Thread: The Universe, Finite or Infinite?

I can't vote for anything.
It is too hard to get a hold of the immeasurable complex, to be able to get an imagination of how it could be.

Originally posted by Sortilegio
I saw a documental the other day on discovery, where talking about the suns expantion, they assumed that it was possible in the many years for that to come, that we would have the technology to move the plantes

Yeah, if we don't destroy ourselves or our planet first. People are just too itchy with the big red button for me to believe we'll last another 4 billions years.

from a logical point of view, the universe has to be infinite. How can it even be finite? What happens at the end? are there walls or something? Even outside of it, there is space. Basically it seems impossible to me that universe could be finite. That doesn't make sense. What happens to it? How can it ever stop?

Originally posted by sephiroth clock
Even outside of it, there is space.

No, that's part of the definition. The universe is defined as all space and all time. It started expanding approximately 13.4 billion years ago and, according to our most recent astronomical observations, it will continue to do so ad infinitum. Whether the universe is finite or infinite is a matter of geometry - if it has a closed geometry, it is finite; if it has an open geometry, it is infinite. That geometry was determined at the moment of the Big Bang. Either it has always been spatially infinite or it has always been spatially finite.

Originally posted by Peregrinus

No, that's part of the definition. The universe is defined as all space and all time. It started expanding approximately 13.4 billion years ago and, according to our most recent astronomical observations, it will continue to do so ad infinitum. Whether the universe is finite or infinite is a matter of geometry - if it has a closed geometry, it is finite; if it has an open geometry, it is infinite. That geometry was determined at the moment of the Big Bang. Either it has always been spatially infinite or it has always been spatially finite.

I'm saying its logically impossible for it to have ever been spatially finite then I guess. Can you picture a finite universe? Doesn't work...

Originally posted by sephiroth clock
I'm saying its logically impossible for it to have ever been spatially finite then I guess. Can you picture a finite universe? Doesn't work...

Sure, a finite universe is one with a closed geometry. The three dimensional equivalent would be the surface of a sphere. Start at point A and start walking in one direction. Eventually you'll come back to your starting point. That's a finite universe.

Originally posted by Peregrinus

Sure, a finite universe is one with a closed geometry. The three dimensional equivalent would be the surface of a sphere. Start at point A and start walking in one direction. Eventually you'll come back to your starting point. That's a finite universe.

But you would have to apply that to 3dimensions , the surface of a sphere is 2d but space is 3d+time . But what if you look at things from the beggining . the instant before the big bang there was no space , then it was there , did it just instantly pop up to infinity or did space grow with time , and if so then it must still be growing and thus hasnt reached infinity . I dunno , does that sound at all logical .

Originally posted by Darkmatic

An infinite universe is in some ways easier to imagine than a finite one. Since the universe is supposed to be everything that exists, it seems intuitive that it should go on forever. Of course an infinite universe is impossible to picture, but we can get at what it means by saying that no matter how far you go there will always be more space and galaxies. It is hard, however, to reconcile this picture with the idea that the universe is expanding. If it's already infinite, how can it expand?

To see how, remember that by expansion we mean that the distance between galaxies is increasing. Suppose right now there is a galaxy every million light years or so. After a long enough time this infinite grid of galaxies will stretch out so that there is a galaxy every two million light years. The total size of the universe hasn't changed—it's still infinite—but the volume of space containing any particular group of galaxies has grown because the separation between the galaxies is now larger.5

What about a finite universe? This phrase sounds like a contradiction because if the universe ends somewhere then we would naturally want to know what was beyond it, and since the universe includes everything, whatever is beyond that edge should still be called part of the universe. The resolution of this paradox is that even if the universe is finite, it still doesn't have an edge. If I head off in one direction and resolve to keep going until I find the end of the universe, I eventually find myself right back where I started. A finite universe is periodic, meaning that if you go far enough in any direction you come back to where you started.

Trying to picture a closed (finite) universe is in some ways even harder than trying to picture an open (infinite) universe because it is easy to mislead yourself. For example, people often compare a two-dimensional closed universe to the surface of a balloon. This analogy is helpful because such a surface has the property of being periodic in all directions, and it is easy to picture the expansion of such a universe by imagining the balloon being blown up. In fact, this analogy is like the rubber sheet analogy I used before, except now the sheet has been wrapped up to form a sphere. The problem is that this picture immediately leads to the question of what is inside the balloon.

