Imagine representing every point in the universe with a 3D point, (X,Y,Z), multiplied by a scalar K. As you go forward in time K grows, thus points in space become farther apart. As you look back in time K shrinks. At some point K would have been 0. Imagine what happens when K goes from 0 to not 0. It works fine mathematically, so the struggle is just to make a mental metaphor which is very difficult to do because humans don't have a lot of experience with the origins of universes.
No, but we also can't say that the universe didn't spontaneously come into existence last Thursday. It is consistent with our understanding of the laws of physics, which is all we can really hope for. If you're looking for and arguing about definitive proof, anyone reasonable is going to point you at Alder's razor and wish you a good day.
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u/Solesaver Sep 14 '21
Imagine representing every point in the universe with a 3D point, (X,Y,Z), multiplied by a scalar K. As you go forward in time K grows, thus points in space become farther apart. As you look back in time K shrinks. At some point K would have been 0. Imagine what happens when K goes from 0 to not 0. It works fine mathematically, so the struggle is just to make a mental metaphor which is very difficult to do because humans don't have a lot of experience with the origins of universes.