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Laser in outer space

  1. Jul 29, 2009 #1
    ok, second question today:

    if we shine a laser (ideal laser; no spreading out whatsoever of the ray) in earth's atmosphere, at some distance the intensity of the laser will die out due to it hitting air particles.

    what if we shine it in a vacuum? e.g outer space
    My guess is that it will continue forever without dying out (as long as its path is constantly vacuum). This is why Hubble can detect galaxies far far away...

    Is my argument correct?

    Thank you!
  2. jcsd
  3. Jul 29, 2009 #2


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    Science Advisor

    Of course it is, why wouldn't it be? Lasers are just light, after all.
  4. Jul 29, 2009 #3
    Your assumptions are correct for an ideal laser. Unfortunately all lasers have a divergence angle that is dependent on both the wavelength and the inverse of the beam diameter at it's smallest spot. That is a blue laser with higher energy will diverge slower than a red one, etc.
  5. Jul 29, 2009 #4


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    Homework Helper

    Even an ideal laser beam diverges, unless "ideal" also means infinitely thick.

    The reason that the HST can detect and resolve distant galaxies has nothing to do with an ideal laser. The light from distant galaxies is pressumed to be diffuse, basically isotropic, and incoherent. The ability of the HST, as opposed to your naked eye here on Earth, to dectect and resolve a distant light source, such as a galaxy, is due to the design of the HST (e.g. light collection area and exposure).
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