How is there a limit to the space between atoms?

Question

I recently learned what it really means when people say space is constantly expanding. At first I thought it just meant more matter is getting created on the outer areas of the universe or something. But it’s moreso space in the spacial sense is expanding between everything, like a balloon being inflated. This opened up a realm of stuff I hadn’t thought about, with my brain struggling to comprehend how there is finite ‘space’ in that sense. Like how does existence itself have a limit to size? For distance as a concept to exist, the space between atoms has to be finite, and doesn’t break down infinitely. But my brain can’t comprehend this, similar to how it can’t comprehend there being nothing before the big bang. It obviously can’t be infinite because there’d be no existsnce as we know it, but how can it be finite and exist at all?

I guess the question is, how is there a limit to the space between atoms?

In: 127

Answer 1

Nobody really knows. The main theory at the moment is that yes, everywhere is constantly getting more space, and thus every pair of atoms is becoming ever so slightly further apart constantly. Like, if there’s a pair of atoms floating in space somewhere now one kilometre apart from each other, then in two minutes they’ll be like… *does back of the napkin math* about five quadrillionths of a metre further away from each other because more space will have become in between them.

For atoms that are bound into structures here in the solar system, the forces that bind them will ensure that the atoms stay in the distances they used to – they’ll keep falling into their spots of matching attraction and repulsion.

As for why the Universe has finite size now – it’s only been expanding at a finite rate for a finite time, right? Scientists say that this rate has changed with time and it’s now faster than it used to be. We don’t know what will happen eventually. It’s not out of the question that the rate will change to a negative one and space will start shrinking. It’s not out of the question that time itself will end eventually. If none of these happen, then for any distance you can name, the span of the universe will exceed it eventually.