Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!mhuxt!houxm!mtuxo!mtunh!mtung!mtunf!ariel!vax135!petsd!pesnta!hplabs!sri-unix!mcgeer%ucbkim@Berkeley From: mcgeer%ucbkim%Berkeley@sri-unix.ARPA Newsgroups: net.physics Subject: Re: Light Message-ID: <388@sri-arpa.ARPA> Date: Fri, 12-Jul-85 17:39:41 EDT Article-I.D.: sri-arpa.388 Posted: Fri Jul 12 17:39:41 1985 Date-Received: Wed, 17-Jul-85 06:17:49 EDT Lines: 32 From: Rick McGeerFrom: ihnp4!inuxc!inuxd!claus@BERKELEY (David Claus) Subject: Re: Light Article-I.D.: <778@inuxd.UUCP> In-Reply-To: Article(s) <345@sri-arpa.ARPA> The speed of light is not always constant. Einstein assumed that the speed of light was constant through any round trip. The speed of light through one leg of that trip can be greater than the speed through another leg. Take for example a light pulse being sent from the earth to the moon and back. Light will travel faster on the way back than on the way there because of gravity effects. Does general relativity take this into account somehow? It is proven that gravity bends light waves (through sun eclipse experiments) so why shouldn't gravity also increase the speed of the light wave? Has there been an experiment that has measured the speed of light during a one way trip through some gravitational potential? Most measurements I've heard of involve the reflection back and forth of a light wave here on earth. Can anyone explain this to me. Dave Claus AT&T/Indy Gravity won't accelerate a light wave. *Nothing* accelerates a light wave in a vacuum. Instead, the wavelength is affected, in much the same way that the wavelength of light varies as the observer's velocity wrt to the source varies. Rick.