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Historical divergence 2008-02-03 00:22:00 From ancient times until the 17th century, astrologers constantly desired more accurate astronomical tables, and for this reason, they instigated and even funded many important developments in astronomy. The role of astrology as an important motivation for astronomical research diminished as the works of Galileo and others solved the problems in celestial mechanics that were of interest to astrologers, and as belief in astrological influences or correlations became extinct among astronomers. The needs of modern navigation and physics became more important motivators for astronomical research.Astrology and astronomy began to take divergent paths during the rise of the rational and the scientific method in the Western World. The science of astronomy as we know it today (mathematical, mechani Read more:divergence
, Historical
Distinguishing characteristics 2008-02-03 00:18:00 * The primary goal of astronomy is to understand the physics of the universe. Astrologers use astronomical calculations for the positions of celestial bodies along the ecliptic and attempt to correlate celestial events (astrological aspects, sign positions) with earthly events and human affairs. Astronomers consistently use the scientific method, naturalistic presuppositions and abstract mathematical reasoning to investigate or explain phenomena in the universe. Astrologers use mystical/religious reasoning as well as traditional folklore, symbolism and superstition blended with mathematical predictions to explain phenomena in the universe. The scientific method is not consistently used by astrologers. * Astrologers practice their discipline geocentricically [12] and they consider the uni Read more:characteristics
Overview Astrology 2008-02-03 00:18:00 Historically, most cultures have not made a clear distinction between the two disciplines, lumping them both together as one. In ancient Babylonia, famed for its astrology, there were not separate roles for the astronomer as predictor of celestial phenomena, and the astrologer as their interpreter; both functions were performed by the same person. This overlap does not mean that astrology and astronomy were always regarded as one and the same. In ancient Greece, presocratic thinkers such as Anaximander, Xenophanes, Anaximenes, and Heraclides speculated about the nature and substance of the stars and planets. Astronomers such as Eudoxus (contemporary with Plato) observed planetary motions and cycles, and created a geocentric cosmological model that would be accepted by Aristotle -- this mod Read more:Astrology
, Overview
Astrology and astronomy 2008-02-03 00:15:00 Astrology and astronomy are historically one and the same discipline (Latin: astrologia), and were only gradually recognized as separate in western 17th century philosophy (the "Age of Reason").Since the 18th century they have come to be regarded as completely separate disciplines. Astronomy, the study of objects and phenomena beyond the Earth's atmosphere, is accepted as a science [1][2][3] and is a widely studied academic discipline. Astrology, which uses the apparent positions of celestial objects as the basis for psychology, prediction of future events, and other esoteric knowledge, is not widely regarded as science and is typically defined as a form of divination[4][5][6][7][8][9][10]. Read more:Astrology
Other areas of inquiry Cosmology 2007-12-03 23:47:00 Cosmologists also study: * whether primordial black holes were formed in our universe, and what happened to them. * the GZK cutoff for high-energy cosmic rays, and whether it signals a failure of special relativity at high energies * the equivalence principle, and whether Einstein's general theory of relativity is the correct theory of gravitation, and if the fundamental laws of physics are the same everywhere in the universe Read more:areas
Dark energy 2007-12-03 23:46:00 If the universe is to be flat, there must be an additional component making up 71% (in addition to the 25% dark matter and 4% baryons) of the density of the universe. This is called dark energy. In order not to interfere with big bang nucleosynthesis and the cosmic microwave background, it must not cluster in haloes like baryons and dark matter. There is strong observational evidence for dark energy, as the total mass of the universe is known, since it is measured to be flat, but the amount of clustering matter is tightly measured, and is much less than this. The case for dark energy was strengthened in 1999, when measurements demonstrated that the expansion of the universe has begun to gradually accelerate.However, apart from its density and its clustering properties, nothing is known abo
Dark matter 2007-12-03 23:46:00 Evidence from big bang nucleosynthesis, the cosmic microwave background and structure formation suggests that about 25% of the mass of the universe consists of non-baryonic dark matter
, whereas only 4% consists of visible, baryonic matter. The gravitational effects of dark matter are well understood, as it behaves like cold, non-radiative dust which forms around haloes around galaxies. Dark matter has never been detected in the laboratory: the particle physics nature of dark matter is completely unknown. However, there are a number of candidates, such as a stable supersymmetric particle, a weakly interacting massive particle, an axion, and a massive compact halo object. Alternatives to the dark matter hypothesis include a modification of gravity at small accelerations (MOND) or an effect f
