The End of the Universe?

Factual Questions
1

Pretty good title for a thread, eh?

Okay, this is way out there, but it just popped into my mind and it’ll keep banging around in there (nothing to stop it!) until I let it out.

I’ve been reading about how the cosmologists are starting to think that the universe will “die” a “heat death”. That is to say, it will never crunch but expand forever. A googolplex years from now, it’ll still be expanding (very, very slowly).

Well, I got to wondering about something: what <i>creates</i> space-time? Gravity?

Okay, I warned you that this would be way out there, but I was thinking: is it conceivable that when space becomes extremely, umm, drawn out that it will start to break apart?

I’ll admit that much of my motivation for hoping this is that the idea of “heat death” is infinitely depressing. It’d be preferable to see the universe disappear back into superspace and give some other universe a kick at the can.

Yet I’ve never read anything about what happens “after” the heat death; it’s always implied that there <i>is</i> no “after”, and that also bothers me because I was attached to the idea of a closed universe, as that got rid of all those pesky infinities.

Any comments on this?

2

The term heat death was first used to describe what happens to a static (not expanding or contracting) universe when all of the energy has been converted to heat and reached equlibrium. There would be no usable energy and everything would run down.

What happens to a universe that expands forever is more like a cold death. The temperature approaches absolute zero. The distance between particles eventually becomes so distant that there is no way for any interaction between particles. In a sense, that is the end of time. There are no reactions; no events to mark time.

I don’t see how space could “break apart”.

“What creates space-time? Gravity?”
Space-time was created by the Big Bang. New space is not created; existing space expands. Gravity is the distortion of space time - the distortation is created by mass.

3

> I don’t see how space could “break apart”.
> …
> Space-time was created by the Big Bang. New
> space is not created; existing space expands.

That’s my point: how far can space “stretch” before it ceases to be able to be space? After all, we’re not talking about an ideal vacuum (i.e. nothingness) but the seething mass of virtual particles.

Sorry about the “heat death” boo-boo, by the way. There goes my Nobel Prize. :frowning:

4

Which begs the question… Where does it expand to? Nothingness? Is there unlimited nothingness past the edge of the existing universe, does it wrap around the edges, or does a barrier exist?

If we make the assumption that nothing moves faster than light, is the universe spherical with a radius of c x age of the universe?

5

There is no nothingness. There is no edge of the existing universe. There is no barrier. The universe does not have an edge anymore than the surface of the earth has a boundry.

Space is not a thing. The expansion of space is not limited by the speed of light or by any other upper bound.

6

There is no ‘edge’ to the universe. The way I understand it (from Stephen Hawking) is to think of a big sphere. It has a finite size but you can walk forever and never find an edge or a barrier. Theoretically if you setoff from earth and travelled long enough and fast enough you would return to the earth even though you flew in a ‘straight’ line away from the earth.

As to what the universe expands ‘into’ I guess nothingness is as good an answer as any. Basically it has no definition, is infinitely and infinitely small and time does not exist.

There is some talk here that suggests that space is stretching like a rubber band and therefore should either pull back (shrinking space) or tear. I don’t know that space can be thought of in such a manner. I’ve never heard of space as being described as elastic and as far as I know it can ‘stretch’ (for lack of a better word) indefinitely. Does it pull back or resist being stretched? Not that I’ve heard of.

The problem here is what is space? If ‘outside’ our universe isn’t space (i.e. what the universe expands ‘into’) then what is space ‘inside’ our universe? The only answer I can think of is, “It’s just, you know, space…a place to move around in as it were.” Obviously that answer doesn’t cut it but I can’t think of better.

7

How can something be expanding if there is not a leading edge? Perhaps this is a semantics problem… If the theory is that all matter and energy in the universe burst forth from a single point in space (ie. an expanding universe), it should logically follow that the maximum radius of spherical projection would be the maximum speed times the time elapsed since the explosion, yes?

So, spherical in a fourth physical dimension that we cannot perceive, correct? (Or has this contour been observed somehow?) Should it follow that if the universe was small enough, we would be able to look in any direction and see our galaxy when it was younger? At minimum, we would see galaxies headed toward us rather than away, correct?

