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Topic: Expansion of the universe

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	Universe - Wikipedia, the free encyclopedia
		We live in the centre of the universe that we observe, in apparent contradiction to the Copernican principle which says that the Universe is more or less uniform and it has no distinguished centre.
		Secondly, whether or not the universe is multiply connected, is unknown.
		Currently the evidence suggests not only that there is insufficient mass/energy to cause a recollapse, but that the expansion of the universe seems to be accelerating and will accelerate for the whole of eternity (see accelerating universe).
	en.wikipedia.org /wiki/Universe (1235 words)

	Dark energy - Wikipedia, the free encyclopedia
		During the late 1990s, observations of type Ia supernovae suggested that the expansion of the universe is accelerating.
		For the shape of the universe to be flat, the mass/energy density of the Universe must be equal to a certain critical density.
		Specifically, when the volume of the universe doubles, the density of dark matter is halved but the density of dark energy is nearly unchanged (it is exactly constant in the case of a cosmological constant).
	en.wikipedia.org /wiki/Accelerating_universe (2582 words)

	Scientific American: Misconceptions about the Big Bang (Site not responding. Last check: 2007-11-05)
		Since this discovery, the expansion and cooling of the universe has been the unifying theme of cosmology, much as Darwinian evolution is the unifying theme of biology.
		The expansion of the universe is like Darwinian evolution in another curious way: most scientists think they understand it, but few agree on what it really means.
		Cosmologists sometimes state that the universe used to be the size of a grapefruit, but what they mean is that the part of the universe we can now see--our observable universe--used to be the size of a grapefruit.
	www.sciam.com /print_version.cfm?articleID=0009F0CA-C523-1213-852383414B7F0147 (3457 words)

	Expansion of the Universe
		The Universe has 3 spatial dimensions, but it is easier to visualize an analogy to its expansion for the 2-dimensional surface of a balloon.
		The expansion of the Universe appears to be like this, but in 3 rather than 2 space dimensions, which makes it much harder to visualize, but it is possible to describe it mathematically.
		If instead of viewing the expansion of the balloon from the outside I place myself on one of the dots on the balloon's surface, I appear to be stationary and I see the other dots moving away from me (and in my immediate area I see the apparent curvature of the balloon's surface decreasing).
	csep10.phys.utk.edu /astr162/lect/cosmology/expansion.html (883 words)

	Frequently Asked Questions in Cosmology
		If the expansion of the Universe is accelerating due to a cosmological constant, then the expansion was slower in the past, and thus the time required to expand by a given factor is longer, and the distance NOW is larger.
		The age of the Universe is determined from its expansion rate: the Hubble constant, which is the ratio of the radial velocity of a distant galaxy to its distance.
		The vast majority of the entropy of the Universe is in the cosmic microwave background radiation because the vast majority of particles in the Universe are the photons of the CMB.
	www.astro.ucla.edu /~wright/cosmology_faq.html (4741 words)

	Dark energy -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-11-05)
		Invoking such an effect is currently the most popular method for explaining the observations of an accelerating universe as well as accounting for a significant portion of the (additional info and facts about missing mass) missing mass in the universe.
		More importantly, observations made by (United States astronomer who discovered that (as the universe expands) the speed with which nebulae recede increases with their distance (1889-1953)) Edwin Hubble showed that the universe appears to be expanding and not static at all.
		Inflation postulates that some repulsive force, qualitatively similar to dark energy, resulted in an enormous and exponential expansion of the universe slightly after the ((cosmology) the cosmic explosion that is hypothesized to have marked the origin of the universe) Big Bang.
	www.absoluteastronomy.com /encyclopedia/d/da/dark_energy.htm (2580 words)

	Expansion of the Universe Is Accelerating, Data Suggests
		The universe is expanding at an accelerating rate, according to startling new evidence suggesting that a mysterious antigravity force permeates "empty" space and is counteracting the pull of gravity on a cosmic scale.
		Most astronomers agree that the universe began in a Big Bang up to 15 billion years ago, when all of time and space were contained in a single dense point - a singularity - which abruptly expanded outward in a fireball of particles.
		The emerging picture of the universe represented in the spate of recent findings appears to reanimate a controversial concept known as the "cosmological constant", which Einstein first proposed in his theory of general relativity.
	www-tech.mit.edu /V118/N8/bexpand.8w.html (662 words)

