# Stability of neutron [duplicate]

Possible Duplicate:
How come neutrons in a nucleus don't decay?

It is known that free neutron decays in 15 minutes on average. Why is it much more stable when "placed" in nuclei?

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## marked as duplicate by Qmechanic♦, dmckee♦Feb 9 '12 at 19:46

Thanks, Adam. Does it mean that $\beta^{-}$ decay leads to nuclei with higher energy state? Perpetuum mobile? –  Murod Abdukhakimov Feb 9 '12 at 10:48
@JohnRennie I doubt it.. Proton's don't decay: en.wikipedia.org/wiki/Proton_decay . More accurately, they haven't been observed to. Many experiments have been set up to find out if they decay, but they haven't found anything, pushing half-life estimates to $10^{(\text{I think 37)}} y$. Proton decay is predicted by many of the new theories, though. –  Manishearth Feb 9 '12 at 12:57