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Pyryn t1_jedsxbh wrote

Reply to comment by Pegajace in ELi5 If the universe is expanding, what is it expanding into? by cashmoneyhash

I feel like this has to be a pretty clear argument for there being at least 4 spatial dimensions. The production of new "space/universe" essentially from...."nowhere." Reminds me of the idea of if a 3 dimensional sphere were to pass through a 2 dimensional space, to the 2 dimensional observer - this sphere would simply be a slice (or really, a line - to them) that simply goes from nothing, to smaller, to larger, to smaller, then back to nothing - all without the two dimensional observer ever having an awareness as to even the idea that the object they're witnessing essentially "appear out of thin air, then disappear" exists within 3 dimensions.

The production of new "space/universe" being generated everywhere across the universe, at all times, to me - would mean an expectation that this added space is coming into existence from a 4 dimensional (spatial) existence. If new "space" were being generated from a central locus, then perhaps something else - but the whole "everything, everywhere, all at once" aspect really has me imagining only that its production must be borne of a 4th dimensional space.

If that's irrational or if there are theories stronger than that - please let me know, but intuitively it's the only thing that would make sense (when considering the idea of imagining a 3 dimensional object in a 2 dimensional space, which would appear, under those conditions, exactly the way we view the view the expansion of spacetime in 3 dimensions)

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EcchiOli t1_jee1v55 wrote

A highschool physics teacher tried to explain it to us, before sighing and saying we'd see if we pursue education in this field otherwise screw it, with the idea that we measure the position of things as if they're in a grid.

One moment the nearby grid is 1 million blocks wide for the x, y and z axis. The following moment, the grid measures the same things but it's a 1 million and 1 blocks for the x, y and z axis. Some moments later, it's now 1 million and 2 blocks, still for the very same things inside. From our perspective on the inside, it gives an impression of getting further away.

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