Can someone explain the layer dividing earth and space.

How thick is the layer?

When you cross the border you instantly float which seems weird and amazing.

I've heard that for airtrafic the border is set at 100 kilometres of height, but I believe the real border (where you experience weightlessness) is at another height.

Originally posted by NLDelta9
How thick is the layer?

When you cross the border you instantly float which seems weird and amazing.

The atmosphere gets thinner as you go up and past a certain height there's no longer any 'atmosphere' to speak of. You don't become instantly weightless at any altitude though unless you accelerate into an orbit which implies your centrifugal force is equal to the pull of earth's gravity and the 'magic' speed for this to occur is about 7 miles per second in low earth orbit. If you were stationary the earth would pull you down so fast the increasing atmospheric density would cause enough friction to burn you up.

Gravity obeys the inverse square law as you get further from the source.

reply to post by NLDelta9

Astronauts in Low Earth Orbit (LOE) on the Space Station and the Space shuttle are subjected to about 97% of the gravity we feel here at the surface. They don't experience weightlessness due to the lack of gravity, but rather because they and their spacecraft are "falling" together ot the same relative rate... it's sort of like the feeling you get in an elevator that begins to drop very quickly -- you feel "light on your feet". That's also how that airplane nicknamed the "vomit comet" can re-create the weightless conditions on the Space Station -- because it flys on a path that simulates the "free fall" of the Station and Shuttle.

Something in orbit is not floating -- it is actually falling towards the Earth. But since it is also moving sideways relative to the Earth's surface, it will never hit the Earth because the Earth is a sphere and the surface "curves away" from the object before it can hit that surface. THAT is the definition of 'orbit'. That's why the Space Station, the shuttle, and anything else in LOE need to move at 17,000 mph -- so it can move "sideways" fast enough to fall clear of the Earth's surface curving away under it.

Here's a few Wikipedia articles on weightlessness and Orbits. The "Newton's Cannonball" article is short and to the point:

Weightlessness

Newton's Cannonball

Orbit

[edit on 2/27/2008 by Soylent Green Is People]