The whole concept of the Big Bang is a mind warp. The whole explosion must have happened in some… space-time thing to begin with. What was that immense point of matter and energy in? What was “around” it? We’ll never know.
I think there are some philosophical definitions in the way. The Universe is everything we know, it is made of space and time, so of course it cannot expand into any space as it contains all of it.
We don't know what's outside the Universe, so we can't say there is nothing, and we can't say there's anything, we don't know what it is expanding into, or if "expansion" even makes sense outside the Universe. If we somehow find out what's outside the known Universe, that will inevitably become part of the known Universe, so we will never know what's outside the Universe.
Consider a bubble rising to the surface of a pond. As the bubble breaches the surface, it extends beyond the surface and expands as the pressure reduces.
If you consider the surface of the water as a 2D plane, the bubble expands into a third dimension perpendicular to the others. The bubble's surface is made of the same water as the surface of the pond, and there is no hard boundary between them. The bubble pushes part of the 2D plane into the third dimension, which results in the water having more surface area than the total possible area of the 2D plane.
Area (space) has been created without creating matter or energy. The surface is simply extended into an extra spatial dimension.
The way I like to interpret the big bang is as a higher dimensional structure folding or knotting itself such that a bubble is forced into a 3D space. The bubble expands and thus creates more volume than is possible in the lower-dimensional surface the bubble was formed on. This is my ill-informed interpenetration of M-theory.
Dunno why, but much of mathematics and the universe in general makes much more sense to me when viewed in terms of dimensionality. Our universe is 'just' a 4D slice of a higher dimensional structure, and I find a certain kind of beauty in that. In another life, I'd have been a string theorist
Instead of thinking of it as a bang in an existing space-time, the way to conceptualize it is the collapsing of a universal wave function from a superposition of all possible universal states. Of which our universe is just one potential possibility. Space time is a function of the collapsing state.
I think I understand that to a certain extent. But where does the universal wave function exist to begin with? There must be some construct it exists within.
Why? I would look at Occam’s razor, believing there must be an outer layer (or a creator of god) just leads to an infinite regress. It’s much more likely that the thing is just eternal according to that logic
