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Author Topic:   infinite space
crashfrog
Member (Idle past 1467 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 16 of 125 (65121)
11-08-2003 10:16 AM
Reply to: Message 15 by Beercules
11-08-2003 8:42 AM


An infinite universe would have infinite mass, but that mass would be distributed throughout an infinite volume of space. So the average density (plus initial conditions) will determine if the universe will collapse.
Ok, so you get infinity over infinity. That's one, isn't it?
...so what does that mean? Is "one" enough?
Now, what are some of the other so called contradictions associated with infinite space?
Well, why would the universe be infinite in every direction in space, but only infinite in one direction of time (the future)? That seems weird to me.
Just to be sure, we're clear on the fact that there's no way to tell who's right here, right? There's no conclusive evidence for either an infinite or finite universe. So, does it really matter? Honestly the reason I believe in a finite universe is that it just seems, I dunno, simpler. Also I don't believe that infinity can physically exist, but that's just me, I suspect.

This message is a reply to:
 Message 15 by Beercules, posted 11-08-2003 8:42 AM Beercules has replied

Replies to this message:
 Message 27 by Beercules, posted 11-09-2003 1:29 PM crashfrog has replied

  
Chiroptera
Inactive Member


Message 17 of 125 (65182)
11-08-2003 6:09 PM
Reply to: Message 14 by crashfrog
11-08-2003 2:34 AM


quote:
Well, I would assume that a universe of infinite size would contain infinite mass. Therefore I don't see how a universe of infinite mass could expand at all - it should immedately collapse. Could it even expand?
I'm no expert in this, but I believe if the mass density of the universe had been too small, then it would be open, meaning, essentially, that it would extend forever in all directions. And would expand forever.
Paradoxically, it is when the mass density is great enough that the universe will eventually collapse - but that implies a closed universe, one that has finite total volume.
As it is, the latest I've heard is that the universe may very well be perflectly flat (over large scales), meaning that it does extend forever. Also, the latest observations seem to indicate that there is a repulsive force (akin to Einstein's cosmological constant) that is described in the term "dark energy".

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Sylas
Member (Idle past 5261 days)
Posts: 766
From: Newcastle, Australia
Joined: 11-17-2002


Message 18 of 125 (65197)
11-08-2003 7:07 PM
Reply to: Message 10 by :æ:
11-07-2003 2:30 PM


Re: Infinite Space
:: writes:
The latest news that I've heard on this front, however, is that the universe has now been considered finite and shaped like a soccer ball. This comes in accordance to observed density fluctuations in the cosmic microwave background which were inconsistent with an entirely flat spacetime, and the math makes the most sense if the universe is instead shaped like a dodecahedron. Here's an article about those observations: Universe is Finite, "Soccer Ball"-Shaped, Study Hints.
Caution. A statement like the universe has now been considered finite and shaped like a soccer ball might convey the idea that this is a new discovery accepted by a significant number of scientists.
This is one report, by one group, in an area that is wide open. Quoting your link:
quote:
Weeks cautions that his team's model of a finite, dodecahedral-shaped universe, while promising, is hardly a proven theory. "There's more work to be done, he said. "It could be affirmed, or it could be refuted."
Well, it did not take long for the refutation to arrive. Indeed, the refutation was arguably already in place just shortly before the 12-sided finite universe claim! For details, see this popular account: Cosmic Soccer Ball? Theory Already Takes Sharp Kicks extracted from the New York Times. For a more technical press release, see MSU physicist at center of debate over universe shape . For the gory details, see Constraining the Topology of the Universe.
The two teams involved; Cornish et al for large and infinite, and Weeks at all for small with twelve-sided symmetry, are likely to work together to test this further. But I think the 12-sided model is very much a long shot by a small group which was interesting, but speculative and already pretty much dead.
Cheers -- Chris

This message is a reply to:
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danjuns
Inactive Junior Member


Message 19 of 125 (65246)
11-08-2003 9:48 PM
Reply to: Message 12 by crashfrog
11-07-2003 7:35 PM


Re: Infinite space
Crashfrog,
Our universe may have bounds, but that doesn't mean that there isn't something other than our universe beyond those bounds. Infinite space is much more than just our universe, actually, it's infinitely more than just our universe. There are infinite universes within infinite universes, infinitely.
You said that it is NOT possible to move infinitely towards 0 without ever reaching 0 because at a certain point the difference between 0 and the measurement becomes undetectable. No offence, but what I think you are forgetting or not realizing is that just because something is undetectable by us doesn't mean it doesn't exist. A nano second is an undetectable amount of time to the human brain, but that doesn't mean it doesn't exist. Visable light are the only frequencies of electro magnetic radiation detectable by the human eye, and yet we are aware of the existance of radio waves, micro waves, infra red, ultra violet, x-rays and gamma rays. A measurement that seems infinitely small in our existance, can seem infinitely big in another.
Space is not the only thing that exists within infinity. both time and space are infinite. And they are infinite in an infinite amount of ways. AS ARE YOU AND I.

