Exploring a Finite Universe: Understanding its Challenges

[SpaceTiger]

If the universe was finite then for any given point there must exist another point within a finite distance at which motion in any direction will not increase the distance between the two.

Not if that point is itself moving! Think again about the expanding balloon analogy. Any two points on the surface of the balloon are receding from one another as the balloon expands.

 

[Chronos]

The FRW model pretty much excludes that concept, Thor. I do not understand your point. Are you conserving energy, or ignoring it? What I do see is an effort to introduce an Arpian twist into this discussion.

 

[Garth]

If the universe was finite then for any given point there must exist another point within a finite distance at which motion in any direction will not increase the distance between the two.

Bend it, twist it, tie it in a knot, a finite Universe is hogwash.

Are you considering spherical space?

In which case your two points would be each other's antipodes.
In a static universe your statement would be true, just as on the Earth's surface any direction moved from the South Pole takes you closer to the North Pole, what is hogwash about that?

In an expanding universe these distances would be increasing, but still the distance between the two antipodean points would be a maximum of all distances in the universe at anyone cosmological epoch.

Garth

 

[Balence]

There's no necessity for something "outside" of a finite universe. It need not be embedded in another space to reproduce what we observe.

Your absolutly right, it doesn't have to be something. It could be nothing, empty space, going on infinitly. Our observations are limited by our finite knowledge.

 

[Balence]

The universe we live in is probably like a membrane (finite of course, but expanding nonetheless)...like an expanding balloon. But then you ask, "what's outside the membrane?" Well, my answer would be the higher dimensional universes. Overall, it would seem that it would be infinite, but then we'd have to go into religion.

Please define higher dimension. I know the proper definition of dimension is: A measure of spatial extent, expecially width, heigth, or length. Its not feasible for their to be any further dimensions, unless you count time, which isn't spatial but has a relationship to distance none the less. As from what I've learned of many of the theories of extra dimensions, the extra dimensions are mathimatical fillers for theory equations that did not make sense. (string theory for example) Like me saying two plus two equals five because of the other dimension. Also how is an infinite universe religion? Higher dimensional universes sounds much more religious. Wheres occams razer when you need it?

 

[SpaceTiger]

Your absolutly right, it doesn't have to be something. It could be nothing, empty space, going on infinitly.

In GR and QFT, "empty space" is something. I'm saying that there need not be anything other than the universe we observe and that this universe could be finite in size.

 

[Balence]

In GR and QFT, "empty space" is something. I'm saying that there need not be anything other than the universe we observe and that this universe could be finite in size.

There either has to be something or nothing out side the observable universe, if there's nothing, it stretches on infinitly having the potential to be filled by something. Also nothing must have the potential to produce something, or we will never find a complete answer to the beggining of the universe, thus the nothing out side our obserable universe has or will give way to new matter or energy. As nothing stretches on infinitly given infinite time mean that probally there's "stuff" out side our observable universe and its impossible to know what because its unubservable. Much like trying to see beyond the horizon.

 

[SpaceTiger]

There either has to be something or nothing out side the observable universe, if there's nothing, it stretches on infinitly having the potential to be filled by something.

Nothing is just nothing, it doesn't stretch out infinitely and it's not the same as empty space. The concept of "outside" isn't even necessary here. The universe, by definition is all that there is. It doesn't make sense to talk about anything outside of it and there's no reason that it can't be finite.

As nothing stretches on infinitly given infinite time mean that probally there's "stuff" out side our observable universe and its impossible to know what because its unubservable.

Most current theories do suggest that there is stuff outside of our observable universe, but when we talk about a finite vs. infinite universe, we're usually talking about the entire universe, even that which is unobservable.

This will be hard for you to understand without a little background in general relativity. You might want to browse the "Special and General Relativity" forum a bit.

 

[Balence]

Anything that is finite has boundries. It would seem logicaly that this conflicts with the universe being all there is, as that definition should include what's inside, outside, and the boundries themselves. Even with the curvature of space creating a finite boundry for humans or any other form of matter or energy to travel, does not make the universe finite. Perhaps the limitations due spacecurvature is what's ment by the term universe, and I am taking it a bit literally. Though I still believe an "outside" would be more than relevant and logical.

 

[Garth]

Anything that is finite has boundries.

