The Strong Force Carrier
the discovery of the strong force, one could finally explain why the
nucleus of an atom did not fly apart. Hideki Yukawa (The Nobel Prize in Physics 1949)
proposed that the strong force between protons and neutrons in the
nucleus occured through the exchange of pi (p)
mesons (q q-bar particles). However, in the more modern view, there
is a problem. The strong force is only supposed to affect particles
with "color" charge, and protons and neutrons are "color" neutral.
Physicists realized that mesons and baryons, such as neutrons and protons
in the nucleus can overlap. So while the "color" neutral protons and
neutrons do not interact with each other, their quarks do. The strong
force occurs through the exchange of gluons between quarks in different
protons and neutrons. This process "glues" the nucleus together. It is
similar to how neutral atoms bind together to make molecules.
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