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
The Elements of Moral Philosophy died. Since then, his son Stuart has written the fifth edition and the sixth edition, which was released in April 2009. An 8th edition was released in October 2014. The book has been translated into Italian, Portuguese, Chinese, Indonesian, Korean, Spanish, Norwegian, Swedish, Persian and Albanian. It is known for its accessibility to a wide readership. David Fordyce wrote a book with the same title—however, aside from the titles, these books are largely unrelated. The Elements of Moral Philosophy The Elements of Moral Philosophy, by James Rachels and Stuart Rachels, is an ethics textbook. It explains a number of moral