	Italian, US cosmologists present explanation for accelerating expansion of the universe
		This accelerating expansion seemed to be explicable only by the presence of a new component of the universe, a "dark energy," representing some 70 percent of the total mass of the universe.
		These ripples were stretched by the expansion of the universe and extend today far beyond our cosmic horizon, that is over a region much bigger than the observable universe, a distance of about 15 billion light years.
		In their current paper, the authors propose that it is the evolution of these cosmic ripples that increases the observed expansion of the universe and accounts for its acceleration.
	www.eurekalert.org /pub_releases/2005-03/indf-iuc031605.php (836 words)

	IslamiCity.com - The Expansion of the Universe (Site not responding. Last check: 2007-11-05)
		The expansion of the Universe is one of the most imposing discoveries of modern science.
		It was first suggested by the general theory of relativity and is backed up by physics in the examination of the galactic spectrum; the regular movement towards the red section of their spectrum may be explained by the distancing of one galaxy from another.
		Having called modern concepts on the formation of the Universe to mind, reference was made to the evolution that took place, starting with primary nebula through to the formation of galaxies, stars and (for the solar system) the appearance of planets beginning with the Sun at a certain stage of its evolution.
	islamicity.com /Science/Expansion.shtml (1658 words)

	EBTX - Accelerated Expansion of the Universe - What does this mean?
		The H=50 is a bigger universe than the H=100 because when you divide 100 into the speed of light to obtain the "size" of the universe (in megaparsecs), you get a smaller value than with c/50.
		If the expansion of the universe is accelerating, it means that the observable universe will become smaller and smaller with the passage of time...
		Given the universe as it presently exists, it might appear to be justified to extrapolate universal expansion at an accelerated rate...
	www.ebtx.com /ntx/snap2001.htm (2151 words)

	Ebtx - Expansion of the Universe
		Because confinement shrinks as a function of the R, there is an apparent expansion of the universe when confinement (D) is taken as the standard of measure.
		This means that an object seen at the edge of the observable universe, using the Compton wavelength of the proton as a baseline, would be seen to be receeding from the viewer at 1/2 the velocity of light.
		The age of the universe divided by the time required to traverse the confinement at unit velocity always approximates the square root of the baryon number.
	ebtx.com /ntx/ntx11.htm (660 words)

	Expansion of the Universe
		The universe was created about 15 billion years ago in an event called the Big Bang.
		Around a microsecond after the Big Bang, the universe was populated predominantly by quarks and gluons.
		Eventually the universe cooled enough to allow quarks and gluons to condense into nucleons, which subsequently formed hydrogen and helium.
	www.lbl.gov /abc/wallchart/chapters/01/4.html (198 words)

	Open Questions: Expansion of the Universe, Dark Energy, Quintessence
		The accelerating expansion of the universe detected in 1998 has stimulated several theories of "dark energy" or "quintessence".
		Attempts to determine the amount of matter in the universe, both visible and invisible, indicate that the total mass of such matter is at most 35% of the amount required for a "flat" universe.
		Evidence continues to accumulate that cosmic expansion is accelerating, which would imply higher estimates for the age of the universe.
	www.openquestions.com /oq-co005.htm (1175 words)

	WMAP Cosmology101: Formation of the Elements
		The Big Bang model was a natural outcome of Einstein's General Relativity as applied to a homogeneous universe.
		However, in 1917, the idea that the universe was expanding was thought to be absurd.
		The specific form of Hubble's expansion law is important: the speed of recession is proportional to distance.
	map.gsfc.nasa.gov /m_uni/uni_101bbtest1.html (288 words)

