(Steve Mazerski) writes:

until recently I was of the vague impression that gravity diminishes
very quickly in space which is why occupants of orbiting vehicles
appeared weightless...

Gravity does not "diminish very quickly in space;" as Newton showed,
it obeys an inverse square law. Hence, at twice the Earth's raius,
the gravitational acceleration toward the Earth is still 1/4th gee,
at three earth radii, it is still 1/9th gee, etc. --- and the gravitational
accleration at the altitude of low earth orbit is so close to 1 gee as to
make no practical difference.

Astronauts _appear_ "weightless" because they are MOVING AT ORBITAL VELOCITY,
just like their spacecraft, and both they and they spacecraft have the _same_
acceleration toward the Earth. Since they are BOTH accelerating at the SAME
RATE in the SAME DIRECTION, their _RELATIVE_ acceleration is _ZERO_, and they
=APPEAR= to "float" _RELATIVE_ in the spacecraft cabin. However, in reality,
+BOTH= they and their spacecraft are falling toward the Earth at a about a gee.

For the same reason If you were in an elevator and the cable broke, both
the elevator =AND= you would fall toward the Earth at the local value of
the gravitational acceleration, and you would _FEEL_ "weightless."
This is =NOT= because gravity has "gone away," but because in a gravitational
field, =EVERYTHING= falls with _EXACTLY THE SAME ACCELERATION_.


-- Gordon D. Pusch

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