Formation and evolution of large-scale structure 2007-12-03 23:40:00 Understanding the formation and evolution of the large
st and earliest structures (ie, quasars, galaxies, clusters and superclusters) is one of the largest efforts in cosmology. Cosmologists study a model of hierarchical structure formation in which structures form from the bottom up, with smaller objects forming first, while the largest objects, such as superclusters, are still assembling. The most straightforward way to study structure in the universe is to survey the visible galaxies, in order to construct a three-dimensional picture of the galaxies in the universe and measure the matter power spectrum. This is the approach of the Sloan Digital Sky Survey and the 2dF Galaxy Redshift Survey.An important tool for understanding structure formation is simulations, which cosmologists use to s Read more:Formation
Big Bang Nucleosynthesis 2007-12-03 23:38:00 Big Bang Nucleosynthesis is the theory of the formation of the elements in the early universe. It finished when the universe was about three minutes old and its temperature fell enough that nuclear fusion ceased. Because the time in which big bang nucleosynthesis occurred was so short, only the very lightest elements were produced, unlike in stellar nucleosynthesis. Starting from hydrogen ions (protons), it principally produced deuterium, helium-4 and lithium. Other elements were produced in only trace abundances. While the basic theory of nucleosynthesis has been understood for decades (it was developed in 1948 by George Gamow, Ralph Asher Alpher and Robert Herman) it is an extremely sensitive probe of physics at the time of the big bang, as the theory of big bang nucleosynthesis connects Read more:Big Bang
Big Bang Nucleosynthesis 2007-12-03 23:38:00 Big Bang Nucleosynthesis is the theory of the formation of the elements in the early universe. It finished when the universe was about three minutes old and its temperature fell enough that nuclear fusion ceased. Because the time in which big bang nucleosynthesis occurred was so short, only the very lightest elements were produced, unlike in stellar nucleosynthesis. Starting from hydrogen ions (protons), it principally produced deuterium, helium-4 and lithium. Other elements were produced in only trace abundances. While the basic theory of nucleosynthesis has been understood for decades (it was developed in 1948 by George Gamow, Ralph Asher Alpher and Robert Herman) it is an extremely sensitive probe of physics at the time of the big bang, as the theory of big bang nucleosynthesis connects Read more:Big Bang
The very early universe (Areas of Study Physical Cosmology) 2007-12-03 23:37:00 While the early, hot universe appears to be well explained by the big bang from roughly 10-33 seconds onwards, there are several problems. One is that there is no compelling reason, using current particle physics, to expect the universe to be flat, homogeneous and isotropic (see the cosmological principle). Moreover, grand unified theories of particle physics suggest that there should be magnetic monopoles in the universe, which have not been found. These problems are resolved by a brief period of cosmic inflation, which drives the universe to flatness; smooths out anisotropies and inhomogeneities to the observed level; and exponentially dilutes the monopoles. The physical model behind cosmic inflation is extremely simple, however it has not yet been confirmed by particle physics, and ther Read more:Study
Timeline of the Big Bang 2007-12-03 23:35:00 Observations suggest that the universe as we know it began around 13.7 billion years ago. Since then, the evolution of the universe has passed through three phases. The very early universe, which is still poorly understood, was the split second in which the universe was so hot that particles had energies higher than those currently accessible in particle accelerators on Earth. Therefore, while the basic features of this epoch have been worked out in the big bang theory, the details are largely based on educated guesses. Following this, in the early universe, the evolution of the universe proceeded according to known high energy physics. This is when the first protons, electrons and neutrons formed, then nuclei and finally atoms. With the formation of neutral hydrogen, the cosmic microwave Read more:Timeline
Equations of motion 2007-12-03 23:34:00 The equations of motion governing the universe as a whole are derived from general relativity with a small, positive cosmological constant. The solution is an expanding universe; due to this expansion the radiation and matter in the universe are cooled down and become diluted. At first the expansion is slowed down by gravitation due to the radiation and matter content of the universe. However, as these become diluted, the cosmological constant becomes more dominant and the expansion of the universe starts to accelerate rather than decelerate. In our universe this has already happened, billions of years ago.
