Eli5 if the universe is everything but it is constantly expanding, what is it expanding into?
In: 22
Let’s say the Universe is like a plume of smoke, that is expanding into the air, which is the nothingness of space. The Universe is expanding into the nothingness, and making it part itself. Just as smoke would expand into the air by diffusion.
Make sense?
We don’t know. We don’t know if something outside of the universe exists in the first place. The big bang possibly created space itself, so asking so “where” isn’t a meaningful question outside of the universe.
What we know is that the distance between us and far away stars becomes bigger. Space itself is somehow growing.
There is no “into”, there is only nothing. No space, matter. Literally nothing. Unfortunately this concept is hard to wrap our brains around because our whole existence is based on the opposite of nothing so we can’t really picture nothing (because there’s nothing to picture).
Also, don’t think of the universe as a place. The universe is a thing. The universe is the collective of everything that exists.
The geometry of the universe is hard to wrap one’s mind around, but there doesn’t seem to be an “edge” that is expanding “into” something.
All points in the universe are equally considered the center, because from what we can tell, there is no absolute center. So, I don’t think the universe is expanding “into” anything, because we have not been able detect that *our* region is heading into some new foreign territory.
The universe appears the same to us in all directions, and all regions are relatively equal. The distance between all regions just happens to be increasing.
What about the 2D balloon analogy:
The universe is like the surface of a balloon. By blowing up the balloon the surface area gets larger, pushing things apart. But there is no center and no edge pushing out into the nothingness.
Question: can’t we say only the matter/dark matter is expanding? So that the “nothing” that’s between the stars is the same nothing as “outside” the universe just without the radiation and CMB… As I am not aware of there being a hard border of the universe. The big bang created the matter but did it also create the free space it occupies? Of not isn’t it to where it is expanding?
Well imagine it like a balloon, the space itself is streching, same way a baloon stretches when we blow it and becomes bigger in size(no pun intended).
“Expansion” is a mathematical model.
Imagine a 2D ant living on the surface of a spherical balloon. The ant exists on the surface and can only move around on the surface. To the ant, there is no such thing as the direction “into the balloon” or “out from the surface of the balloon”.
If the balloon is inflated, all of the points in the balloon move away from all of the others (when you measure distance along curves over the surface which connect the points). In every experiment the ant can perform, it seems as though his universe is expanding, even though he has no concept of the space it is “expanding into”.
Similarly, we do experiments and the results are well described by a model which “embeds” the universe we live in into a hypothetical space with one additional dimension, with the “surface” we live in expanding within that hypothetical space.
There is a good chance that what we are expanding “into” is either a lower or a higher dimensional non-space.
When you inflate a balloon, where is the surface going?
Latest Answers