Slightly wild question about light, energy & finite/infinite universe?

Question

So, okay, I was just thinking (crazy concept, I know).

So, consider, with reference to conservatin of energy: If the universe is infinite (giant vacuum with stars and galaxies that came from the big bang; I'm still not sold on the big bang or the big suck), and stars radiate energy in the form of photons, and convection happens on a 3D cosmic scale (or at least we consider energy as concentrated and wanting to escape, kind of like pressure), will galaxies and/or the universe eventually radiate off all of its energy into whatever lies beyond the galaxies?

IE, if we assume we're in an infinite void, and the very edges of the universe /galaxy are radiating photons outward into empty space, within nothing to absorb them, pull them, etc. Will the universe become less energeting through essentially evaporative cooling. IE, the photons / electrons / whatever readiating out into empty space removes energy from the universe.

What happens if the galaxy/universe radiates away all of its energy into empty space?

Obviously this would take billions of trillions of years, as energy works its way from the middle of galaxies to the outer reaches.

But seriously, what would happen if there was no energy left in the universe? Would it all collapse? If so, how, if there's no energy?

Of course this assumes the universe is infinite, or without boundary. If not, how would we define the boundary. What would happen if we crossed it? Or would the boundary just keep getting further and further away the further we went? No, for this thought experiment we'll assume there is no wall at the end of the universe and it just goes on forever in all directions.

Physics types preferred. No one-liners. Logical line of reasoning if you please.

I guess my questin is just what happens when something radiates away all its energy. Does it collapse, or does it just sit there? Or does some other process happen?

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Responses to answerers:

Okay, interesting thought about somehow photons and electrons being created at the edge of the universe. I guess my thought is on he order of the stars and whatnot at the very fringes of the universe are radiating in all directions, some of those stars on the very leading edge of the universe must be radiating into empty space.

So, what happens if those photons, eklectron or whatever all get radiated, and more get supplied from interally in the galaxy, then get re-radiated out into empty space. What happens once all energy gets radiated out into empty space?

I'll leave everyone to considerfor a bit. Would love to hear interesting answers!

Nick N: I was planning on it. *wink*

Oh, and not completely naive about it, had done a tiny amount of reading on it a long time ago, just was wondering what folks thought about it. Hmm, good to put a name to it. Heat Death of the Universe. Kinda' poetic...

http://encyclopedia.thefreedictionary.com/heat+death+of+the+universe (heat death)
http://www.physlink.com/Education/AskExperts/ae181.cfm
http://encyclopedia.thefreedictionary.com/big+crunch (big crunch)
http://encyclopedia.thefreedictionary.com/Oscillatory+universe
http://encyclopedia.thefreedictionary.com/Ultimate+fate+of+the+Universe

A few interesting articles to spur discussion.

Wise one:
I see the point you're trying to make. However, I could also point out a flaw in the balloon logic.

I'm questioning in terms of an infinite universe, rather than a bounded universe. The balloon would have a bound to it, and a certain elasticity. It would be a basically closed system. But what happens if I pop the balloon, and there is no longer an elastic boundary, and the innard go flying out into space, radiating, if you will, into a vacuum with little or no resistance. So, there's no balloon shell exerting inward force... (Well, okay, gravity is a force, granted. But assuming particles are escaping into the void at velocities well in excess of the pull of gravity, IE photons, highly accelerated electrons, etc.)

What then?

Answer 1

This is a matter of debate among cosmologists right now. It all depends on how much matter exists. If there is enough matter, then the universe will eventually stop expanding (including light photons) from the gravity of all other matter and begin to contract down to a super black hole at the very end of time. (the big crunch theory)

From our exploration of the sky, astronomers don't see enough matter to stop the expansion. However, they expect that there is more to see than the 15 billion light years we have seen so far. Also, the only things we can see are objects that emit light. If there is enough "dark matter" in the universe, then we get the big crunch.

If, however, there is not enough matter, then the end will come like you describe. The stars will eventually go out, photons will gradually lose energy. Eventually even sub-atomic particles will come to a stop and the whole universe will drift apart at absolute zero.

Happily, we won't be around to see it so it is not something you need to worry about in your lifetime.

Answer 2

Assuming that the universe is expanding in an infinite void, time is infinite, and diverging particles' gravitational attraction to each other tapers off infinitely approaching, but never reaching zero, Eventually all matter and all energy, which are both affected by gravity as Einstein proved, should turn around back toward the origin and crash together again in the center of the universe. So what I'm saying is that I think the big crush theory and the big bang theory are both happening / going to happen. I also like to think that the big crush may be a cause for another big bang, but I guess that is because I don't beleive in god and I want to beleive that something like this planet with these stars may exist again after all the stars in the universe die...

Answer 3

If we ignore the theory that everything will eventually (and I mean eventually!) get pulled back together again by gravity, then yes, energy will dissipate in the form of light and heat.

It won't really get transferred to anything else, since there is nothing else, so the universe will never run out of energy (any expanding energy is still in the universe, being the sum of all parts as it is).

