# Chronos got me Thinking -- Finite or Infinite Universe **URL:** \ **Category:** Factual Questions\ **Created:** [June 5, 2000, 4:46pm UTC](https://boards.straightdope.com/t/chronos-got-me-thinking-finite-or-infinite-universe/21456 "2000-06-05T16:46:19Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [June 5, 2000, 4:46pm UTC](https://boards.straightdope.com/t/chronos-got-me-thinking-finite-or-infinite-universe/21456/1 "2000-06-05T16:46:19Z")
Chronos posted the following bit in this thread: [http://63.97.40.4/sdmb/showthread.php?threadid=25996](http://63.97.40.4/sdmb/showthread.php?threadid=25996) > [@](#): > > The number of stars in the Universe. At a rough estimate, that’s, oh, let’s say infinity. Know what you get when you multiply infinity by anything other than zero? If the Universe is, in fact, infinite, as seems likely, then not only is life inevitable, but an infinite number of species is inevitable. Just looking for some clarification here–I thought this deserved it’s own thread since it diverges from the post linked above. Sorry if I’m mistaken in that… As I understood it current thinking is that the Universe is both Finite _and_ Infinite at the same time. Think of it like this–The Earth is a great big sphere and completely smooth (just for ease of picturing this). While the Earth is finite in size you could walk essentially forever and never come to the ‘end’ making it appear infinite. Also, if the Universe is truly Infinite and there are an Infinite number of galaxies/suns/planets out there then wouldn’t that suggest an Infinite amount of energy released at the Big Bang? If so wouldn’t the entire Universe be awash in infinite energy levels probably precluding the existence of life (at least as we experience it)? If the Universe is finite in age then doesn’t it _have_ to be finite in size (i.e. it expanded from a singularity with the speed of light a limiting factor it can’t be infinite…just REALLY big)? ---
**Author:** ![Ike\_Witt](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ike_witt/32/283_2.png) [@Ike\_Witt](https://boards.straightdope.com/u/Ike_Witt)\ **Post date:** [June 5, 2000, 5:07pm UTC](https://boards.straightdope.com/t/chronos-got-me-thinking-finite-or-infinite-universe/21456/2 "2000-06-05T17:07:13Z")
Since the Universe has a starting point, it is finite. However, for all intents and purposes the Universe is infinite to humans. The reason being is that we can’t even manage to cross the smallest portion of our own solar system in a short amount of time. The times required for interstellar or intergalactic travel makes the Universe seem as though it is infinite. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [June 5, 2000, 5:33pm UTC](https://boards.straightdope.com/t/chronos-got-me-thinking-finite-or-infinite-universe/21456/3 "2000-06-05T17:33:48Z")
Some clarifications on what I said before: A truly infinite Universe is one of several possibilities currenttly under serious consideration. Another very real possibility is that it’s finite in size, but loops around like an Asteroids screen (if you fly off one edge of the screen, you come back on the the other side). Yet another is that it’s finite like the surface of the Earth. The first two possibilities are generally prefered today, as the evidence seems to be pointing to a flat Universe, but the case is not yet ironclad to eliminate the third. What I was getting at, is that a truly infinite Universe is still a reasonable possibility, with the conseqences I mentioned. Besides which, even if it is finite, it’s awfully big. Yes, an infinite Universe would imply an infinite amount of energy in the Big Bang. Some theories of the Bang can accept this, some can’t. Note, too, that even the theories which require finite energy can still allow for arbitrarily large finite energies. No, the finite age of the Universe does not limit its size. The speed of light is not a limiting factor in the Universe’s expansion, but it is a limit on the portion of the Universe that we can see. If there’s a civilization at just under 15 Gly from us (assuming an age of 1.5\*10[sup]10[/sup] years), then the Universe would look pretty much the same to them as to us. In one direction, at the edge of their sight range, would be where we are now, and they could look the same distance in the other direction, too. ---