8

Let me clarify that I know we don’t see them heading toward us, so that should indicate something about the contour and/or size of the universe.

9

If only it were that simple. It may be more logical if this were a “closed” universe (expand/collapse), but it appears to be a “flat” universe (expand forever). The balloon analogy may lead one to the conclusion that there is a higher dimension of space that we cannot perceive, but it’s just an analogy and there is no evidence of a higher dimension that we can hang our hat on.

The universe appears to have been boundless (infinite) from the beginning. Space does not have an edge but must either be infinite or curve back on itself in some incredibly complex way that our Earth-grown minds have a hard time imagining.

As far as “where does space come from?” …that is equally confusing. Rather than new space being added, it’s an expansion/dilation of space that already exists. In a sense, the expanded universe already exists if you consider the whole possible timeline, but since we only experience time one second at a time in only one direction, we can not yet access the “new” space.

Or maybe it was sneezed out of a giant cockroach. It’s enough to warp one’s mind. I’m certainly still trying to make sense of the snippets I get from the scientific sources intended for public info. The actual science of it is a whole mathematical world that you need post-grad college degrees to understand.

10

It must? Why is that? Why isn’t a limited universe possible? (A huge, currently imperceptible limit is still a limit.) I’d call “curving back on itself” a limit, because you’d go distance X and end up where you started, just as the earth as a limited circumference. If that is the case, the limit would be a fourth dimensional one, if I understand that concept correctly.

Let’s not forget one might make a distinction between the concepts of edge of the universe and the edge of existence of matter and energy. Can we agree there is a finite amount of matter and energy in the universe? And from that, can we agree that there is a theoretical fixed sphere, with radius X that, from our limited point of view, will currently contain all that matter and energy at time T, but not at time T+1?

If that is so, I fail to see why X could never reach an upper limit (or hit the wall, if you will). Incredibly unlikely, yes, and contrary to all observed phenomena, but you wouldn’t be able to observe an edge unless something actually hit it, correct?

11

and

from here.

DrMatrix sir–If the events needed to mark time do stop occurring, would it be more correct to say that time would still need to be expressed mathematically, perhaps as a constant or zero, or would it really be eliminated entirely from the equations used in trying to express a unified universe? In other (very badly phrased) words, does the end of time also mean the elimination of previous time as a necessary concept?

12

Curving back on itself may be a limit, but it’s not an edge in 3D space. Curving back on itself is a possibility, but current evidence indicates that the universe is “flat” and is boundless (i.e., you would never reach your starting point no matter what distance X you went).

Higher dimensions of space are a way to visualize it, but there’s no evidence of them. I’m not sure how the smaller space dimensions of String Theory play into this.

There may be infinite matter, but spread out over infinite space.

Matter did not shoot out from a central point, rather it formed all across the universe shortly after the Big Bang (which happened everywhere at once).

The only edge astronomers see is in time…back when the universe was young and opaque (no light transmitted). But that was 12-15 billion years ago. If you were magically transported to the farthest place we can see (12-15 billion light years from here), you would still be surrounded by boundless space (no edge in space).

13

Yes! This is precisely the kind of discussion I wanted to hear!

Okay, I’ll admit that my original post was “way out there”, seeing as it put forth the idea that “our” space could be stretched to the breaking point and subsequently disintegrate, but I think that if ever there was a “spiritual” dimension to hard science, this has got to be it! I mean, we’re talking about the Big Question, here, aren’t we?

I am, however, a tad disappointed (perhaps wrongly so) that people haven’t been talking about “superspace”. To me, it seems that our quantum vacuum must have emanated from something at a higher order.

Let me get really weird, now (as if this thread wasn’t weird enough already). I posit that “superspace” breaks every rule that we hold dear – including (gasp!) logic. No, I’m not getting all mystical, here. I’m saying that I think that logic is an “If, Then, Else” situation which is firmly tied to the ideas that we hold to be immutable.

To put it another way, is the “ultimate reality” from which space derives accessible to us? Can the rational mind even begin to imagine a “superspace” where nothing is sacred?

I toyed with this concept a few weeks ago. I tried to imagine a superspace where logic didn’t function because (for example) causality was meaningless.

