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Can you move fast enough towards light so that it has a period of 0?

by stu dent
Tags: light, period
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stu dent
#1
Nov20-12, 11:14 PM
P: 20
at what speed must i be moving towards a beam of light in order for the wavelength to have a period of 0?

would it be the speed of light? would it need to be greater than the speed of light? if so, what period would it be at if i were movign at the speed of light?

i mean, maybe the question is dumb, and the answer is obvious that it would be the speed of light, but with relativity, the answer seldom turns out to be obvious i find.
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bcrowell
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Nov21-12, 12:15 AM
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Quote Quote by stu dent View Post
would it be the speed of light?
Yes. The Doppler shift factor is [(1-v/c)/(1+v/c)]1/2, which only equals zero for v=c. Since you can't move at v=c, this never happens.
stu dent
#3
Nov21-12, 09:50 PM
P: 20
ya.. but light does.

it's almost kind of predictable that would be the case, and yet, an interesting thought.

and predictably i guess again, as v→-c it goes to infinity.


here's a related question. how do we know whether or not there's a bunch of stuff in outer space that's moving away, or towards us, by rates of speed that would yield a period, as of yet, undetected by us? or detected by us, and yet, unrecognized.


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