Is the universe infinite or finite?

[Polymath257]

Yes, I understand that. I also understand that the surface of the globe has potentially an infinite number of co-ordinates on it’s surface.

I’m not saying the universe has to have a boundary, because I have no idea if that’s true or not; but everything in the observable universe, including the surface of a globe, does have limits, which are definable by context.

For a form to be without limits, it must be without a centre. And it must be unmeasurable.

That is not necessarily true. There is no center to the surface of the Earth *on* the surface of the Earth.

In your scenario above, one returns to one’s starting point by following the boundary.

Once again, the *surface itself* has no boundary. You never fall off the edge of the Earth. The *interior* of the Earth is irrelevant to that.

And, like has been said, there are three dimensional analogs (three dimensional manifolds) that have finite volume and are not bounded (that they can be boundaries of four dimensional manifolds is irrelevant).

 

[firedragon]

So you don't want to address the issues I raised?

Sorry, I cannot engage anymore because this will end up being the same exchange of rhetoric. I will tell you you didnt answer my questions, and you absolutely didnt whatsoever but you seem to think you did. I just think you have no clue of what I asked but then you think you know everything so it will go nowhere.

So I will stop now. You can say what you like now. No problem.

Have a good day. And thank you very much for engaging. I did learn a lot.

 

[Polymath257]

Sorry, I cannot engage anymore because this will end up being the same exchange of rhetoric. I will tell you you didnt answer my questions, and you absolutely didnt whatsoever but you seem to think you did. I just think you have no clue of what I asked but then you think you know everything so it will go nowhere.

So I will stop now. You can say what you like now. No problem.

Have a good day. And thank you very much for engaging. I did learn a lot.

if I didn't answer the question it is because I didn't understand what you were asking.

You asked if the universe is finite or infinite. I answered that nobody knows, but both are logical possibilities.

I mentioned the cyclic universe (along with other examples) and you talked about a proof that such is impossible. I pointed out that the proof makes assumptions that are likely to be invalid, and so does not apply.

How are those NOT answers to your questions?

 

[firedragon]

if I didn't answer the question it is because I didn't understand what you were asking.

You asked if the universe is finite or infinite. I answered that nobody knows, but both are logical possibilities.

I mentioned the cyclic universe (along with other examples) and you talked about a proof that such is impossible. I pointed out that the proof makes assumptions that are likely to be invalid, and so does not apply.

How are those NOT answers to your questions?

I cannot brother. Its alright. Thanks for all the input Truly appreciate it. Everyday is a learning.

 

[sayak83]

You mean its specially flat.

But I understand that by infinite you mean in size. But yet, Hawkins calculates the expansion of the universe at such critical rate that a one part of one billions of the radius different would collapse the universe. The claim of course is that the universe is a closed system. Anyway, scientists are also considering not only euclidian geometry, but also Lobachevskian & Riemannian.

Anyway, I would like to hear your explanation on the 5 decimal places.

Lets say that the flat universe with omega at 1 is given and its expanding infinitely, it still does not go back to the beginning of the universe. If there was a beginning according to the Big Bang model, can the universe still be infinite?

The solution is that the universe was infinite at the Big Bang itself. Which of course would mean that the Big Bang was not the beginning... most cosmologists now think this as well. Just because known physics cannot calculate how stuff behaves at very high energy densities found at Big Bang.... does not mean the universe began at that point of time. It is more accurate to say we can only backtrack to the time of the Big Bang using currently understood laws of physics. Before that we do not know because we do not know how physics behaves at these high densities.
Also there is nothing paradoxical about an expanding infinite space. The scale lengths of space are expanding (think of a ruled graph paper of infinite extent where all the squares are becoming larger with time). Also it does not need to expand into anything. There need not be anything beyond. It's simply swelling away.

 

[firedragon]

Also there is nothing paradoxical about an expanding infinite space. The scale lengths of space are expanding (think of a ruled graph paper of infinite extent where all the squares are becoming larger with time). Also it does not need to expand into anything. There need not be anything beyond. It's simply swelling away.

What you have explained is an expansion within a boundary. That does not make it infinite, but rather a finite universe expanding infinitely. Thats what you have presented.

Do you also believe that the universe is infinitely expanding yet also existed infinitely?

 

[sayak83]

What you have explained is an expansion within a boundary. That does not make it infinite, but rather a finite universe expanding infinitely. Thats what you have presented.

Do you also believe that the universe is infinitely expanding yet also existed infinitely?

No. Where did I say anything about a boundary? Think of an infinitely extending plane paper ruled with square grid. Now imagine that the length of each side of these squares is doubling with time. So if the side of a square was 1 cm at time t, it becomes 2 cm in time t+1 and so one. So each square is becoming larger over time... hence the entire paper is stretching outwards uniformly. But even though it stretches... ie expands.... at always remains infinite in extent.

