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Earth's atmosphere photographed from the International Space Station.The orange and green line of airglow is at roughly the altitude of the Kármán line. [1]The Kármán line (or von Kármán line / v ɒ n ˈ k ɑːr m ɑː n /) [2] is a conventional definition of the edge of space.
Outer space (or simply space) is the expanse that exists beyond Earth's atmosphere and between celestial bodies. [1] It contains ultra-low levels of particle densities , constituting a near-perfect vacuum [ 2 ] of predominantly hydrogen and helium plasma , permeated by electromagnetic radiation , cosmic rays , neutrinos , magnetic fields and dust .
This is because the distance between Earth and the Sun is not fixed (it varies between 0.983 289 8912 and 1.016 710 3335 au) and, when Earth is closer to the Sun , the Sun's gravitational field is stronger and Earth is moving faster along its orbital path. As the metre is defined in terms of the second and the speed of light is constant for all ...
As Earth's natural satellite, the moon is our planet's closest space neighbor and companion, joining us for the over 365-day journey around the sun.But "close" is a relative term in the expanding ...
Assuming that space is roughly flat (in the sense of being a Euclidean space), this size corresponds to a comoving volume of about 1.22 × 10 4 Gpc 3 (4.22 × 10 5 Gly 3 or 3.57 × 10 80 m 3). [ 29 ] These are distances now (in cosmological time ), not distances at the time the light was emitted.
One astronomical unit (au), the distance from the Sun to the Earth, is just under 5 × 10 −6 pc. The most distant space probe, Voyager 1, was 0.000 7897 pc from Earth as of February 2024. Voyager 1 took 46 years to cover that distance. The Oort cloud is estimated to be approximately 0.6 pc in diameter
A low Earth orbit (LEO) is an orbit around Earth with a period of 128 minutes or less (making at least 11.25 orbits per day) and an eccentricity less than 0.25. [1]
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