Space exploration began with the launch of Sputnik and Astrophysics was born as the application of physics to the phenomena observed by Astronomy, which etymologically means laws of the stars.
There are 2759 entries in this glossary.| Term | Definition |
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| Lepton Era |
The period from one-millionth of a second to one second after the primordial Big Bang. During this interval, the behaviour of the universe was dominated by the lighter elementary particles, such as electrons and neutrinos, together with a tiny proportion one-billionth of protons and neutrons.
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