This question comes from taking the analogy too literally. Nothing in general relativity says that a two-dimensional closed universe would have to exist as a sphere inside a three-dimensional space; the theory only says that such a universe would have certain properties (e.g. periodicity) in common with such a sphere. For this reason I think it is useful to keep the balloon in mind as a convenient analogy but it is ultimately best to think of the closed universe as a three-dimensional space with the strange property that things which go off to the right eventually come back again from the left.

What does expansion mean in a closed universe? Since this universe has a finite size, it makes sense to talk about that size increasing. Again suppose that there is now a galaxy every million light years. Suppose also that if I were to head off in a straight line I would travel 100 billion light years before coming back to where I started, passing about 100,000 galaxies on the way. If I take the same journey billions of years later, the number of galaxies won't have changed but the distances between them will have doubled, so the total distance for the round trip will now be 200 billion light years.

That article is from 2000, and since then, the WMAP experiment has shown that the density of massenergy in the universe is very, very near the critical density, such that its geometry is in all likelihood very nearly flat. The 2D equivalent would be a plane, like a stretched out rubber sheet.

Did that make sense?

I believe the universe to be finite, and that there is more universes at the end (though you don't have to reach the end to reach them), but that the end its unreacheable, and the universe is seemingly infinite, as the end is so far.

I didn't read all the posts but my belief about the universe is that its sort of a sphere shape and if you go to the edge you will instintly appear on the other end opposite to were you went out of, when ever I think about the universe it gets me all confused, another idea that i had is that there is always going to be space no matter what, everything takes up space, so space it just a nothingness so it's infinite, it's hard to come up with this type of thing

This may sound weird...

I can't believe in a physical infinite universe because "infinite" cannot be described in physical means. I can't believe in a finite universe because you can divide something infinite times and always get an answer. But... if something can't be small enough to lack measures... something can't be big enough to have infinite measures. And if time is just a concept, when it all started? If we can't tell... we can tell we live here since eternity. But that don't make sense, either. But if time is not a concept, it CAN exist or not. So, we could say we live here since the time was created. This don't make much sense, but... i think the world was created when anything changed. If we have more than one action, we have "time".

Still, if time really exists, then everything already happened. So we could also say the world was created in the future. Or in the past. Or now. The feeling of existance is too complex for me to understand

Finite or infinite, only thinking that the world exists drives me crazy. I know that we are more than unions of atoms... and sight is just a sense, like almost everything we feel. Everything seem just a dream. It's like will alone created all things. Thinking this way, eveything is really connected. I am you, you are me, and everything is nothing. Time has made nothing seem greater and greater. Until "nothing got stable". Stable enough to call it a "world". So there will always be nothing. Infinite is all but nothing. The universe is both finite and infinite. Matter is thought, thought is existance, existance is action, action is time, time creates matter. Things in life come back all the time. Why? Because, fortunately or infortunately... you're part of this infinite and eternal...nothing.

Non-sense, huh?

By universe I assume we mean the physical universe, and so I agree that it is a question of space. Since space comes from the finite, it cannot be infinite because the greater cannot come from the lesser. Space is therefore indefinite and not infinite. To be infinite it would have to have absolutely no boundaries at all, which can be proven false just by the fact that ordinary thought is outside of space, thus limiting it.

Originally posted by syzygy
By universe I assume we mean the physical universe, and so I agree that it is a question of space. Since space comes from the finite, it cannot be infinite because the greater cannot come from the lesser. Space is therefore indefinite and not infinite. To be infinite it would have to have absolutely no boundaries at all, which can be proven false just by the fact that ordinary thought is outside of space, thus limiting it.

Explain how thought, which is not physical, can be "beyond" physical space and how that would at all affect whether space is infinite (something determined at the moment of the Big Bang based on the density of matter in the universe).

Originally posted by Peregrinus

Explain how thought, which is not physical, can be "beyond" physical space and how that would at all affect whether space is infinite (something determined at the moment of the Big Bang based on the density of matter in the universe).

I'm a little confused on what you are asking. You agree that thought is not physical, so what do you want me to explain? It is not localizable; space does not apply to it. For something to be infinite, it would have to include everything, and since space does not include thought, it is not infinite.

Originally posted by syzygy

I'm a little confused on what you are asking. You agree that thought is not physical, so what do you want me to explain? It is not localizable; space does not apply to it. For something to be infinite, it would have to include everything, and since space does not include thought, it is not infinite.

