Virtual particle clouds surrounding charge cores
The electron core is surrounded by virtual particles, photons that dissociate into fermion and anti-fermion pairs. The virtual photons have no effect on the charge, but the positive virtual fermion in each pair is attracted near the electron core (which is negative), while the negative virtual fermions is repelled. Therefore there is an outward (radial) ‘polarisation’ of the virtual matter cloud, and this effect largely shields the electric charge of the electron core! If electrons collide at higher and higher energy, you penetrate further through the shielding cloud, so the electromagnetic force increases. This shielding effect was measured and confirmed quantum electrodynamic (QED) predictions in 1997, by Levine, Koltick, et al.
Like electrons, a quark core is surrounded by virtual particles, namely gluons and pairs of quarks and their anti-quarks. Because of the strong nuclear force, the virtual gluons, unlike photons, do have a strong force charge called ‘colour’ charge (to distinguish it from electric charge). This means that both the virtual gluon cloud and the overlapping cloud of quark and anti-quark pairs interfere with the forces away from the core of a quark. While there are two types of electric charge (arbitrarily named positive and negative), there are three types of nuclear colour charge (arbitrarily named red, green, and blue in quantum chromodynamics, QCD). If the quark core carried ‘red’ charge, then in the surrounding cloud of virtual quark pairs, the virtual anti-red quarks will be attracted to the red quark core, while the virtual red quarks will be repelled to a greater average distance. This effect shields the colour charge of the quark core, but the overlapping cloud of virtual gluons has colour charge and has the opposite effect. The overall effect is to diffuse the colour charge of the quark core over a volume of the surrounding virtual particle cloud. Therefore, the net colour charge decreases as you penetrate through the virtual cloud, much as the earth’s net gravity force falls if you were to go down a tunnel to the earth’s core. Thus, if quarks are collided with higher and higher energies, they will penetrate further through the virtual cloud and experience a reduced colour charge. When quarks are bound close together to form nucleons (neutrons and protons), they therefore interact very weakly because their virtual particle clouds overlap, reducing their net colour charge to a very small quantity. As these trapped quarks move apart, the net colour charge increases, increasing the net force, like stretching a rubber band! This makes it impossible for any quark to escape from a neutron or proton. Simply put, the binding energy holding quark together is more than the energy to create a pair or triad of quarks, so you can never isolate a single quark. Attempts to separate quarks by collisions require so much energy that new pairs (mesons) or triads (baryons and nucleons) of quarks are formed, instead of breaking individual quarks loose.
A nucleon, that is a neutron or proton, has no overall ‘colour’ charge, because the ‘colour’ charges of the quarks within them cancel out exactly. Pairs of quarks, mesons, contain one quark with a given colour charge, and another quark with the anti-charge of that. Triads of quarks, baryons and nucleons, contain three quarks, each with a different colour charge: red (R), blue (B) and green (G). There are also Anti-colours, AR, AB, and AG. Common sense tells you that the gluons will be 9 in number: R-AR, R-AB, and R-AG, as well as B-AR, B-AB, and B-AG, and finally G-AR, G-AB, and G-AG, a 3x3 = 9 result matrix.
If you search the internet, you find a page dated 1996 by Dr James Bottomley and Dr John Baez which addresses this question: ‘Why are there eight gluons and not nine?’ They point out first that mesons are composed of quark and anti-quark pairs, and that baryons (neutrons, protons, etc.) are triads of quarks. Then they argued that the combination R-AR + B-AB + G-AG ‘must be non-interacting, since otherwise the colourless baryons would be able to emit these gluons and interact with each other via the strong force – contrary to the evidence. So there can be only eight gluons.’ Fair enough, you subtract one gluon without saying which one (!), to avoid including a general possibility that makes the colour charge false. (Why does the term ‘false epicycle’ spring to mind?) I love the conclusion they come to: ‘If you are wondering what the hell I am doing subtracting particles from each other, well, that’s quantum mechanics. This may have made things seem more, rather than less, mysterious, but in the long run I'm afraid this is what one needs to think about.’ All the utter horses*** of colour force QCD is officially sold as being ‘beautiful’! (What sort of person looks at horses*** and calls it beautiful?)
‘The quantum theories of gravity also have infinities in the terms with couplings, but the "dippy process" that is successful in getting rid of the infinities in quantum electrodynamics doesn’t get rid of them in gravitation. So … we have no reasonable theory.’ – Richard P. Feynman (1918-88), QED, The Strange Theory of Light and Matter, 1990, p151. (Whoops: I’ve quoted Feynman way out of a real context. What he was really saying was that there is an official quantum gravity called Dr Lisa Randall’s ‘big brane’ horses*** theory of quantum gravity, which is so ‘beautiful’ everyone cries! Buy Randall's book Warped Passages and see all the answers to everything!)