<s>[INST] What's the half life of a helium 6 isotope? [/INST] Helium has nine known isotopes, ranging from helium-2 to helium-10. However, only helium-3 and helium-4 are stable. All radioisotopes are short-lived, the longest-lived being helium-6 with a half-life of 806.92 (24) milliseconds. It decays by emitting a beta particle and sometimes a deuteron.</s>\ <s>[INST] How does one go about carbon dating fossils? [/INST] 