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Comment by vikingerik | Hacker News Reader

For normal nuclei it does, but when you get up into a solar mass sized blob of them, gravity exceeds it. That's because the repulsion is going in all directions and nets out against itself but all the gravity points inwards cumulatively.

(Edit because we got a little confused in the replies: If it were all protons, they would repel and overcome gravity. But real matter isn't that, it's always protons and neutrons and electrons with close to no net repulsion so gravity wins.)

Similarly, radioactive nuclei (alpha emitters and spontaneous fission) happen because the electromagnetic repulsion exceeds the strong force, which has a very short range and doesn't reach across those large nuclei.

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> That's because the repulsion is going in all directions and nets out against itself but all the gravity points inwards cumulatively.

Is that true? All of the protons repel all other protons with the electric force and attract with the gravitational force, and it seems like gravity is just much weaker at all distances...

I haven't thought about this very hard though.

Think of three protons in a line, A-B-C. Proton B is repelled in both directions so experiences no net force.

Now think of 10^50 protons in a line. They're all experiencing net gravity towards the middle.

A is repelled outward, B is not repelled, C is repelled outward.

With gravity, A is attracted inward, B is not attracted, C is attracted inward.

Your idea doesn't generalize. With A-B-C-D-E, only C experiences no net forces along the horizontal axis, while all the others (A, B, D, E) are repelled outward. Therefore the electromagnetic force is not cancelled as you seem to imply.

Of course, in practice, we don't know what the inside of a black hole is like, as quantum gravity is very much unsolved.

Okay, but A and B are both repelled outward and it explodes.

So the conclusion is any proton star would just explode? That's what I already thought.

We like to say gravity is "weak", however it seems to operate on many orders of magnitude larger distances.

Even if you make the argument that the energy complicit in the strong/weak forces is cumutavily much greater than the energy due to gravity, I'm still not sure "weak" is the right word for the job...

Gravity onstensibly runs at infinite speed over infinite area (the effect of gravity waves non-withstanding).

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