Isotopes of helium a thousand times lower than helium-4 (2.17 K). This difference is explained by quantum statistics, since helium-3 atoms are fermions, while helium-4 atoms are bosons, which condense to a superfluid more easily. The most common isotope, , is produced on Earth by alpha decay of heavier radioactive elements; the alpha particles that emerge are fully ionized nuclei. is an unusually stable nucleus because its nucleons are arranged into complete shells. It was also formed in enormous quantities during Big Bang nucleosynthesis. Terrestrial helium consists almost exclusively (99.99986%) of this isotope. Its boiling point of 4.2 K is the lowest of
Stone boiling Stone boiling Stone boiling is a moist-heat cooking method. It involves placing heated rocks into a water-filled container to heat the liquid to the point where it can be used to cook. This method of food preparation is a fuel-intensive process and it often requires the heating and reheating of stones before the water reaches an effective cooking temperature. Indigenous peoples in what is now Canada and the United States of America, especially on the West and Northwest Coast, used stone boiling. Cooking this way allowed for a more controlled temperature which made the extraction of fats and oils easier