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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 .
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. It is not universally accepted.
It is approximately equal to the mean Earth–Sun distance. It was formerly defined as that length for which the Gaussian gravitational constant (k) takes the value 0.017 202 098 95 when the units of measurement are the astronomical units of length, mass and time. [1] The dimensions of k 2 are those of the constant of gravitation (G), i.e., L 3 ...
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 ...
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 ...
The calculated stellar distance will be in the same measurement unit as used in Distance earth-sun (e.g. if Distance earth-sun = 1 au, unit for Distance star is in astronomical units; if Distance earth-sun = 1.5813 × 10 −5 ly, unit for Distance star is in light-years).
The largest unit for expressing distances across space at that time was the astronomical unit, equal to the radius of the Earth's orbit at 150 million kilometres (93 million miles). In those terms, trigonometric calculations based on 61 Cygni's parallax of 0.314 arcseconds, showed the distance to the star to be 660 000 astronomical units (9.9 ...
China has put its own space station in orbit and regularly sends crews there. The emerging global power aims to put a person on the moon before 2030, which would make it the second nation after ...