From: utzoo!henry
Newsgroups: net.space
Title: acceleration is relative 
Article-I.D.: utzoo.2332
Posted: Tue Aug  3 19:12:09 1982
Received: Tue Aug  3 19:12:09 1982

Comparing the direction of "down" will not reliably distinguish
between gravity and acceleration.  Consider the acceleration of
the surface of a sphere expanding at an increasing rate.  This is
a pretty exact simulation of not just the force but also the shape
of gravity.

The "twin paradox" is not a paradox because the supposed symmetry
of acceleration is not present.  One twin is accelerating with respect
to the large, gravitating mass of the universe;  the other is not.

					Henry Spencer
					utzoo!henry