Needless to say, my logical mind rebelled. But that’s precisely the point. Just how much can we distance ourselves from the universe we inhabit when we have no means to have an external view?

I’m suggesting, here, that there’s no way for physicists (the paragon of “hard” science) to perform the most important “double-blind” science! We’re all stuck in the web of our own universe, and we have no way to stand outside it. We don’t know where space comes from, and we may never know.

That last assertion is a bummer, I know. But if we don’t know why the Big Bang happened, can we really be so sure that we know what the ultimate fate of our universe will be?

14

No, but it could be interpreted as an edge in 4D, correct?

I was under the impression that the Big Bang theory contended that all matter and energy was concentrated at a single point and exploded outward, and from there it has been expanding from that point. Now you’re saying it happened everywhere? Has the theory been modified in this respect?

Forgive me for being skeptical, but I don’t think anyone can say with absolute certainty what does or does not exist 12 billion light-years away. I will grant you that in all probability, space is infinite in 3D, but given the inherently mysterious nature of the subject, I cannot discount the possibility, however remote, of a bounded, finite universe, even in 3D. Infinite for all practical purposes, yes, but we are talking about the entire cosmos here, not 1=0.999… Our universe could be entangled with some sort of weird anti-universe, destroying everything a few billion light years away, but no one here would ever live to observe it. (A dumb idea, but not an impossible one.)

Crimony, we can’t even agree about the internal nature of our own universe–how do you expect to discuss that? :smiley:

4D space is enough to make me a little dizzy. Speculate on external universe interactions if you like, but I’m going to try to figure out as much as I can on the innards of this one first.

15

**Humble Servant **

Let me see if I can explain:

Science in general and physics in particular deal only with what can be observed and measured. After the universe has expanded enough, everything that can decay will have decayed and particle density will eventually become so sparse that there is no way for any further activity. Then there is nothing that can observe or measure the passage of time. In what sense does something (the passage of time) that cannot be observed or measured exist? What distinguishes one moment from another?

16

If I might elaborate for DrMatrix…

All time is comparison of movement. We observe that the earth takes a relatively consistent path around the sun and call one revolution a year. If a certain car moves from point A to point B while the earth makes one revolution, then we say the car took a year to travel that distance. If, however, a particular universe has no movement, there are no reference points. Time does not exist within a “frozen” universe.

If you were an outside observer to that universe, however, you could, referencing your stopwatch, note the time that the universe froze, but the universe would remain exactly the same at any time after that point, so time would no longer have any meaning for it.

Does that help?

17

What, no jokes about restaurants and self-killing cows yet?

You people disappoint me :wink:

18

Of course not, Coldfire. We have none of that nonsense in General Questions.

Besides, no one goes to that restaurant anyway. I mean, the food is good and all, but it has no atmosphere.

:smiley:

19

Define atmosphere, and gimme cites!

OK, I’ll just go back to the Nuthouse that is MPSIMS :wink:

20

Sincere thanks to DrMatrix and mrblue92 for the enlightenment.

If I send the boggling part of my brain to the corner to suck its thumb, I think I can grasp that there can be no time in a universe without movement. But if we say we need an observer or measuring device to mark the passage of time, are we treating time as a special case, or are we only saying that nothing, not time, not matter, not space, not energy, can exist without an observer (everything belongs in the box with the cat)? If this is the case, couldn’t we say (modifying DrMatrix’s original phrasing): “The distance betweeen particles eventually becomes so distant that there is no way for any interaction between particles. In a sense, that is the end of time, matter and the universe. There are no reactions; no events to mark time, matter or the universe.” I don’t think this is what I would want to say–but why, then, should we treat time as a special case (if it can be expressed numerically just like matter and energy)?

I promised myself I wasn’t going to hijack this thread, but the Mods did it first (note that we DID already have a Douglas Adams reference in Phobos’ sig line), so here is my favorite literary expression of time:

“Time is the stream I go a-fishing in. I drink at it; but while I drink I see the sandy bottom and detect how shallow it is. Its thin current slides away, but eternity remains. I would drink deeper; fish in the sky, whose bottom is pebbly with stars.”–Thoreau, Walden, Chap. II.