Re: why don't all quarks attract each other

Dear Divad,

Both quarks (the fundamental constituents of protons and neutrons from
which all matter is composed) and gluons (the carriers of the strong
nuclear force) possess a charge analogous to ordinary electric charge,
but different, so it is given a different name -- "color charge".  And
I must repeat the standard disclaimer that it has nothing to do with
the colors of visible light; "color"is just a whimsical name used to
describe this new type of particle interaction.

Any two color charged particles will attract each other via the strong
nuclear force.  The strong nuclear force does not behave anything like
the electric force in its dependence on distance.  The electric force
is very large when two electrically charged bodies are near each other;
and the electric force gets smaller as the electrically charged bodies
are moved further apart.  In contrast, the strong nuclear force is very
small when the color charged objects are near each other (this property
is called "asymptotic freedom" in the jargon); and the force is constant
(not directly proportional as you stated) as the two colored objects
are separated.  Because the strong force does not decrease with 
distance, the energy required to permanently separate two color charged
objects is infinite.  In other words, two color charged objects cannot
ever be separated (this property is called "confinement").

Now you might be saying to yourself, "Wait a minute!  My shoe contains
quarks and a football contains quarks, but I know that I can separate
these two objects by any distance that I like."  Ah, but the protons
and neutrons that make up the shoe and football are not color charged.
Protons and neutrons are each composed of three color-charged quarks,
and the three color charges cancel to produce a color neutral proton
or neutron.  Color neutral objects can be permanently separated.

The force of gravity has little effect in the particle world because
the gravitational field strength is about 10^40 times weaker than the
strong field strength.  To put this ratio 10^40 =
10,000,000,000,000,000,000,000,000,000,000,000,000,000 in perspective,
it is like comparing the mass of the entire planet Earth to the mass
of a single bacterium.  In fact, of the four fundamental forces --
strong nuclear, weak nuclear, electromagnetic, and gravitational --
gravity is by far the weakest.

--Randall J. Scalise    http://www.phys.psu.edu/~scalise/