Physical cosmology Reference Libraries

Page 2 of about 21 Articles
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...

2004-10-19 04:45:41

Multiverse -- The term Multiverse was invented in December 1960, by Andy Nimmo, then vice chairman of the British Interplanetary Society, Scottish Branch, for a talk on the Everett many-worlds interpretation of quantum physics which had been published in 1957, to the branch. This was given in February 1961, and the word with its original definition, "an apparent universe, a multiplicity of...

Massive Compact Halo Object MACHO
2004-10-19 04:45:41

Massive Compact Halo Object (MACHO) -- Massive compact halo objects, or MACHOs, are a type of astronomical body proposed as one possible explanation for the presence of dark matter in galactic halos. A MACHO is a small chunk of normal baryonic matter, far smaller than a star, which drifts through interstellar space unassociated with any solar system. Since MACHOs would not emit any light of...

Doppler Effect
2004-10-19 04:45:41

Doppler Effect -- The Doppler effect is the apparent change in frequency or wavelength of a wave that is perceived by an observer moving relative to the source of the waves. For waves, such as sound waves, that propagate in a wave medium, the velocity of the observer and the source are reckoned relative to the medium in which the waves are transmitted. The total Doppler effect may therefore...

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...

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...

Big Bang
2004-10-19 04:45:41

Big Bang -- The Big Bang theory is the dominant theory in cosmology about the early development and current shape of the universe. According to this theory, the universe expanded rapidly starting 13.7 0.2 billion years ago. Extrapolating the history of the universe backwards using current physical models leads to a gravitational singularity, at which all distances become zero and...

Accelerating Universe
2004-10-19 04:45:41

Accelerating universe -- In the late 1990s, observations of type I supernova produced the unexpected result that the expansion of the universe appears to be accelerating. These observations appear more firm as new data has appeared. This means that the speed with which a distant galaxy recedes from us increases over time. If this trend continues, eventually we won't be able to see any...

Word of the Day
  • The deadly nightshade, Atropa Belladonna, which possesses stupefying or poisonous properties.
  • A sleeping-potion; a soporific.
  • To mutter deliriously.
The word 'dwale' comes from an Old English word meaning 'error, doubt, delusion.'