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

  1. Nov 20, 2012 #1
    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.
     
  2. jcsd
  3. Nov 21, 2012 #2

    bcrowell

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    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.
     
  4. Nov 21, 2012 #3
    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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