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Photon pressure is definitely one of the most amazing phenomenon that I have heard in a while.

Some examples:

  1. The pressure from the photons emitted by the Sun can perturb the motion of artificial satellites as the momentum is exchanged creating a perturbing force.

  2. The Space Environment Research Centre in Australia intend to use high powered lasers to perturb the orbit of space debris, sending space junk in to our atmosphere with the intention that it will burn up!

Question

It has most certainly happened to everyone in the community where you've gone to bed only to realise that you've forgot to close the door. On a much smaller scale, yet equally as annoying as space debris.

What would be the magnitude of photon pressure required to cause a force big enough to close a bedroom door?

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  • $\begingroup$ Photon pressure isn't any different from mechanical pressure: what is the pressure that you need to close your bedroom door, assuming a certain active area? Then, compute the power that should have your torch ;-) $\endgroup$
    – Massimo Ortolano
    Commented Jul 11, 2017 at 15:22
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    $\begingroup$ Scary stuff: en.wikipedia.org/wiki/Yarkovsky_effect. Nearly as scary as how lazy some people can be :) $\endgroup$
    – user154420
    Commented Jul 11, 2017 at 15:28
  • $\begingroup$ I think the sun doesnt exert much photon pressure, the solar flares that are emitted are burst of ultraviolet radiations, that disturb the magnetosphere and the information transmitted by satellites. $\endgroup$
    – Ajinkya Naik
    Commented Jul 11, 2017 at 15:39
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    $\begingroup$ Scale, scale, scale. Because the relationship between impulse $J$ and power $P$ for optical transfer is quite simple ($P = cJ$ with $c$ the speed of light) and the speed of light is a big number, you should be able to deduce the effect that enough light to cause the swing would have on the door without a lot of computation. Mirroring the surface will increase the impulse while reducing the thermal load, but because of the limits of achievable reflectivities even that won't be enough. $\endgroup$
    – dmckee --- ex-moderator kitten
    Commented Jul 11, 2017 at 15:49

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