Exploring an Infinite Universe: Science & Facts

In summary, the conversation discusses different theories and opinions about the size and nature of the universe. While some believe it is finite and unbounded, others argue that it could be infinite. The concept of a "three-dimensional torus" is also mentioned as a possible explanation. Ultimately, the exact size and nature of the universe is still unknown and remains a philosophical problem.
  • #1
Supaiku
32
0
I'm wondering if there's science that supports an infinite (in some way) universe
 
Astronomy news on Phys.org
  • #2
I believe you'll find that it's the other way around. Since we know when the universe began, and how fast it's expanding, we know that it has to be of finite size. It's generally thought to be unbounded, though, so you can go in the same direction forever without hitting the end.
 
  • #3
The only thing infinite about the universe is its future.
We see that it is expanding at an accelerating rate.
This implies that temporally its infinite; no future crunch.
 
  • #4
ARRRRGGGG! If the universe is finite, what is Outside the universe?!? This puzzels me.
 
  • #5
It puzzles everyone. We just have to get over it. :biggrin:

The problem is that there isn't really any 'outside'.
 
Last edited:
  • #6
Well put, danger. The universe is a pretty weird place. It defies common sense - and offends just about every other sense sooner or later. How does something come from nothing, something not come from nothing ... or vice-versa? At some point there is no escape from saying 'dammit, nobody knows, that's just the way it is so live with it. So it's perfectly OK to say the universe is unbounded and there is nothing outside the universe. These premises are irrefutable by definition.
 
  • #7
I don't feel it is a problem: Critical points in my opinion can offer some assistance in understanding some perplexing questions about the Universe. It makes perfect sense to me to accept a bifurcation as the cause of the Big Bang: a critical point separating the pre-existence from our own existence without needing to understand what "tipped" the pre-existence past this bifurcation point. Our world is FULL of non-linearities, critical points, and abrupt qualitative changes. I'm convinced the non-linear world I see outside of my window is but a thumbprint of a larger phenomenon that created our Universe. This too allows me to come to terms with an "endless" and "timeless" Universe: At some point (in time and space), a bifurcation point is reached which changes the qualitative nature of existence rendering our metric concepts inapplicable in the same manner as rendering "swimming" so when the water temperature drops below freezing. Works for me anyway. :smile:
 
Last edited:
  • #8
ARRRRGGGG! If the universe is finite, what is Outside the universe?

Well, another Universe is outside ours. Just ask any Graviton. :smile:
 
  • #9
Danger said:
Since we know when the universe began, and how fast it's expanding, we know that it has to be of finite size.

I will not agree with this. The universe could as well be (spatially) infinite. Most observations actually points at a flat universe, i.e. an infinite universe.
Why do you say the universe has to be of finite size?
The size of the universe could be infinite already at the Big Bang (which is when the universe had an infinite density).
 
  • #10
My opinion is that the universe is what is called in mathematics, a "three-dimensional torus". There are no edges, but it isn't infinite. Think of an ant on a beachball walking around on its surface. The universe is a three-dimensional flat surface that wraps around a four-dimensional sphere.
 
  • #11
The_Bled said:
My opinion is that the universe is what is called in mathematics, a "three-dimensional torus". There are no edges, but it isn't infinite. Think of an ant on a beachball walking around on its surface. The universe is a three-dimensional flat surface that wraps around a four-dimensional sphere.
Sure, that's also possible. No one knows wheter the universe is infinite or not. (And it certainly does not care about "opinions" :tongue2: )
 
  • #12
EL said:
Sure, that's also possible. No one knows wheter the universe is infinite or not. (And it certainly does not care about "opinions" :tongue2: )

Well, since there are so many theories and nobody has ever flown to the edge of the universe, I think I'm stickin' to that.:wink:
 
  • #13
The_Bled said:
Well, since there are so many theories and nobody has ever flown to the edge of the universe, I think I'm stickin' to that.:wink:
I notice the "wink", but may I ask why you choose to stick to just one option?
 
  • #14
EL said:
I notice the "wink", but may I ask why you choose to stick to just one option?

I don't just stick to one option... that just seems to be like the most plausible theory to me. But... you don't know which one is right, so you talk about all of them... Whatever, back to the infinite universe topic. :rolleyes:
 
  • #15
After 100 years of observational cosmology, I would say that the (spatially) finite/infinite universe controversy is still completely unresolved. Not only are the data fully consistent with either possibility, but we have a successful theory (inflation) that suggests that the present-day universe would look pretty much the same either way.
 
  • #16
I think it is a philosophic problem .And ...the universe is finite ,but it have no boundary.It seems like ...you walking on the ground but never fall over the cliff and leave our Earth ~~

^_^
 
  • #17
SpaceTiger said:
. . . we have a successful theory (inflation) that suggests that the present-day universe would look pretty much the same either way.

Is this a cause for pause? Should not a "successful" theory account for only ONE possibility? I don't enjoy criticizing, esp. a field I love but to me, that's like saying the results suggest it's less than one and bigger than one at the same time.
 
