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Big Bang Reference Libraries

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Cosmology
2014-01-12 00:00:00

Image Caption: The Hubble Extreme Deep Field (XDF) was completed in September 2012 and shows the farthest galaxies ever photographed by humans. Each speck of light in the photo is an individual galaxy, some of them as old as 13.2 billion years; the observable universe is estimated to contain more than 200 billion galaxies. Credit: NASA/Wikipedia What is Cosmology? I once commented to an...

Large-Scale Structure of the Cosmos
2004-10-19 04:45:44

Large-Scale Structure of the Cosmos -- Stars are organised into galaxies which in turn appear to form clusters and superclusters, separated by voids. Prior to 1989 it was commonly assumed that the superclusters were the largest structures in existence, and that they were distributed more-or-less uniformly throughout the universe in every direction. However, in 1989, Margaret Geller and...

Cosmology
2004-10-19 04:45:44

Cosmology -- area of science that aims at a comprehensive theory of the structure and evolution of the entire physical universe. Modern Cosmological Theories Present models of the universe hold two fundamental premises: the cosmological principle and the dominant role of gravitation. Derived by Hubble, the cosmological principle holds that if a large enough sample of galaxies is...

Redshift
2004-10-19 04:45:42

Redshift -- Redshift is the phenomenon that the frequency of light when observed, under certain circumstances, can be lower than the frequency of light when it was emitted at the source. This usually occurs when the source moves away from the observer, as in the Doppler effect. More specifically, the term redshift is used for the observation that the spectrum of light emitted by distant...

Quasar
2004-10-19 04:45:42

Quasar -- A quasar (from quasi-stellar radio source) is an astronomical object that looks like a star in optical telescopes (i.e. it is a point source), but has a very high redshift. The general consensus is that this high redshift is cosmological, the result of Hubble's law and that their redshift indicates that they are typically very distant from Earth; we observe them as they were...

Event Horizon
2004-10-19 04:45:41

Event Horizon -- The event horizon is a boundary beyond which information will never reach an observer. An event horizon is a mathematical construct and not a physical object and a person passing through an event horizon will not notice any odd behavior. From an outside observer however, an object passing though an event horizon will appear redder and dimmer and will appear to freeze at the...

Quintessence Dark Energy
2004-10-19 04:45:41

Quintessence (Dark Energy) -- Quintessence or dark energy is a hypothetical form of energy postulated to exist in order to explain observations of an accelerating universe. This energy would act like a vacuum pressure, pushing things apart. Other attempts to explain these recent observations involve a non-zero cosmological constant, which has the same effect. Indeed, sometimes...

Cosmological Constant
2004-10-19 04:45:41

Cosmological Constant -- The cosmological constant (usually denoted by the Greek capital letter lambda: Λ) is a value occurring in Einstein's theory of general relativity. The units of Λ are 1/second2; its value is unknown but believed to be positive based on recent observations. The constant is proportional to the energy density of the vacuum ρ, where π is Pi, G is the...

Inflation
2004-10-19 04:45:41

Inflation -- Inflation is the idea - first proposed by Alan Guth (1981) - that the nascent universe passed through a phase of exponential expansion that was driven by a negative vacuum energy density (positive vacuum pressure). This expansion can be modelled by a non-zero cosmological constant. As a direct consequence of this expansion, all of the observable universe is posited to have...

Cosmic Background Radiation
2004-10-19 04:45:41

Cosmic Background Radiation -- The Big Bang theory predicts that the early universe was a very hot place and that as it expands, the gas within it cools. Thus the universe should be filled with radiation that is literally the remnant heat left over from the Big Bang, called the cosmic microwave background radiation, or CMB. When any patch of the sky is observed where no individual sources...

Word of the Day
saggar
  • A ceramic container used inside a fuel-fired kiln to protect pots from the flame.
The word 'saggar' may come from 'safeguard'.
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