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The authors also argue that due to the immense size of the universe, even if another habitable planet like Earth does exist elsewhere, meaning that the Earth is not the only planet in the universe with complex life, such planets would still only appear in relatively small numbers compared to planets that are habitable only to bacteria. Such ...
The Earth is the center of motion of the universe, with circular motion being perfect because Earth was at the center of it. There can be only one center of the universe, and as a result there are no other inhabited worlds within it besides Earth. As such the Earth is unique and alone in this regard.
In 2013, astronomers using the Kepler space telescope's data estimated that about one-fifth of G-type and K-type stars (sun-like stars and orange dwarfs) are expected to have an Earth-sized or super-Earth-sized planet (1–2 Earths wide) close to an Earth-like orbit (0.25–4 F 🜨), [83] yielding about 8.8 billion of them for the entire Milky ...
The physical universe is widely seen to be composed of "matter" and "energy". In his 2003 article published in Scientific American magazine, Jacob Bekenstein speculatively summarized a current trend started by John Archibald Wheeler, which suggests scientists may "regard the physical world as made of information, with energy and matter as incidentals".
Earth's rotation period relative to the Sun—its mean solar day—is 86,400 seconds of mean solar time (86,400.0025 SI seconds). [157] Because Earth's solar day is now slightly longer than it was during the 19th century due to tidal deceleration , each day varies between 0 and 2 ms longer than the mean solar day.
Neutron:proton ratio freezes at approximately 1:6. The sphere of space that will become the observable universe is approximately 10 light-years in radius at this time. Lepton epoch: 1 s ~ 10 s: 10 10 K ~ 10 9 K (1 MeV ~ 100 keV) Leptons and antileptons remain in thermal equilibrium—energy of photons is still high enough to produce electron ...
The Earth was formed at 4.54 Gya, and the earliest evidence of life on Earth dates from at least 3.8 Gya from Western Australia. Some studies have suggested that fossil micro-organisms may have lived within hydrothermal vent precipitates dated 3.77 to 4.28 Gya from Quebec , soon after ocean formation 4.4 Gya during the Hadean .
Earth (0.98–1.02 AU) [D 6] is the only place in the universe where life and surface liquid water are known to exist. [102] Earth's atmosphere contains 78% nitrogen and 21% oxygen, which is the result of the presence of life. [103] [104] The planet has a complex climate and weather system, with conditions differing drastically between climate ...