As stars die and go cold, which I'm thinking should eventually happen universally (like my pun?) as the energy available for creation of new ones is depleted, that's basically the end of the line.

Everything becomes extremely extremely cold, nothing is left with enough mass to implode and create any sort of cool reactions, and you're left with a whole heap of rocks sitting around doing nothing, or everything eventually getting sucked into black holes that just become larger and larger.

Not really an end to the story, I guess. That's how I see it, anyway.

Answer 4

Great Question , there is a lot of energy in the universe that we cant see or detect yet as modern animals here on earth , remember how far we have come in such a short time . ie some schools still teaching the world is flat etc . . try not to expect it all right away knowledge takes time . think about how water would expand in the form of steam in a balloon , like setting as the heat source of the stars expanding the steam, the steam in turn expanding the outer edge of the balloon , the balloon or universe would be filled pretty equally with the steam like the universe is spread out pretty equally and still expanding , its taken billions of years to expand this far , as water cools (its logical to assume the cooling of the universe would also take billions of years ) it would not be instant to freeze the universe from condensing into a smaller balloon size like steam condenses back into water ,and as it would decrease in size the amount of energy would increase again per area of space more like the expanding and contracting of our breathing .

Answer 5

The thing is no one was there when the universe was created. Science only VERY recently ( as in in the last 5 years) came up with a WORKING theory. While the big bang theory has been around in some form or other. It is only within the past couple years that scientists came up with a theory to explain the discrepancy between the redshift data, and the estimated length of time it would take the universe to evolve to its present state. ( They say that cosmic microwave background temp was higher in the past and that explains the discrepancy) There still are ys with the theory, but none are completely fatal to the story. That being said. The object of science is not to PROVE any theory. It is to observe, and draw conclusions. Not that it hurts to come up with theories before we have all the data, but if we are doing all this research just to prove that it is possible that there is no "higher being" then, well, that's not REAL SCIENCE. Not to mention that there are no holes in creation theory. (Yeah that's right I said it.) Now having said all that before everyone decides to give me a thumbs down because I believe in and eternal conscious being rather than eternal unconscious particles, I just want to say, I do what I feel is right and I only answer to myself. Whatever said "conscious being" never said anything to me, so why should I worry about what said being thinks, when he isn't concerned with telling me. Also, by the way, geniuses, most of the scientists that came us with the major scientific discoveries were creationist.

Answer 6

Your question, as posed isn't valid. You are assuming that the universe exists as you experience it. It doesn't.

Space and time are a single concept. Space time has curvature. This is well established from emperical results predicted by the General Theory of Relativity. Think of the earth. If I throw a ball away from me, it may leave my proximity to a place far away, but it doesn't leave the earth. Similarly, the curvature of space time determines the boundry conditions for all matter. It all wraps upon itself in 4 dimensions.

A question for you to ponder. Where did all of the energy/matter in the universe come from? And I expect you to go deeper than it all came from the big bang. Where did the energy/matter originate from.

Answer 7

First I should say lovingdaddyof2 's answer is interesting but not acceptable,curvature is itself in 4-D spacetime but it exist because of the existence of matter. So you cannot say the universe curves to itself as an acceptable "fact",of course it can be presented as a hypothesis but there are only a few phenomenons explained by it.

There are some discoveries related to this subject, one is the discovery of an acceleration universe and the other is the prediction of the existense of dark matter and dark energy. One of the consequences of the discovery of an accelerating universe is :
Consider an observer at the edge of the universe (if it exist in particular). The observer according to acceleration expansion is indeed accelerating. So when he/she observes a light (as an example of energy) escaping the universe ,he/she also observes a phenomenon (due to his/her acceleration) called redshift or gravitational redshift for that light beam. (Redshift meaning that the light beam's frequency eventualy shifts to a lower frequency) This redshifting continues until the frequency approaches 0. This means that an observer at the edge of the universe does not observe energy escaping it.

The other discovery , the prediction of the existense of dark matter and energy, was due to some anstronomical observations some leading to the calculation of the kinetic rotational energy of glaxies and some leading to the calculation of their total observable mass and energy. Using the universal law of gravitation and some other calculation ,they found that inside the glaxies must lie some undetectable energy called dark energy.(mass and energy are equivalent concepts)
This means that dark energy (if truely exist) is not observable so it cannot emit all its energy to pure vacuum!

And at last I should say,according to Mach's Principle matter and thus energy constructs the geometry so even if energy escapes the universe it does not decrease the toral energy of the universe but expands the universe itself.

Answer 8

The energy would not just disappear it changes form. What you're naively asking about has already been predicted and is called the heat death of the universe.

Ignore people like daddyof2 who say it's an invalid question

Answer 9

I see what you're saying. But I think that at the edges of the universe photons, electrons, etc. are being created, not being pulled out of already existing stars (that is just what I think). But I admire your intelligence for thinking of this.

Answer 10

Galaxies, the elements and energy comprise only 4% of the universe. The remaining 96% of the universe is comprised of dark energy (26%) and dark matter (70%). My guess is if the galaxies radiate off all of their energy it becomes dark energy leaving the universe totally comprised of dark energy and dark matter.