Particle physics in cosmology 2007-12-03 23:34:00 Particle physics, which deals with high energies, is extremely important in the behavior of the early universe, since it was so hot that the average energy density was very high. Because of this, scattering processes and decay of unstable particles are important in cosmology.As a thumb rule, a scattering or a decay process is cosmologically important in a certain cosmological epoch if its relevant time scale is smaller or comparable to the time scale of the universe expansion, which is 1 / H with H being the Hubble constant at that time. This is roughly equal to the age of the universe at that time. Read more:Particle
History of physical cosmology 2007-12-03 23:31:00 Modern cosmology developed along tandem observational and theoretical tracks. In 1915, Albert Einstein developed his theory of general relativity. At the time, physicists were prejudiced to believe in a perfectly static universe without beginning or end. Einstein added a cosmological constant to his theory to try to force it to allow for a static universe with matter in it. The so-called Einstein universe is, however, unstable. It is bound to eventually start expanding or contracting. The cosmological solutions of general relativity were found by Alexander Friedmann, whose equations describe the Friedmann-Lemaître-Robertson-Walker universe, which may expand or contract.In the 1910s, Vesto Slipher and later Carl Wilhelm Wirtz interpreted the red shift of spiral nebulae as a Doppler shift t Read more:physical
, History
Energy of the cosmos 2007-12-03 23:31:00 Light elements, primarily hydrogen and helium, were created in the Big Bang. These light elements were spread too fast and too thinly in the Big Bang process (see nucleosynthesis) to form the most stable medium-sized atomic nuclei, like iron and nickel. This fact allows for later energy release, as such intermediate-sized elements are formed in our era. The formation of such atoms powers the steady energy-releasing reactions in stars, and also contributes to sudden energy releases, such as in novae. Gravitational collapse of matter into black holes is also thought to power the most energetic processes, generally seen at the centers of galaxies (see quasars and in general active galaxies).Cosmologists are still unable to explain all cosmological phenomena purely on the basis of known conven Read more:Energy
Physical cosmology 2007-12-03 23:30:00 Physical cosmology, as a branch of astronomy, is the study of the large-scale structure of the universe and is concerned with fundamental questions about its formation and evolution. Cosmology involves itself with studying the motions of the celestial bodies and the first cause. For most of human history, it has been a branch of metaphysics. Cosmology as a science originates with the Copernican principle, which implies that celestial bodies obey identical physical laws to those on earth, and Newtonian mechanics, which first allowed us to understand those motions. This is now called celestial mechanics. Physical cosmology, as it is now understood, began with the twentieth century development of Albert Einstein's theory of general relativity and better astronomical observations of extremely
Criticisms 2007-12-03 23:29:00 Because Astrobiology relies mostly on scientific extrapolations, over solid, factual evidence, the authenticity of astrobiology as a science can be questioned. Astrobiology is more theoretical than scientific. While other branches of science remain heavily theoretical, there is a greater degree of mathematical, pragmatic and/or observational evidence supporting the theories. For example, while science cannot prove string theory, there is a great deal of mathematical computation which implies the existence of strings of energy. Such evidence does not exist with Astrobiology, save for an asteroid segment which is believed to have fossilized Martian microbes. [55] the University of Glamorgan, UK, started just such a degree in 2006.[56]Characterization of non-Earth life is extraordinarily unse
Political Support 2007-12-03 23:29:00 In the United States, President George W. Bush's Fiscal Year 2007 NASA Budget cut funding for astrobiological research by 50 percent.[53] In the 2007 plan, $89 million will be cut from astrobiological research, partly because of a $2.3 billion error in the Space Shuttle Budget.[54] In a letter to the astrobiological community in the United States, SETI chief executive Thomas Pierson and former NAI director Baruch Blumberg said the following: "Action is needed immediately to prevent the slowing down, or even cessation, of astrobiological research".[54] Hiroshi Ohmoto, the director of the Astrobiology Research Center in Penn State, said the following in response to the budget cuts to astrobiology:[54] Astrobiology is the reason we go into space, to answer fundamental questions about the o Read more:Support