The question is whether space is physically finite or infinite. "Thought" is a word we use to describe the product of electrochemical neural processes, and in that sense, it is certainly grounded in the physical. Thought is a perceptual product of a physical reaction, although not physical itself. (A dream is the same as a thought – the six-headed fluffy puppy dog you dreamed about as a kid is not physically real, but the electrochemical reactions which gave rise to your perception of that dog are physically real.)

The mind can conceive of things which do not exist (or rather, which we do not know exist), but that does not in any way compromise the physical extent of space. Space could be a repeating pattern, like a checkerboard tablecloth, of infinite extent (the tablecloth is infinitely large), and yet not containing all possibilities. The pattern could repeat while space itself does not. That would still be a spatially infinite universe, although it would not contain all conceivable possibilities.

Originally posted by Peregrinus

The question is whether space is physically *finite or infinite. *

We already tried to have this conversation. To add an epithet to the word "infinity" is an absurdity, but that is a question of orientation towards the vertical (something the modern mind has lost sense of). You seem to think that something can be infinite within limits, but that makes no sense to me and that's why I use the term indefinite.

Space is relative, and so it will inevitably need two points of reference. A line is formed from the space between these two points. No matter how far the distance between these points, even if it beyond our comprehension, it will always be finite. It can only be infinite if there is only one point, and so it is indefinite.

Originally posted by syzygy
We already tried to have this conversation. To add an epithet to the word "infinity" is an absurdity, but that is a question of orientation towards the vertical (something the modern mind has lost sense of). You seem to think that something can be infinite within limits, but that makes no sense to me and that's why I use the term indefinite.

A physically indefinite universe would require that the boundaries of the universe be nebulous or otherwise uncertain. In a spatially infinite universe, the boundaries simply do not exist, and there is therefore no uncertainty about their state or location. Those are two completely different concepts, as I explained in that lengthy, apparently-pointless previous conversation. If you insist on holding personal definitions for words which contradict the definition accepted by anyone educated in the English language or capable of reading and understanding a dictionary, then holding conversations with you about these subjects will continue to be an unenlightening and futile endeavor, one in which I am unwilling to again engage. No one else seems to have this misunderstanding but you, so I doubt that it is due to my inability to properly explain the intricacies of the English language or their application to modern science.

Space is relative, and so it will inevitably need two points of reference. A line is formed from the space between these two points. No matter how far the distance between these points, even if it beyond our comprehension, it will always be finite. It can only be infinite if there is only one point, and so it is indefinite.[/b]

Space is infinite when there can always be found another point beyond the one to which you are currently measuring. You are limiting yourself conceptually when you try to measure infinity. It cannot be done, and any attempt to do so is nonsensical. When space extends ad infinitum, continuing always farther than the farthest point you have yet reached, it is infinite. Not indefinite. The boundaries are not in question. They simply do not exist.

Originally posted by Peregrinus
Space is infinite when there can always be found another point beyond the one to which you are currently measuring. You are limiting yourself conceptually when you try to measure infinity. It cannot be done, and any attempt to do so is nonsensical. When space extends ad infinitum, continuing always farther than the farthest point you have yet reached, it is infinite. Not indefinite. The boundaries are not in question. They simply do not exist.

Not in any way that out minds are capable of perceiving.

There really is no reason to ponder this question.
But can you think of another question that we cannot even make a educated guess about or philosophically ponder ideas. There just isn't one.

Originally posted by Peregrinus
A physically indefinite universe would require that the boundaries of the universe be nebulous or otherwise uncertain. In a spatially infinite universe, the boundaries simply donot exist, and there is therefore no uncertainty about their state or location. Those are two completely different concepts, as I explained in that lengthy, apparently-pointless previous conversation. If you insist on holding personal definitions for words which contradict the definition accepted by anyone educated in the English language or capable of reading and understanding a dictionary, then holding conversations with you about these subjects will continue to be an unenlightening and futile endeavor, one in which I am unwilling to again engage. No one else seems to have this misunderstanding but you, so I doubt that it is due to my inability to properly explain the intricacies of the English language or their application to modern science.

How can you talk about infinite space? You have no way of proving that. It is indefinite as far as I can see, and I have already shown how the boundries are set in the vertical dimension which the modern mind convently leaves out...such dark times. A boundry in either the horizontal or vertical is still a boundry. And if we are going to to use words in their proper sense in order to take into account every possibility, then such a thing as "physical infinity" is an absurdity clear and simple. For the last time, I understand the "standard" definition so please stop insisting that I don't. Unfortunately, it leaves out a very important dimension to reality that we have lost a sense of.