 

[RestlessSoul]

The surface itself has no boundary. There is no place where you 'fall of the edge of the Earth'. So the *two* dimensional surface is finite in area and not bounded.

In a similar way, it is possible for a *three* dimensional geometry to be both finite in volume and not bounded.

Does this three dimensional geometry exist within the context of a fourth dimension? And if so, isn’t this fourth dimension (which may or may not be time) the limit, or boundary, of this hypothetical geometry? In which case, conceivably, the point at which the universe becomes either infinite or finite, may be the point at which space becomes time.

 

[firedragon]

No. Where did I say anything about a boundary?

I didnt say you said it. But that's fine.

Think of an infinitely extending plane paper ruled with square grid. Now imagine that the length of each side of these squares is doubling with time. So if the side of a square was 1 cm at time t, it becomes 2 cm in time t+1 and so one. So each square is becoming larger over time... hence the entire paper is stretching outwards uniformly. But even though it stretches... ie expands.... at always remains infinite in extent.

So that paper has a boundary. Doesnt it? Just like in the Hot Big Bang model. That means it has a radius. And the radius is expanding.

Isn't it?

 

[The Sum of Awe]

If the universe is finite, what lies beyond the boundary?

"Nothing is what rocks think about." - Aristotle

 

[sayak83]

I didnt say you said it. But that's fine.



So that paper has a boundary. Doesnt it? Just like in the Hot Big Bang model. That means it has a radius. And the radius is expanding.

Isn't it?

No. The paper has no boundary. It extends to infinity.

 

[firedragon]

No. The paper has no boundary. It extends to infinity.

1. Which model of the universe are you referring to?
2. If it extends to infinity how could it have a radii? How does that conform with the Hot Big Bang model?

 

[stvdv]

This question comes out of curiosity to find the arguments of those who make both sides of the word "or". If this is a false dichotomy I would like to hear the other options to this as well.

Is the universe infinite or finite?

IF I am "finite" then I would not be able to know if the universe is "infinite"
IF I am "infinite" then I would be better equipped to answer such question

 

[Polymath257]

Does this three dimensional geometry exist within the context of a fourth dimension?

Yes, although the four dimensional geometry can also be curved.

And if so, isn’t this fourth dimension (which may or may not be time) the limit, or boundary, of this hypothetical geometry?

Actually, the exact opposite. The three dimensional cross-section that is space (at a particular time) is the boundary that separates the past and the future.

In general, the boundary of a higher dimensional figure is a lower dimensional one. So, the two dimensional surface of the Earth is the boundary of the three dimensional interior (and the three dimensional exterior). The three dimensional 'space' at a particular time is the boundary of the four dimensional past spacetime and of the four dimensional future spacetime.

But, and this is important, there is no *requirement* that a bounded figure be the boundary of anything. It makes perfect sense to talk about a sphere without talking about the interior ball. It is curved, finite, has no boundary, etc.

In which case, conceivably, the point at which the universe becomes either infinite or finite, may be the point at which space becomes time.

According to the current understanding (which may well be wrong, of course), if space is finite at one time, it is finite for all other times. So if it is infinite at one time, it is infinite at all other times.

 

[Tiberius]

A surface is a boundary, surely?

In a technically sense. But since I am on the surface of the Earth now, I could say that I am at the boundary of Earth, and that just paints the wrong picture.

 

[firedragon]

In a technically sense. But since I am on the surface of the Earth now, I could say that I am at the boundary of Earth, and that just paints the wrong picture.

My God.

 

[gnostic]

@firedragon

I think you need to realize and understand that every astrophysics or cosmological models on the physical cosmology of the universe, are proposed solutions that are largely still theoretical (maths-based solutions) THAT ARE YET to be observed, tested and verified.

The Big Bang theory, for instance, is current the most active and researched model and the only model have its predictions “tested”, but some of the questions that this only “scientific theory” remained open, and unanswered.

For instance, your question to the universe to be finite or infinite, as @ChristineM and @Polymath257 have tried to explain to you, the finite/infinite are tied to the possible shapes of the universe, which the Big Bang model (and based on General Relativity & Cosmological Principle) have proposed several different shapes of the universe.

See and read WMAP’s Introduction To Cosmology: The Foundations Of The Big Bang.

So far, it would seem that the universe is flat, therefore infinite, BUT they don’t know for sure...so the real answer to the question is, “they don’t know”, yet.