Not true - otherwise sailors would still be worried about 'falling off the end of the world'.

Garth

 

[Balence]

Not true - otherwise sailors would still be worried about 'falling off the end of the world'.

Garth

Sailors never were astronauts though, "the world" is still finite and still has its boundries which have been crossed.

 

[setAI]

ultimately I think that the very idea of a universe finite or infinite with a 'boundary' is wrong-headed- a thing like a universe emerges from the relationships of a causal network- the metrics of distance/duration are established by the relationships of the elements in the network- a boundary is only an arbitrary concept of where one can fit the abstract map of such a causal set in an imaginary mathematical space- but there is no reason for that map-space to exist in any physical way- the elements and events that arise in a causal network don't connect to any kind of outside boundary- causality and the metrics of space and time that emerge from it propagate locally through the elements/events in the network ONLY- there is no spatial/temporal analog of a 'boundary' to be fenced-in by-

given this- my thinking is that emergent systems of relationships that arise form causal networks -like universes [whether they are infinite or finite]- are boundary invariant

 

[VikingF]

In the paper "Philosophical Implications of Inflationary Cosmology" by Joshua Knobe, Ken D. Olum and Alexander Vilenkin, there is a theory saying that the universe actually is infinite (see ch 2.2). I am no cosmologist, but the way I understand it, this is somehow a consequence of the inflation theory. I don't quite understand this, because I thought it almost was a "proven fact" that our universe is finite, and not infinite...?

Anyway, here is the paper:
http://arxiv.org/pdf/physics/0302071

 

[SpaceTiger]

In the paper "Philosophical Implications of Inflationary Cosmology" by Joshua Knobe, Ken D. Olum and Alexander Vilenkin, there is a theory saying that the universe actually is infinite (see ch 2.2).

You might want to check out this paper by Linde (a big name in inflationary theory):

http://arxiv.org/abs/hep-th/0408164"

People often assume, for simplicity, that the universe would have trivial topology. If this is not the case (and Linde's paper suggests that it shouldn't be), then an inflationary universe can be finite.

Keep in mind that much of this stuff is a long way from experimental testing -- science is probably a long way from providing a definitive answer to the finite/infinite question.

 

[Chronos]

The betting window is still open on the finite vs infinite universe. The universe may be finite, but appears to be fairly huge. Some additional papers worth considering:

CMB Anisotropy of the Poincare Dodecahedron
http://www.arxiv.org/abs/astro-ph/0412569

A Cosmic Hall of Mirrors
http://www.arxiv.org/abs/astro-ph/0509171

Extending the WMAP Bound on the Size of the Universe
http://www.arxiv.org/abs/astro-ph/0604616

 

[Balence]

ultimately I think that the very idea of a universe finite or infinite with a 'boundary' is wrong-headed- a thing like a universe emerges from the relationships of a causal network- the metrics of distance/duration are established by the relationships of the elements in the network- a boundary is only an arbitrary concept of where one can fit the abstract map of such a causal set in an imaginary mathematical space- but there is no reason for that map-space to exist in any physical way- the elements and events that arise in a causal network don't connect to any kind of outside boundary- causality and the metrics of space and time that emerge from it propagate locally through the elements/events in the network ONLY- there is no spatial/temporal analog of a 'boundary' to be fenced-in by-

given this- my thinking is that emergent systems of relationships that arise form causal networks -like universes [whether they are infinite or finite]- are boundary invariant

Theories for finite univeres I've researched have a shape whether its a hypersphere or a dodecahedron and a way for it to seem boundless whether its mirrors or traveling so far you return to where you started. A good example I feel is a pac man game (no offense). It has a shape and is boundless for pac man. As pac man travels he notices he always returns to his starting point even if traveling in a strait line, he correctly concludes that the curvature of digital space must be the cause. He also assumes the universe must be finite. However one day he tries an experiment. He finds a large dot and specialy marks it then travels in a strait line counting all the small dots till he returns to his large dot. He counted 1000 dots so he can rightfully assume that the distance across his universe is 1000 dots. He then repeats the experiment with other large dots and compares his finding thus being able to pin point where the warp occurs, or where the boundry of his possible travels. He can then do a thought experiment in which he travels 10,000 dots from the large one without traveling through the warped space. He then can consider the possibility of an infinite universe. My point is that a finite universe by nature has boundries. In the end I come to the same conclusion of universes being boundry invairiable and since a finite universe must have a boundry I personaly conclude that the universe must be infinite. Additionaly the hyperspere uses multiple dimensions to prove it correct. For one pac man is not 2D he is made of pixels which are 3D, they have length width and height regardless of how small. Second its impossible to conceive these dimensions because we are 3D (the theories own argument) therefore it seems scientificly unsound.

