the potential energy stored by an object (for instance due to its position in a field), the elastic energy stored in a solid object, chemical energy associated with chemical reactions, the radiant energy carried by electromagnetic radiation, and the internal energy contained within a thermodynamic system. All living organisms constantly take in and release energy. Due to mass–energy equivalence, any object th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Edward Tryon
Edward P. Tryon (September 4, 1940 – December 11, 2019) was an American scientist and a professor emeritus of physics at Hunter College of the City University of New York (CUNY). He was the first physicist to propose that our universe originated as a quantum fluctuation of the vacuum. Early life Tryon was born and raised in Terre Haute, Indiana.gribbin, p.303 He took his first physics course in his junior year at Wiley High School. Academia and intellectual influences Tryon entered Cornell University in 1958. He was influenced by Nobel Laureate Hans Bethe, who was one of his professors. He was especially affected by advice that Bethe gave him: "Our intuition is based on our experiences in the macroscopic world. There is no reason to expect our intuition to be valid for microscopic phenomena." He graduated from Cornell University in 1962, earning a bachelor's degree in physics. He would then go on to do his graduate work at the University of California, Berkeley. There he was v ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Physical Cosmology
Physical cosmology is a branch of cosmology concerned with the study of cosmological models. A cosmological model, or simply cosmology, provides a description of the largest-scale structures and dynamics of the universe and allows study of fundamental questions about its origin, structure, evolution, and ultimate fate.For an overview, see Cosmology as a science originated with the Copernican principle, which implies that celestial bodies obey identical physical laws to those on Earth, and Newtonian mechanics, which first allowed those physical laws to be understood. Physical cosmology, as it is now understood, began with the development in 1915 of Albert Einstein's general theory of relativity, followed by major observational discoveries in the 1920s: first, Edwin Hubble discovered that the universe contains a huge number of external galaxies beyond the Milky Way; then, work by Vesto Slipher and others showed that the universe is expanding. These advances made it possible ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
False Vacuum
In quantum field theory, a false vacuum is a hypothetical vacuum that is relatively stable, but not in the most stable state possible. This condition is known as metastable. It may last for a very long time in that state, but could eventually decay to the more stable state, an event known as false vacuum decay. The most common suggestion of how such a decay might happen in our universe is called bubble nucleation – if a small region of the universe by chance reached a more stable vacuum, this "bubble" (also called "bounce") would spread. A false vacuum exists at a local minimum of energy and is therefore not completely stable, in contrast to a true vacuum, which exists at a global minimum and is stable. Definition of true vs. false vacuum A vacuum is defined as a space with as little energy in it as possible. Despite the name, the vacuum still has quantum fields. A true vacuum is stable because it is at a global minimum of energy, and is commonly assumed to coincide with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
A Universe From Nothing
''A Universe from Nothing: Why There Is Something Rather than Nothing'' is a non-fiction book by the physicist Lawrence M. Krauss, initially published on January 10, 2012 by Free Press. It discusses modern cosmogony and its implications for the debate about the existence of God. The main theme of the book is how "we have discovered that all signs suggest a universe that could and plausibly did arise from a deeper nothing—involving the absence of space itself and—which may one day return to nothing via processes that may not only be comprehensible but also processes that do not require any external control or direction." Publication The book ends with an afterword by Richard Dawkins in which he compares the book to ''On the Origin of Species'' — a comparison that Krauss himself called "pretentious". Christopher Hitchens had agreed to write a foreword for the book prior to his death but was too ill to complete it. To write the book, Krauss expanded material from a lectur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dark Matter
Dark matter is a hypothetical form of matter thought to account for approximately 85% of the matter in the universe. Dark matter is called "dark" because it does not appear to interact with the electromagnetic field, which means it does not absorb, reflect, or emit electromagnetic radiation and is, therefore, difficult to detect. Various astrophysical observationsincluding gravitational effects which cannot be explained by currently accepted theories of gravity unless more matter is present than can be seenimply dark matter's presence. For this reason, most experts think that dark matter is abundant in the universe and has had a strong influence on its structure and evolution. The primary evidence for dark matter comes from calculations showing that many galaxies would behave quite differently if they did not contain a large amount of unseen matter. Some galaxies would not have formed at all and others would not move as they currently do. Other lines of evidence include obs ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Minkowski Space
