What is the Universe expanding into?

In summary, the current best model of the universe is infinite, and even finite and closed models do not expand into anything. The concept of "expansion" in space is a result of slicing 4-dimensional spacetime into 3-dimensional space, where galaxies appear to be further apart in each successive slice. The idea of "creating" spacetime is not currently known or understood.
  • #1
Akshaya dhakal
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If it is everything then what is it expanding into?
As we know universe is everything having every matter and energy. From the observation using Hubble's law it was said that the galaxies are moving away from the Earth which means the universe is expanding. If it is everything then what is it expanding into. Is there some outer edge that it can expand into or any center it is expanding from? Is it infinite?
 
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  • #2
Our current best model of the universe is infinite, yes. But even finite and closed models don't expand into anything. As far as we are aware there is nothing outside the universe for it to expand into.

The thing to remember is that general relativity describes 4d spacetime, and space at any given time is a 3d slice through that. So what we mean when we say that "space is expanding" is that there is a particular way to slice spacetime so that everything looks more or less the same everywhere in a slice, and when we do that, in each successive slice galaxies are slightly further apart. Nothing is expanding into anything because nothing is really expanding - things are just further apart in different slices of spacetime.
 
  • #3
Akshaya dhakal said:
Summary:: If it is everything then what is it expanding into?

As we know universe is everything having every matter and energy. From the observation using Hubble's law it was said that the galaxies are moving away from the Earth which means the universe is expanding. If it is everything then what is it expanding into. Is there some outer edge that it can expand into or any center it is expanding from? Is it infinite?
Doesn't he expansion which basically started at the big bang been create the fime/space continuum in the process? Ex nihilo so to say. It's pretty difficult wrapping ones head around...

Explaining this to someone is pretty steeply up-hill. There are many misconceptions surfacing again and again. Some of the more annoying are people thinking that an explosion in vacuum looks exactly like a fireball in an atmosphere. Also that black holes basically works like a giant vacuum cleaner, gobbling up everything within it's gravitational sphere of influence. I'm sure there are tons of others.

Regards.
 
  • #4
sbrothy said:
Doesn't he expansion which basically started at the big bang been create the fime/space continuum in the process?
This is currently not known.
 
  • #5
DennisN said:
This is currently not known.

What would it even mean to "create time/space continuum"?
 
  • #6
sbrothy said:
Doesn't he expansion which basically started at the big bang been create the fime/space continuum in the process?
No. Spacetime doesn't get "created"; it just is. It is a 4-dimensional geometry that already contains all of the information about "time".

DennisN said:
This is currently not known.
Yes, it is; the answer is no. See above.
 
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1. What exactly is the Universe expanding into?

The Universe is not expanding into anything. It is expanding on its own, meaning that there is no space or matter outside of the Universe for it to expand into. The concept of "expansion" in this context refers to the increase in distance between objects within the Universe, not the expansion into a pre-existing space.

2. Is the Universe expanding into a void or empty space?

No, the Universe is not expanding into a void or empty space. The Universe itself is the entirety of space and all the matter and energy within it. There is no space outside of the Universe for it to expand into.

3. If there is no space outside of the Universe, how can it expand?

The expansion of the Universe is not a movement of matter into pre-existing space. Instead, it is a stretching of space itself. This means that the distance between objects within the Universe is increasing, but there is no movement into a pre-existing space.

4. What is the role of dark energy in the expansion of the Universe?

Dark energy is a mysterious force that is thought to be responsible for the acceleration of the expansion of the Universe. It is believed to make up about 70% of the total energy in the Universe and its repulsive nature is causing the expansion to accelerate.

5. Will the Universe eventually stop expanding?

It is currently believed that the expansion of the Universe will continue indefinitely, with no signs of slowing down or stopping. However, this is based on our current understanding of the Universe and could change as we gather more data and make new discoveries.

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