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My understanding is that the universe expanding includes even individual atoms and I would guess that would mean the orbits of electrons, etc. If this is so, for things to continue to "keep working" would not constants for different forces have to change?

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I was confused about this, too, when hearing for the first time about cosmology. The expansion of the universe does NOT include individual atoms, humans, planets, stars or galaxies. If that would be the case, we would not be able to notice this expansion.

In the first two cases, the electromagnetic forces binding the objects together are magnitudes stronger than any gravitational force, and in the case of galaxies (and the objects in them), the mass/energy density of the galaxies is much higher than the average mass/energy density of the universe. Because of that, galaxies themselves have 'decoupled' from the expansion of the universe and form gravitationally bound objects.

The universe as a whole is modeled in the simplest cosmological models as a uniform 'fluid' of matter and radiation (and dark energy, although nobody knows what that is). This is useful, because in the early times the contrast in density was not as strong as today, and still today the universe seems to be quite uniform on very big scales (on average).

Since we observe galaxies drift apart from each other, is seems that 'everything' was closer together in the beginning, therefore more dense and hot. This is possible (even when, of course, everything still attracts everything else gravitationally), as long as for some reason everything was drifting apart from the beginning (the why of that is a different question). But even in the early universe, this expansion, describes by gravity, made the uniform content of the universe drift apart, hence expand, but this did NOT affect the elementary particles, because the forces that describes their behavior and bind them together (quarks to protons and neutrons; electrons, protons and neutrons to atoms, although is only happens after the universe has cooled enough so these bound states are possible) are much stronger than gravity.

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