**Author:** ![Silo](https://avatars.discourse-cdn.com/v4/letter/s/ac91a4/32.png) [@Silo](https://boards.straightdope.com/u/Silo)\ **Post date:** [June 5, 2000, 6:06pm UTC](https://boards.straightdope.com/t/chronos-got-me-thinking-finite-or-infinite-universe/21456/4 "2000-06-05T18:06:40Z")
It’s finite, just so damn big it is seemingly infinite. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [June 5, 2000, 6:50pm UTC](https://boards.straightdope.com/t/chronos-got-me-thinking-finite-or-infinite-universe/21456/5 "2000-06-05T18:50:11Z")
This one is starting to hurt my head… So, after the Big Bang was space pretty much instantly infinite? Or, is the volume of the Universe growing as we speak (kinda like a balloon inflating growing ever larger)? If it is kinda like the balloon analogy how fast is the ‘edge’ (I know we can’t find the edge since it’d be in 4-D space) moving? Light speed? If the expanding thing goes does that mean space is stretching? If not stretching then is ‘new’ space being created all around us? If not that then where does all this ‘new’ space come from (I have the feeling the answer is nothing)? The Asteroids screen analogy I get and is how I thought the Universe was supposed to work (or it works with the surface of a sphere analogy too…travel long enough and you return to where you started). Technically I thought if you travelled long enough in a straight line through the universe you’d come back to where you started (except the Universe is growing faster than you can travel so you’d never really make it). What I still have a problem with is infinite energy and/or infinite planets/stars (not to be cinfused with the infinite energy _density_ at a singularity). Even if the whole of ‘space’ blinked into infinite existence didn’t all of the energy (and ultimately stars and what-not) expand from a singularity? If so could you use your HyperSpeed Starship to fly out past the point where there are galaxies (i.e. space that nothing has had time to float into yet)? Ok…so there’s too many questions in there and some answers may never be known. I’m just curious as to what the ‘best guess’ is today among astrophysicists and their kind. ---
**Author:** ![Achernar](https://avatars.discourse-cdn.com/v4/letter/a/e274bd/32.png) [@Achernar](https://boards.straightdope.com/u/Achernar)\ **Post date:** [June 5, 2000, 7:55pm UTC](https://boards.straightdope.com/t/chronos-got-me-thinking-finite-or-infinite-universe/21456/6 "2000-06-05T19:55:16Z")
I wish I could contribute something noteworthy to this thread, but it looks like everything I had to say has been said. (I suppose I could describe some freaky Cosmologies of My own, but that’s not necessary. :)) But I can clear up one aspect of the confusing terminology: **Jeff\_42** said that “the Universe is both Finite _and_ Infinite”. When you say “Infinte” here, I think the word you’re looking for is “Unbounded”. Without boundaries, just like the surface of the Earth. The Universe can be Finite and Bounded, Finite and Unbounded, or Infinite and Unbounded. I do sort of have a problem with people equating some small number like, say, 10[sup]80[/sup] with Infinity. Infinity doesn’t care how many zeroes you tack onto the end. So I think there’s a _big_ difference between real Infinity, and “seemingly infinite to humans”. ---
**Author:** ![HorseloverFat](https://avatars.discourse-cdn.com/v4/letter/h/8e8cbc/32.png) [@HorseloverFat](https://boards.straightdope.com/u/HorseloverFat)\ **Post date:** [June 5, 2000, 8:03pm UTC](https://boards.straightdope.com/t/chronos-got-me-thinking-finite-or-infinite-universe/21456/7 "2000-06-05T20:03:24Z")
Until we can be certain of the amount of mass in the universe we can’t be sure if its closed/finite or open/infinite. The last couple high-profile experiments on dark matter and background radiation suggest an open, ever expanding, universe. ---
**Author:** ![John\_Kentzel-Griffin](https://avatars.discourse-cdn.com/v4/letter/j/ccd318/32.png) [@John\_Kentzel-Griffin](https://boards.straightdope.com/u/John_Kentzel-Griffin)\ **Post date:** [June 5, 2000, 8:17pm UTC](https://boards.straightdope.com/t/chronos-got-me-thinking-finite-or-infinite-universe/21456/8 "2000-06-05T20:17:18Z")
**Jeff\_42** The singularity at the Big Bang was “everywhere”. It was not a localized explosion. You can’t travel past the edge of the explosion because there is no edge. I don’t think any new space is created; it just gets streched. “How fast is the edge moving? light speed?” The speed is not constant. And light speed has no meaning outside the universe. The balloon anology is not perfect. It is just one way of visualizing a finite expanding universe. The hyperspace that the universe is embedded in has no real existance. **Chronos** The asteroid screen is a torus. Is this really a possibility? I have trouble understanding how the universe went from a singularity to infinite size. If the universe is infinite, was the singularity also infinite or a single point? I’ve also got a question. IIRC, if the total mass in the universe is less than or equal to some critical value, the universe is infinite. Wouldn’t this make the density zero? **Achernar** I’m not sure how the universe could be bounded. What is past the boundry? ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [June 5, 2000, 8:21pm UTC](https://boards.straightdope.com/t/chronos-got-me-thinking-finite-or-infinite-universe/21456/9 "2000-06-05T20:21:38Z")
Chronos, I’ve never quite understood how to get from a finite universe (which must have existed if the Big Bang came from a point, or at least from some small volume) to a universe which is today infinite. Even with an inflationary theory, going from finite to infinite would seem to require a discontinuous jump, not a continuous evolution. Or was the universe already infinite when it was only a point (whatever the hell that means :rolleyes: ). ---
**Author:** ![John\_Kentzel-Griffin](https://avatars.discourse-cdn.com/v4/letter/j/ccd318/32.png) [@John\_Kentzel-Griffin](https://boards.straightdope.com/u/John_Kentzel-Griffin)\ **Post date:** [June 5, 2000, 8:53pm UTC](https://boards.straightdope.com/t/chronos-got-me-thinking-finite-or-infinite-universe/21456/11 "2000-06-05T20:53:23Z")
**MysterEcks** That is only a problem with a finite _bounded_ universe, which I don’t think is a possibility. The universe could be finite and unbounded as the surface of a hypersphere. ---
**Author:** ![Dinsdale](https://avatars.discourse-cdn.com/v4/letter/d/97f17d/32.png) [@Dinsdale](https://boards.straightdope.com/u/Dinsdale)\ **Post date:** [June 5, 2000, 8:57pm UTC](https://boards.straightdope.com/t/chronos-got-me-thinking-finite-or-infinite-universe/21456/12 "2000-06-05T20:57:39Z")
Mr X But all the ones next door are contracting right now. God took care of all these details. My view as a non-scientist has long been “finite but expanding.” Expanding into what? Same answer as what existed before the big bang - I have no idea. Gotta limit the headache inducing queries somehow. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [June 5, 2000, 9:50pm UTC](https://boards.straightdope.com/t/chronos-got-me-thinking-finite-or-infinite-universe/21456/13 "2000-06-05T21:50:59Z")
> [@](#): > > Jeff\_42 said that “the Universe is both Finite and Infinite”. When you say “Infinte” here, I think the word you’re looking for is “Unbounded”. Without boundaries, just like the surface of the Earth. The Universe can be Finite and Bounded, Finite and Unbounded, or Infinite and Unbounded. Thanks Achernar…that is what I meant. Finite and Unbounded. I tend to go with Dr Matrix and his possible assertion, ‘The universe could be finite and unbounded as the surface of a hypersphere.’ > [@](#): > > The main problem with a finite universe is that then there is nothing stopping another one right next to it. It must therefore be infinite. Is there some reason there can’t be many universes? I mean, it might be weird and there’d really never be any way to know (I don’t think they can interact) but is there any reason why it absolutely can’t be this way? Here’s how I thought the Beginning was supposed to work. 1. There is nothing. True nothing…no time, no meaningful measure of any kind. The nothing is infinitely big or infinitely small or the size of a basketball…again, measurement is meaningless. 2. Big Bang happens. Like most explosions we are familiar with today it starts to expand like a sphere except this is a hypersphere (4-D spacelike). It expands ‘into’ the nothing mentioned in #1. 3. As the expansion continues energy densities drop eventually allowing the formation of particles then atoms then molecules and eventually stars and planets. 4. Some 15 billion years later I write this. – Conclusion, the Universe should be finite in size. I believe it should be unbounded (hypersphere) for no reason beyond the fact it appeals to me (good science huh?). Basically I can’t picture a bounded universe…hard enough picturing this other stuff. Still, I’m more than open to having my mind changed. Possibilities I’m unsure of (at least a few of them): - In #2 above I say the Big Bang happens and assume the ‘edge’ (for lack of a better term…I know it’s vague) coincided with the ‘blast front’ (again weak terminology…bear with me) basically defining the size of the Universe. The other possibility I see that could allow for an infinite universe is that ‘space’ essentially blinked into infinite being (call it a side effect of multiple dimensions unraveling and leaving dimension 1,2,3 and 4 behind) and the Big Bang singularity exploded into the space that was already there. - The Big Bang wasn’t a singularity. You get your instant infinite space (as mentioned above)and energy blinks into to being all over the place due to the stress of the whole space creation deal (not as weird as it sounds…energy spontaneously creates itself still today). This energy eventually coalesces and voila! Galaxies and what-not in an infinite universe. I know I’m all over the place here but I’m trying to narrow in on what the answer (as best we can figure) is. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [June 5, 2000, 11:36pm UTC](https://boards.straightdope.com/t/chronos-got-me-thinking-finite-or-infinite-universe/21456/14 "2000-06-05T23:36:11Z")
Quoth DrMatrix: > [@](#): > > The asteroid screen is a torus. Is this really a possibility? Yup, it sure is, as well as various other tesselated topologies. There was a _Scientific American_ article about it about a year ago… Do you still subscribe? [gloat]As it happens, too, one of my professors is the main guy investigating that possibility.[/gloat] For those in the audience with less mathematical background than you or I, BTW, a torus (Asteroids screen) is distinct from a sphere in several ways: A torus is flat, meaning that you can lay a piece of paper smoothly on an Asteroids screen, whereas you have to crincle it around the edges to lay it on a globe. Also, on an Asteroids screen, how long it takes you to reach your starting point depends on your direction: if you pick an angle whose tangent is irrational, you’ll actually never _quite_ get back to your starting point, although you’ll pass really close by it. Quoth Jeff\_42: > [@](#): > > (not as weird as it sounds…energy spontaneously creates itself still today) Jeff, do you have a cite for that? That sounds like Hoyle’s steady state theory, but nobody but Hoyle (well, no active cosmologists, anyway) accept that anymore. ---
**Author:** ![HorseloverFat](https://avatars.discourse-cdn.com/v4/letter/h/8e8cbc/32.png) [@HorseloverFat](https://boards.straightdope.com/u/HorseloverFat)\ **Post date:** [June 6, 2000, 12:19am UTC](https://boards.straightdope.com/t/chronos-got-me-thinking-finite-or-infinite-universe/21456/15 "2000-06-06T00:19:31Z")
> [@](#): > > \*\* > Chronos, I’ve never quite understood how to get from a finite universe (which must have existed if the Big Bang came from a point, or at least from some small volume) to a universe which is today infinite. Even with an inflationary theory, going from finite to infinite would seem to require a discontinuous jump, not a continuous evolution. > > Or was the universe already infinite when it was only a point (whatever the hell that means :rolleyes: ). > \*\* Using words like infinite is ,if I understand correctly, shorthard for an infinitly expanding universe. Spacetime that eventually contracts is the finite universe as it has a limit to maximum size. ---
**Author:** ![MysterEcks](https://avatars.discourse-cdn.com/v4/letter/m/f475e1/32.png) [@MysterEcks](https://boards.straightdope.com/u/MysterEcks)\ **Post date:** [June 6, 2000, 8:26am UTC](https://boards.straightdope.com/t/chronos-got-me-thinking-finite-or-infinite-universe/21456/16 "2000-06-06T08:26:15Z")
Hi everyone. I just want to take a moment to get it on the record that the banned MysterEcks above is/was an imposter. See [http://boards.straightdope.com/sdmb/showthread.php?threadid=26456](http://boards.straightdope.com/sdmb/showthread.php?threadid=26456) You’ll have to forgive me for not commenting on the topic of this thread–I don’t know enough about it to contribute intelligently, so I’ll refrain from contributing unintelligently. All I know is it’s damn big. ---
**Author:** ![Phobos](https://avatars.discourse-cdn.com/v4/letter/p/3d9bf3/32.png) [@Phobos](https://boards.straightdope.com/u/Phobos)\ **Post date:** [June 6, 2000, 12:09pm UTC](https://boards.straightdope.com/t/chronos-got-me-thinking-finite-or-infinite-universe/21456/17 "2000-06-06T12:09:35Z")
In any topology (open, flat, closed) the universe is infinite in the sense that you cannot reach an edge…either it goes on forever or space curves back on itself. As was pointed out, current evidence indicates that the universe is “flat” (Euclidean, infinite expansion). Even during the early inflationary period, when the universe was “smaller” in extent than it is today, it was still without an edge due to its curvature. The time=0 state (when the universe appeared to be a point…or really really small…or a pea instanton or whatever) is not understood. ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [June 6, 2000, 12:56pm UTC](https://boards.straightdope.com/t/chronos-got-me-thinking-finite-or-infinite-universe/21456/18 "2000-06-06T12:56:44Z")
