eli5: If space is expanding faster than light in all direction. Why hasn’t the space between our atoms expanded to infinite?
In: 530
Space isn’t expanding at a speed (distance per time), so you can’t compare it to a speed like the speed of light. Space is expanding at a rate (proportion per time).
What that means is that if you imagine three galaxies in a line, `A-B-C`, after some time, expansion will increase the spacing to `A–B–C`. The distance between A and B increased by one dash, while the spacing between A and C increased by two dashes; the speed at which A is moving away from C is twice the speed at which A is moving away from B, because the distance between A and C is twice the distance between A and B.
To get a speed from the expansion rate you need to multiply the rate by the current distance between the objects.
Back to “space is expanding faster than the speed of light”: the correct statement is that there are things far enough from us that they are moving away from us faster than the speed of light. Expansion isn’t ripping atoms apart or doing other very noticeable-to-humans things because the current rate of expansion is so low that at the scale of atoms, or even at the scale of our solar system, the increase in distance due to expansion is negligible, and it’s overcome by other forces.
We are observing that the rate of expansion is itself increasing, so if it keeps increasing there will be a time when even atoms will be torn apart by expansion, but that’s not for a long while.
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