Unanswered Questions

Beyond the Proton, Neutron, and Electron

Can quarks be free, or are they always bound in the proton or neutron?

There have been many searches for free quarks but they have never been observed. The theory that describes the interactions between quarks and gluons, quantum chro-modynamics (QCD for short), says that quarks can never break free because the more that the gluons are stretched, the stronger the force they exert. In this way they act like springs whose force also increases the more they are stretched.


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