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Flat ending light beam

  1. Aug 3, 2016 #1
    This is sort of SF in the sense that it's not scientifically accepted or reviewed.
    The "idea" comes from other people and it is that a usually round light beam of a certain diameter, like 30-50-100-similar cm diameter, extends slowly and even stops midair. It's flat at the end.
    Like a straight cylinder of semi transparent colored light with a perfectly straight 90 degree bottom end.

    It's the physically possible? How?

    PS: might be accompanied with various physical effects such as appearing to be solid or semi solid in nature, not blinding, no heat.
  2. jcsd
  3. Aug 3, 2016 #2

    Simon Bridge

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    Are you thinking of an effect like a light-sabre only more geometrically precise?

    The short answer is "no". But you knew that already when you said, "not scientifically accepted or reviewed".
    Basically, light cannot extend slowly. Even if you did get what you asked for, nobody would be able to see it unless some light was not confined to the cylinder. However, the appearance of what you were after is acheivable.... ie in movies, or maybe by a holographic projection.
  4. Aug 3, 2016 #3


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    If the light moves in a fluorescent, highly refractive medium, say n=2, the cylinder may probably be seen as motionless by an observer moving at c/2 outside that medium...
  5. Aug 3, 2016 #4


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