Originally posted by Peregrinus

Space is infinite when there can always be found another point beyond the one to which you are currently measuring. You are limiting yourself conceptually when you try to measure infinity. It cannot be done, and any attempt to do so is nonsensical. When space extends ad infinitum, continuing always farther than the farthest point you have yet reached, it is infinite. Not indefinite. The boundaries are not in question. They simply do not exist.

Good luck trying to prove any reality to the first statement, because there is none. It is a nice idea, but you are leaving out a very important issue. And, infinity cannot be measured, which is why it is pointless to say that space, which can be measured, can ever be infinite. The greater cannot come out of the lesser. I don't know why you think I'm trying to measure the infinite; just because we can't find a boundry doesn't make it infinite, it is indefinite at best. It is the same as trying to prove the existance of God; something there is no answer to because it is asking the wrong question. Not to get into a religious discussion, but it is the perfect example because they are basically the same thing. God transcends existance, the infinite transcends space. To try to limit these things to something below them immediately creates an absurdity (which is why many people have problems with religion - those who claim to have an authority to religious ideas bring them down to a level at which they make no sense). Sorry to mention God, but religion and philosophy cannot be separated like this forum tends to think. Herein lies the fault of all Western, modern philosophy from finding any truth beyond its small domain. It tries to separate itself into distinct parts, which granted is a useful thing that has found many interesting things, but it is only useful to a certain extent. The problem lies in that it tries to extend itself beyond its limits; where it immediately fails to have any legitimacy.

Originally posted by syzygy+--><div class='quotetop'>QUOTE(syzygy)</div>

How can you talk about infinite space? You have no way of proving that.[/b]

Did you fail to read the information I linked about the recent findings of WMAP, or are you simply ignoring them? Our best data currently suggest that the universe has a flat geometry and is therefore spatially infinite.

<!--QuoteBegin-syzygy
It is indefinite as far as I can see, and I have already shown how the boundries are set in the vertical dimension which the modern mind convently leaves out...such dark times.

Then you need to have your eyes checked. Spacetime is composed of three spatial dimensions - including the "vertical" as defined by a 3D coordinate system - and one temporal one. Add on a half dozen more if string theory turns out to be correct. Read up on physics before posting nonsense about missing "vertical dimensions" in a thread about the physical extent of the universe.

Originally posted by syzygy
For the last time, I understand the "standard" definition so please stop insisting that I don't. Unfortunately, it leaves out a very important dimension to reality that we have lost a sense of.

So you choose to use a word in the standard lexicon (in this case "indefinite"), completely ignore its accepted meaning and attempt to apply it to a concept which is already adequately described by another term accepted throughout the entire scientific community (i.e. "spatially infinite")? That is absolutely asinine. If you want to use a term to describe this ill-conceived philosophy of a missing vertical dimension which has somehow been lost to modernity, make up a word - don't borrow something already in use and incite a pointless debate about your personal semantics when the discussion is about the physical extent of the universe. Call this vertical dimension idea "the-super-duper-über-infinity", but do not dispute the accepted use of "physically-" or "spatially infinite". That which extends without bounds is infinite. If the spatial extent of the universe extends without bounds, it is by definition infinite. There is no obscurity, no uncertainty, no ambiguity about having "no boundaries" - there is nothing in that concept that makes it "indefinite," so stop raping the English language and come up with your own terms if you wish to describe a new concept.

Originally posted by syzygy+--><div class='quotetop'>QUOTE(syzygy)</div>

And, infinity cannot be measured, which is why it is pointless to say that space, which can be measured, can ever be infinite.[/b]

If space is truly infinite, its extent cannot be measured. This is what I stated in my previous post had you actually bothered to read and understand it.

<!--QuoteBegin-syzygy
Just because we can't find a boundry doesn't make it infinite, it is indefinite at best.

And here we have it! The very crux of your continued misunderstanding. When I (or any other scientist discussing the physical extent of the universe) speak of space as being "infinite," I do NOT mean that it has some boundary which we have yet to discover. I mean that it has NO BOUNDARY WHATSOEVER. That which has NO BOUNDARY is appropriately termed infinite. That is why I call it "infinite". I call it "infinite" because I mean that if the total massenergy in the universe is below the critical mass, it has NO BOUNDARY. Not an unknown boundary, not an undiscovered boundary, not a nebulous, ill-defined, indefinite boundary, but NO BOUNDARY AT ALL.

