Cozmodius

Whoa...I hope ya'll can come with sumthin' better than this. Not expanding into anything? Is that the same thing as expanding into nothing?

C'mon now, give me something of substance here...hopefully complete with a scientific theory or 2...don't make me think that your "Not expanding into anything" theory is somewhere on a par with the "In the beginning God created the heavens and the earth" theory, because if so I have little patience for either.

Cozmodius

Hahahahahah...Since this is what I have been pointed to as a reference, perhaps YA'LL need to read it again...this time with understanding. It doesn't say that the universe is not expanding into anything, it says "the Universe is not expanding into anything that we can see' . The bottom line is IT ADMITS that it has NO IDEA what the universe is expanding into...and further more it ENCOURAGES YOU TO NOT EVEN ASK THE QUESTION!!! A better example of religious dogma I have rarely seen!

Friar Bellows

Sure, the theory is called general relativity. That's the underlying physical theory we use to create models of the large-scale universe, models which do not require the expanding universe to be embedded in anything. If you do actually have any interest in studying this theory (and the underlying mathematics), let me know, and I'll provide you with references and links. I'm studying it at the moment (I'm using that last word in its geological sense ).

The lesson for you, Cozmodius, is this: there is no short cut to knowledge and understanding. The fact that you are a self-employed father of two is irrelevant. You want to learn about the universe? You put in the hours. You don't have the hours? Tough. Live with the fact that you will have to rely on popularised web sites and books for the rest of your life and thus never have your questions about the universe properly and thoroughly answered.

Paul2

Currently it's imposible to see outside of our universe. Would you rather i make something up for you? Here, the universe is expanding into an enormous bowl of jello. Cherry flavored if you must know. There, problem solved. Now, if you'd read the rest of what you quoted, you should come to an understanding of why it's pointless to think about it.

Shadowy Man

So, basically, you are not really interesting in learning, you just want the $2 answer to the $20,000 question.

Well, sorry to tell you, but General Relativity is not an easy theory to comprehend. In fact, it took someone as smart as Einstein to figure it out in the first place. Some people even make a career out of studying it! But rest assured that it is a well proven theory, whether you personally understand it or not. I'd even be willing to say that sometimes your life even depends on the theory's accuracy.

The basic answer is that the standard concept of "expansion" is of the growth of a single object's size as measured in a three-dimensional space. This conception is incorrect when thinking about space itself expanding. There is no need to postulate a higher dimensional framework for space to be expanding into. It is an inappropriate understanding of the word "expansion".

Next you'll be asking how quickly an electron spins.

Cozmodius

Damm...I really expected ya'll to come at me with something better than ya have so far. I happen to have a pretty healthy layman's understanding of both The Big Bang AND the Theory Of Relativity...and I did read ALL of what I quoted.

I see very little difference in you telling me that "Whereof one cannot speak, thereof one must be silent" and some Bible Thumper telling me that "If it's not in the good book, then it isn't true".

At least 1 of you stated that the universe is expanding into a bowl of cherry jello (yum), which makes an infinite amount of sense more than to not even ask the question...at least we have a starting point then...a theory to disprove if you will.

A statement like "There is no need to postulate a higher dimensional framework for space to be expanding into" tells me that you are quite satisfied with the knowledge you have attained on the subject up until this point, and there is no need to attempt to learn anymore. I wonder what old Uncle Al would have felt about that?

Or maybe you are stating that the universe is infinite and therefore is expanding into itself? This is a positive I would LOVE to see you prove.

Paul2

Actually i said that i was making some up for you.

Um, it's like asking if god can make a rock so big that he himself can't pick it up. you get it now?

It appears that this thread is going in circles, as the universe isn't expanding into anything.

Shadowy Man

And what we are saying is that this is not sufficient. Most layman's interpretations of the Big Bang Theory and GR are wrong.