 

[Balence]

I don't quite understand this, because I thought it almost was a "proven fact" that our universe is finite, and not infinite...?

Finite universes is taught as almost proven fact by many teachers and professers. The idea of a finite universe is very comforting vs an infinite one because we can fully understand (over time) a finite universe. A infinite universe can have a large number of possible contradicting laws and is very chaotic thus limiting what we can hope to understand. Though I personaly believe over time we will find laws to explain the chaos. Additionaly history has shown man prefers to be as important as can be, an infinite universe makes us even smaller and more insignificant.

 

[Balence]

Keep in mind that much of this stuff is a long way from experimental testing -- science is probably a long way from providing a definitive answer to the finite/infinite question.

I agree, only time will tell for sure. Hopefully though it will be rather soon so I can start my victory dance.

 

[Teecher]

...He counted 1000 dots so he can rightfully assume that the distance across his universe is 1000 dots. He then repeats the experiment with other large dots and compares his finding thus being able to pin point where the warp occurs, or where the boundry of his possible travels.

Care to explain how Mr. Pac-Man made this last deduction?

 

[SpaceTiger]

I agree, only time will tell for sure. Hopefully though it will be rather soon so I can start my victory dance.

Your ideas are not falsifiable and can't really be called science. Basically, it sounds like you're asserting that any self-contained finite universe must be embedded in a larger space (as per the "boundaries" you speak of). I disagree with you on philosophical grounds, but we can never disprove your assertions any more than we can disprove the existence of a "creator". If this infinite space you speak of is out of causal contact with our universe, then there's nothing we can do to detect it.

 

[Balence]

Care to explain how Mr. Pac-Man made this last deduction?

He conveniently has a living space in which every straight line of dots going horizontaly have 1000. Conveniently each big dot is one small dot down and to the right of the first big dot. Conveniently the horizontal dots are equal to the vertical so both dimensions are 1000. Using the big dots as markers packman can create a map that would show a declining line of big dots slanting through the center of his finite space. From this he can conclude where the warp is. You can also try drawing it out on graph paper. If this doesn't work then he kept getting digispace sick and figured it must be that warped space. I really wanted to get to the point and wanted to get off pac man so I skiped how he might figure this out.

 

[Balence]

Your ideas are not falsifiable and can't really be called science. Basically, it sounds like you're asserting that any self-contained finite universe must be embedded in a larger space (as per the "boundaries" you speak of). I disagree with you on philosophical grounds, but we can never disprove your assertions any more than we can disprove the existence of a "creator". If this infinite space you speak of is out of causal contact with our universe, then there's nothing we can do to detect it.

At this point my theory does loose scientific value due to the fact we can not currently detect this infinite space. However, many current finite theories have even less scientific value and are widely accepted as known truth despite the inability to properly test them thus making them even more unscientific. According to occams razor an infinite universe is more feasible than a finite one. I only assume one thing that is rational, and keep it simple. Finite theories assume alot, much of which is "inconcievable" to us, (irrational) have simular instances in history, (earth being in the center, spontaneous generation) finnaly, and coinciding with my last point, the idea is very alluring as the universe is more predictable if its finite. Additionaly there are several different finite universe theories out there. My point is that while infinite universe theory can be compared to theories of a "creator" its much more closer to compare "creator" with finite theories.

 

[SpaceTiger]

He conveniently has a living space in which every straight line of dots going horizontaly have 1000. Conveniently each big dot is one small dot down and to the right of the first big dot. Conveniently the horizontal dots are equal to the vertical so both dimensions are 1000. Using the big dots as markers packman can create a map that would show a declining line of big dots slanting through the center of his finite space. From this he can conclude where the warp is.

How does he know where to put the big dots such that they pass through the center?

