From: utzoo!decvax!cca!Wedekind.ES@PARC-MAXC@sri-unix Newsgroups: net.space Title: Supernova, Gravity, Etc Article-I.D.: sri-unix.2575 Posted: Mon Aug 9 11:32:18 1982 Received: Tue Aug 10 02:33:32 1982 This is in response to Mike Knudsen' comment that a supernova's center of mass (more precisely, the path that the center of mass follows) remains unchanged by the explosion. This doesn't mean that the gravitational force on external bodies remains unchanged. The gravitational force DOES stay the same in the special case where the exploding mass retains a spherically symmetrical density, as Newton first showed. In particular, it's the same as if all the mass were at the CM. But in the general case it can get bigger or smaller, and change direction too. You can see all this if you imagine simple cases (where the star splits in half, for instance, and one half lands on your doorstep!). The galaxies where we see jets shooting off across the line of sight - they're not pulling on us quite as hard as they used to. This isn't surprising, since CM is linear with position and gravity force isn't. cheers, Jerry