Shadowy Man

That is not what that statement is saying at all. It says that the theory of GR works without the presence of a higher dimension. One is completely free to postulate a higher dimension - in fact, some current theories suggest that there may be as many as ten or eleven spatial dimensions, only three of which are readily accessible, and the rest are "rolled up" at very small scales - this suggestion has observational consequences - implications for gravity on small scales - and can thus be tested.

What we are saying about standard GR and cosmology is that the space-time metric can expand without an external manifold. Sorry if those are $20 words that you'll have to go look up, but the theory is not trivial - it takes some effort to learn. In fact, I took a semester long course on gravitational physics during my undergrad years. The reason why layman's interpretations are usually wrong, or at best simply inadequate, is that most people won't understand what things like Riemann curvature tensors are without at least a good background in math and physics. So things get simplified down to the point where they may no longer be accurate.

Jesse

Cozmodius, the basic answer is that general relativity defines the notion of "expansion of space" in a completely consistent and self-contained way which allows for definite predictions about what we'll observe in the universe, and unless there is some way to state the question "what is the universe expanding into" within this mathematical framework, the question probably doesn't make sense.

How much do you know about general relativity? The basic idea, which you may know already, is that it explains gravity in terms of "curved spacetime". It's sort of possible to picture this by imagining a 2-dimensional universe, in which all the inhabitants live on a sheet of zero thickness--but unbeknowst to them, the sheet is capable of curving, and this affects the path of a flatlander moving through it.

Ordinarily, you'd think that for a 2-dimensional surface to have "curvature" it must be sitting in a higher, 3-dimensional space. Mathematically, this is like saying that you need three coordinates instead of two to describe this curved surface--an x coordinate, a y coordinate, and a z coordinate. But mathematically it is also possible to completely describe curved surfaces using features that are purely intrinsic to the surface itself--for example, at any point on the surface you might look at the sum of the angles of a triangle at that point (on a flat surface it'll be 180 degrees, but on a surface with positive curvature, like a sphere, it'll be more, and on one with negative curvature, like a saddle, it'll be less...also, I had to edit my comment because I originally said 'an arbitrarily small triangle at that point', but actually an arbitrarily small region of curved space will get arbitrarily close to perfect flatness).

The mathematics of describing curved surfaces in terms of purely intrinsic features, without the need for a higher-dimensional "embedding space", is tensor mathematics, and that is the mathematical framework used to state the theory of curved spacetime in general relativity. Because curved spacetime can be completely described in terms of intrinsic features in this way, it follows that even if our universe was sitting in some higher-dimensional space, if general relativity is correct than this would not lead to any new predictions in any possible experiment. The notion of a higher-dimensional embedding space would be completely useless as far as general relativity is concerned, just like the notion of absolute velocity in special relativity. I suppose that doesn't mean either idea couldn't still be true in some sort of metaphysical sense, but by Occam's razor we should be inclined to discard them (although it is still possible that a higher-dimensional embedding space might turn out to be physically meaningful in some future theory of quantum gravity which would replace general relativity--I think such a higher-dimensional space is actually used in some versions of 'brane theory', which is an extension of string theory).

There are some additional complications to the idea of a higher-dimensional embedding space. Just as a one-dimensional line can be curved into a corkscrew which needs 3 dimensions rather than 2 to be embedded into, there are possible ways our universe could be curved that could not be embedded in a euclidean space of one higher dimension--it's possible that tensor mathematics would even allow for types of curvature that could not be embedded in any finite-dimensional euclidean space. And if you think curved spaces need a higher-dimensional euclidean space to sit in, what is so special about euclidean spaces that they themselves don't need to sit in a space of a higher dimension? Would you accept the idea of a perfectly flat 2-dimensional universe, or would you think there must be some 3-dimensional space around it? If so, why wouldn't a flat 3-D universe need to be sitting in a flat 4-D space, which would need to be sitting in a flat 5-D space, etc.? And I suspect that from a mathematical point of view it would be just as possible to 'embed' a flat space in a higher-dimensional curved space as the opposite--so why say that a curved space 'needs' a higher-dimensional flat space to sit in, but not say that a flat space needs a higher-dimensional curved space to sit in?