Expanding Universe
Related Category: Astronomy: General
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More on Expanding Universe
Universe - totality of matter and energy in existence.
Expanding Universe :
The expanding Universe, the dynamic state of the extragalactic realm, is the discovery of which has transformed 20th-century cosmology.
The great question is: what lies beyond the expanding universe? Is there anything? If time is relative to your position and speed in the universe, then time cannot possibly exist outside of the universe.
An expanding universe was actually predicted by Albert Einstein's theory of general relativity. But Einstein believed that the Universe should be static because that was more perfect, and many people agreed.
a) The Age of the Expanding Universe
Astronomers can estimate the distance of each galaxy of a certain type from its apparent size or brightness. The smaller and fainter a galaxy appears, compared to similar galaxies, the farther away it must be.
EXPANDING UNIVERSE
The expanding universe is a model of the universe in which galaxies are receding from one another at a speed proportional to their separation - it is based on the observed Doppler redshift of distant galaxies.
The Expanding Universe
The discovery of the expanding universe was Edwin Hubble's preeminent contribution to modern cosmology, and as we have already discussed, ...
Expanding universes need not continue to expand forever. They do so if their average density is below a critical value. But if their average density exceeds this value then at some time in the future the expansion will be reversed into contraction.
In an expanding universe, the gravity field created by the matter within the universe will tend to slow down its expansion.
Future of an expanding universe
Recent observations suggest that the expansion of the universe will continue forever. If so, the universe will cool as it expands, eventually becoming too cold to sustain life....
and the heat death of the universe ...
The Expanding Universe
However, the most famous Doppler shift of light is probably the one observed in distant galaxies.
This view of the expanding universe requires us to reinterpret the cosmological redshift. (Sec. 24.5) Up to now we have explained the redshift of galaxies as a Doppler shift, a consequence of their motion relative to us.
In models of the expanding universe, the further things are from Earth, the faster they move away from us. This movement is not considered to be a straightforward travel, like a rocket for example, but a movement due to the expansion of space itself.
(a) Theory that the expanding Universe was never in a state of appreciably higher density - i.e., that there was no "big bang" - and that matter is constantly being created out of empty space in order to maintain the cosmic matter density.
This was a key piece of evidence suggesting an expanding Universe and supporting a Big Bang model. hydrogen The most abundant element in the Universe, its most common isotope has a single electron orbiting a proton..
1927 - Georges Lemaître discusses the creation event of an expanding universe governed by the Einstein field equations ...
In an expanding universe, some regions of the past can be unobservable ("particle horizon"), and some regions of the future cannot by any means be influenced (event horizon); in both cases, ...
The models that LeMaitre and Friedmann came up with had an expanding Universe. The general scheme of the model is that the universe started out much smaller and much hotter.
Therefore, in an expanding universe, new matter must be continually created. This violates a central rule of nature known as the law of the conservation of mass.
Before going on to galaxy formation and evolution, it is worthwhile to look at the connections between cosmological models and basic tenets of general relativity for the commonly-considered instance of an expanding Universe in the Friedman model.
Cepheid distances are the first step to obtaining not just the distances of other galaxies but of establishing the nature of the whole expanding Universe.
I have been trying to understand the idea of an expanding Universe. As I understand what I have read, this concept is based on relativity.
One unavoidable conclusion of an expanding universe is that in our past the universe had a much higher density; if we extrapolate far enough back in time, we find a time of infinite density; we define this time as the beginning of the universe.
However, in an expanding Universe, the radiation density falls faster than the matter density and the Universe became matter-dominated.
This theory describes an expanding Universe that stays in perfect balance like a pool kept full to overflowing by a trickle from a faucet. The "faucet" of the Universe would be the continuous creation of matter from energy.
After three minutes the rapidly expanding universe was too cold and the reactions stopped, leaving 98 atoms of helium for every 1000 of hydrogen and a very small amount of lithium.
One of the unresolved problems in the expanding universe model is whether the universe is open (that is, whether it will expand forever) or closed (whether the universe will contract again).
Edwin Hubble discovers that galaxies are moving away from each other, implying an expanding universe
1965
Arno Penzias and Robert Wilson discover the cosmic microwave background, supporting the Big Bang theory ...
The theory that the universe began with a violent explosion from which the expanding universe of galaxies formed.
Binary Stars
Pairs of stars that orbit around their common center of mass ...
[9.1] THE ORIGINS OF COSMOLOGY / THE EXPANDING UNIVERSE
[9.2] BIG BANG VERSUS STEADY-STATE
[9.4] THE BIG BANG ...
dark energy: The energy of empty space that drives the acceleration of the expanding universe.
dark matter: Nonluminous material that is detected only by its gravitational influence.
Small period changes in a stars radial velocity have been used to detect exoplanets. In an expanding universe a galaxy with a larger radial velocity generally lies further from the observer than one with a smaller radial velocity.
He based his theory on the work of Einstein and De Sitter, and independently derived Friedmann's equations for an expanding universe.
red shift
The Columbia Encyclopedia, Sixth Edition
red shift
World Encyclopedia
The Red Shift: Discovering an Expanding Universe
American Decades ...
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39. Big Bang Theory
The theory that the universe began with a violent explosion from which the expanding universe of galaxies formed.
expanding universe (cosmology)
galaxy (astronomy)
gamma-ray burster (astronomy)
gravitation (physical force)
infrared astronomy
infrared source (astronomy)
meteoritics (science)
moon (natural satellite)
physical science
planet ...
The rate at which clusters are forming has slowly decreased over the last seven billion years due to the effects of dark energy, a force used to explain the acceleration of the expanding Universe.
dark at night contrasted to a simple argument that shows that the sky should be uniformly bright, due to there being a star in every line of sight in an infinite and uniform universe. The paradox is resolved by the redshift of the expanding universe.
We're thirty thousand light-years from galactic central point.
We go 'round every two hundred million years.
And our galaxy is only one of millions of billions
in this amazing and expanding universe.
We've tried to get this sense of awe, and of continuous learning, into the AstroCappella project: the Pluto (planet or Kuiper Belt object?) controversy makes an appearance in the song Nine Planets. The expanding universe is mentioned in several ...
 See also: Universe, Time, Galaxies, Light, Galaxy
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