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Ultimate Fate Of The Universe
The ultimate fate of the universe is a topic in physical cosmology, whose theoretical restrictions allow possible scenarios for the evolution and ultimate fate of the universe to be described and evaluated. Based on available observational evidence, deciding the fate and evolution of the universe has become a valid cosmological question, being beyond the mostly untestable constraints of mythological or theological beliefs. Several possible futures have been predicted by different scientific hypotheses, including that the universe might have existed for a finite and infinite duration, or towards explaining the manner and circumstances of its beginning. Observations made by Edwin Hubble during the 1930s–1950s found that galaxies appeared to be moving away from each other, leading to the currently accepted Big Bang theory. This suggests that the universe began very dense about 13.787 billion years ago, and it has expanded and (on average) become less dense ever since. ... [...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] |
Dark Energy
In physical cosmology and astronomy, dark energy is an unknown form of energy that affects the universe on the largest scales. The first observational evidence for its existence came from measurements of supernovas, which showed that the universe does not expand at a constant rate; rather, the universe's expansion is accelerating. Understanding the universe's evolution requires knowledge of its starting conditions and composition. Before these observations, scientists thought that all forms of matter and energy in the universe would only cause the expansion to slow down over time. Measurements of the cosmic microwave background (CMB) suggest the universe began in a hot Big Bang, from which general relativity explains its evolution and the subsequent large-scale motion. Without introducing a new form of energy, there was no way to explain how scientists could measure an accelerating universe. Since the 1990s, dark energy has been the most accepted premise to account for the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Robert Woodrow Wilson
Robert Woodrow Wilson (born January 10, 1936) is an American astronomer who, along with Arno Allan Penzias, discovered cosmic microwave background radiation (CMB) in 1964. The pair won the 1978 Nobel Prize in Physics for their discovery. While doing tests and experiments with the Holmdel Horn Antenna at Bell Labs in Holmdel Township, New Jersey, Wilson and Penzias discovered a source of noise in the atmosphere that they could not explain. After removing all potential sources of noise, including pigeon droppings on the antenna, the noise was finally identified as CMB, which served as important corroboration of the Big Bang theory. In 1970, Wilson led a team that made the first detection of a rotational spectral line of carbon monoxide (CO) in an astronomical object, the Orion Nebula, and eight other galactic sources. Subsequently, CO observations became the standard method of tracing cool molecular interstellar gas, and detection of CO was the foundational event for the field ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arno Penzias
Arno Allan Penzias (; born April 26, 1933) is an American physicist, radio astronomer and Nobel laureate in physics. Along with Robert Woodrow Wilson, he discovered the cosmic microwave background radiation, which helped establish the Big Bang theory of cosmology. Early life and education Penzias was born in Munich, Germany, the son of Justine (née Eisenreich) and Karl Penzias, who ran a leather business. His grandparents had come to Munich from Poland and were among the leaders of the Reichenbach Strasse Shul. At age six, he and his brother Gunther were among the Jewish children evacuated to Britain as part of the Kindertransport rescue operation. Some time later, including the Nobel Lecture, December 8, 1978 ''The Origin of Elements'' his parents also fled Nazi Germany for the U.S., and the family settled in the Garment District of New York City in 1940. In 1946, Penzias became a naturalized citizen of the United States. He graduated from Brooklyn Technical High Scho ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Steady State Model
In cosmology, the steady-state model, or steady state theory is an alternative to the Big Bang theory of evolution of the universe. In the steady-state model, the density of matter in the expanding universe remains unchanged due to a continuous creation of matter, thus adhering to the perfect cosmological principle, a principle that asserts that the observable universe is practically the same at any time and any place. While from the 1940s to the 1960s the astrophysical community was equally divided between supporters of the Big Bang theory and supporters of the steady-state theory, it is now rejected by the vast majority of cosmologists, astrophysicists and astronomers, as the observational evidence points to a hot Big Bang cosmology with a finite age of the universe, which the steady-state model does not predict. History In the 13th century, Siger of Brabant authored the thesis ''The Eternity of the World'', which argued that there was no first man, and no first specimen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fred Hoyle
Sir Fred Hoyle FRS (24 June 1915 – 20 August 2001) was an English astronomer who formulated the theory of stellar nucleosynthesis and was one of the authors of the influential B2FH paper. He also held controversial stances on other scientific matters—in particular his rejection of the "Big Bang" theory (a term coined by him on BBC Radio) in favor of the " Steady State" hypothesis, and his promotion of panspermia as the origin of life on Earth. He also wrote science fiction novels, short stories and radio plays, and co-authored twelve books with his son, Geoffrey Hoyle. He spent most of his working life at the Institute of Astronomy at Cambridge and served as its director for six years. Biography Early life and career Hoyle was born near Bingley in Gilstead, West Riding of Yorkshire, England. His father, Ben Hoyle, who was a violinist and worked in the wool trade in Bradford, served as a machine gunner in the First World War. His mother, Mabel Pickard, had studied ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cepheid Variable