	The expansion of the universe
		Until the dawn of the 20th century, the only view prevailing in the world of science was that “the universe has a constant nature and it has existed since infinite time”.
		At the beginning of the 20th century, the Russian physicist Alexander Friedmann and the Belgian cosmologist Georges Lemaitre theoretically calculated that the universe is in constant motion and that it is expanding.
		Scientists compare the expanding universe to the surface of a balloon that is inflated.
	www.55a.net /eng/16.htm (337 words)

	SPACE.com -- Universe Expansion is Accelerating, UK and Australian Researchers Say
		A team of UK and Australian astronomers has discovered new, independent evidence that the expansion of the universe is accelerating.
		Three years ago, two teams of astronomers rocked the scientific world by finding evidence that the expansion of the universe is accelerating rather than slowing down as had generally been expected because of the gravitational attraction between the matter within it.
		Their results show that the universe is full of dark energy, completely consistent with the earlier supernovae results.
	www.space.com /scienceastronomy/astronomy/universe_expansion_020320.html (561 words)

	Evidence mounts that the expansion of the Universe is accelerating (November 1998) - News - PhysicsWeb
		Evidence mounts that the expansion of the Universe is accelerating (November 1998) - News - PhysicsWeb
		Evidence mounts that the expansion of the Universe is accelerating
		One consequence of this "inflationary" model is that the Universe is "flat" with a value of Omega equal to one.
	physicsweb.org /article/news/2/11/3/1 (604 words)

	Expanding Universe
		But when Einstein began to apply his theory to the structure of the universe, he was dismayed to find that it predicted either an expanding or contracting universe--something entirely incompatible with the prevailing notion of a static universe.
		Hubble, who had been the first to establish that the universe included many other galaxies outside of our own, noticed something else: the galaxies were receding from us at a velocity proportional to their distance.
		However, this provides only an upper limit to the age of the universe, and is based on the present rate of expansion, as observed by the recession of distant galaxies.
	archive.ncsa.uiuc.edu /Cyberia/Cosmos/ExpandUni.html (1154 words)

	The Hubble Expansion (Site not responding. Last check: 2007-11-05)
		Additionally, the present age of the Universe can be assessed vis-a-vis the Hubble constant: the inverse of the Hubble constant has units of time.
		If all the lengths in the universe double in 10 million years then something that was initially 1 megaparsec away from us will end up a further megaparsec away.
		These teams were the first to report evidence, from the type of plot above, that the expansion of the universe today is being dominated not by matter but by dark energy, causing distant supernovae to appear fainter than they would in a purely matter dominated universe.
	astron.berkeley.edu /~mwhite/darkmatter/hubble.html (582 words)

	Hubble Measures the Expanding Universe
		Alternatively, the universe is pervaded by a mysterious 'dark force' pushing the galaxies farther apart, in which case the Hubble measurements point to an even older universe.
		The universe's age is calculated using the expansion rate from precise distance measurements, and the calculated age is refined based on whether the universe appears to be accelerating or decelerating, given the amount of matter observed in space.
		A rapid expansion rate indicates the universe did not require as much time to reach its present size, and so it is younger than if it were expanding more slowly.
	science.nasa.gov /newhome/headlines/ast25may99_1.htm (1035 words)

	Big Bang Cosmology Primer
		A possible explanation is that right after the big bang the Universe began a period of exaggerated outward expansion, with particles flying outward faster than the current speed of light.
		One can measure the density of the universe by observing the local group of galaxies and assuming that the Universe is all the same.
		That density is called the critical density, and the ratio of the observed density to the critical density is given by the Greek letter omega.
	cosmology.berkeley.edu /Education/IUP/Big_Bang_Primer.html (1809 words)

	Equivalence and Expansion of the Universe - Bad Astronomy and Universe Today Forum
		I love a theory that the expansion is part of large-scale spacetime curvature, where relativity plays the central role in not only the acceleration of the universe but also the expansion itself.
		If BB theory is correct and the universe was very compact at some point in the past then time them must have been incredibly dilated.
		It is unravelling with the expansion of the Universe.
	www.bautforum.com /showthread.php?t=26669 (2738 words)

