Do protons decay?

Is it possible that these fundamental building blocks of atoms have a finite lifetime? The stuff of daily existence is made of atoms, and all those atoms are made of the same three things: electrons, protons and neutrons. Protons and neutrons are very similar particles in most respects. They’re made of the same quarks, which are even smaller particles, and they have almost exactly the same mass. Yet neutrons appear to be different from protons in an important way: They aren’t stable. A neutr...