At what altitude are you considered to enter 'Space'?

Answer 1

The official boundary of space defined by the Fédération Aéronautique International is 100 Km or about 62 miles

Answer 2

The French define it as 100 miles, the US says anyone that goes above 50 miles is an "astronaut", and atmospheric drag becomes evident at 75 miles. Choose your definition! None of these are high enough for a stable orbit, however, since the atmosphere doesn't just stop, it just becomes thinner and thinner. Even at 150 miles, there's still a tiny bit of drag, although some satellites do orbit this low, though they aren't expected to last very long. The source below gives a very good definition of atmospheric effects at differing altitudes.

Answer 3

The exosphere (from the Greek words exo = out(side) and sphaira = ball) is the uppermost layer of the atmosphere. On Earth, its lower boundary at the edge of the thermosphere is estimated to be 500 km to 1000 km above the Earth's surface, and its upper boundary at about 10,000 km. It is only from the exosphere that atmospheric gases, atoms, and molecules can, to any appreciable extent, escape into outer space. The main gases within the exosphere are the lightest gases, mainly hydrogen and helium, with some atomic oxygen near the exobase.

The atmosphere in this layer is sufficiently rarefied for satellites to orbit the Earth, although they still receive some atmospheric drag.

Exobase, also called the critical level, the lowest altitude of the exosphere, is defined in one of two ways:

The height above which there are negligible atmospheric collisions between the particles and
The height above which the constituent atoms are on purely ballistic trajectories.
The exact altitude at which the exosphere ends and space begins is not well-defined, and attempting to attach a specific value to it is not particularly useful.

Answer 4

In my view you have to be out of the solar system. That means we haven't started yet. You can't really count circlings of the earth or quick hops to local lumps of rock as space travel.

According to WIKIPEDIA, space is set at the Karman line. That's 100km up. But really you have to be outside the influence of a star. Sometimes that's called Outer Space.

Answer 5

Around 60 miles up

Answer 6

There is no real physical answer but 'space' is generally considered to start at a height of 100Km.

Answer 7

trouble with the french is can you trust anything they say?

i was watching Q.I. the other day and this question came up. stephen fry said it was 62 miles but jeremy clarkson said the above.

its not my opinion okay!!

Answer 8

About a foot above my shoulders

Answer 9

http://en.wikipedia.org/wiki/Earth%27s_atmosphere

According to that, after about 50 miles, you are considered an astronaut.

Answer 10

110,000 feet . This is the Ionosphere
and it is black not blue like the sky.