# If everything in the universe doubled in size overnight, would it be noticeable?

By my understanding, if everything doubled in size, such as the Sun and the Earth, and because the space in between them (which is nothing) can't expand, would the gravities greatly change and the Earth be pulled into the Sun?

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What do you mean with everything ? If the electron charge/charge distribution is different but same "distance"(whatever it means, you should know that there is no knowable dynamic position of an electron) then there is nothing we could conclude by physics, because your suppositions break physics(it was obtained from a different world than yours) –  HDE Dec 20 '12 at 14:21
yeah there's a big difference if it's just the big stuff like Sun and Earth doubling in size and whether the elementary things like proton, neutron and electron double in size –  raindrop Dec 20 '12 at 14:22
Well I meant if everything with a physical mass I guess. I'm a noob with physics but I just want to understand –  dizzytri99er Dec 20 '12 at 14:33
I think if all subatomic particles doubled in size, there would be no observable change in size of the Earth. If you double the size of protons and electrons for instance, because force between them is determined by the central position of these objects, the force between them will remain the same, and therefore the radius of the atom will not change. –  Mew Dec 20 '12 at 14:40
yeah the critical factor in determining size of atom is the radius of atom (plus the tiny 0.5 radius of electron which is small even if you double it) –  raindrop Dec 20 '12 at 15:03

It doesn't really matter to the atoms if things double in size. It's like the Moon becoming the size of the Earth, it's something 'normal' that happens often in our universe: things become bigger and smaller. Another example is gases of clouds becoming giant stars, that isn't just 'double' but more like increasing $10^{30}$ in 'size' (from separate molecules to forming giant stars)

Note that in some superdense objects (like neutron stars) the strong gravitational force has a direct effect on distances on the molecular scale.

On a side note, remember, not all equations are linear. Equations such as that for (classical physics) gravity, $$F_g=GMm/r^2$$ are non-linear. If the distance between two objects double, and their volume doubles while their density remains constant, we have a problem.

(need to add some equations on what happens when doubles)

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