Why doesn't a photon orbit?

Discussion in 'Physics & Math' started by Quantum Quack, Jul 2, 2004.

  1. Quantum Quack Life's a tease... Valued Senior Member

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    Hi,
    Just a question that has puzzled me for a while.

    We know that light is bent as it passes a large gravitational mass. ( yes?)

    The question as implied in the thread heading is why doesn't light orbit that mass?

    Possibly the velocity is such that it can escape that pull of that mass but in extreme cases like black holes etc would not we see photons orbiting that mass at 'c'?

    Sorry if this question appears silly but some understanding would be appreciated.
     
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  3. Crisp Gone 4ever Registered Senior Member

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    Light can orbit black holes. We would not see it of course (the light doesn't reach us!) so from the moment you spot light orbiting something, you're in deep trouble

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  5. Quantum Quack Life's a tease... Valued Senior Member

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    unless a reflective object was falling to the centre. wouln't we see the light reflected in some manner?

    The reflected light would of course be also trapped but on the appropriate horizon some would be seen to escape.....don't you think?

    If this was the case wouldn't you expect to see some sort of light effect on the periphery?
     
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  7. Quantum Quack Life's a tease... Valued Senior Member

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    also if light is orbiting and continually being added to from external sources wouldn;t that end up with an pretty intense amount of photonic activity orbiting a black hole...
     
  8. John Connellan Valued Senior Member

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    An astronomical (in both senses of the word) laser?!

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  9. Quantum Quack Life's a tease... Valued Senior Member

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    and....and......and....because light is coming in from all directions it would be....a....you guessed it......a spherical laser.....

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  10. Quantum Quack Life's a tease... Valued Senior Member

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    seriously though, doesn't this pose a rather interesting paradox if you like, for current thinking on the nature of light?
     
  11. Crisp Gone 4ever Registered Senior Member

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    Where is the paradox ? Much light in the neighbourhood of black holes ? The numbers seem scary ? Remember that a black hole in itself is extremely extreme already: huge amount of mass, loads of particle/light activity (x-rays, ...), so what would be so peculiar about a (relatively) few photons ?
     
  12. Quantum Quack Life's a tease... Valued Senior Member

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    you don't think light traveling in a circle an unusual state then?
     
  13. swansont Registered Senior Member

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    To add a bit - light only travels at c, regardless of energy (unlike other objects that orbit) - so there's only one orbit available to the photon, which is at the Schwarzschild radius.
     
  14. Paul T Registered Senior Member

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    Based on GR, that circular trajectory is actually straight in space-time. So, the rule that light travel in straight line still applies, not in space but in space-time.
     
  15. Quantum Quack Life's a tease... Valued Senior Member

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    Actually I am not all that worried about this, I am more concerned about the practical considerations.
     
  16. Paul T Registered Senior Member

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    I have no idea what kind of practical consideration were you referring to. Can you describe more about it ?
     
  17. Quantum Quack Life's a tease... Valued Senior Member

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    Well, I was hoping you might describe what ramifications an obiting photon storm may invoke?

    John C suggested a Laser in jest.....but when you think about it wouldn't it lead to a black hole being rather easy to detect as some photons escape their orbit or are deflected etc.....

    And also what sort of emmission would a photon storm obiting a black hole promote. I really have no idea and hope that expert opinion may be forthcoming.

    Also as photons a continually being added to the orbit what do you think would be the outcome? ( if all is as speculated this would already be occuring)
     
  18. Fallen Angel life in every breath Registered Senior Member

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    quantum quacks questions made me think of another one... if there are all these photons orbiting at Schwarzschild's radius, is it possible for some of them to tunnel through and escape? or is it that to them there is no potential energy barrier to tunnel through because they are traveling in a "straight line" through a curved space-time?
     

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