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Just a simple question =D

  1. Mar 25, 2009 #1


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    Hi all.

    Its my first post here...

    Would just like to ask about the light wave interference patterns of light. I just occurred to me about the light coming from the eon-old stars interfering with light from another... Would it cause a magnified ripple that would cause us to wrongly see the stars or their positions?

  2. jcsd
  3. Mar 25, 2009 #2
    Welcome to PF!!!!

    As far as I know, light from one source does not interfere with light from another.

    That is not the same thing as a "double-slit" experiment.

    In any event, I'm sure there is more to this. Perhaps others more knowlegeable can answer more clearly.
  4. Mar 25, 2009 #3


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    Gold Member

    Yes, any number of light beams (or photons) can pass through the same point without interfering with each other. In that sense, it's just like waves on a pond.

    You only get interference when light waves are in phase - normally because they're coming from the same source - a la a two-slit setup.
  5. Mar 26, 2009 #4


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    The interference of photon photon does not change their direction, so star observed wil not be influenced by this. They will be influenced by any gravitational field they pass through, so for extremely exact measurements one has to take that into account ( nobody bothers as it is a very small effect). Plus that any magnetic or electric field has the potential to twist the plane of polarization of any photon passing through, but not the direction ( might be wrong about this). If you add refraction of the unseen interstellar medium (e.g. hidrogen gas around or solar system) to the fact that the star moved quite a bit from the time it emitted the observable light, it's quite clear that nobody will ever know the exact position of any star.
  6. Mar 26, 2009 #5


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    Staff: Mentor

    In order for interference to happen, there needs to be a coherent phase to the light beams - there isn't. Light from a star is just a bunch of random photons.
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