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As the universe expands and the matter in it thins, the gravitational attraction decreases (since it is proportional to the density), while the cosmological repulsion increases. Thus, the ultimate fate of the ΛCDM universe is a near-vacuum expanding at an ever-increasing rate under the influence of the cosmological constant.
This suggests that the universe began very dense about 13.787 billion years ago, and it has expanded and (on average) become less dense ever since. [1] Confirmation of the Big Bang mostly depends on knowing the rate of expansion, average density of matter, and the physical properties of the mass–energy in the universe.
The Big Bang is a physical theory that describes how the universe expanded from an initial state of high density and temperature. [1] The notion of an expanding universe was first scientifically originated by physicist Alexander Friedmann in 1922 with the mathematical derivation of the Friedmann equations.
The Big Bang event 13-14 billion years ago initiated the universe, and it has been expanding ever since. Scientists in 1998 disclosed that this expansion was actually accelerating, with dark ...
This is an accepted version of this page This is the latest accepted revision, reviewed on 24 December 2024. Problem of the lack of evidence for alien life despite its apparent likelihood This article is about the absence of clear evidence of extraterrestrial life. For a type of estimation problem, see Fermi problem. Enrico Fermi (Los Alamos 1945) The Fermi paradox is the discrepancy between ...
For years, scientists have been troubled by an unusual feature of our universe. It appears to be expanding faster today than it did in the past
Given our assumed half-life of the proton, nucleons (protons and bound neutrons) will have undergone roughly 1,000 half-lives by the time the universe is 10 43 years old. This means that there will be roughly 0.5 1,000 (approximately 10 −301 ) as many nucleons; as there are an estimated 10 80 protons currently in the universe, [ 41 ] none ...
In “The Secret Life of the Universe: An Astrobiologist's Search for the Origins and Frontiers of Life,” readers won't walk away with a clear-cut answer to that question.