  • #18
The_Bled said:
I don't just stick to one option... that just seems to be like the most plausible theory to me. But... you don't know which one is right, so you talk about all of them... Whatever, back to the infinite universe topic. :rolleyes:

The thought of a finite universe makes me sleep better at night too, it's easier for me to accept a universe with a finite amount of matter than an infinite amount...but, who says I'm supposed to sleep well at night:wink: .
Anyway, as you say, back to the main topic...
 
  • #19
saltydog said:
Is this a cause for pause? Should not a "successful" theory account for only ONE possibility? I don't enjoy criticizing, esp. a field I love but to me, that's like saying the results suggest it's less than one and bigger than one at the same time.

Well, no, I wouldn't say it's like that at all, nor do I think that every theory has to give us definite answers. Inflation is saying that we shouldn't be surprised that we're having trouble distinguishing between the finite and infinite universe. One of the main points of inflation was that it explained, without fine-tuning, how the universe could appear almost perfectly flat. In doing so, it also made other predictions that were testable, some of which have been verified.

If it happens that the universe conspires to make certain things difficult to observe, then we'll just have to live with that. If we rejected all such theories, there would be no quantum mechanics or chaos theory.
 
Last edited:
  • #20
mars2 said:
I think it is a philosophic problem .And ...the universe is finite ,but it have no boundary.It seems like ...you walking on the ground but never fall over the cliff and leave our Earth ~~
^_^

Think of a 2D universe situated on the surface of a sphere. The area of this universe is finite, but anyway it has no boundaries where the 2D beings living there can "fall over a cliff".
Now you of course have to generalize this picture to a universe with 3 spatial dimensions, where the "area" is replaced by the "volume". Although our brains cannot really handle this generalization, this would give you a hint of how a universe could be finite and still unbounded.
 
  • #21
Danger said:
I believe you'll find that it's the other way around. Since we know when the universe began, and how fast it's expanding, we know that it has to be of finite size. It's generally thought to be unbounded, though, so you can go in the same direction forever without hitting the end.

actually, I think it is infinite yet bounded.
 
  • #22
Now you're just teasing... :tongue:

What I was getting at is that if it formed a finite time ago, and is expanding at finite speed, it can't be infinite. There's a maximum size that it could have reached by now. 'Infinite' implies that it had no beginning, not just no end.
Perhaps I'm using the wrong definition of 'infinite' here, but that's what it means to me.
 
  • #23
ComputerGeek said:
actually, I think it is infinite yet bounded.
How?

Garth
 
  • #24
The universe is defined by what we as individuals percieve. As we all believe that we can only percieve up to a certain distance, then the universe is finite without question. And since there is no diference as to whether I look in this direction or in that direction, we can see equally far in all directions, so at any given moment in time the universe is spherical with me as the origin of that sphere.

Further I would add that speculating about what is outside our universe, as we believe that it can never be interacted with, is an exercise in philosophy at best. And philosphy can be very ...
 
Last edited:
  • #25
EL said:
Think of a 2D universe situated on the surface of a sphere. The area of this universe is finite, but anyway it has no boundaries where the 2D beings living there can "fall over a cliff".
Now you of course have to generalize this picture to a universe with 3 spatial dimensions, where the "area" is replaced by the "volume". Although our brains cannot really handle this generalization, this would give you a hint of how a universe could be finite and still unbounded.

Oh~~It is so involuted.:zzz:
 
  • #26
Danger said:
What I was getting at is that if it formed a finite time ago, and is expanding at finite speed, it can't be infinite.

Why can it not? If the universe was (spatially) infinite at Big Bang, which may have been the case, it should of course be infinite now also. (Or are you just talking about the today observable universe?)
 
  • #27
mars2 said:
Oh~~It is so involuted.:zzz:

Sorry, I can't find "involuted" in my dictionary...what does it mean?:redface:
 
  • #28
EL said:
If the universe was (spatially) infinite at Big Bang, which may have been the case,
:confused: You lost me on that one. How could it have been infinite when it formed? If it started at zero volume/infinite density, and is now at medium volume/medium density, then it had to have passed through small volume/high density on the way.
 
  • #29
Danger said:
How could it have been infinite when it formed?
Why not? Why must it have been finite?
If it started at zero volume/infinite density
Why must it have startet at zero volume?
The Universe started as a singularity of infinite density, but not necesary of zero volume. Think of an infinite plane with small dots on it, representing the matter distribution today. Now proceed backwards in time, i.e. move the dots closer and closer together, until you reach an infinite density, i.e. the singularity. The plane still has an infinite area though! You get my point?
This of course requires an infinite amount of matter in the universe.

Hence the Universe could always have been spatially infintie, although the density has changed with time.

Edit: Just to make it clearer: When I say "move the dots closer and closer", I of course mean that the space between the points shrinks, not that some force acts on the dots.
 
Last edited:
  • #30
I'm going to wait for an expert's take on this. Again, I might be misusing the term 'infinite'. To my mind, the only way that something can have infinite density is if it has zero volume.
 
