# Light's Life

1. Oct 17, 2005

### Mau

Light's 'Life'

Hello everybody:
Let me first introduce myself. I am a Sophomore in High School that has a self-found interest in theoretical physics. I have never taken a formal physics class and I have only learned bits and pieces from random shows on PBS, readings on the Internet, and a few books. This means that my logic will probably be flawed somewhere because I only know a little bit - I have also made a few conclusions through my own thinking that may have been proven otherwise. I enjoy thinking about mind teasers and problems of the sort.

So, to get back to my reason for this post: I am interested in light and it's 'life.' I had an interesting problem enter my mind when I was thinking in looking back in time by going faster than light (theoretically impossible, I know).

The scenario is as follows: let us say that person A is inside a perfect sphere with a radii of 10m. The sphere's surface area is light, sound, radio proof - nothing can escape or get in. Now, we place a really bright light source in the sphere so that it lights up the entire sphere. Now, for some reason or another, the light source goes away extremely fast (in less than one nanosecond). The question on my mind is wether the sphere remains bright or goes dark?
The light cannot escape, so it cannot go anywhere and it must remain inside the sphere. It can defuse (I believe light gets wider the further it goes - like a flash light), but it'll just end up bouncing around in the sphere.

So what happens? To me it seems like that it would stay bright, but if I lock myself in my basement and then turn off the lights it goes dark. The light has to go somewhere. Where does the light go?

However, what if you replaced that light source with a some sort of gas. The gas would stay in the sphere and it could be detected depending on the type of gas.
The thing that troubles me the most is that when you put light from other stars into the picture. This light is traveling possibly thousands of light years and it still reaches our planet without turning into something else. How is this any different from the light just bouncing around in a 10m sphere?

If anyone could provide any insight to this question then that would be fantastic! It's a problem that has haunted my mind for a while now and I'm seeking an answer.

Thank you very much in advanced!
- Mau

P.S - If I have posted this in the wrong forum, feel free to move it.

Last edited: Oct 17, 2005
2. Oct 17, 2005

### GENIERE

3. Oct 17, 2005

### Mau

Thank you very much for that reply. It was a thought that had crossed my mind, but for some reason or another, I ignored it. :-)

One question remains: where does the light go? Does it become heat / energy? I am picturing light falling into a wall similar to how a bouncy ball falls towards the ground. As it keeps bouncing, it loses it's GPE and it's converted into heat stored into the ground (I believe I have that right).

Also, I'm sorry if this thread seems like a re-post of the one linked above. I had trouble searching for my question--there are no good keywords that I could think of.

- Mau

4. Oct 18, 2005

### Danger

Welcome to PF, Mau, but when exactly did I say that you could move in with me?
Oh well... I guess there's room enough for both of us in the Zone, but you're going to have to pay half the rent.

5. Oct 18, 2005

### Mau

So this is what teachers mean by attention to details ;) :)

6. Oct 18, 2005

### Danger

Right. And quit hogging the blankets.

7. Oct 19, 2005

### Mk

Oh c'mon I was going to post that!

I think all the light ends up getting absobed into the mirror.