Alone or in company, protons are built to last. Not so neutrons.
While protons will endure far longer than the age of the universe, a loose neutron bids adieu in only minutes to hours, experiments have shown. The neutron's swan song, a process called beta decay, transforms the particle into a proton, an electron, and an antineutrino.
However, neutrons in stable nuclei last indefinitely.
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