As that webpage pointed out (that if you read the link I had provided) in the disclaimers, the shapes could be even more complicated than depicted:

Before we discuss which of these three pictures describe our universe (if any) we must make a few disclaimers:

• Because the universe has a finite age (~13.77 billion years) we can only see a finite distance out into space: ~13.77 billion light years. This is our so-called horizon. The Big Bang Model does not attempt to describe that region of space significantly beyond our horizon - space-time could well be quite different out there.
• It is possible that the universe has a more complicated global topology than that which is portrayed here, while still having the same local curvature. For example it could have the shape of a torus (doughnut). There may be some ways to test this idea, but most of the following discussion is unaffected.

They currently don’t know which shape the universe is.

The other cosmological models, whether they tried to attach to the Big Bang theory (eg the cyclical or oscillating universe model, or the Multiverse model) or some complete “alternative” models that astrophysicists tried to replace the Big Bang model, these models are only proposed solutions, are still only theoretical and untested, therefore not “scientific theory”.

 

[viole]

oes this three dimensional geometry exist within the context of a fourth dimension?

Not necessarily. Manifolds (surfaces) do not need to be embedded into a higher dimensional space. That would also lead to a recursion of spaces since the embedding space is also a surface.

We have also no problem to imagine our familiar three dimensional space without the need of a fourth space dimension. And what else is our familiar three dimensional space but a three dimensional flat surface?

Ciao

- viole

 

[viole]

Please provide an explanation to the conflict of cyclic universe model and the problems of thermodynamics.

If, as it seems, the arrow of time has a thermodynamics origin, then to say that entropy increases with time is a tautology. Like saying that things had a much lower entropy in the past. It is like asking: how is it possible that all bachelors are not married?

Ciao

- viole

 

[firedragon]

I think you need to realI’ve and understand that every astrophysics or cosmological models on the physical cosmology of the universe, are proposed solutions that are largely still theoretical (maths-based solutions) THAT ARE YET to be observed, tested and verified.

Mate. I never said that one model is infinite. It is some of the atheists who said that one of the models that suits them is absolute. One atheist even gave a model that he cooked up. So hopefully some will read this.

For instance, your question to the universe to be finite or infinite, as @ChristineM and @Polymath257 have tried to explain to you, the finite/infinite are tied to the possible shapes of the universe, which the Big Bang model (and based on General Relativity & Cosmological Principle) have proposed several different shapes of the universe.

Maybe you like to side with your kind. But you should note, that I never said that they were wrong. I just asked them questions that they didnt answer. For example one proposed the cyclic universe model, and the other of course just got very angry for no reason. So maybe you should tell me which model have I proposed to be absolute and infinite in this thread.

So far, it would seem that the universe is flat, therefore infinite, BUT they don’t know for sure...so the real answer to the question is, “they don’t know”, yet.

I have explained this to one of the people you mentioned above. In detail. But thanks.

They currently don’t know which shape the universe is.

But some atheists here do. And they have said that some models are definitely absolutely. You defended them as well. So you are practicing a bias. A double standard. I see that all the time.

I asked a few questions that came up from the investigation of the causal structure of space time. Atheists here proposed certain models as their preferred ones but they were not argued considering the questions. Showed that there are three different geometric models considered what was proposed was only one which is when Omega is one. Of course it was not understood and retorted back with a bit of rhetoric. Angry rhetoric. Its funny really.

Also, even though euclidian metrics is the most prevalent along with a specially flat universe, asymptotically Euclidean metrics is considered although cosmologists like Penrose are interested in a finite region rather than at infinity. Connected, disconnected asymptotically Euclidean metrics. Now you should note that some positive claims were made. I mean 100% assured, poise claims. And when questioned, the response is an insult. When asked a very specific question about the radii, the hot Big Bang model, the Hartle and hawking no boundary model and the radii calculation in it, the response is of course a snide remark.

So mate. Rather than responding for others and taking sides, just provide your insight which is a far better approach to make.

Now that you made some comments, can you specifically explain very clearly without any frills how you would explain the thermodynamic problems posed in the cyclic universe model? You seem to know the responses of the others very well so maybe you know the questions I asked. You should.

The density parameter at a rapid expansion in inflation would be pushed towards omega=1 and of course the geometry to flatness and the prediction that stems from inflation is that the universe is flat according to Guth. Everyone gets this. Since the discovery of dark energy so cosmic microwave background and supernovae calculations show that it adds Omega m approximately 0.69 so that the Omega is plus 1 or 1+ or - 0.01. Thats why I asked the specific question specifying Omega at 1. But of course the question was not understood, not clarified, but rhetoric was the issue.

I would suggest that rather than eternally delving in a quest to debunk others no matter what, and engaging in good conversation trying to understand others, and if not understood ask for clarifications, and if something is not known being candid, is the way to go.

Thanks and cheers. I appreciate your post.