If space is expanding in all directions, does that mean distances between atoms are getting longer, and therefore physical objects are getting bigger?
In: Planetary Science
No, it does not. The expansion is very slight over short distances so other forces dominate. Even gravity, generally the weakest of the four fundamental forces, overpowers the effects of expansion so it really only impacts very distant galaxies. Objects on a human scale are unaffected.
For now and the foreseeable future. No.
Space is being created in between the atoms, but the amount of space is so small the forces that holds molecules together is so much more powerful that it utterly overcomes it.
Same can be said for the forces that hold, planets, stars, solar systems, and galaxies together.
It’s only the gulfs between galaxies where the expansion of the universe is able to win. And for galaxies that are relatively close to each other (EG our galaxy and Adromeda), it’s not even able to do that.
However, scientists have hypothesized that if this expansion starts to get faster and faster, then those forces won’t be able to hold together. This is called the “Big Rip” end of the universe scenario. Where first galaxy fling themselves apart, then solar systems, then planets, then objects, then atoms, then subatomic particles and blackholes. Leading to a situation of countless fundamental particle, each essentially with its own universe to itself.
Fortunately, current measurements don’t seem to support this happening, and even before that they didn’t think it would happen for many billions of years.
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