In 1946, [scientist:Willard Libby] proposed a method that revolutionized archaeology: determining age by the decay of radiocarbon. The clock ticks: every 5730 years, half of the atoms vanish. But why so slowly? For a light nucleus, this is an anomaly — typical lifetimes are millions of times shorter. The mystery held for seven decades.
The answer was hidden in the nitrogen nucleus that carbon turns into. When a neutron inside 14C emits an electron, it becomes a proton, and 14N is born. Calculations showed that the nitrogen nucleus spends almost all its time in a "wrong" shape (D-wave), and the transition into it from carbon is strongly hindered. Three-nucleon forces, interactions involving three particles at once, act as a strict gatekeeper, preventing the process from speeding up.
Physicists from the NLEFT collaboration have for the first time brought together two approaches: first-principles lattice calculations and the nuclear shell model. It turned out that the key to longevity is the fine-tuning of the contact interaction between two nucleons combined with pion exchange among three. Shift these parameters slightly, and the half-life would collapse by orders of magnitude.
Thus nature has given us a perfect chronometer for the last 50,000 years of history.
If the half-life of 14C were typical for light nuclei (seconds or minutes), the Shroud of Turin and the Dead Sea Scrolls would have remained without reliable dating.