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The Big Bang is a physical theory that describes how the universe expanded from an initial state of high density and temperature. [1] The concept of an expanding universe was scientifically originated by physicist Alexander Friedmann in 1922 with the mathematical derivation of the Friedmann equations.
Swenson, Jim, Answer to a question about the expanding universe Archived 11 January 2009 at the Wayback Machine; Felder, Gary, "The Expanding universe". NASA's WMAP team offers an "Explanation of the universal expansion" at an elementary level. Hubble Tutorial from the University of Wisconsin Physics Department Archived 9 June 2014 at the ...
Thus, an accelerating universe took a longer time to expand from 2/3 to 1 times its present size, compared to a non-accelerating universe with constant ˙ and the same present-day value of the Hubble constant. This results in a larger light-travel time, larger distance and fainter supernovae, which corresponds to the actual observations.
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 ...
The prevailing theory is that the universe will cool as it expands, eventually becoming too cold to sustain life. For this reason, this future scenario popularly called "Heat Death" is also known as the "Big Chill" or "Big Freeze". Some of the other popular theories include the Big Rip, Big Crunch, and the Big Bounce. [1] [2]
Big History covers the formation of the universe, stars, and galaxies, and includes the beginning of life as well as the period of several hundred thousand years when humans were hunter-gatherers. It sees the transition to civilization as a gradual one, with many causes and effects, rather than an abrupt transformation from uncivilized static ...
The physical universe is defined as all of space and time [a] (collectively referred to as spacetime) and their contents. [10] Such contents comprise all of energy in its various forms, including electromagnetic radiation and matter, and therefore planets, moons, stars, galaxies, and the contents of intergalactic space.
The chronology of the universe describes the history and future of the universe according to Big Bang cosmology. Research published in 2015 estimates the earliest stages of the universe's existence as taking place 13.8 billion years ago, with an uncertainty of around 21 million years at the 68% confidence level. [1]