Mirror Sphere

Okay, this might be a really goofy question but I’ve had quite a bit to drink tonight. So here goes:

Imagine an ideal one-way mirror, such that the mirrored side reflects all light and the non-mirrored side lets all light pass through. If a sphere were constructed of this material with the reflective surface on the inside, what would happen? Light may enter the sphere but may not pass back out. Would it just heat up and explode or what? If so, would that be immediate or would it take time to build up?

My nephew asked me this question a while back and tonight, in my drunken stupor, it’s been rattling around in my head. Whaddaya think?

This is pretty easy for you to test. Camera shops sell lightmeters, or if you attend a major university or know someone who does you can probably track down a truly sensitive lightmeter. After you do that just get ahold of a strong flashlight-

Measure the light from the flashlight directly, note it. In the same room and atmospheric conditions (I suggest you make sure your humidity levels are the same and there are no new dust particles in the air for both phases of the test) measure the strenght of the light reflected off of a mirror. If the instrument is sensitive enough you will note a diminished reflection. There is no such thing as a perfect mirror, in fact all a conventional mirror does is reflect along the visible spectrum plus and minus a bit.

Visible light changes as it loses energy. If you were to speed away from tyhe sun at near lightspeed you would soon outrun the visible spectrum you are used to and begin to see by other wavelenghts. While energy cannot be destroyed, it can and usually is converted to other formns of energy. Radiant energy is what you would get inside your sphere, as the light slowed it would become infra-red, violet, etc on down the line. Depending on how much light you had to begin with you will end up with some increase in heat, but you won’t get some ever increasing heat globe unless you continue to sent in light to be transformed to heat energy. A flashbulb would make only so much heat after it changed, no amount of reflection is going to multiply that.

Look up “red-shift” and “doppler effect visual spectrum”. I read somewhere that if we were to travel at those near C speeds then we may become blind or we may find ourselves seeing by radiowaves or other bands higher up the spectrum.

Eventually, it would probably get so full that no more light could enter.

Not like you would notice it though. If light couldn’t get out, then you couldn’t see what was inside.

There really aren’t “one-way” mirrors, just some that mask the light on one side with a mirror or a painting (like the ones on the back windows of pick-up trucks, with pictures of fish, etc.)

So, anyway, all of these DO leak light.

If you put a lightbulb inside an actual solid space, though, like inside a metal box, it would indeed heat up.

I don’t see how, even in the wildest sci fi theory, you can have a “perfect one way mirror” if it any lets any light in at all. One way mirrors, by their nature, are typically fairly poor mirrors with respect to truly efficient reflectivity and need special lighting to be used effectively. An “ideal” one way mirror is sort of a contradiction in terms.

With respect to the "perfect mirror’ interior issue this is also impossible as the photon packets would have to strike a physical surface and be perfectly reflected with absolutely no loss of energy. This violates … well lots of laws and the thermodynamic police will slap the entopy cuffs on you pretty fast for this kind of monkey business.

see http://boards.straightdope.com/sdmb/showthread.php?threadid=37237

for fuller discusion of the perfect mirror fallacy.

Here’s a question that is slightly off topic (or on topic, depending if you are a glass half full or half empty type of person)…

I have pondered this for a while, but what would you see if you were inside of a sphere with a mirrored surface (and presumably had a source of light)? I mean your reflection would be reflecting on every surface, and the reflection of you relflection would be reflecting and so on and so on… Would is be just on big smear of color or a weird medly or what?

Help me please. It makes my head throb just thinking about it (or maybe that’s the booze…).

I agree Corvus that your slightly off topic topic poses a fascinating problem. A slightly concave mirror acts as a magnifying mirror (as with a shaving mirror or those amusing curved mirrors in old fairgrounds) but I imagine one with a much deeper concavity, like a hemisphere would invert your image - ie make you appear upside down. Also producing a stronger magnification, so maybe you would just see a giant upsidedown eyeball? As you say, completing the sphere would add further complications and I cannot work out the result.

Does anyone know if a sphere, mirrored on the inside and large enough for an observer inside, has ever been tried?

Re the OP: I thought a “one way mirror” is actually symetrical and depends on the lighting. If you are on the dark side you see through it, if on the brightly lit side you see your reflection. In which case the sphere of the OP would appear reflective on the outside. ?

I’d be willing to guess that the OPer understands that there is no such thing as a perfect 1 way mirror. It’s all a gedangken type question.

That being said, what if it were a regular mirror lining the inside of the sphere, and there was a light source in the center (or better off center?) that produced more photons than were lost due to normal loss during relection?

I work in a deli, and for our hotline, we have a case with a curved glass cover facing the customers, and sliding doors on our side (if you shop at publix, you know what I’m talking about.)

The doors are, in fact, mirrored on one side, and transparents on the other side. The however, they allow the same amount of light through, either way. One side simply appears darkly tinted, and the other appears mirrored. However, it’s not reversable… which makes me think… what if you had a really bright set of headlights, and one-way glass covers with the outside as the mirrored surface. During the day, you’d have a really neat, metallic dome… turn on the lights, and bright light shines through the mirror.

I sppose you could come close to perfection if the substance were polarized and you made the light do a freqency shift once it passed through.