- uploaded: Nov 26, 2012
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The outer space or empty space , also simply called space , refers to the relatively empty regions of the universe outside the atmospheres of celestial bodies. Space is used outside to distinguish it from airspace (and terrestrial areas). The outer space is not completely empty of material (ie, not a perfect vacuum ) but containing a low particle density, gas predominantly hydrogen as well as electromagnetic radiation . Although it is assumed that outer space occupies almost the entire volume of the universe and has long been considered mostly empty, or filled with a substance called ether , now known to contain most of the matter in the universe. This matter is made of electromagnetic radiation, cosmic particles, neutrinos without mass and even forms of matter not well known as dark matter and dark energy . In fact in the universe each of these components contributes to the total area , according to estimates, in the following proportions: cold condensed matter (0.03%), stellar matter (0.5%), neutrinos (massless particles, 0.3%), dark matter (25%) and dark energy (75%). The physical nature of the latter is still little known. Only known by some of its properties that print gravitational effects in the period of revolution of the galaxies , on the one hand, and the accelerated expansion of the universe or cosmic inflation on the other.
There is no clear boundary between Earth's atmosphere and space, as the density of the atmosphere gradually decreases as the altitude increases. However, the International Aeronautical Federation has established the Kármán line at an altitude of 100 kilometers as a working definition for the boundary between atmosphere and space. This is used because, as Theodore von Kármán calculated, above an altitude of about 100 km, a typical vehicle would have to travel faster than orbital velocity in order to get enough aerodynamic lift to steady himself. U.S. designates people traveling above an altitude of 80 km as astronauts . During atmospheric reentry , the altitude of 120 km marks the boundary where atmospheric drag becomes noticeable.
Outer space within the Solar System is called interplanetary space , which turns into interstellar space at the heliopause . The vacuum of outer space is not really empty, is populated in part with several dozen types of molecules organic discovered by microwave spectroscopy . According to the Big Bang theory , the black body radiation of 2.7 K in temperature was the big bang and the origin of the universe fills the space, as well as cosmic rays , which include atomic nuclei ionized and various subatomic particles . There are also gas, plasma , dust, meteors and material left from previous releases and UAVs that are a potential hazard to spacecraft . Some of this space debris re-enters the atmosphere.
The absence of air makes outer space ideal locations for astronomy at all wavelengths of the electromagnetic spectrum . The images and other data from unmanned spacecraft have provided information on the planets , asteroids and comets in our solar system.
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