# What happens when monochromatic light travels for eternity?

1. May 25, 2015

### jimmylegss

So I shoot a light beam out in space of monochromatic light, it would spread out right? So over time it should spread out over a infinite distance? If we assume the universe is finite? And since the light beam has a finite amount of energy, that means it will be reduced to zero.

If this is so, and the universe dies a heat death, it would take an infinite amount of time for this to happen? Which means it will not happen? Because you would then be able to pinpoint the exact time on this infinity scale. And that is impossible. Because that would make it a finite amount of time again.

In other words really, the conclusion is, if you spread a finite thing out over an infinite space, it will stop existing. But it will take an infinite amount of time, so therefore it cannot happen. Because you will never reach that point. So something about the time dimension coming before the other dimensions?

Like counting from two to three in exponentially smaller steps. You never reach three, so as far as the counter is concerned three does not exist.

How do planck lengths come into this? Since there seem to be minimum amounts in our universe that something can exist. So is there a minimum wave length or amplitude? Once it would go beyond that, it technically no longer exists?

Is there some implication that if a lightbeam would travel into infinite emptiness, it will never reach a destination? If it will never be measured again, or interact, does it even exist anymore? What about the uncertainty principle (where laws of physics can be temporarily broken). If there is nothing more to measure for an eternity, then a light beam stops existing? Since existence is basically the chance of interacting some point in the future? If that is reduced to zero, it stops existing?

Last edited: May 25, 2015
2. May 25, 2015

Staff Emeritus
Is there a specific question in there?

3. May 25, 2015

### jimmylegss

Where do I get it wrong?

4. May 25, 2015

### phinds

"You never reach three, so as far as the counter is concerned three does not exist." Right, but you are using that to (to extend the analogy) conclude that three does not exist at all, which is silly.

5. May 25, 2015

### jimmylegss

By the counter I mean the entity counting from two to three in exp smaller steps. Because if you add in a counter in that context plus element of time, three does not exist.

6. May 26, 2015

### Staff: Mentor

Jimmy, I can't begin to make heads or tails of your post. I recommend starting with a single question and not chaining together answers to your own questions to make other questions. Thread locked.