Go into a windowless room with two mirrors placed opposite each other, so that you see an endless tunnel of self-contained images in each – that’s the light bouncing back and forth between them, right?
Now turn off the light. It goes dark. Light does not (visibly) continue to bounce back and forth between the mirrors.
Well, of course not, the surfaces are not perfectly reflective, and the photons bounce in all directions, not focused like a laser, and the whole room is not mirrored. But would it be possible to rig up a set of mirrors, or a blown spherical mirror or something, that would keep photons reflecting within the system indefinitely?
And if you were inside that space, could you see by the light? Or would your body absorb too much of it and turn everything dark?
I don’t know why this topic garners such interest. Not only on this Board, where it’s popped up numerous times, but also elsewhere. theodore Sturgeon used the idea in “Microcosmic God”, if I rember correctly.
But if you want to make something that will trap photons and measurably darken a room (as Sturgeon wanted to), just put a sheet of blacl construction paper in it – it’s more effective and efficient than a mirror box.
If you want to trap a photon and keep it bouncin around forever, then the materials we have aren’t very good for it. As I pointed out in the linked thread, if you have a mirror that differs from perfect reflectivity by a factor of 1/N, then the characteristic number of bounces before your photon is probably absorbed is about N bounces. So, even if your box has mirrors with 0.999999 reflectivity (99.9999%), you’ll only get a million bounces. For a box you can hold in your hand, with light travelling 186,000 miles in a second, that photon gets absorbed in way shorter time than you can measure. And 99.999% reflectivity is absurdly high.
if you had a perfect reflector, like the Stasis Field of science fiction, or if there were some effect that alowed perfect reflectivity of photons, you might be able to store your energy in the form of photons. But until and unless you can find such unobtainium, you’re better off keeping your energy in batteries, kinetic energy storage, and the like. And if you want Perpetual Light in a box, in a scientific rather than a religious sense, you should build yourself a low-power laser system, where you are constantly feeding in photons to balance the ones flowing out. Or use your electricity to run a low-wattage LED or lightbulb like that one in the california fire station in Livermore California (which I see just celebrated its 110 anniversary of continuous light on Saturday):
The answer from that thread is that it’s theoretically possible to use a perfect curved mirror in a small space to create a light path that is “longer” (in light years) than the age of the universe (in years). However, this is not a true solution to the problem. The consensus was that there is no true solution.
As noted, with (impossibly) perfect mirrors you could keep the photons trapped. But the instant you stick your eye in the way, or deflect some, to see them, a bunch will be absorbed. So the act of observing would soon kill the process.
Are you thinking of the cat in the box or of the premise of a certain organized religion that discourages inquiry in favor of determined belief in the absence of evidence?
We often speak of “total internal reflection” with prisms and the like, but it’s not perfect either. Even if nothing else, you’ll get some quantum tunneling of light escaping (though this will be very small, if the wavelength is small compared to the distance to other optical elements). In practice, the biggest problem will probably be that the material you make the prism out of isn’t perfectly transparent.
No, it’s not a schrodinger’s cat proposition. If the photons are traveling in a straight line unimpeded, you won’t be able to see them. Light is traveling past the Earth all the time without us seeing it - otherwise the night sky would look like a Kiss laser show. Only when you start the smoke machines can you see the lines of light criss-crossing the stage, because the smoke particles are now deflecting some of the photons toward your retinas.
So in a perfect system, at some point you’d have to re-focus the photons toward your eye or a camera in order to test whether they’re still flowing. It’s destroying to observe, not destroying by observing.
I see where you’re going - but that feels a bit like a distinction without a difference, perhaps there is better illustration that would show the difference in the two?
Schrodinger’s cat isn’t killed or saved by the observation. The point is that for the purposes of formulaic expression, the cat can be assumed to be both until observation confirms which of two equally likely events have occurred. This allows the equation to continue in its usefulness despite the impossibility of certain conjectures being ascertained.
This is different than, say, a quantum entanglement experiment, in which the act of observing the entanglement destroys the connection.
Yes, but the something pretty much has to be a black hole (it’d be theoretically possible with an object slightly less dense, but no such objects are hypothesized to exist). And all such orbits are unstable.
What’s going on with the cat is what is usually known as collapse of the wave function. Another way to think of it is that you have the potential to live in a number of possible states but can only live in exactly one of them at a point in time. Before you check on the status of the cat, there are two states of the cat that you could experience. Once you observe the cat the wave function collapses to a single possibility, which is what you experience. You cause the collapse by your observation, but you didn’t interact in any direct way with the cat to keep it alive or cause its death.
With the photon, if you observe it it hits your retina then it’s just gone, because it’s energy was absorbed to cause a chemical reaction that allowed you to see it. You cannot see a photon without destroying it.
sigh OK, so much for that get-rich-quick-scheme . . .
It’d be perfect for hanging my black velvet Elvis panting!