Is the universe infinite or finite?

[firedragon]

Correct, you didn't say size as you said you did

That was a separate statement. Here you go.

But I understand that by infinite you mean in size.

And for the 3rd time i will present this picture

And for the second time repeat the explanation

Alright. Can you see in this picture of yours it says Omega = 1 for the flat universe? My question I asked 3 times was based on that, before you gave this image because everyone knows this. Here you go again.

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

2. 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?

 

[ChristineM]

That was a separate statement. Here you go.

Ok, misunderstanding,

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

And i i ha provided my explanation each time you have asked, my explanation is that the measurement has been taken and the results are explained in the picture.

2. 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?

No, it has the potential to continue expanding into infinity.

Yes the universe can potentially expand into infinity

 

[Polymath257]

I said "closed system" referring to the universe deemed a closed system. Like a thermos.

Closed system - Wikipedia

Maybe you are thinking I am here to debunk you but I am not and I did not. so there is no need whatsoever to try to have a debate unless it is called for. Be a little patient if you can and try and understand what someone says.

And for the third time, I will ask this question.

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

2. 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?

You are using two different definitions of the term 'closed'. For thermodynamics, a closed system is simply one where there is conservation of energy within the system. So the universe is closed in that sense.

When discussing whether the universe is finite or infinite, the term 'closed' refers to the spatial geometry of a time slice. Closed in this case means the same as 'finite volume'.

Whether the universe is open (infinite volume) is linked to the question of its average curvature. The curvature is usually described by a parameter called Omega. If Omega<1, then the universe is negatively curved (like in hyperbolic geometry) and if Omega>1, then the universe is positively curved (like a sphere). if Omega=1, it is said to be flat.

If space is positively curved (Omega>1), then it will be closed (finite volume). If it is flat or negatively curved, it can be open or closed depending on large scale structure. What we know is that Omega=1 to within 5 decimal places of accuracy, so it is very close to being flat. But it is still possible for Omega <1 or Omega>1, so we simply do not know if the universe is infinite or not.

Furthermore, even if the universe is flat or negatively curved, it is *possible* for it to still be closed (contrary to what many physicists and therefore the lay public think). For example, there is a three dimensional generalization of a torus (a bagel shape) that is flat and closed. it is possible that the universe has this large scale geometry even if it turns out to be flat.

In answer to your second question, yes, it is quite possible that even if Omega=1 that the universe is spatially infinite. If Omega=1, then that is actually a more 'likely' situation. And yes, that is the case even though time is finite into the past (the universe has a beginning).

 

[Polymath257]

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

It is possible to be finite and have no boundary if space is curved. There is a higher dimensional version of a sphere that has finite volume, but has no boundary. Such a geometry for space is the default if space is positively curved.

 

[Polymath257]

Interesting question. It had a beginning so is finite in the past, it is flat so potentially infinite (potentially is the key). So we have to assume it is finite in size (93 billion light years (gave or take a bit)). But potentially able to continue expanding for infinity.

A LOT of care is required to be accurate in this context.

The universe is about 13.7 billion years old. The farthest things we can see are over 11 billion light years away. BUT, and this is important, they were that far away when the emitted the light we now see. Since they were moving away and light moves at a finite speed, those galaxies are NOW about 90 billion light years away. But we won't *see* that fact for another 90 billion years.

Now, even if the universe is finite, we know that curvature is very small and that means the observable universe is a very small part of the whole geometry. So the actual size of the whole universe would be MUCH larger than that 90 billion light year figure.

So what is the universe expanding into?

In a very literal sense, the answer to this is 'into the future'.

When we say that the universe is expanding, we means that corresponding volumes in later time slices are larger. In terms of the spacetime geometry, this means that some piece at one time slice is larger than the corresponding piece at an earlier time slice. The 'direction of expansion', which is essentially a gradient is a vector pointing into the future.

An analogy might make this easier to understand. Imagine a globe with usual latitude and longitude lines. Imagine different latitudes correspond to different times, with north pointing in the direction of later times.

Starting at the south pole (the Big Bang), the latitude lines (space) get larger (expand) as you move north (into the future).

So, if you are at one latitude line and ask which direction latitude expands, what is the answer? The only possible answer is 'to the north', which in this analogy is the same as 'into the future'.

Some say there is infinite space for it to expand into, other believe it makes its own space as it expands.

There is no law of conservation of space (or volume).

A conundrum that will keep cosmologists in work for many years to come.

 

[Polymath257]

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.

A few atheists have been making a similar argument to "the universe is infinite" in this very forum when discussing the Kalam Cosmological Argument, which is the reason for this thought experiment if I may put it that way. Now before anyone derails the thread saying "this is a strawman" let me make it clear that this is not an atheists position in general, but a few do make this positive claim, thus what are the philosophical or/and scientific reasonings for this?

Some care is required here. The universe can be spatially finite or infinite and be temporally finite or infinite.

The spatial infiniteness of the universe is usually not relevant for the Kalam argument. The issue there is whether the universe is *temporally* infinite into the past. Well, *one* of the issues there.