Let's try a simpler example to ensure that we're on the same page. Suppose Pac-Man is confined to one dimension (a line). You see him on the screen, moving along the line. From your point of view, he keeps moving to the edge of your screen until he reaches the "warp" point and then comes out the other side. But does this warp point have any significance to Pac-Man? On an initially unmarked line, is there any point along the line that is different from the other? No, from his point of view, it's just a line seeming to extend off infinitely in either direction. He can determine the size of his finite universe by simply marking a point and seeing how long it takes to come back to it. However, there's way for him to know if that point is on the edge or the center of your screen.

The situation is similar in 2-D. The initially unmarked landscape is just a plane seeming to go off inifinitely in all directions. He can mark any set of points that he likes, but there's no way for him to know where these points lie in relation to the center of your screen or the "warp", as you put it.

 

[SpaceTiger]

At this point my theory does loose scientific value due to the fact we can not currently detect this infinite space.

We could never detect infinity to start with, but what's worse is that there is no hypothetical observation that could prove your theory wrong. You could always just say that we're out of causal contact with this extra universe.

However, many current finite theories have even less scientific value and are widely accepted as known truth despite the inability to properly test them thus making them even more unscientific.

All current scientific theories are hypothetically testable, but many are beyond the reach of current technology. Your theory is not falsifiable even in principle.

According to occams razor an infinite universe is more feasible than a finite one.

Actually, occam's razor says nothing about an infinite versus a finite universe. If, however, we discovered that the universe was finite, one could invoke occam's razor to support the case for a universe with no boundaries.

My point is that while infinite universe theory can be compared to theories of a "creator" its much more closer to compare "creator" with finite theories.

I think you've misunderstood. I'm not comparing infinite theories to theories of a creator, I'm comparing your "universe with boundaries" idea to that of a creator. Infinite universes are commonplace in mainstream science.

 

[setAI]

an odd thing- you can in principle prove the universe is finite- if it is- but can you EVER prove or even know if it is infinite? I would think that locality makes it impossible even in principle-

 

[SpaceTiger]

an odd thing- you can in principle prove the universe is finite- if it is- but can you EVER prove or even know if it is infinite? I would think that locality makes it impossible even in principle-

To the best of my knowledge, there's no way to prove (or even find evidence for) an infinite universe. However, a proper scientific model can still be disproven even if it predicts an infinite universe.

 

[Intuitive]

Hi SpaceTiger.

My intuition would say that the Universe is infinite in diameter although I know it could never be proven so it would always remain a mystery, A Universe with infinite Super Galaxies that never end.

I tend to believe this because to my knowledge an edge has never been found and that Nature abhores a Vacuum and likes to fill it's space.

I wanted to ask if Scientist are steering more to the infinite Universe concept?

 

[SpaceTiger]

A Universe with infinite Super Galaxies that never end.

Infinite Super Galaxies? Where is that coming from?

I tend to believe this because to my knowledge an edge has never been found

There is a definite "edge" to the observable universe, but right now there's no way to know how much lies beyond that.

and that Nature abhores a Vacuum and likes to fill it's space.

That's not really relevant, the question concerns the amount of space, not what fills it.

I wanted to ask if Scientist are steering more to the infinite Universe concept?

Not to my knowledge. I think the majority view is that the universe is much larger than we can currently observe, but it's still unclear how large.

 

[Intuitive]

Hi SpaceTiger

Infinite Super Galaxies? Where is that coming from?

It was a general self belief only, I don't believe a vast void exists with nothing in it, Strictly empirical.

There is a definite "edge" to the observable universe, but right now there's no way to know how much lies beyond that.

Is Science saying that the observabale Universe is thinning out?
I never realized that Science had come that far as to see an edge, My apollogies if this is the case.

That's not really relevant, the question concerns the amount of space, not what fills it.

But doesn't the Universe follow the same rules as the rules of a Vacuum?

Not to my knowledge. I think the majority view is that the universe is much larger than we can currently observe, but it's still unclear how large.

I understand, Thanks.

P.S
I really do respect your knowledge and position in this forum, I do look up to you.

 

[Balence]

How does he know where to put the big dots such that they pass through the center?