This message is a reply to:
 Message 12 by crashfrog, posted 11-07-2003 7:35 PM crashfrog has replied

Replies to this message:
 Message 21 by NosyNed, posted 11-09-2003 12:40 AM danjuns has replied
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danjuns
Inactive Junior Member


Message 20 of 125 (65249)
11-08-2003 9:58 PM
Reply to: Message 3 by Adminnemooseus
08-27-2003 5:38 PM


Re: Topic closed, to help conserve space
Don't worry, I thought it was funny!

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NosyNed
Member
Posts: 8996
From: Canada
Joined: 04-04-2003


Message 21 of 125 (65283)
11-09-2003 12:40 AM
Reply to: Message 19 by danjuns
11-08-2003 9:48 PM


Re: Infinite space
As for moving to "0" there is also the possiblity that space is quantized. In which case there are not an infinite number of little steps between where you are and "zero".

This message is a reply to:
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DNAunion
Inactive Member


Message 22 of 125 (65285)
11-09-2003 1:35 AM
Reply to: Message 21 by NosyNed
11-09-2003 12:40 AM


Re: Infinite space
quote:
As for moving to "0" there is also the possiblity that space is quantized. In which case there are not an infinite number of little steps between where you are and "zero".
If the following is considered off topic, then let this side thought die here.
I was wondering when I heard Crashfrog express the same idea (but was too busy then to post), is that the solution to Zeno's Paradoxes? For example, I have heard that Zeno (or someone influenced by Zeno) stated something along the following lines:
If someone is standing a short distance from you - say just 10 feet - and shoots an arrow directly at your heart, that you don't have to worry about moving. Why? Because before the arrow can reach you it has to first travel half way to you; and after doing that, before it can reach you it still has to go half of the remaining distance; and after that, before it can reach you it still has to go half of the remaining distance, and so on indefintely. Since division by 2 in the process of calculating the new remaining distance for any given step produces a non-zero number, the result of the following division will likewise produce a non-zero number. Consequently, the remaining distance will approach closer and closer to 0, but will never actually reach it. And since there will therefore always be some distance remaining between the arrow and you, it can never reach you.
Now, even with space being quantized, it seems that one still can't divide any non-zero distance by 2 and end up with 0...well, unless one rounds down to the nearest quantum (1 / 2 = 0.5 = 0). But Crashfrog brought up a point about quantum uncertainty (which exists independent of our human ability to measure something) and I think quatum foam (which exists at the smallest possible scales), such that the distinction between a distance of 0 and one of "nearly 0" can vanish. Is that the general idea?
PS: I realize that there is already an answer to the paradox that involves calculus, but I am looking for a less mathematical solution.
[This message has been edited by DNAunion, 11-09-2003]

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Replies to this message:
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danjuns
Inactive Junior Member


Message 23 of 125 (65287)
11-09-2003 3:03 AM
Reply to: Message 22 by DNAunion
11-09-2003 1:35 AM


Re: Infinite space
As far as moveing infinitely towards 0 goes, think of it this way. Picture every particle of our universe shrinking at the exact same rate and speed. Because we would be shrinking at the same rate as everything else, we could theoretically shrink infinitely without even relizing anything was happening.(THEORETICALLY!)
Alot of people will tell you that as you move infinitely towards 0, you reach a point where the measurement is so small that it might as well be 0. This is ONLY true from our point of view. If you want any chance at all of wrapping your head around the idea of infinite space, you have to realize that our point of view is irrelevant.
There are infinite points of view.

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Replies to this message:
 Message 26 by crashfrog, posted 11-09-2003 6:35 AM danjuns has replied

  
crashfrog
Member (Idle past 1467 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 24 of 125 (65291)
11-09-2003 6:30 AM
Reply to: Message 19 by danjuns
11-08-2003 9:48 PM


No offence, but what I think you are forgetting or not realizing is that just because something is undetectable by us doesn't mean it doesn't exist.
No, with quantum uncertainty, that's exactly what it means. Uncertainty isn't a failure on our part to build sensitive enough instruments. It's not an engineering problem. It's a fundamental constraint on matter in the universe. We know that because apparently even the universe can't keep track - the virtual particles (which we know exist) that flit in and out of existence are evidence of this.
And they are infinite in an infinite amount of ways. AS ARE YOU AND I.
There is no part of me that is infinite. I am finite in total, and so are you.

This message is a reply to:
 Message 19 by danjuns, posted 11-08-2003 9:48 PM danjuns has replied

Replies to this message:
 Message 29 by danjuns, posted 11-09-2003 2:38 PM crashfrog has replied

  
crashfrog
Member (Idle past 1467 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 25 of 125 (65292)
11-09-2003 6:33 AM
Reply to: Message 22 by DNAunion
11-09-2003 1:35 AM


I realize that there is already an answer to the paradox that involves calculus, but I am looking for a less mathematical solution.
I think it's simpler than that.
All you have to do is realize that for each decending half-distance, you cover it in half the time, if you're moving at constant speed. Eventually you're stuck at an infinitely small distance from your destination, but you cover it instantaneously.
But, if you feel quantum mechanics is a better solution for you, well, they're both right.

