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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.
According to the Big Bang theory, the very early universe was an extremely hot and dense state about 13.8 billion years ago [21] which rapidly expanded. About 380,000 years later the universe had cooled sufficiently to allow protons and electrons to combine and form hydrogen—the so-called recombination epoch.
The universe's size is unknown, and it may be infinite in extent. [14] Some parts of the universe are too far away for the light emitted since the Big Bang to have had enough time to reach Earth or space-based instruments, and therefore lie outside the observable universe. In the future, light from distant galaxies will have had more time to ...
Scientists say they are rethinking how the weather works after creating a 3D map of an exoplanet 900 light-years away and discovering a world with jet streams fueling wild storms.
An infinite universe (unbounded metric space) means that there are points arbitrarily far apart: for any distance d, there are points that are of a distance at least d apart. A finite universe is a bounded metric space, where there is some distance d such that all points are within distance d of each other.
Discovered through gamma-ray burst mapping. Largest-known regular formation in the observable universe. [8] Huge-LQG (2012–2013) 4,000,000,000 [9] [10] [11] Decoupling of 73 quasars. Largest-known large quasar group and the first structure found to exceed 3 billion light-years. "Giant Arc" (2021) 3,300,000,000 [12] Located 9.2 billion light ...
The history of the universe after inflation but before a time of about 1 second is largely unknown. [22] However, the universe is known to have been dominated by ultrarelativistic Standard Model particles, conventionally called radiation, by the time of neutrino decoupling at about 1 second. [23]
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.