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This is an accepted version of this page This is the latest accepted revision, reviewed on 6 January 2025. 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 the ...
The redshift hypothesised in the Big Bang model would by itself explain the darkness of the night sky even if the universe were infinitely old. In the Steady state theory the universe is infinitely old and uniform in time as well as space. There is no Big Bang in this model, but there are stars and quasars at arbitrarily great distances.
A.Wilson's drawings of sunspots. In 1965 astronomer Ernst Julius Öpik wrote the article "Is the Sun Habitable?" in which he described that in 1774 Alexander Wilson of Glasgow, remarking that sunspots are apparently lower than the rest of the surface of the Sun, hypothesised that the interior of the Sun is colder than its surface and possibly suitable for life. [1]
1. First postulate (principle of relativity) The laws of physics take the same form in all inertial frames of reference.. 2. Second postulate (invariance of c) . As measured in any inertial frame of reference, light is always propagated in empty space with a definite velocity c that is independent of the state of motion of the emitting body.
Outer space, especially the relatively empty regions of the universe outside the atmospheres of celestial bodies; Vacuum, a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure; Free space, a perfect vacuum as expressed in the classical physics model
The nature of both dark energy and dark matter is unknown. Dark matter, a mysterious form of matter that has not yet been identified, accounts for 26.8% of the cosmic contents. Dark energy, which is the energy of empty space and is causing the expansion of the universe to accelerate, accounts for the remaining 68.3% of the contents. [8] [97] [98]
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The most striking aspect is that it requires a different definition of what it means to be a void. Instead of the general notion that a void is a region of space with a low cosmic mean density; a hole in the distribution of galaxies, it defines voids to be regions in which matter is escaping; which corresponds to the dark energy equation of ...