What does the Universe exapand into?

[HG009]

What does the universe expands into? Its a really big question that has been stuck in my head

 

[Orodruin]

That is not how expansion works. That the universe expands means that space itself is getting bigger.

 

[phinds]

What does the universe expands into? Its a really big question that has been stuck in my head

HG009 you keep asking very basic questions, apparently without doing any research on your own to see if you can find the answer. Keep in mind that this is not a Q&A forum where you just ask a question and get an answer. We expect some effort on the part of people who ask questions and it would seem that you have not made any effort to research the topics you ask questions about.

A trivial Google search would have answered this question. Please make some effort on your own.

 

[HG009]

Actually You know that Google answers Aren't always correct...universe expands about about 67.36 kilometers per second...

so consider the universe as a balloon Whisch is expanding into air

Similar way What does universe expands into?

*nothing can expand into nothing*

 

[Orodruin]

Actually You know that Google answers Aren't always correct...universe expands about about 67.36 kilometers per second..

No, these are the wrong unit even. Expansion is not a speed, it is a rate.

so consider the universe as a balloon Whisch is expanding into air

This analogy is useful but, as many analogies, cannot be taken too far. Considering the embedding space as a space in which the balloon expands is taking it too far.

Similar way What does universe expands into?

*nothing can expand into nothing*

Well, you are wrong there because it seems to be exactly what is occurring. Likely you have an erroneous mental picture if how expansion works. You should be thinking about the balloon analogy in terms of a two-dimensional being that has no access to anything outside the balloon surface. Everything can be described by what is on the surface, the embedding three-dimensional space is not necessary.

Writing your question with the erroneous assumption in bold is not going to make the assumption true.

 

[HG009]

That is not how expansion works. That the universe expands means that space itself is getting bigger.

Yeah I know but what is it expanding into if it isn't expanding into something That means space is infinite or something else

 

[Orodruin]

what is it expanding into if it isn't expanding into something

That is not how expansion works. That the universe expands means that space itself is getting bigger.

 

[PeroK]

Yeah I know but what is it expanding into if it isn't expanding into something That means space is infinite or something else

It's means that your simplistic 7th grade view of science is not sufficient to explain and understand the universe; not to mention all other areas of physics and related sciences.

 

[Ibix]

The universe is not a 3d structure, it is a 4d structure. Space now is a different 3d slice through the 4d structure from space a moment ago. So asking what it's expanding into doesn’t really make sense - each slice has a larger scale factor than any earlier slice, but nothing has actually expanded. We're just looking at a different thing.

Can I suggest that you probably don't want to label your threads "A"? That means you have a graduate level understanding of the topic and want answers that are basically nothing but integrals. I don't think that's what you want, and if you label your questions appropriately (and show evidence that you've at least skimmed the Wiki page on the topic) you are more likely to get straight replies.

 

[MikeC111]

Due to human experience with physical 3D objects, it's hard to wrap your head around something that is finite but has no edge and no outside, assuming the Universe is finite. It's not quite so hard if you assume it is infinite. So perhaps an infinite rubber sheet analogy would be better than a balloon analogy in that respect. Do we know yet for sure whether or not it has positive curvature?

 

[Ibix]

So perhaps an infinite rubber sheet analogy would be better than a balloon analogy in that respect.

I'd be wary of any analogy. There's always a way to misinterpret them.

Do we know yet for sure whether or not it has positive curvature?

No. And note that if it is actually exactly flat then we may never know, since direct measurement of curvature would always have associated error bars.

 

[PeroK]

Due to human experience with physical 3D objects, it's hard to wrap your head around something that is finite but has no edge and no outside, assuming the Universe is finite. It's not quite so hard if you assume it is infinite. So perhaps an infinite rubber sheet analogy would be better than a balloon analogy in that respect. Do we know yet for sure whether or not it has positive curvature?

This is one of the advantages of learning mathematics. It's not just about dumb calculations, but it opens up your mind to new ways of thinking. For example, I can conceive of a sphere (surface) or a circle (curve) being "all there is" and not necessarily embedded in a larger 3D space.

It's not a trick and it's not transcendental, but it is a product of having studied and understood mathematics.

 

[anorlunda]

Due to human experience with physical 3D objects, it's hard to wrap your head around something that is

Human experience, intuition, and common sense are based on our experiences on Earth. It should not be surprising that things on the scale of the universe, or small stuff in the quantum realm are outside our experience and can't be imagined. Our brains are not wired to visualize such things.

Learn a little humility and accept that your can not wrap your head around some things that are true.

 

[geordief]

This is one of the advantages of learning mathematics. It's not just about dumb calculations, but it opens up your mind to new ways of thinking. For example, I can conceive of a sphere (surface) or a circle (curve) being "all there is" and not necessarily embedded in a larger 3D space.

It's not a trick and it's not transcendental, but it is a product of having studied and understood mathematics.

So could the universe have an intrinsic (and dynamic) shape?

Could it be an expanding surface of a sphere or even an expanding surface of a distorted sphere ?(something with the same topology)

And are you saying these "surfaces" would have no thickness ?

 

[PeroK]

So could the universe have an intrinsic (and dynamic) shape?

Could it be an expanding surface of a sphere or even an expanding surface of a distorted sphere ?(something with the same topology)

And are you saying these "surfaces" would have no thickness ?

I'm saying none of those things. What I'm saying is that without mathematics you don't have the language or intellectual tools to analyse these questions adequately.

