From: utzoo!decvax!ucbvax!mhtsa!eagle!harpo!ihps3!ihnss!knudsen
Newsgroups: net.space
Title: Supernova, Gravity, Etc
Article-I.D.: ihnss.126
Posted: Thu Aug  5 15:16:18 1982
Received: Sun Aug  8 07:34:40 1982

HOLD IT!  Basic hih-school physics states that the center of mass
of an object cannot change (or its net momentum change) merely
thru action of forces generated WITHIN that object --
rather, OUTSIDE forces are required.
The example often used is a hand grenade flying thru outer space;
if it explodes, the center-of-gravity/mass of all the fragments
(& gases, etc) continues to move as before.
Substitute a star for the grenade, comes the supernova explosion,
and, presto, the center of mass stays ewhere it was.

I think someone was wondering how much mass of the star would be changed
into ENERGY a la E=mc^2, which *would* cause an instant change in mass.
This change is radically different from the percentage of star matter
that is merely blown away into space -- probably the 50~90% guesses
are close.

PS: If matter and energy are the same thing, and you have a volume of
space with a VERY high energy flux, does it exert gravity
(ie, distort space around it)?
--mike knudsen ihnss!knudsen