Proton Decay?

How the death of one tiny particle could end the universe

 Esther Inglis-Arkell

No one has observed any evidence for proton decay. That might be disappointing professionally for physicists, but it's good news for the universe. If it turns out to be possible, proton decay could be the beginning of the end of everything. Here's why.

How do we start with protons and end with the end of the universe? We begin with what's in those protons. Inside protons are quarks. Quarks are one of the two most basic particles we can find. Quarks are subject to the strong force, the force that keeps a nucleus together. Each quark has essentially been assigned a baryon number of one third. The most famous baryons are protons and neutrons which have three quarks each, amounting to a baryon number of one. (Also famous are the antiprotons, which have a negative baryon number. So if a proton and antiproton were simultaneously created, the overall baryon number of the system is zero.) Because the charge of the quarks in protons and neutrons is a little different, the two particles have different charges. They also have slightly different masses. The neutron is a little chunkier, which means it can be involved in a change that involves the other fundamental piece of matter in the universe.

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Leptons are separate from quarks. They are things like the electron, the neutrino, and their counterparts the antineutrino and antielectron. None of them are affected by the strong force. They have lepton numbers, and their anti-counterparts have negative lepton numbers./.../