crummer@AEROSPACE.ARPA (06/18/85)
From: Charlie Crummer <crummer@AEROSPACE.ARPA> > Received: by sri-unix.ARPA (4.12/4.16) > id AA24360; Fri, 14 Jun 85 19:25:58 pdt > Message-Id: <8506150225.AA24360@sri-unix.ARPA> > Date: Tue, 11-Jun-85 22:06:44 PDT > To: physics@sri-unix > From: ucbcad!tektronix!teklds!azure!chrisa@UCB-Vax.ARPA (Chris Andersen) > Subject: Re: speed > Article-I.D.: <256@azure.UUCP> > In-Reply-To: Article(s) <359@osiris.UUCP> <56@rtp47.UUCP>, > <11222@brl-tgr.ARPA> <1428@ecsvax.UUCP> > > > > The problem is that NOT all motion is relative. Inertial reference > > frames are equally valid, which says something quite different. The > > twin at rest is at rest in one inertial reference frame the whole time. > > The traveling twin has to use her rocket motor to change directions, so > > that twin is NOT at rest in an inertial frame for the whole time. > > That's the non-symmetry in the Twin Paradox. > > > I wonder, can the twin who remains behind *really* be considered > to be in an inertial reference frame? After all, he is subject to the gravity > of the earth. Doesn't that make his reference frame non-inertial? > > -- > > D Gary Grady > > Duke U Comp Center, Durham, NC 27706 > > (919) 684-3695 > > USENET: {seismo,decvax,ihnp4,akgua,etc.}!mcnc!ecsvax!dgary > Chris Andersen > USENET: tekronix!azure!chrisa The gravitational field of the earth is a red herring in this case. Just have the experiment performed in intergalactic space where space-time is approximately flat. --Charlie