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Re: About The Speed Of Light

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Posted by Bruce on December 30, 2000 21:49:55 UTC

As the object crosses the event horizon its speed is exactly c.
Interestingly enough both GR and Newton arrive at the same conclusion. If your interested in seeing how GR derives the following expression from the Schwarzchild metric and how Newton would derive the same expression I'll be happy to show you.
Newton would express it
v=(2M/r)1/2 (note:all units are meters, including M).
and GR
drshell/dtshell= - (2M/r)1/2
r=2M is the event horizon so when you substitute 2M for r in both expressions you get v expressed as a fraction of the speed of light. So when
then v=c (for r=2M).
Great book by Kip Thorne. The prologue is really neat.

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