Light in a sphere

If you put light inside a sphere, and the sphere was made out of reflective material - the light should bounce around it forever, right?

What would happen if you shinned a lazor in it? More and more light would get added,

Nah, it should come right out. It's physically impossible to construct an object that takes light through a hole and never lets it bounce out (excepting a very very black box and other such tomfoolery). Of course instead of a hole you could use a one way mirror.

Where are you going with this, anyways? Photon cannons you say? That's cool, I guess. Good luck on inventing that perfect reflector in the meantime.

Even if you did get a perfect reflector, Werner Heisenberg would like to have a word with you.

Even if photons get reflected, the intensity of the reflection would be less than that of its source due to the multiple deflections. Light is only a photonic emanation, not something that will just go on forever. If you put a mirror on earth and make it visible to the stars, will the stars receive the same light back which they themselves emitted? Obviously not. The distances between mirrors within the sphere would have to be small in order to just carry such a reflection of light, but because there is distance, photons loose momentum.
No? Make a sphere of mirrors pass light into it and stop the source, what happens to the light inside the sphere? It eventually stops just as it source has. It's that simple.

>>2
Hmm, is it actually geometrically impossible to fire a laser into a hole in a sphere in such a way that the reflected beam never hits the hole again?  I'm not sure.

In any case, since the speed of light is finite, you could theoretically shoot the light in and close the hole before the light ever had a chance to get out.

>>4
You're a retard.

Hmm, is it actually geometrically impossible to fire a laser into a hole in a sphere in such a way that the reflected beam never hits the hole again?  I'm not sure.

Me neither but I highly doubt it given that the hole is of a finite size (err... it's not infinitely small). Also, it wouldn't have to exit the hole in the same direction that it entered.

>>4
particles, especially photons, don't necessarily just loose energy because time passes as they exist.

if you are implying bouncing off an object would (generally) cause them to be absorbed or loose energy you would be correct, but the entire point of OP's post is the inside is perfectly reflective, thus no energy is lost.

>>6

just cover up the hole after you fire the light inside, and uncover and fire more inside when you can be sure (calculate) relatively little to no light will escape.

you could construct a gravety well that would pull light into it, then remove the gravity when you want the light you added to escape. what happens to light inside a black hole anyway?

>>8
Becomes heat, probably. Black holes are entropy machines.

You are a mirror.

Before you stands another mirror.

What do you see when you look at it?

>>10
The thing's hollow...it goes on forever...and...my god, it's full of stars!

Ok, I can abide this no longer.

Let us suppose that the mirrors are perfect reflectors
Let us suppose that there are no dead spaces between the mirrors (i.e. there are no edges that the light can strike that will cause it to stop reflecting so much)
Let us suppose that our huge spherical mirror also formed a perfect vacuum where there were no atoms or free particles in the space.
Let us suppose that this perfect sphere were able to defy any effects of quantum mechanics and it was able to keep all particles from ever entering within the space.


Now, with all of those assumptions, would the stream of photons continue forever?  No.  Why?  Because while photons are fairly stable, they still have a half-life.  There would come a moment in time when all of the photons will have simply broken down and the energy that the photons once were made of will be absorbed by the mirror itself.  The 2nd law of thermodynamics would take over within this closed system.

Would the light become more intense?  No.  Why?  Because that would violate the first law of thermodynamics.  Since light is made of photons, and since photons of specific frequencies have specific energies, then you cannot create more photons just by colliding the reflections.  It just doesn't work that way.  There would have to be an increase in energy in order to increase the intensity of the light.

>>12
while photons are fairly stable, they still have a half-life.

http://en.wikipedia.org/wiki/Photon
Mean lifetime:     Stable[1]
The photon does not decay spontaneously in empty space.

You have failed, please die.

>>12
Photon decay is hypothetical, my good sir

was wiki just quoted in a very interesting debate thereby ruining it? Yes, Yes it was...

This is just standard blackbody radiation.  It doesn't matter if the cavity is lined with mirrors or not.  The important part is that light enters, but doesn't leave (def of blackbody).

In a classical setting, there would be an infinite amount of energy (ultraviolet catastrophe).

Quantum mechanically, whatever photons you add, will just increase the temperature of the blackbody radiator.

>>14
I'll ask my QFT friend, but I don't think photons can decay.

Instead of using photons and mirrors, what if you used electrons and diodes?
It would lead to a sphere full of electrons!

If you tried to do this experiment, the photon would collide with an anti-photon and the two would annihilate each other.

particles, especially photons, don't necessarily just loose energy because time passes as they exist.
loose
"Loose" means "not tight". Energy can't be tight, so it can't be loose, loosened etc.

eventually the waves might face destructive interference which would destroy them all.

>>20
DESTROY US ALL

>>20
MAKE MUTANTS OF US ALL