A Cepheid variable () is a type of star that pulsates radially, varying in both diameter and temperature and producing changes in brightness with a well-defined stable period and amplitude. A strong direct relationship between a Cepheid variable's luminosity and pulsation period established Cepheids as important indicators of cosmic benchmarks for scaling galactic and extragalactic distances. This robust characteristic of classical Cepheids was discovered in 1908 by Henrietta Swan Leavitt after studying thousands of variable stars in the Magellanic Clouds. This discovery allows one to know the true luminosity of a Cepheid by simply observing its pulsation period. This in turn allows one to determine the distance to the star, by comparing its known luminosity to its observed brightness. The term ''Cepheid'' originates from Delta Cephei in the constellation Cepheus, identified by John Goodricke in 1784, the first of its type to be so identified. The mechanics of stella ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gravitational Singularity
A gravitational singularity, spacetime singularity or simply singularity is a condition in which gravity is so intense that spacetime itself breaks down catastrophically. As such, a singularity is by definition no longer part of the regular spacetime and cannot be determined by "where" or "when". Gravitational singularities exist at a junction between general relativity and quantum mechanics; therefore, the properties of the singularity cannot be described without an established theory of quantum gravity. Trying to find a complete and precise definition of singularities in the theory of general relativity, the current best theory of gravity, remains a difficult problem. A singularity in general relativity can be defined by the scalar invariant curvature becoming infinite or, better, by a geodesic being incomplete. Gravitational singularities are mainly considered in the context of general relativity, where density apparently becomes infinite at the center of a black hole, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metric Expansion Of Space
The expansion of the universe is the increase in distance between any two given gravitationally unbound parts of the observable universe with time. It is an intrinsic expansion whereby the scale of space itself changes. The universe does not expand "into" anything and does not require space to exist "outside" it. This expansion involves neither space nor objects in space "moving" in a traditional sense, but rather it is the metric (which governs the size and geometry of spacetime itself) that changes in scale. As the spatial part of the universe's spacetime metric increases in scale, objects become more distant from one another at ever-increasing speeds. To any observer in the universe, it appears that all of space is expanding, and that all but the nearest galaxies (which are bound by gravity) recede at speeds that are proportional to their distance from the observer. While objects within space cannot travel faster than light, this limitation does not apply to the effects of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Monthly Notices Of The Royal Astronomical Society
''Monthly Notices of the Royal Astronomical Society'' (MNRAS) is a peer-reviewed scientific journal covering research in astronomy and astrophysics. It has been in continuous existence since 1827 and publishes letters and papers reporting original research in relevant fields. Despite the name, the journal is no longer monthly, nor does it carry the notices of the Royal Astronomical Society. History The first issue of MNRAS was published on 9 February 1827 as ''Monthly Notices of the Astronomical Society of London'' and it has been in continuous publication ever since. It took its current name from the second volume, after the Astronomical Society of London became the Royal Astronomical Society (RAS). Until 1960 it carried the monthly notices of the RAS, at which time these were transferred to the newly established '' Quarterly Journal of the Royal Astronomical Society'' (1960–1996) and then to its successor journal '' Astronomy & Geophysics'' (since 1997). Until 1965, MN ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Georges Lemaître
Georges Henri Joseph Édouard Lemaître ( ; ; 17 July 1894 – 20 June 1966) was a Belgian Catholic priest, theoretical physicist, mathematician, astronomer, and professor of physics at the Catholic University of Louvain. He was the first to theorize that the recession of nearby galaxies can be explained by an expanding universe, which was observationally confirmed soon afterwards by Edwin Hubble. He first derived "Hubble's law", now called the Hubble–Lemaître law by the IAU, and published the first estimation of the Hubble constant in 1927, two years before Hubble's article. Lemaître also proposed the "Big Bang theory" of the origin of the universe, calling it the "hypothesis of the primeval atom", and later calling it "the beginning of the world". Early life After a classical education at a Jesuit secondary school, the Collège du Sacré-Coeur, in Charleroi, in Belgium, Lemaître began studying civil engineering at the Catholic University of Louvain at the age of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Friedmann Equations
The Friedmann equations are a set of equations in physical cosmology that govern the expansion of space in homogeneous and isotropic models of the universe within the context of general relativity. They were first derived by Alexander Friedmann in 1922 from Einstein's field equations of gravitation for the Friedmann–Lemaître–Robertson–Walker metric and a perfect fluid with a given mass density and pressure . (English translation: ). The original Russian manuscript of this paper is preserved in thEhrenfest archive The equations for negative spatial curvature were given by Friedmann in 1924. (English translation: ) Assumptions The Friedmann equations start with the simplifying assumption that the universe is spatially homogeneous and isotropic, that is, the cosmological principle; empirically, this is justified on scales larger than the order of 100 Mpc. The cosmological principle implies that the metric of the universe must be of the form : -\mathrms^2 = a(t)^2 \, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
