If the universe is constantly expanding, what is it expanding into?

Question

Been bugging me since I saw the advert for teaching!

Answer 1

The answer is that it really isn't expanding into anything. If you're confused, it's a kind of confusing idea. Also, remember that almost by definition the universe is everything that exists, so to some extent it's meaningless to talk about what's "outside" the universe (of course, that stops no one from wondering... ;) ).

Of course, that doesn't really help you much, so there's two examples, one of which is a really common one which leads to a misleading answer and one is the one I use when thinking of this issue which gives you a better idea. The first and common one is to imagine/pretend that the universe is two-dimensional (e.g. you can move left or right or forward or backward, but up and down have no meaning), and specifically that the universe is the surface of a balloon. Now, if put little stickers with galaxies on them on the balloon, and measure the distance between these stickers with a tape measure stretched along the surface of the balloon (the tape measure can't go through the balloon because the area inside the balloon isn't a part of our 2D universe) you have a universe. Now blow into the balloon, causing it to expand. The stickers on the balloons surface will stay attached to the points they were attached to, and the part of the balloon between all the stickers will expand, so that if you again take out your tape measure and measure the distances between the stickers, the distances will have increased. This gives you an idea of how the universe (the 2D surface of the balloon) can be expanding. However, in this case you can go, "Ah-ha!, but the balloon is expanding into the air", which makes you think that the real universe must be expanding into something. This may even be part of why you asked the question. But, as I said first, the universe basically by definition contains everything, so we have a contradiction.

This brings me to my second example, and the one I use. Imagine that the universe is a two dimensional surface made of square bricks. This surface is either infinite or has some chape such that it has no edges (it might be a sphere or what not). Now, define the width of one of these bricks as some unit of length (a mile, a light-year, a million light-years, an inch, whatever). Let's say one brick has a width of one light-year for the purpose of this discussion (but also note that you could make it correspond to, say, one billionth the width of an atomic nucleus or any other very, very small distance). Now, let me again stress that a brick is one light-year wide (and hence has a square area of one square light-year or one light-year squared) *by definition*, and thus a brick in this example is *always* this size.

Now, with that in mind, you could imagine putting galaxy stickers on random bricks (yes, I know a galaxy is thousands of light-years wide, but bear with me). If you pick two such stickers, and count the number of bricks between them you get their distance, because each brick is one light-year wide, the distance between them. Now, you let time pass, and as time passes rows and columns of bricks are inserted between existing rows and columns (and everytime you insert a row you also must insert a column and vice versa) in some mechanical, predicatable fashion. Now, after some amount of time of this, you go back to the two stickers you picked and count the number of bricks between them, and you'll have found that the number has gone up, so that the distance between them has increased (because each block is defined as being one light year wide). Now the stcikers never moved, they were always on the same brick, it's just that there are, as time passes, more bricks separating them.

If this seems like a hokey example, remember that we could make the bricks any size we like, including smaller than any particle or atom or whatever. So, we change the example to make the bricks of a really, really small size so that we can't see this happening. But the bricks are still there, and are always the same size, and as time passes between two points there will be more and more bricks, meaning that the distance between something on any two bricks will always be increasing.

Moreover, we never had to talk about expanding into anything or such, just had to talk about there being more bricks. This is the key point: the universe isn't expanding into anything, it's just that there is more space between any two points in the universe as time passes.

I hope I haven't confused you, and I certainly hope I've helped. In the end, that last key point is what you should keep in mind even if my example doesn't help you at all (as I said, it's something I thought of to kind of clarify the idea in my own mind; you might be able to come up with your own example).

Answer 2

supposedly, there are three theories.
after the Big Bang, there was enough force to project matter far out into space. When the universe dies, scientists are expecting the universe to expand forever, implode, meaning everything will collapse into a single point, or explode. It all depends on the curvature of the universe. If we have a flat universe, it'll expand forever, if it's curven inward, it'll implode, and if there is an outward curve, then it explodes.
So far, people think the universe is flat.

Answer 3

According to M-theory, our universe is one of 10 to the 500th in existance. If that's true, then our universes' expansion is insignificant. Our universe would be the equivalent of a grain of sand on all the worlds beaches. And Brane theory says that all of these countless universes exist within 1/8th of an inch of each other and in 11 dimensions. Just enter those theories into a search engine and prepare to be dizzy.

Answer 4

Good quesiton.

It's just expanding, I guess.

Answer 5

A black hole. Basically, nothing. A beautiful use of negative space.

Answer 6

Empty space. A vaccum.

Answer 7

its expanding into space..coz theres lots of it...

Answer 8

Excellent question. Here's another one. If the "big bang" is true, where did the matter come from and who "lit the fuse"?

Now tell me there's no God!

Answer 9

space

Answer 10

Its self. get your head around that.