Geology (Methodology > Division Astrobiology) 2007-12-03 23:28:00 The fossil record provides the oldest known evidence for life on Earth.[37] By examining this evidence, geologists are able to better understand the types of organisms that arose on the early Earth. Some regions on Earth, such as the Pilbara in Western Australia are also considered to be geological analogs to regions of Mars and as such might be able to provide clues to possible Martian life. Read more:Division
, Methodology
Life in the Solar System 2007-12-03 23:28:00 The three most likely candidates for life in the solar system (besides Earth) are the planet Mars, the Jovian moon Europa, and Saturn's moon, Titan.[38][39][40][41][42] This speculation is primarily based on the fact that (in the case of Mars and Europa) the planetary bodies may have liquid water, a molecule essential for life as we know it for its use as a solvent in cells.[43] Water on Mars is found in its polar ice caps, and newly-carved gullies recently observed on Mars suggest that liquid water may exist, at least transiently, on the planet's surface,[44] [45] and possibly in subsurface environments such as hydrothermal springs as well. At the Martian temperatures and pressures, such liquid water is likely to be highly saline.[46] As for Europa, liquid water likely exists beneath the Read more:System
, Solar
Biology (Methodology > Division Astrobiology) 2007-12-03 23:26:00 Extremophiles (organisms able to survive in extreme environments) are a core research element for astrobiologists. Such organisms include biota able to survive kilometers below the ocean's surface near hydrothermal vents and microbes that thrive in highly acidic environments.[33] Characterization of these organisms—their environments and their evolutionary pathways—is considered a crucial component to understanding how life might evolve elsewhere in the universe. Recently, a number of astrobiologists have teamed up with marine biologists and geologists to search for extremophiles and other organisms living around hydrothermal vents on the floors of our own oceans. Scientists hope to use their findings to help them create hypotheses on whether life could potentially exist on certain moo Read more:Division
, Methodology
Narrowing the task (methodology Astrobiology) 2007-12-03 23:25:00 When looking for life on other planets, some simplifying assumptions are useful to reduce the size of the task of astrobiologists. One is to assume that the vast majority of life-forms in our galaxy are based on carbon chemistries, as are all life-forms on Earth.[22] While it is possible that non carbon-based life exists, carbon is well known for the unusually wide variety of molecules that can be formed around it. However, it should be noted that astrobiology concerns itself with an interpretation of existing scientific data; that is, given more detailed and reliable data from other parts of the universe (perhaps obtainable only by physical space exploration) the roots of astrobiology itself--biology, physics, chemistry--may have their theoretical bases challenged. Much speculation is ent
Astronomy (Methodology > Division Astrobiology) 2007-12-03 23:25:00 Most astronomy-related astrobiological research falls into the category of extrasolar planet (exoplanet) detection, the hypothesis being that if life arose on Earth then it could also arise on other planets with similar characteristics. To that end, a number of instruments designed to detect 'Earth-like' exoplanets are under development, most notably NASA's Terrestrial Planet Finder (TPF) and ESA's Darwin programs.[27] Additionally, NASA plans to launch the Kepler mission in 2008, and the French Space Agency has already launched the COROT space mission.[28][29] There have also been several less ambitious ground-based efforts are also underway (see exoplanet).The goal of these missions is not only to detect Earth-sized planets but also to directly detect light from the planet so that it may Read more:Astronomy
, Division
, Methodology
Rare Earth hypothesis 2007-12-03 23:24:00 In the book Rare Earth
: Why Complex Life is Uncommon in the Universe, Peter Ward, a geologist and paleontologist, and Donald Brownlee, an astronomer and astrobiologist, propose that life as we know it is rare in the universe.[19][20] They suggest that microbial life, however, is probably common in the universe, because of recently discovered extremophiles.[21] The book argues that the chances of all the conditions that occurred to create the Earth occurring again would be rare; thus intelligent life would be rare. One important factor focused on in the book is planetary habitability (see section below).Peter Ward, one of the authors, said the following:[1] How do we define life as we do know it? Life on Earth has DNA, a specific genetic code. It also uses only 20, and the same 20, amino
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