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 Be the first pioneers to continue the Astronomy Discussions at our new Astronomy meeting place...The Space and Astronomy Agora Re: Speed Of Light Forum List | Follow Ups | Post Message | Back to Thread Topics | In Response ToPosted by Cly/">Cly on November 11, 1999 03:13:12 UTC

: : If you were, say, at a point on the edge of the galaxy, spinning round at 250000000mph, you are travelling at 0mph in relation to the galaxy, so equal accelerations in either direction mean that you would end up travelling at the same speed with relation to the galaxy, because you started with a relative velocity of 0.

: : One the second point however, there is a problem. One of the basises for relativity is that, no matter how fast you are travelling, if you turn a torch on, the light from it will appear to travel away from you at the speed of light. So, if the sun is the torch, no matter whether its travelling in front of or behind the planet, the light takes the same amount of time to get there.

: doen't that kinda mean that the light is traveling in two different speeds?

Light ALWAYS travels at the same speed no matter what the speed or direction of the observer, but if the source is moving away or towards you at any appreciable percentage of lightspeed, it will show this energy loss (away from) or gain (towards) as a change in color, thus the 'redshift' of galaxies, moving away from our's, for example. They can tell how fast they're moving away by the ammount of redshift.

Hope this helps, if not try 'Understanding Physics, Light, Magnetism, and Electricity' by I. Asimov, \$5 paperback.