	Expansion of the Universe
		Since three dimensional space can be considered to be the surface of space-time which is four dimensional, then the centre of the universe is not located in space but in time, at the moment of the Big Bang singularity itself....
		The centre of the universe is therefore everywhere (in the same way as the centre of the surface of the Earth is also everywhere).
		To say that the expansion happened everywhere at once and then to say that the universe was infinitely small at the outset is simply a prime example of word play.
	www.suite101.com /discussion.cfm/astronomy/12287/149651 (542 words)

	Astronomy Today Forum - cosmology - expansion of the universe
		Mystery forces [vacuum pressure, dark energy, cosmological constant] are not needed to explain the accelerating expansion of the universe.
		The expansion of the universe with an acceleration increasing with distance is the observable effect of this tidal force.
		Early in the life of the observable universe it was compact and internal gravity ruled the motions of its dispersing parts.
	www.astronomytoday.com /forum/about30.html (2730 words)

	sciforums.com - Expansion of the Universe
		A possible mechanism is that the universe expands and cools, so that individual `particles` are no longer in contact with any other subatomic particle,(by virtue that the speed that space expands is greater than the speed of light).
		And if dark energy is accelarating the expansion of universe, it is only natural to detuct that this energy was there when the universe begun and even before the universe begun, and we are expanding into that energy, which is only accelarating the process!!!!
		A denser boundary to the universe (aka percolation theory) is predicted, though the probability is that we already are located near to a boundary rather than near the centre.
	www.sciforums.com /showthread.php?p=750175 (2757 words)

	New Theory Links Neutrino's Slight Mass To Accelerating Universe Expansion
		Two of the biggest physics breakthroughs during the last decade are the discovery that wispy subatomic particles called neutrinos actually have a small amount of mass and the detection that the expansion of the universe is actually picking up speed.
		That tension fuels the expansion of the universe, she said.
		Physicists have pursued evidence that could tell whether the universe will continue to expand indefinitely or come to an abrupt halt and collapse on itself in a so-called "big crunch." While the new theory doesn't prescribe a "big crunch," Nelson said, it does mean that at some point the expansion will stop getting faster.
	www.sciencedaily.com /releases/2004/07/040728090338.htm (912 words)

	Physics News Update (Site not responding. Last check: 2007-11-05)
		The accelerating expansion of the universe, the notion that the big bang enlargement of spacetime is not slowing down but actually gathering speed, has received new experimental support in the form of supernova observations made by the Hubble Space Telescope (HST).
		Previous evidence for such a cosmic acceleration consisted of studies of the dimness of remote supernovas (Update 355), and represented a major revision for some scientists who had long thought that the mutual gravity among galaxies would slow or even reverse the cosmological expansion.
		The new data are in line with the accelerating-expansion hypothesis employing the mysterious mechanism usually referred to as "dark energy." The energy of the universe would be divided up as follows: 29% in the form of matter (dark plus luminous) and 71% as dark energy.
	www.aip.org /enews/physnews/2004/split/675-1.html (169 words)

	ipedia.com: De Sitter universe Article (Site not responding. Last check: 2007-11-05)
		A de Sitter universe is one with a positive cosmological constant and zero matter density.
		There is no Big Bang in a de Sitter universe - expansion is self-similar from an infinite time in the past to an infinite time in the future.
		The model has practical implications as an approximation during the future of the Universe when the cosmological constant is likely to dominate (assuming no changes from the present version of the standard Big Bang model), and during the early universe during a hypothesised period of inflation.
	www.ipedia.com /de_sitter_universe.html (196 words)

	THE EXPANSION OF THE UNIVERSE (Site not responding. Last check: 2007-11-05)
		Thus the size of the Universe is probably constantly increasing and this increase will become bigger the further away the galaxies are from us.
		The speeds at which these celestial bodies are moving may, in the course of this perpetual expansion, go from fractions of the speed of light to speeds faster than this.
		This is true in the case of the Muntakab, a book of commentaries edited by the Supreme Council for Islamic Affairs, Cairo.
	www.geocities.com /islam_the_true_path/quranexpansion.html (260 words)

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