  • #31
EL said:
The Universe started as a singularity of infinite density, but not necesary of zero volume.
I fail to understand how the universe could have been spatially infinite at the beginning of time. For every cosmological model the volume contained within every boundary at the big bang is zero because for a zero scale factor a(t=0) = 0 the volume element is zero (or all distances are zero in the singularity). A different situation arises as soon as one considers any time slightly greater than zero, avoiding the singularity.
 
  • #32
hellfire said:
I fail to understand how the universe could have been spatially infinite at the beginning of time. For every cosmological model the volume contained within every boundary at the big bang is zero because for a zero scale factor a(t=0) = 0 the volume element is zero (or all distances are zero in the singularity). A different situation arises as soon as one considers any time slightly greater than zero, avoiding the singularity.

I agree with that using the term "spatially infinite" at t=0 may not really have any meaning, since as you say the scale factor is zero. However, what I wanted to point out is that it need not have started as what we intuitively think of as a point either. I.e. the reasoning Danger is using, that it has to be of finite size, does not hold.
The point I wanted to make is that even though the Universe started as a singularity, it may be infinite at any t>0. Wheter one call it infinite or not at t=0 is more of a personal taste.
Anyway, we do not really know how to describe the universe as time approaches zero, since we don't know about what laws will hold.
 
  • #33
Danger said:
:confused: You lost me on that one. How could it have been infinite when it formed? If it started at zero volume/infinite density, and is now at medium volume/medium density, then it had to have passed through small volume/high density on the way.

I think Ned Wright addresses this in a fairly straightforward manner:

http://www.astro.ucla.edu/~wright/infpoint.html" [Broken]
 
Last edited by a moderator:
  • #34
SpaceTiger said:
I think Ned Wright addresses this in a fairly straightforward manner:
http://www.astro.ucla.edu/~wright/infpoint.html" [Broken]

Yes! And the question adressed is what confuses many people, since it is simply not the whole thruth. The Universe (i.e. the whole Universe) doesn't have to be concentrated into one point at the Big Bang.
 
Last edited by a moderator:
  • #35
Thanks, ST. It's not all that straight-forward to me, though, because I'm missing most of the educational background to follow it properly. I'll certainly read as much as I can when I have more time, but the math is really going to mess me up. :frown:
 
<h2>1. What is an infinite universe?</h2><p>An infinite universe is a theoretical concept in which the universe has no boundaries or limits in terms of size or content. This means that the universe goes on forever, with no end or edge.</p><h2>2. How do scientists explore an infinite universe?</h2><p>Scientists explore an infinite universe through various methods such as telescopes, satellites, and space probes. They also use mathematical models and simulations to study the universe and its properties.</p><h2>3. Is there any evidence for an infinite universe?</h2><p>Currently, there is no concrete evidence for an infinite universe. However, some theories and observations, such as the cosmic microwave background radiation, suggest that the universe may be infinite.</p><h2>4. What are some implications of an infinite universe?</h2><p>If the universe is truly infinite, it would mean that there are an infinite number of galaxies, stars, and planets. It would also suggest that there may be other forms of life in the universe, as the chances of life evolving on other planets would increase with an infinite number of planets.</p><h2>5. How does the concept of an infinite universe challenge our understanding of the universe?</h2><p>The concept of an infinite universe challenges our understanding of the universe because it goes against our intuition and common sense. It also raises questions about the origins and fate of the universe, as well as the possibility of multiple universes.</p>

1. What is an infinite universe?

An infinite universe is a theoretical concept in which the universe has no boundaries or limits in terms of size or content. This means that the universe goes on forever, with no end or edge.

2. How do scientists explore an infinite universe?

Scientists explore an infinite universe through various methods such as telescopes, satellites, and space probes. They also use mathematical models and simulations to study the universe and its properties.

3. Is there any evidence for an infinite universe?

Currently, there is no concrete evidence for an infinite universe. However, some theories and observations, such as the cosmic microwave background radiation, suggest that the universe may be infinite.

4. What are some implications of an infinite universe?

If the universe is truly infinite, it would mean that there are an infinite number of galaxies, stars, and planets. It would also suggest that there may be other forms of life in the universe, as the chances of life evolving on other planets would increase with an infinite number of planets.

5. How does the concept of an infinite universe challenge our understanding of the universe?

The concept of an infinite universe challenges our understanding of the universe because it goes against our intuition and common sense. It also raises questions about the origins and fate of the universe, as well as the possibility of multiple universes.

Similar threads

  • Astronomy and Astrophysics
Replies
11
Views
2K
  • Astronomy and Astrophysics
Replies
25
Views
2K
  • Astronomy and Astrophysics
4
Replies
114
Views
10K
  • Cosmology
Replies
12
Views
1K
Replies
17
Views
2K
  • Cosmology
Replies
11
Views
2K
Replies
5
Views
1K
  • Astronomy and Astrophysics
Replies
5
Views
1K
Replies
11
Views
1K
Replies
17
Views
3K
Back
Top