In actuality, the air in earth's atmosphere
becomes thinner and thinner as you move towards
outer space, but there is no finite line that
marks where our atmosphere ends and space begins.
However, there are several ways to describe how
far one must go to be "out of Earth".
line, which is 100 kilometers (62 miles) from the
earth's surface, is often used as the
internationally accepted border between earth's
atmosphere and space. However, you must travel
only 50 miles above the earth's surface to be
designated as an astronaut. Finally, for a
spaceship coming towards earth, it begins to feel
the effects of the atmosphere at a height of 120
kilometers (74.6 miles) above the earth's
So to answer your question simply,
a good estimate for the beginning of outer space
would be roughly 100 kilometers (62 miles).
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