Reference Terms
from Wikipedia, the free encyclopedia

Outer space

Outer space, also simply called space, refers to the relatively empty regions of the universe outside the atmospheres of celestial bodies.

Outer space is used to distinguish it from airspace (and terrestrial locations).

Contrary to popular understanding, outer space is not completely empty (i.e. a perfect vacuum) but contains a low density of particles, predominantly hydrogen gas, as well as electromagnetic radiation.

Note:   The above text is excerpted from the Wikipedia article "Outer space", which has been released under the GNU Free Documentation License.
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