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crashfrog
Member (Idle past 1467 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 26 of 125 (65293)
11-09-2003 6:35 AM
Reply to: Message 23 by danjuns
11-09-2003 3:03 AM


Because we would be shrinking at the same rate as everything else, we could theoretically shrink infinitely without even relizing anything was happening.(THEORETICALLY!)
No, because we'd observe everything moving away from everything else - not just distant galaxies, ala Hubble, but all matter in the universe, like our component atoms, would appear to move away from everything else as they shrunk towards their centers.

This message is a reply to:
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Replies to this message:
 Message 30 by danjuns, posted 11-09-2003 2:44 PM crashfrog has replied

  
Beercules
Inactive Member


Message 27 of 125 (65324)
11-09-2003 1:29 PM
Reply to: Message 16 by crashfrog
11-08-2003 10:16 AM


quote:
Ok, so you get infinity over infinity. That's one, isn't it?
No, there is nothing logically inconsistent about that. An infinite volume of space (cosmological principle assumed to be correct)has an infinite amount of galaxies, which in turn have an infinite amount of stars, etc. That's what you get from infinity. Counter intuitive, but consistent.
quote:
Well, why would the universe be infinite in every direction in space, but only infinite in one direction of time (the future)? That seems weird to me.
Well it would seem odd to have a bunch of infinites in continuous space and 3 other dimensions but not time. But that is still just an arbitrary choice, ie. imposing human preferences on the universe. There's also no guarantee that time did in fact have a beginning. That is because we already know the standard model is wrong.
quote:
Just to be sure, we're clear on the fact that there's no way to tell who's right here, right?
Yes. Both an infinite universe and a finite one are logically consistent. Cosmological models based on GR also allow for both possibilities, given enough intital assumptions.
quote:
There's no conclusive evidence for either an infinite or finite universe. So, does it really matter? Honestly the reason I believe in a finite universe is that it just seems, I dunno, simpler.
Believe it or not, an infinite universe is the simplest solution for a flat universe. In order for it to be finite, it must have a multiply connected topology, ie. a shape with a hole(s) in it. And since infinities show up in so many other places, an infinite volume of space doesn't seem so odd. I think time is the lone hold out right now.

This message is a reply to:
 Message 16 by crashfrog, posted 11-08-2003 10:16 AM crashfrog has replied

Replies to this message:
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Brad McFall
Member (Idle past 5033 days)
Posts: 3428
From: Ithaca,NY, USA
Joined: 12-20-2001


Message 28 of 125 (65326)
11-09-2003 1:36 PM
Reply to: Message 27 by Beercules
11-09-2003 1:29 PM


I hope this helps.
It is my understanding that Cantor notion of ordertypes makes this
Well it would seem odd to have a bunch of infinites in continuous space and 3 other dimensions but not time. But that is still just an arbitrary choice, ie. imposing human preferences on the universe.
not a "human" preference but the negative is pantheism instead of the positive application to a "number continuum". Even if NosyNed is correct that a QM discretness need necessarily apply the strech may be made up of sets of actual iinfinites but Russel's history of logic (not history of physics) with its implcations for harmonic analysis for example seems to still be keeping the nature of science from reCovering this possible science of nature.

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danjuns
Inactive Junior Member


Message 29 of 125 (65344)
11-09-2003 2:38 PM
Reply to: Message 24 by crashfrog
11-09-2003 6:30 AM


It's POSSIBLE that our universe MAY be quantized. But infinite space consists of a hell of alot more than just our universe.
When I talk about infinite space, I am reffering to something infinitely more complex than just our universe.
You should not dismiss the idea of infinite space just because you believe our universe is quantized. There could be an infinite amount of quantized universes existing within infinite space, all with their own range on the infinite spectrum of time, size, speed and frequency. In other words, a measurement that is so small that It can't exist in our quantized universe, could to another universe be so big that it doesn't exist in their quantized universe.
Our universe is an infinitely small part of infinite space.

This message is a reply to:
 Message 24 by crashfrog, posted 11-09-2003 6:30 AM crashfrog has replied

Replies to this message:
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danjuns
Inactive Junior Member


Message 30 of 125 (65348)
11-09-2003 2:44 PM
Reply to: Message 26 by crashfrog
11-09-2003 6:35 AM


I meant that everything has to shrink relitive to each other, including the space between the atoms. The atoms would move towards each other at the same rate at which they are shrinking.

This message is a reply to:
 Message 26 by crashfrog, posted 11-09-2003 6:35 AM crashfrog has replied

Replies to this message:
 Message 34 by crashfrog, posted 11-09-2003 2:58 PM danjuns has replied

  
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