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devious_
Dec5-04, 07:02 AM
If a spaceship is travelling at c and a beam of light is emitted through it. The beam of light would be travelling at c relative to the object. Correct?

How about if there's an observer, what would the speed of the beam of light be relative to him. c?

And if the spaceship was instead travelling at 0.6c, would the speed of light relative to it still be c?

Doc Al
Dec5-04, 07:12 AM
Yes to all: The speed of light with respect to any object or observer will be c.

devious_
Dec5-04, 08:02 AM
Great. Thanks. :)

pervect
Dec5-04, 09:40 PM
If a spaceship is travelling at c

A spaceship can't travel at c, though it can get arbitrarily close.

pmb_phy
Dec6-04, 01:03 AM
A spaceship can't travel at c, though it can get arbitrarily close.Well... there is that whole Alcubierre warp drive thingy.

E.g. see Fundamental limitations on "warp drive" spacetimes, Francisco S. N. Lobo, Matt Visser, Class.Quant.Grav. 21 (2004) 5871-5892

Online at - http://xxx.lanl.gov/abs/gr-qc/0406083

Pete

Doc Al
Dec6-04, 07:42 AM
If a spaceship is travelling at c A spaceship can't travel at c, though it can get arbitrarily close.
Oops... I must have missed that statement by devious_ in my quick reading. Good catch, pervect.