While watching a program on TV the documentary indicated the Universe is expanding.
OK fine, but what is it expanding into. The answer was nothing. But what contains this nothing. How big is it?
I am looking for a similar parallel that can help me understand that concept.
I guess the way I see it is if the universe is finite and expanding. It must take up a set space. So it is getting bigger it is taking away space from something.
Nothing contains it and it isn’t any size. It’s nothing. It doesn’t exist. A better way to phrase it is to say that there is no medium into which the universe is expanding.
The universe doesn’t take up space. The universe is space. By definition, the universe is everything that exists. There is nothing outside the universe, because nothing but the universe exists.
Think of it this way. What exists north of the north pole? Answer: nothing. It’s a meaningless question. A similiar quesion would be “what exists outside of the universe”. The answer is “nothing”. Not because nothing is there, but because “outside of the universe” doesn’t even exist.
Yeah, it’s confusing. “Nothing” is a concept that the human mind simply cannot intuitively understand.
I remember arguing for about a year with a friend over this - happy memories.
Nothing - in the philosophical sense - does not exist. By it’s own definition it is the absence of something and in this absence there is no such thing.
Nothing - in the mathematical sense - does exist. And it’s value is one. This is according to some sort of bizarre set which a mathemitician told me about.
There is no way to answer ‘how big’ it goes on endlessly. If there was a barrier to it, it would not be ‘nothing’, it would be part of the material universe that is expanding. So, there is literally nothing there – no particles, no matter, no anything. It can’t have an end because there would have to be something on the other side of the “end”. And that ‘end’ in turn would be part of the universe, that is expanding into nothing.
What you are really trying to understand is the concept of ‘infinite’ – without end.
Think of it this way… if you shoot some light off in one direction, it should eventually loop back and return to you from the other direction. (Think of the universe as being tiny; this explanation would not actually work as the universe may be expanding at a speed greater than light.) Anyway, you record how far this light traveled, and so you determine the size of the universe. Do it again in a little while, and you should get a larger size. How did this happen? Apparently you just got more space. Everything in the universe just got a little farther apart, but why?
The space had to come from somewhere, right? Well, not really. It just comes out of nothing, which by definition does not exist. This defies logic, and as many of the more complex theories and laws suggest, this is ok.
I was thinking the same thing a couple days ago… I still dont understand “nothing” I mean… when i think of nothing, i think of black, but im pretty sure that its not black… but no color at all… but how can something have no color. O wait, its not a “something.” DAMNIT!!!
And now to my question… if the universe is expanding so quickly, id assume that there are billions of galaxies being created as we speak? Is that correct? Is there any possibility that there is another universe? I know that there is probably no definate answer, but what is the current understanding?
Finally, can anyone suggest any books that i can read about this topic? Please try to keep them as simple as possible.
It sounds like you’re imagining the expansion of the universe as something like an exploding dandelion – the seeds move further apart, but they’re moving out into air. You can go and stand at a point beyond any the seeds have reached, that is, ‘outside’ the universe.
IANAE, but It may help to instead think of the universe as closed – you cannot go beyond the ‘edges’ of the universe. You can’t travel in nothing; you can only go as far as something else has been. The boundaries of the universe expand as things move further apart, but it’s more like a balloon being inflated – you still can’t go outside the balloon, but there’s more ‘space’ now and it takes longer to travel from one end to the other. (Of course, the balloon would have to be shaped like a 4D mobius strip, but… still. Okay, bad example.)
Or just think of it like one of those video games where if you walk off one side of the screen, you end up on the other. No matter how much you enlarge the screen, your character can’t actually leave it. I’m pretty sure we don’t know, definitively, whether it’s true that there’s really nothing beyond the boundaries of the universe (seeing as all the fancy measuring equipment we have is only an extension and refinement of our own senses), we just can’t go there or look outside.
From the only perspective we have access to, the universe is all there is, so everything that’s not the universe is nothing.
Here’s a mental exercise that can help you understand what physicists mean when the talk about an expanding universe. Imagine a two-dimensional universe - one where everything lies on a surface. The surface could have a lot of different shapes, but lets’s say it’s a sphere. If the sphere was big enough, a creature living on it might not be aware that its universe was closed - that if it kept going in the same direction it would eventually come back to the same place. Now imagine that there are objects on this sperical surface, and that something causes the sphere to expand like a balloon being inflated. The objects on the sphere would get farther apart. Any creatures on the sphere wouldn’t experience it as expansion - it would just look to them that everything was moving away from everything else. A smart creature could conclude that this movement indicates that their universe is expanding. But to a two-dimensional creature, it would be hard to visualize the expansion, because it involves an extra dimension outside of the surface it lives on.
Our three-dimensional universe is expanding in much the same way. Our evidence for it is that the objects in the universe (galaxies, for example) are moving away from each other more-or-less uniformly. It is hard for us to visualize how this expansion takes place, because it involves dimensions outside of the three we are used to thinking about.
The current thinking is that the universe is open or flat, rather than closed. But I think you misunderstand what closed means. It does not mean that the universe is contained within an expanding sphere. In the balloon analogy the universe is not contained within the balloon, but rather the balloon represents a 2D universe expanding. The universe is the surface of the balloon, not the contents.
Open, flat, or closed – The universe does not have an edge.
Doc, it’s not intended to be literally true; I’m just trying to get the OP away from the idea of the universe having a boundary and an exterior. Talking about “expansion” encourages that idea; talking about mutual recession does not.