 

[geordief]

I'm saying none of those things. What I'm saying is that without mathematics you don't have the language or intellectual tools to analyse these questions adequately.

I understand ,but some of us don't have the ability to acquire those tools and yet can still be curious as to what is being discussed.

 

[LastScattered1090]

What does the universe expands into? Its a really big question that has been stuck in my head

This is just re-iterating what others have said, but maybe it will help. It's an answer I gave in a different forum. If it does not have the rigour needed for PF, let me know:

“The Universe” refers to everything that exists: all space, matter, and energy. So no, there is no surrounding emptiness that the Universe is expanding “into”. Instead what’s happening is indeed an expansion of space itself (which you can think of as creation of new space, if you like). So the distance between any two objects will increase by a certain factor (the Hubble constant) in one second. Since every distance increases by the same factor (i.e. by the same percentage), bigger distances increase by more in the same time interval, and thus grow faster. This explains Hubble’s Law: farther-away objects recede faster, because they are separated from us by more empty space in the first place.

That's the basic answer I gave before. From this point forward, I'm ad-libbing:

The question of what is the topology (basically the "overall shape") of the Universe is separate from that. A flat (meaning Euclidean) 3D, infinite space is possible, and even favoured by the observational data. But it is not the only space that permits this behaviour. The Universe could be like a 3D analogue of the 2D surface of a sphere. It's finite in volume, and curves back on itself (so that if you go far enough in any given direction, you'll end up back where you started). But it has no edges, and no centre. That's because there's no point on a spherical surface that is special. And in this "balloon" analogy, the interior and exterior of the sphere have no meaning. The entire "Universe" is the surface. The surface has no "edges" because 2D creature living on it has no way leave the surface or fall off it. Our Universe could be a 3D analogue of this 2D space. As others have pointed out, the math of GR says that a 3D space can exhibit curvature without needing to be embedded in a higher-dimensional space that it "curves into". This is not something easy for me to intuit or visualize, but something described clearly and precisely by the equations.

Other, stranger topologies have been proposed. I've seen a toroidal Universe theorized i.e. a Universe shaped like a torus (a doughnut, roughly). Again, I think the idea is that the actual 3D space would be a higher-dimensional analogue of the 2D surface of the type of torus we're familiar with. Like the hypersphere, this would be finite, but unlike the sphere, it would have Euclidean geometry! I.e. it would behave like a "flat" space: parallel lines would never converge, and the sum of the three angles of a triangle would always be 180 degrees. It would also have two distinct radii of curvature, meaning that there would be a "short way" and a "long way" to go around the entire Universe. Topology is weird :)

 

[Vanadium 50]

but some of us don't have the ability to acquire those tools and yet can still be curious as to what is being discussed.

How does this differ from "I'd like to be able to speak a foreign language but don't want to learn a foreign language?"

 

[berkeman]

How does this differ from "I'd like to be able to speak a foreign language but don't want to learn a foreign language?"

Hmm, so you're saying that he is using us as Google Translate?

 

[geordief]

How does this differ from "I'd like to be able to speak a foreign language but don't want to learn a foreign language?"

In that it is possible to not have adequate intellectual and other resources to accomplish the task.

You are doubting my bone fides apparently.?

 

[phinds]

You are doubting my bone fides apparently.?

I think what's in doubt is your ability to really internalize the indisputable fact that math is the language of science and pidgen-science, which is what you get without math, will not be as informative as you hope for it to be.

 

[sbrothy]

What does the universe expands into? Its a really big question that has been stuck in my head

I saw this paper in a other thread somewhere. It might do some good here
"Expanding Confusion: common misconceptions of cosmological horizons and the superluminal expansion of the Universe."
- - - - https://arxiv.org/abs/astro-ph/0310808

 

[Ibix]

So could the universe have an intrinsic (and dynamic) shape?

Not really, because 'shape' is used to mean a region of a larger space. A square is a shape, and it's a region of a larger 2d plane. The whole point is that this isn't a line of thinking that makes sense in GR. Spacetime has geometry and topology, but not shape.

 

[Ibix]

Instead what’s happening is indeed an expansion of space itself (which you can think of as creation of new space, if you like).

I'd say it's better to realize that spacetime is 4d and "all of space now" is a more-or-less arbitrary 3d slice through it. "All of space a little later" is a different slice through it. So you're looking at different slices with different scale factors - nothing is actually expanding.

 

[Vanadium 50]

You are doubting my bone fides apparently.?

No, I am doubting the degree of progress you will make without putting the necessary intellectual effort in. As they say, there is no royal road to mathematics.

 

[PeterDonis]

What does the universe expands into?

It doesn't expand into anything. The expansion of the universe is a property of the spacetime geometry of the universe as a self-contained thing.

You know that Google answers Aren't always correct...

You can find plenty of cosmology textbooks that will tell you the same thing. So in this particular case, the Google answer you were given is correct.

 

[PeterDonis]

From this point forward, I'm ad-libbing:

Don't. The purpose of PF is not to speculate. It's to help people understand mainstream science.

the topology (basically the "overall shape")

That is not what topology is. Topology has nothing to do with shape; a donut and a coffee cup both have the same topology even though they have very different shapes.

You are correct that a closed universe would have a different topology from a flat or open universe ($S^3$ vs. $R^3$). However, that has nothing to do with the "shape" of either.

A flat 3-torus (which you also refer to) would not be homogeneous or isotropic, so it is not normally considered as a possibility for the topology of the universe.

 

[PeterDonis]

The OP question has been answered. Thread closed.