If I fashioned a perfect hollow sphere out of a one-way mirror, with the mirrored part being on the inside, could I shine a light on this ball allowing the light to pass into the ball where it would become ‘trapped’ bouncing back and forth off the mirrors?
So basically it would be like an eternal lightbulb, like the thing Galadriel gave Frodo, any chance?
If you were to fire light into such a perfect mirrored sphere and close off the hole perfectly before the light had a chance to bounce off the far side and escape, theoretically it would bounce forever. Sure, why not?
The problem is, it requires a perfect mirrored inside with no losses due to various mechanisms (heat?) and no cracks or seams, none of which is possible.
You could, in theory, know light was trapped by subsequently letting it out said hole, which would presumably be measureable for a short time, if such an experiment were doable at all.
Remember, the sphere is a one-way-mirror, so you can actually see inside the sphere, and you can beam the light in after the sphere is closed.
It must be possible to make a hollow object without any seams, imagine if you had a ball of ice and coated it somehow in some molten matter, then when the ice melts the thing would be hollow with no seams. And a puddle of water of course.
If you did what you say, then let’s assume that it worked as adertised. You let the light in and it rattles around.
The light moves fast – 186,000 miles per second. It’s not like you can look in and see it rattling around (Even assuming you could see it – you can’t see the light, after all, unless it’s directed toward your eye.) More to the point, it’s going to get absorbed by the walls very fast, no matter how reflective they are.
Assume a box 1 meter on a side with really highly reflective walls. The speed of light is 3 X 10 to the eighth meters per second, so you’re going to have 30 million bounces inside that box every second. Assume that your walls are 99.9999% reflecting. Typically, the number of bounces you get is about R/1-R (that’s the formula they use for integrating spheres), or pretty near 10000 bounces, before it’s gone. That takes about 0.00003 seconds. Now your light’s gone, absorbed into the walls. Real reflectivities are a lot lower, so it’s gone even faster.
Theodore Sturgeon suggested a somewhat similar idea in his story “Microcosmic God” – a crystal with lots of facets that would “lose” light inside it. It would work, of course, but so would a sheet of black construction paper.
Um, if you can look through the one-way mirror and see what’s inside, it’s not a perfect mirror on the inside. Suppose, instead of a beam of light, you put an apple inside the ball. Could you see it? If so, then light that’s bouncing off the apple is going through the wall of the sphere and into your eyes, and so it’s not a perfect mirror on the inside of the sphere.
If you wanted to pull someone’s leg, you could just paint a sphere flat black and say that it’s absorbing all light and storing it…
Only if the mirror allowed light to escape from the sphere, which would sort of defeat the purpose wouldn’t it ?
You can use a rotatiing cloud of supercooled atoms (Bose Einstein condensate) to trap or “stop” light in what amounts to a black hole. When you warm the cloud up, the light escapes. Here’s a not very detailed link on condensates. Perhaps one of the boards resident physicists can provide a better one.
Ignoring the device suggested, and the fact that there is inherently leakage in one-way mirrors, the answer to the original question is, yes. Black holes trap light. (Maybe that’s why we don’t fully understand them…they do it with smoke and mirrors!)
In practice, there is no such thing as a perfect reflecting surface. Any surface will absorb some fraction of the light that hits it and reflect the rest. The frequencies that are reflected the most efficiently will depend on the surface, but there won’t be any frequency that is reflected 100%. The result is that after a while, your original light gets absorbed and the light being emitted in its place is determined by thermodynamics.
The object you have described is similar to a classical black body. This hypothetical object emits light whose frequency distribution depends only on the temperature of the object, not on its shape or internal characteristics. In order to get visible light, the temperature of the object has to be, say, the temperature of an incandescent light filament. To get light similar to daylight, it would have to be the temperature of the surface of the Sun.
So, yes, you could make the magic object Galadriel gave to Frodo. You just have to figure out how to insulate it so that it doesn’t cool off before he gets home from Mt. Doom. And you could heat it up to its initial temperature by shining light into it. A lot of light.
Wow! I should have searched this one, perhaps my question should have been -
Is every thought that a persons thinks, a thought thats been thought of before, by another thinker (buh!) not including brand names and stuff, just the basic idea?
Smam - I think this shows that even among a sample of “only” 27,000 people (the readership of this board), pretty much any thought you think has already been thunked. I’ve had the same experience on here!
Well, you could measure its gravitational effect on surrounding objects. Of course, that effect would be negligible and probably unmeasureable without a helluva lot of light added to your sphere but nevertheless the effect would be there.