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 Lowest Animal essay with these words: "Man is the Reasoning Animal. Such is the claim." The Lowest Animal The Lowest Animal is an 1896 philosophical essay written by American author Mark Twain. Twain describes fictional experiments he did with animals in which they showed greater civility than humans. In the essay Twain satirizes human nature by describing a series of experiments he supposedly conducted at the London Zoological Gardens. Twain takes Darwin's evolution theory that humans evolved from earlier ancestors, or “lower animals,” and turns it upside down. He describes deeds done by powerful people against the helpless, and states the many