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djinnisequoia t1_iy5s99k wrote

Reply to comment by RLDSXD in Depictions of atomic nuclei often show distinct and individual protons and neutrons, is this accurate? by ZTYTHYZ

This is a wonderful, accessible explanation. Thank you. I have a couple of questions, kind of remedial ones.

You say that gluons carry color charge between quarks, and they must constantly be exchanged to conserve color charge. Does that mean that quarks with two different charges would ordinarily cancel (leaving nothing presumably? or leaving each with a neutral charge?) but are exchanging gluons to shift their own color charge fast enough to avoid cancelling but then must immediately shift back again? In other words, what happens to a quark when a gluon is received from another?

Second, the virtual particles that particles emit to repel each other -- do they cost any energy for a particle to create/destroy them? Can a particle just do that indefinitely?

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RLDSXD t1_iy699lk wrote

You’re welcome!

In the same way that atoms are bound states between electrons and protons having an equal amount of positive and negative charge to have a net neutral charge, quarks are bound within nucleons by having a combination of color charges that result in a net neutral charge. However, there is always an imbalance; as a quark emits a gluon to change its color charge in order to balance out with the other quarks, color charge is conserved with that gluon, which alters the color charge of the quark that absorbs it, knocking the quarks back out of balance and forcing another quark to emit another gluon to change its color charge, which repeats the cycle. Here’s a helpful visual: https://commons.m.wikimedia.org/wiki/File:Quarks.gif

It’s also helpful to mention I was inaccurate in my initial comment; there are six color charges, not three. RGB and anti-RGB. Quarks only have RGB charges, whereas gluons are any of 9 combinations of color-anticolor charges. So a quark emits a gluon to change its color charge, the gluon has a color-anticolor charge to conserve color charge, and then must change the color of another quark when it is absorbed as the anticolor charge of the gluon and color charge of the quark cancel out, leaving the initial color charge the emitting quark gave off.

It can be thought of as potential energy being converted into the virtual particles. Since the negative charge of electrons repel each other more powerfully the closer they get together, at a certain distance it becomes more energetically favorable for virtual particles to be spontaneously emitted than it is for the electrons to exist that closely together. They can exchange the particles indefinitely, but the energy still comes from an outside force shoving them into one another, otherwise they would just redirect and never collide again.

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