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Originally Posted by Nuclear
I agree the concept is really hard to comprehend and understand, and the idea of infinity in both math and science is probably one of the most fascinating.
There is an analogy though that helped me understand it quite a bit better though. The comments are correct, in the context of the big bang the universe is invite, always and forever, its the nature of this infinity that changes.
Essentially prior to the big bang, what you have is a singularity of infinite density and infinite mass, but zero (and I mean absolute zero space). When this singularity "opens" for lack of better terminology, it shifts to infinite space of infinite mass but a finite density. The only thing that changes after this point in time is the density.
Essentially, imagine a theoretical ruler, one that is infinite in length. Then imagine a standard inch on it. Each inch is subdivided into 1/12", 2/12", 3/12" and so on. Now, imagine a force stretching this inch to double its original length, doing it to every inch along the ruler simultaneously. Each subdivision is twice as far apart as it was before, but has the length of the ruler itself changed?
No, it was infinite in length before, and it is still infinite now despite each part that makes it up being twice as long. Now just imagine each subdivision being a particle or piece of mass, and you essentially have a picture of universal expansion without an edge.
The cone analogy that you often see doesn't describe the edge of the universe in that sort of sense, think of it more like a description of density change.
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Okay, I understand the ruler analogy. Thanks. But this would mean the universe went from absolute zero space to infinite space in a nanonanonanonanonanosecond? It seems strange there is no interim where the universe is 1 foot across, then 10 miles across, then 1,000, then 1,000,000, etc.
Can you have infinite space and infinite mass? It seems if this was the case then density would always be 1, or at least unchanging. If the universe is expanding wouldn't it by definition be getting less dense? Or does its infinite nature undo that?
(Infinity in math is a mind-blower......like all the even and odd numbers to infinity is the same as just all the odd numbers to infinity. One is a subset of the other, but they are still the same in "quantity").
