I did try a search.
Anyway, If you are in a room with a light, completely lined with mirrors and turn out the light why doesn’t the light keep bouncing around the room? If light can travel here from millions of light years away, shouldn’t the light at least slowly fade away? I’m sure this won’t work otherwise people would already be lighting their houses this way.
Don’t we bounce light (laser) off of mirrors on the moon and back?
Mirrors are not completely reflective, for one thing. But let’s put that aside for the moment. Let’s suppose that you are in a room that’s completely reflective, including everything in the room and yourself even. How do you actually percieve the fact that the room is bright? By your eyes absorbing the light. Some is absorbed by the air as well.
Yes, you can get a laser beam to travel to the moon and back. That is far easier than getting the same laser beam to travel the same distance through an atmosphere and involving a couple hundred reflections.
A laser beam does travel through atmoshere.
Are you suggesting this would work in a vacuum?
And I realize your eyes absorb some of the light, but all of it INSTANTLY? Seems unlikely. I understand that the light would eventually be absorbed, but seems like it should take a little while. What if the room was PERFECTLY square? Wouldn’t some of the photons bounce back and forth unimpeded until you stepped into their path?
atmosphere!
Well, not instantly; just very quickly 
Imagine you had a room that was 30m long. If you had a photon bouncing from one side to the other after the light is switched off, it’ll cross the room about 10 million times in one second. It’s probably going to hit something on one of those occasions.
I suppose if you had perfect mirrors, and perfectly straight walls and a perfect vacuum, a small number of photons might bounce from one wall to the next and back without hitting anything. So theoretically, if you could somehow guess where they were (since you wouldn’t be able to see them) and you could move close to light speed, you could pop your eye up in front of them and see a brief flash of light.
Doesn’t seem likely though, does it?
On the same subject, does the light in the dark room decay? What does it decay into?
Cool. I thought up the same thing about 20 years ago. I thought I’d solved the world enegy problems.
My idea was to take two satalites with mirrors and put them one light minute apart, aim a brite light from one to the other and leave it on for one minute. I thought that in the vacuum of space the light would just bounce back and fourth and would only degrade a little when space dust or something drifted in between.
Then I thought if we moved them closer together the light might get brighter and brighter. When I asked my science teachers about it they couldn’t even answer me. After about 5 years of wondering I came to the conclusion that it wouldn’t work for a light source
because if the light was only going from mirror to mirror you wouldn’t see it unless you poked your head up between them. But even today I wonder how long the light would bounce back and fourth. I think your Idea is basically the same.
I think they’d both work but you can’t see the light going between mirrors, only what gets reflected to your eyes by dust atmosphere etc… so I guess it would be neat to seal light in a box for 50 years but it would be kinda useless. I guess the main question is WOULD it work ? Anyone definate ?
Well, even if we had 100% reflective surfaces(which we don’t), we would still have the problem of geometry. Now, I haven’t tried to calculate all the possibilities to see if it is possible to trap light in a goemetric shape, and I believe it isn’t because the light would fly out even before we could think about closing the shape. But let’s say we could make an ENORMOUS geometric shape made entirely of 100% reflective material and vaccumed(sp?). Then we could trap light in it forever. And if we had a material that is reflective on one side and transluscent on the other, we could “feed” light to the light prison.
Can you spell light battery? If we plugged, let’s say, a fiber optics cable in the shape, we would get a light feed. There’s a thing called photovoltaic cells, too.
But of course, this is all pure fantasy… (but often fantasy lives next door to reality)
You definitely cant get an unlimited energy source from this method. You could only get out as much energy as you put in, less probably.
So this is one of those ‘if-a-tree-falls-in-the-woods…’ things. When you leave a room that is lit, it becomes dark (in a sense) because you are not there to see the light?
Photon-math is not my field, but it still SEEMS like the light should at least fade. Well, that’s why I turn to you guys!
Thanks.
Those “if a tree falls in the woods…” phrases are really dumb. How can one say in all sanity that a falling tree doesn’t make a sound wave(ie. air displacement) because nobody’s there to hear it?? Physics don’t depend on us, WE depend on them!
BTW Darkcool, it’s not because you can’t see something that it means it isn’t there. Radio waves can’t be seen, but yet they are everywhere.
And photons don’t loose energy by travelling. They transfer their energy when they hit something(not reflective). Otherwise, how could we see distant astronomical objects billions of light-years away?
oops, that should’ve been:“don’t lose energy” 
Not all the photons are absorbed at the same time. So it does fade. Just REALY FAST!!
You can do this to an extent already. Just line your room with mirrors on the walls, ceiling, and floor, and you can reduce the wattage of light bulbs in your house and have the same amount of ambient light. It’s like the effect you get from paining walls white instead of black- with black (or dark) walls, you need more lighting to have the same amount of ambient light, because the walls absorb most light that hits it. White walls reflect much more light, so the room looks much brighter (and is). You can take it to the extreme with perfectly mirrored walls. You don’t need any special geometry, either.
The light would continue to bounce around forever, with no energy lost, if you had perfectly reflective walls. Of course, as soon as you put something in the room (like your head), light will be absorbed by it, unless that’s reflective too. I suppose you could wear reflective clothes, and have mirror-covered furniture, but then there wouldn’t be much to see in the room!
Since light moves so fast, even if the mirror is only 99.999999% reflective, it would lose most of it’s energy very quickly, since at each reflection 0.0000001% would be lost.
Arjuna34
Jesus, Ranma, chill. I just used that phrase as a convienience! I get the concept.
We did this once before, I think. Let me try and remember what we decided:
OK, take a hollow ball lined with our magical prefectly reflective surface that we have patented for billions of dollars. If we get light in that ball, that exact amount of light will bounce around forever, assuming the surface is perfectly continuous - no cracks, no interatomic space, etc. But how do you get the light in? You could put a light bulb in there, but then the bulb would absorb light. So the bulb would have to be completely reflective on the outside, yet let light produced on the inside through so it can bounce around. The power source, of course, would also have to be coated.
The other option would be to have a superfast door in the side. You open the door, shoot some light in, and close it in less time than it takes for the light to bounce off the far wall and exit. Once closed, again, the door junctions would have to be indistinguishable from the rest of the surface, or we lose energy as heat, again.
But once you get those minor details worked out, you’re there.
[hijack]
Actually the “tree falling in the woods” thing does make sense if you don’t misquote it. The correct phrasing is:
“If a tree falls in the woods and no one is around to hear it, does it make a noise?”
Clearly it makes a sound, but if noise is defined as a sound that someone finds disagreeable, then the answer is “no”, because no one is around to be annoyed by that particular sound.
[/hijack]
My WAG
Even given mirror inefficiencies, atmospheric absorption and non-reflective room object absorption (ie you), it does bounce around more than it would in a room that wasn’t lined with mirrors and it would fade away more slowly in a mirror lined room but it would do so at speeds that would seem virtually instantaneous to you.
I’m not so sure it even makes a sound. Sure there are sound waves, but does that make sound if there is no organ to receive those waves. If you check the dictionary, sound is defined as the sensation produced by stimulation of the organs of hearing. If there are no organs of hearing stimulated, does it still make a sound? Then, you can always fall back to the old standard: God hears it.