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Can you stand on enough concentrated light?

  1. Aug 31, 2011 #1
    If you had so much condensed light, so a lazer beam, lets say all of the suns energy output put into 1 single beam of light. Could you walk on it? Forget about the heat, the balance you would need and the burn you would get. So your invincible pretty much.

    Can you stand on enough concentrated light?
     
  2. jcsd
  3. Aug 31, 2011 #2
    I think it depends which direction the photons are moving. Photons do impact objects and move them slightly (I think there was a gold foil experiments at some point in time).

    So, I believe it's possible if the photons are opposing the force of gravity by hitting the bottoms of your shoes.
     
  4. Aug 31, 2011 #3
    Yes, but you need a very powerful source and a very good mirror.

    For photon, E=pc where E is the energy, p is momentum and c is speed of light. If you differentiate this by time, you'll get the same relationship between power and force P = Fc. In other words you need 300MW of power per 1N of force (that is if the light is adsorbed or dispersed equally in all directions, half of that if it is reflected fully backwards).
    To support a weight of 100Kg on earth (1KN) you would need a light beam of 150GW.
     
  5. Aug 31, 2011 #4
    Oh my gosh that's more than I wanted to know! Thanks so much well this thread is done LOL and I love that you spread out the equation, I'm going to write down what you have said and do a lil research on this topic o.o. Thanks again!
     
  6. Aug 31, 2011 #5

    Borek

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    Google radiation pressure and solar sails.
     
  7. Aug 31, 2011 #6

    Ryan_m_b

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    Of course the latter is very hard. If the mirror absorbs just a tiny bit of that huge energy source it will melt, warp and deform thus absorbing more and reflecting less and so on and so forth.
     
  8. Aug 31, 2011 #7

    russ_watters

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    The way I read the OP, you're standing on the beam as if it were a physical, structural beam; perpendicular to it, in which case the answer would be no.
     
  9. Aug 31, 2011 #8

    A.T.

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    Why not? You just need shoes with mirror undersides. Placed at the right angle into the horizontal beam they would produce a vertical force component that would balance the weight of your body.

    There would always be a horizontal component away from the source. So you could not remain stationary or walk towards the source. But walking away is no problem.
     
  10. Aug 31, 2011 #9
    Wow, that thought ... didn't ever occur to me ... walking on a rainbow indeed ... :rofl: You're right of course
     
  11. Aug 31, 2011 #10

    Ryan_m_b

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    This doesn't really change what Russ said, the OP seems to be asking about support similar to a solid object. Yes we can come up with purely theoretical examples of how you could stand on a laser but it doesn't change the fact that light does not behave like matter in the manner that was originally asked.
     
  12. Aug 31, 2011 #11

    K^2

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    Any angle would do, but in addition to "lift", you are going to get "drag", so a smaller angle is better than high angle.

    I am absolutely terrified of the energy densities involved, however. That beam of light would have its own gravitational field. And I mean one you'd be able to measure.
     
  13. Aug 31, 2011 #12

    A.T.

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    He asked about walking and standing on a light beam. The answer in vacuum is:

    walking : yes (one way, accelerating)
    standing stationary: no

    In air (ignoring what happens to the air near the beam), you could even walk both ways, or walk in place to remain stationary. But you would need shoes with mirrors and sails.
     
  14. Aug 31, 2011 #13

    Ryan_m_b

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    You would need shoes with near perfect mirrors. The small fraction of energy that is not reflected will heat the mirror, melt/warp it and cause more energy to be absorbed rather than reflected. Try standing on a laser like that and you'll quickly find you have no feet left.
     
  15. Aug 31, 2011 #14

    A.T.

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    That is not what the OP asked about:
     
  16. Aug 31, 2011 #15

    russ_watters

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    Interpretations may vary, but I wouldn't consider waterskiing to be standing on the water either.
     
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