In mathematical physics, Minkowski space (or Minkowski spacetime) () is a combination of three-dimensional Euclidean space and time into a four-dimensional manifold where the spacetime interval between any two events is independent of the inertial frame of reference in which they are recorded. Although initially developed by mathematician Hermann Minkowski for Maxwell's equations of electromagnetism, the mathematical structure of Minkowski spacetime was shown to be implied by the postulates of special relativity. Minkowski space is closely associated with Einstein's theories of special relativity and general relativity and is the most common mathematical structure on which special relativity is formulated. While the individual components in Euclidean space and time may differ due to length contraction and time dilation, in Minkowski spacetime, all frames of reference will agree on the total distance in spacetime between events.This makes spacetime distance an invariant. Beca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Friedmann–Lemaître–Robertson–Walker Metric
The Friedmann–Lemaître–Robertson–Walker (FLRW; ) metric is a metric based on the exact solution of Einstein's field equations of general relativity; it describes a homogeneous, isotropic, expanding (or otherwise, contracting) universe that is path-connected, but not necessarily simply connected. The general form of the metric follows from the geometric properties of homogeneity and isotropy; Einstein's field equations are only needed to derive the scale factor of the universe as a function of time. Depending on geographical or historical preferences, the set of the four scientists – Alexander Friedmann, Georges Lemaître, Howard P. Robertson and Arthur Geoffrey Walker – are customarily grouped as Friedmann or Friedmann–Robertson–Walker (FRW) or Robertson–Walker (RW) or Friedmann–Lemaître (FL). This model is sometimes called the ''Standard Model'' of modern cosmology, although such a description is also associated with the further developed Lambda-CDM model. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nathan Rosen
Nathan Rosen (Hebrew: נתן רוזן; March 22, 1909 – December 18, 1995) was an American-Israeli physicist noted for his study on the structure of the hydrogen atom and his work with Albert Einstein and Boris Podolsky on entangled wave functions and the EPR paradox. The Einstein–Rosen bridge, later named the wormhole, was a theory of Nathan Rosen. Background Nathan Rosen was born into a Jewish family in Brooklyn, New York. He attended MIT during the Great Depression, where he received a bachelor's degree in electromechanical engineering and later a master's and a doctorate in physics. As a student he published several papers of note, one being "The Neutron," which attempted to explain the structure of the atomic nucleus a year before their discovery by James Chadwick. He also developed an interest in wave functions, and later, gravitation, when he worked as a fellow at the University of Michigan and Princeton University. State of science At the beginning of the 20th centur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The Scientist (magazine)
''The Scientist'' is a professional magazine intended for life scientists. Coverage includes articles on recently published research papers, current research, techniques, important career news, profiles of established and up and coming scientists, publishing, research integrity and best practices, as well as other columns and reports of interest to its readers. The editor-in-chief is Bob Grant. Overview The main purpose of the magazine is to provide print and online coverage of the latest developments in life sciences research, technology, careers, and business. Subject matter covered by the magazine includes: groundbreaking research, industry innovations, careers, financial topics, economics of science, scientific ethics, profiles of scientists, lab tools, scientific publishing, techniques, product spotlight, and guides History ''The Scientist'' was founded by Eugene Garfield in 1986. In 1988, Garfield sold ''The Scientist'', part of the ''Institute for Scientific Infor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
A Brief History Of Time
''A Brief History of Time: From the Big Bang to Black Holes'' is a book on theoretical cosmology by English physicist Stephen Hawking. It was first published in 1988. Hawking wrote the book for readers who had no prior knowledge of physics. In ''A Brief History of Time'', Hawking writes in non-technical terms about the structure, origin, development and eventual fate of the Universe, which is the object of study of astronomy and modern physics. He talks about basic concepts like space and time, basic building blocks that make up the Universe (such as quarks) and the fundamental forces that govern it (such as gravity). He writes about cosmological phenomena such as the Big Bang and black holes. He discusses two major theories, general relativity and quantum mechanics, that modern scientists use to describe the Universe. Finally, he talks about the search for a unifying theory that describes everything in the Universe in a coherent manner. The book became a bestseller and sold ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alan Guth
Alan Harvey Guth (; born February 27, 1947) is an American theoretical physicist and cosmologist. Guth has researched elementary particle theory (and how particle theory is applicable to the early universe). He is Victor Weisskopf Professor of Physics at the Massachusetts Institute of Technology. Along with Alexei Starobinsky and Andrei Linde, he won the 2014 Kavli Prize "for pioneering the theory of cosmic inflation." [Baidu] |