In other words, one relevant issue with the Kalam argument is whether time itself can be infinite into the past. That is a *very* different question than whether the universe is spatially infinite (infinite in volume).

The main piece of information about the *temporal* finiteness of the universe is the Big Bang. Under general relativity, it is impossible to extend the notion of time previous to the Big bang, and time is finite into the past. In this case, there would literally be no such thing as 100 billion years ago.

The problem is that we *know* that quantum effects will become relevant at some point in describing the 'early universe' (the early stages of the current expansion) and general relativity simply doesn't take such things into account. And, when we try to extend it to take quantum mechanics into account, all sorts of difficulties are found.

MOST quantum theories of gravity have the 'singularity' of the Big Bang 'smoothed out' and it becomes more of a 'bounce'. In such theories, time *can* be extended previous to the BB and would likely be infinite into the past. But some *other* theories of quantum gravity do NOT have that degree of smoothing and time CANNOT be so extended, making it finite into the past.

The problem is that we don't know which theory of quantum gravity is correct and we have very little data to determine this.

So, even on the issue of whether time is finite or infinite into the past, we simply *do not know*. The data we have supports both possibilities.

My personal guess is that time *is* infinite into the past, but that is only a guess. Nothing more.

I would also add that there are many other problems with the Kalam argument, including hidden assumptions concerning causality and the uniqueness of uncaused events. But that is another discussion.

 

[RestlessSoul]

We’re gonna need a Delorean. And a flux capacitor.

 

[Twilight Hue]

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.

A few atheists have been making a similar argument to "the universe is infinite" in this very forum when discussing the Kalam Cosmological Argument, which is the reason for this thought experiment if I may put it that way. Now before anyone derails the thread saying "this is a strawman" let me make it clear that this is not an atheists position in general, but a few do make this positive claim, thus what are the philosophical or/and scientific reasonings for this?

I think its impossible for a finite universe in an continuum.

I suppose however if a border of some sort exists that 'seals' the universe, it can be seen as finite in that respect, such as a finite universe within an infinite multiverse.

 

[MatthewA]

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.

A few atheists have been making a similar argument to "the universe is infinite" in this very forum when discussing the Kalam Cosmological Argument, which is the reason for this thought experiment if I may put it that way. Now before anyone derails the thread saying "this is a strawman" let me make it clear that this is not an atheists position in general, but a few do make this positive claim, thus what are the philosophical or/and scientific reasonings for this?

That is when you just got figure out what is the truth of the matter, and if others decide not to agree even though what the matter is true by establishing the evidence of whatever claim may be made. Though it is most certainly not worth fighting over depending on whatever the topic is.

This topic being

Is the universe infinite or finite?

I would say that the universe is infinite ~ Is extremely vast, spacious, with many different stars, and even galaxies, and in which is observable if you were somewhere like Alaska, or a place in an area where not many lights from the city can be seen.

So that you can look into the sky, and see the sky beyond the sky - the Stars and Galaxies which have been all created, and continue to go on forever, and ever.

 

[firedragon]

And i i ha provided my explanation each time you have asked, my explanation is that the measurement has been taken and the results are explained in the picture.

You meant Omega? OK OK. No problem. That was just a clarification. There is no need to get offended.

No, it has the potential to continue expanding into infinity.

Yes the universe can potentially expand into infinity

So bottomline is you are saying the universe is not infinite with a beginning but infinite in expansion.

Alright. Thanks.

 

[firedragon]

You are using two different definitions of the term 'closed'. For thermodynamics, a closed system is simply one where there is conservation of energy within the system. So the universe is closed in that sense.

When discussing whether the universe is finite or infinite, the term 'closed' refers to the spatial geometry of a time slice. Closed in this case means the same as 'finite volume'.

Good. I was referring to the universe being a closed system. And no, I didn't refer to two different definitions, only one. The geometry of spacetime was not discussed. But thanks.

 

[firedragon]

Some care is required here. The universe can be spatially finite or infinite and be temporally finite or infinite.

The spatial infiniteness of the universe is usually not relevant for the Kalam argument. The issue there is whether the universe is *temporally* infinite into the past. Well, *one* of the issues there.

In other words, one relevant issue with the Kalam argument is whether time itself can be infinite into the past. That is a *very* different question than whether the universe is spatially infinite (infinite in volume).

The main piece of information about the *temporal* finiteness of the universe is the Big Bang. Under general relativity, it is impossible to extend the notion of time previous to the Big bang, and time is finite into the past. In this case, there would literally be no such thing as 100 billion years ago.

The problem is that we *know* that quantum effects will become relevant at some point in describing the 'early universe' (the early stages of the current expansion) and general relativity simply doesn't take such things into account. And, when we try to extend it to take quantum mechanics into account, all sorts of difficulties are found.

MOST quantum theories of gravity have the 'singularity' of the Big Bang 'smoothed out' and it becomes more of a 'bounce'. In such theories, time *can* be extended previous to the BB and would likely be infinite into the past. But some *other* theories of quantum gravity do NOT have that degree of smoothing and time CANNOT be so extended, making it finite into the past.