> [@](#): > > Using words like infinite is, if I understand correctly, shorthand for an infinitly expanding universe. Whether the universe expands forever or collapses is tied to the spatial curvature of the universe. If the universe has positive curvature (analogous to a sphere), it will eventually collapse. If it has negative curvature (analogous to a saddle) or is flat, it will expand forever. Is it possible for the universe to have negative curvature everywhere, and still be finite? > [@](#): > > In any topology (open, flat, closed) the universe is infinite in the sense that you cannot reach an edge…either it goes on forever or space curves back on itself. Not reaching an edge means unbounded, not infinite (see Achemar’s post). ---
**Author:** ![John\_Kentzel-Griffin](https://avatars.discourse-cdn.com/v4/letter/j/ccd318/32.png) [@John\_Kentzel-Griffin](https://boards.straightdope.com/u/John_Kentzel-Griffin)\ **Post date:** [June 6, 2000, 2:07pm UTC](https://boards.straightdope.com/t/chronos-got-me-thinking-finite-or-infinite-universe/21456/19 "2000-06-06T14:07:35Z")
> [@](#): > > **ZenBeam** wondered: > Is it possible for the universe to have negative curvature everywhere, and still be finite? I remember something about it in _Scientific American_ some time ago. (I didn’t buy that issue, just skimmed it at the bookstore.) It’s prolly what **Chronos** refered to above. I’ll have to go to the library this weekend and see if I can find it. It was some weird shape that “tiled” negatively curved space. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [June 6, 2000, 2:19pm UTC](https://boards.straightdope.com/t/chronos-got-me-thinking-finite-or-infinite-universe/21456/20 "2000-06-06T14:19:18Z")
> [@](#): > > Jeff wrote–(not as weird as it sounds…energy spontaneously creates itself still today) > > Chronos responded– > Jeff, do you have a cite for that? That sounds like Hoyle’s steady state theory, but nobody but Hoyle (well, no active cosmologists, anyway) accept that anymore. Well…there are a bunch of mentions of it in this thread… [http://boards.straightdope.com/sdmb/showthread.php?threadid=24202](http://boards.straightdope.com/sdmb/showthread.php?threadid=24202) **Moriah** > [@](#): > > Call nature crazy, but it loves to randomly create out of nothing a sub-atomic particle and its corresponding anti-particle and have them immediately merge and cancel each other out and disappear. However, when nature does this at an event horizon, one particle may get sucked in, while the other escapes. The escaping particles may be detected one day as a tell tale sign of a black hole. Or… **JonF** > [@](#): > > The material falling into a black hole but not yet inside the event horizon radiates like gangbusters for various reasons, and it appears that black holes themselves emit Hawking radiation (virtual particle pairs appearing near or at the event horizon may not immediately annihilate each other when one of them happens to enter the black hole and the other doesn’t). And… **BorisB** > [@](#): > > The surface of a black hole is still dark - energy can’t leave a black hole except by the theoretical Hawking process. And last (but certainly not least)…🙂 **Chronos** > [@](#): > > First off, Hawking radiation does occur, or at least it’d better, or theoretical physics as we know it is screwed, but for a normal-sized black hole (about the mass of a star or larger), it’s completely insignificant. A stellar-mass black hole has a Hawking temperature on the order of a millionth of a degree above absolute zero. By contrast, the universal microwave background has a temperature of 2.7 degrees above absolute zero. ---
**Author:** ![John\_Kentzel-Griffin](https://avatars.discourse-cdn.com/v4/letter/j/ccd318/32.png) [@John\_Kentzel-Griffin](https://boards.straightdope.com/u/John_Kentzel-Griffin)\ **Post date:** [June 6, 2000, 4:17pm UTC](https://boards.straightdope.com/t/chronos-got-me-thinking-finite-or-infinite-universe/21456/21 "2000-06-06T16:17:24Z")
**Jeff\_42** Hawking radiation is _not_ energy spontaneously being created. The mass of the black hole is reduced by the radiation, so it comes from the black hole. It is just mass-energy being recycled. [Next page](https://boards.straightdope.com/t/chronos-got-me-thinking-finite-or-infinite-universe/21456.md?page=2)