Let's try a simpler example to ensure that we're on the same page. Suppose Pac-Man is confined to one dimension (a line). You see him on the screen, moving along the line. From your point of view, he keeps moving to the edge of your screen until he reaches the "warp" point and then comes out the other side. But does this warp point have any significance to Pac-Man? On an initially unmarked line, is there any point along the line that is different from the other? No, from his point of view, it's just a line seeming to extend off infinitely in either direction. He can determine the size of his finite universe by simply marking a point and seeing how long it takes to come back to it. However, there's way for him to know if that point is on the edge or the center of your screen.

The situation is similar in 2-D. The initially unmarked landscape is just a plane seeming to go off inifinitely in all directions. He can mark any set of points that he likes, but there's no way for him to know where these points lie in relation to the center of your screen or the "warp", as you put it.

He doesn't place the big dots, theyre "convienently" placed. Pac man is still 3D, you can't see 1D without the other two. If nothing else he kept getting space sick at the same point.

 

[Balence]

We could never detect infinity to start with, but what's worse is that there is no hypothetical observation that could prove your theory wrong. You could always just say that we're out of causal contact with this extra universe.

My theory isn't falsifiable so far because I could pose the question of what lays beyond.

All current scientific theories are hypothetically testable, but many are beyond the reach of current technology. Your theory is not falsifiable even in principle.

Its based on principle.

Actually, occam's razor says nothing about an infinite versus a finite universe. If, however, we discovered that the universe was finite, one could invoke occam's razor to support the case for a universe with no boundaries.

A rule in science and philosophy stating that entities should not be multiplied needlessly. This rule is interpreted to mean that the simplest of two or more competing theories is preferable and that an explanation for unknown phenomena should first be attempted in terms of what is already known. Also called law of parsimony.

By deffinition occam razor doesn't directly state anything about infinite vs finite. However it applies to all theories of science and philosophy which include infinite vs finite. An infinite universe is much more simpler and goes by what has been observed for ages.

I think you've misunderstood. I'm not comparing infinite theories to theories of a creator, I'm comparing your "universe with boundaries" idea to that of a creator. Infinite universes are commonplace in mainstream science.

I did misunderstand. However the universe with boundaries is not my idea, it is the neccessity of a finite universe. Infinite universes is an oxymoron. If the term universe means all there is and it is infinite or even finite, there could never be more than one.

 

[Balence]

To the best of my knowledge, there's no way to prove (or even find evidence for) an infinite universe. However, a proper scientific model can still be disproven even if it predicts an infinite universe.

I guess logic and thought experiments don't count?

 

[Balence]

an odd thing- you can in principle prove the universe is finite- if it is- but can you EVER prove or even know if it is infinite? I would think that locality makes it impossible even in principle-

You can't prove a finite universe by principle. You can't disprove an infinite one by principle.

 

[SpaceTiger]

It was a general self belief only, I don't believe a vast void exists with nothing in it, Strictly empirical.

Empirical implies that it has been observed...and it hasn't. In fact, galaxies never get any bigger than a hundred or so kiloparsecs (an observational fact). Larger gravitationally bound objects are known as galaxy clusters.

Is Science saying that the observabale Universe is thinning out?

No, the edge of the observable universe is the maximum distance light could have traveled since the beginning of time (or recombination).

 

[SpaceTiger]

He doesn't place the big dots, theyre "convienently" placed. Pac man is still 3D, you can't see 1D without the other two.

And he receives the meaning of those dots from "on high"? Come on, this is getting ridiculous.

If nothing else he kept getting space sick at the same point.

You can't be serious...

By deffinition occam razor doesn't directly state anything about infinite vs finite. However it applies to all theories of science and philosophy which include infinite vs finite. An infinite universe is much more simpler and goes by what has been observed for ages.

Nope, the number of free parameters in the finite models can be made to be the same as in the infinite ones.

I did misunderstand. However the universe with boundaries is not my idea, it is the neccessity of a finite universe.

There is no need for a boundary anymore than there is need for a creator. It's just a human concept being unnecessarily forced on the natural world.

Infinite universes is an oxymoron. If the term universe means all there is and it is infinite or even finite, there could never be more than one.

The plural was referring to theories of infinite universes -- "Infinite universes are commonplace in mainstream science". That means there are many mainstream theories of the universe that are infinite.