The problem is that we don't know which theory of quantum gravity is correct and we have very little data to determine this.

So, even on the issue of whether time is finite or infinite into the past, we simply *do not know*. The data we have supports both possibilities.

My personal guess is that time *is* infinite into the past, but that is only a guess. Nothing more.

I would also add that there are many other problems with the Kalam argument, including hidden assumptions concerning causality and the uniqueness of uncaused events. But that is another discussion.

I think there there was another thread that discussed the Kalam Cosmological Argument.

Thanks.

 

[MatthewA]

I think there there was another thread that discussed the Kalam Cosmological Argument.

Thanks.

Firedragon, what is the Kalam Cosmological Argument?

 

[firedragon]

That is when you just got figure out what is the truth of the matter, and if others decide not to agree even though what the matter is true by establishing the evidence of whatever claim may be made. Though it is most certainly not worth fighting over depending on whatever the topic is.

This topic being

Is the universe infinite or finite?

I would say that the universe is infinite ~ Is extremely vast, spacious, with many different stars, and even galaxies, and in which is observable if you were somewhere like Alaska, or a place in an area where not many lights from the city can be seen.

So that you can look into the sky, and see the sky beyond the sky - the Stars and Galaxies which have been all created, and continue to go on forever, and ever.

How about the unobservable universe?

 

[firedragon]

Firedragon, what is the Kalam Cosmological Argument?

The Kalam Cosmological Argument is a philosophical argument the speaks of sufficient reason and the impossibility of infinite regression. Every occurrence has a cause, the universe had a beginning which was an occurrence and it had a cause, which means to cause the beginning of the universe there has to be a timeless, uncaused, necessary being.

And the traditional inference to this necessary being is "God". A lot of atheists hate this argument so just like any religious person who wishes to proselytise their religion in every thread some atheists try to argue against this argument in every thread.

 

[MatthewA]

How about the unobservable universe?

Firedragon,

That would have to do with spiritual things, from my own personal opinion; if we are looking past anything observable

~ Faith (in my belief / some disagree -The Christian God of the holy bible ~ and Jesus Christ the Son of God in the bible teach about many things having to do with spiritual understanding.) (Hebrews 11:1)

The Kalam Cosmological Argument is a philosophical argument the speaks of sufficient reason and the impossibility of infinite regression. Every occurrence has a cause, the universe had a beginning which was an occurrence and it had a cause, which means to cause the beginning of the universe there has to be a timeless, uncaused, necessary being.

And the traditional inference to this necessary being is "God". A lot of atheists hate this argument so just like any religious person who wishes to proselytise their religion in every thread some atheists try to argue against this argument in every thread.

The Kalam Cosmological Argument is a philosophical argument that speaks of sufficient reason and the impossibility of infinite regression.

What is an example of what this looks like?

It also sounds like every actions had a cause; and that cause can have other causes to be continued to be caused?

 

[robocop (actually)]

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.

A few atheists have been making a similar argument to "the universe is infinite" in this very forum when discussing the Kalam Cosmological Argument, which is the reason for this thought experiment if I may put it that way. Now before anyone derails the thread saying "this is a strawman" let me make it clear that this is not an atheists position in general, but a few do make this positive claim, thus what are the philosophical or/and scientific reasonings for this?

I think it's infinite, but I have a secret to help me fathom it... maybe it is still generated by a formula.

 

[firedragon]

That would have to do with spiritual things,

No brother. For example, we cannot observe dark matter, imaginary time, many many things in the universe.

It also sounds like every actions had a cause; and that cause can have other causes to be continued to be caused?

Somewhat.

It means Every occurrence has a cause, the universe had a beginning which was an occurrence and it had a cause, which means to cause the beginning of the universe there has to be a timeless, uncaused, necessary being.

 

[Polymath257]

Good. I was referring to the universe being a closed system. And no, I didn't refer to two different definitions, only one. The geometry of spacetime was not discussed. But thanks.

When asking if the universe is infinite or not, the default is that this is a question about space, not time. And whether space is infinite or not depends, in part, on the curvature. In *that* context, closed means finite volume.

 

[Polymath257]

The Kalam Cosmological Argument is a philosophical argument the speaks of sufficient reason and the impossibility of infinite regression. Every occurrence has a cause, the universe had a beginning which was an occurrence and it had a cause, which means to cause the beginning of the universe there has to be a timeless, uncaused, necessary being.

And the traditional inference to this necessary being is "God". A lot of atheists hate this argument so just like any religious person who wishes to proselytise their religion in every thread some atheists try to argue against this argument in every thread.

The problem is that KCA is full of holes. First, an infinite regression is NOT logically impossible. Second, causality is NOT necessary for every event. Third, there is no demonstration that there is only one uncaused cause (in fact, it appears almost every quantum event is one). Fourth, if time is finite into the past, then time itself *cannot* be caused because causes happen in time. Fifth, there is no reason to think an uncaused cause must be necessary. Sixth, there is no reason to think that the universe, even if it had a beginning, had a single event as its beginning.

I can go on, but that is a topic for another discussion.