Why do astronauts seem weightless in orbit?
(Lansing State Journal, November 22, 1995)

It is important to realize that gravity does act upon the space shuttle.  Yet, suppose you are holding a super-slingshot and are on top of a mountain over looking a cliff, and it plummets to the ground.  If you put an identical rock in the slingshot and shoot it horizontally, it will proceed downrange before hitting the earth's surface.  Both rocks take the same amount of time to hit the ground as they fall at the same rate.

Now suppose that our super charged slingshot launches the rock with such a large horizontal velocity that as it falls, the curvature of the earth prevents our falling rock from ever reaching the surface.  This is an orbit.  Astronauts in the shuttle are in orbit, and are thus in a constant state of free fall.  Since the astronauts and shuttle fall at the same rate, a weightless environment results.

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