If you cannot understand a simple standard definition of a unambiguous English word or continue to insist on redefining it contrary to its accepted definition as listed in every respected dictionary in publication just to fit your pseudo-philosophy about missing dimensions because you are too unimaginative or stubborn to come up with your own terms, I am not going to discuss this with you any more.

If someone else would like clarification about this issue because they feel I have not been clear or precise enough in my explanation of physical infinity, I'll expand on this discussion. But it would appear that you, syzygy, are the only one having problems with this concept.

I agree with wombing: Infinite and finite are the same thing.

I believe it is in a way infinite yet its like the earth you could say as you can keep on traveling and eventually you will come back to where you started, the snake eating its own tail is a symbol I love to show what I mean, its a hard discussion and the answer I doubt we will ever truly know

Peregrinus, I have already stated that I know what you are saying, so if I say something that doesn't make sense to you, why don't you ask me to explain further rather than assume I am stupid? For example, when I speak of the vertical dimension in relation to something other than the physical world, why do you think I'm talking about the physical world? If we are going to talk about infinity, then it should include all possible perspectives, and I would think the metaphysical would be the most important! It is this perspective we have lost sight of and I am only trying to make it known to those who are interested. If you are only interested in the physical world, that is fine, but please understand that my perspective includes more than that. This does not mean that what you are saying is wrong, but that it has its place just like everything else. What we now know of as "standard" in reference to the meaning of words and symbols is actually not their original meaning. The modern world has changed many definitions to account for the separation of different studies, but this has unfortunately caused the loss of the larger picture. This was necessary for the time, but I believe it is not necessary anymore and I am trying to make others aware of that.

So again, I completely understand everything you have said before you said it, so please stop thinking I am stupid. If you don't understand something I am saying, just ask me to explain rather than thinking you know everything. The first step to true knowledge is to forget everything you think you know. I am not trying to say that you don't know what you are talking about, obviously you do and I agree with you, so let us have a conversation instead of resorting to assuming the other doesn't know what they are saying. And if you think this topic is only in relation to the physical, please reread the original post.

For example, when I speak of the vertical dimension in relation to something other than the physical world, why do you think I'm talking about the physical world?[/b]

Why? Because, like your improper usage of the word “indefinite,” the term “vertical” refers to something other than that which you intend to describe - namely to a spatial, “one atop another” arrangement. It can also apply to a series of events, such as in the microeconomic strategy of “vertical integration” of the production process. However, nowhere have I come across the use of the word “vertical” to describe some mystical missing dimension. You haven’t even defined this term you made up – you just threw it out there into discussion – and then you expect everyone to know what it means? Sorry, but when you try to tack your own definition onto words which are already in ubiquitous use to describe something completely other than that for which you are attempting to use it, there will be misunderstandings – as evidenced by this entire, ongoing discussion.

If we are going to talk about infinity, then it should include all possible perspectives, and I would think the metaphysical would be the most important![/b]

All that is necessary for something to be infinite is that it have no boundaries. If the physical world has no spatial boundaries, then it is infinite. QED. There is no reason why the existence of anything else which is infinite (be that time, the number line, the number of unique pieces of art that are possible, or even un-described, undefined, hypothetical, mystical dimensions) should compromise the infinitude of space. There are other things in this world which are infinite, and their existence in no way makes space “less infinite”.

If you don't understand something I am saying, just ask me to explain rather than thinking you know everything. The first step to true knowledge is to forget everything you think you know.[/b]

Just because I am confident in what I do know (the definition of “infinite” in this case) does not mean that I am arrogant enough to think that I know everything. It seems a common misconception around these off-topic forums that confidence in the knowledge that one does possess is equivalent with the height of intellectual arrogance and simultaneously the very depth of ignorance which is to assume oneself to be infallible. I have stated neither that space is emphatically infinite nor that it is finite – I do not presume to know that. However, our best current measurements, theory, and understanding suggest that the universe is spatially infinite in that it has a flat geometry. You call that arrogance? I am simply reporting the facts of the day. What we were arguing is not whether space is infinite or finite – that has yet to be fully determined – but whether, if space truly is as it appears now to be – infinite in extent with a flat geometry - it qualifies as “infinite.” Since “infinite” is merely a word – one which has a definition of “that which is without bounds” – then if space meets the definition by having no boundaries, it is infinite, regardless of anything else which might also be infinite.

If you wish to speak of the infinitude of that which encompasses all else, then speak of that, but do not make the mistake of thinking that the existence of one infinity negates the existence of any others.