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Light acts like a wave and also like a series of particles. What I have always wondered is why, if I construct a box with perfect internal mirrors and no gaps when closed, I cannot trap a photon or two in this box and let them out at some later time?

Why doesn’t the light just bounce around inside the box until I open it and let it out?

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My first impression:
Light is too fast. By the time you close the lid, the last photon of light has escaped the box. If you could close the lid fast enought, it could be the case!!!

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Rudi – but if the fast light got out, I would think that equally fast light got in.

Jezza – if I have a box that didn’t cause any loss of energy and ‘captured’ some light, then went down a mine (or cave) several 100 meters into a pitch black section, opened the box – shouldn’t I see a burst of light?

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Apparently, it’s all to do with Cavity Quantum Electrodynamics. Perhaps you may wish to buy this book and take a look at this site

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Well knock me down with a feather – have to put that book on my wish list – wonder if the local library has a copy.

I was actually expecting that the most standard reply would be “don’t be stupid” (but maybe that breaches Rule 18 – hmmm, is it a breach if I tell myself not to be stupid? Or is that just being stupid?)

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QED by the sound of it!

Alan

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QED!

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The study of light and time always facinates me. I always play with the scenario of: If you stand on the corner of a city block, and run around the block at the speed of light, you will be back where you started and see yourself before you started running. So now you are in the future, and know what will happen as you have seen events before they happen.

Light and time are so closely interlinked. The things that you can experience if you can move faster than light…(I can only dream…)

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You also have an interest in limericks if memory serves.
Here is something that may have such multidisciplinary appeal:

There was a young man from Bright
Who could travel much faster than light.
He left home one day
In a relative way
And returned home the previous night.

Alan

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Awesome Alan…this is a classic!

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Tim

Light IS energy that ACTS like a particle.

I would say that the photons will bounce around and after a while the collisions on the surfaces of the box will deplete their “energy” in the form of heat and/or sound and they will disappear

Anyway, how do you know if they are still in the box after you opened the lid because loads of other photons will have burst in by that time?

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I don’t know to what extent the wave-particle duality of photons enters into the argument here. But you are correct in principle, but under some highly idealized conditions, impossible to achieve in practice. If your box consisted of 100% reflective walls (with no energy loss with each reflection) then the photons would keep bouncing around ad infinitum. BUT real reflections aren’t perfect – they involve absorption and reradiation, with some energy “loss”. And because light travels so fast, the many reflections per second would have dissipated all of the perceivable/ measurable light intensity in a very short time.

It’s interesting to think of the idealized situation though. If you had a true point light source inside a perfectly reflective box (nothing for photons to lose energy by interacting with) then when you turned on the light, it would just continue to get brighter and brighter inside the box! I’m sure destructive interference of the incoherent photons would also come into it somehow.

Alan

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