Shoutbox

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Originally posted by MoRiA
Which is why we say that c is the speed of light in a vacuum. It's ever so slightly slower in normal air than it is in a vacuum (but so inperceptibly so that we can just use c in most of our calculations...).

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Yeah I know that , I just thought It was pretty clever (That's also why light slows down 30% in a fiber optic cable)

About that thing with the spaceships:

quote:

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Originally posted by wikipedia
if two cars approach each other from opposite directions, each travelling at a speed of 50 kilometres per hour (31 miles per hour), one expects that each car will perceive the other as approaching at a combined speed of 50 + 50 = 100 km/h (62 mph) to a very high degree of accuracy.

At velocities at or approaching the speed of light, however, it becomes clear from experimental results that this rule does not apply. Two spaceships approaching each other, each travelling at 90% the speed of light relative to some third observer between them, do not perceive each other as approaching at 90% + 90% = 180% the speed of light; instead they each perceive the other as approaching at slightly less than 99.5% the speed of light.

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Source: http://en.wikipedia.org/wiki/Speed_of_light