fermi

noun
  1. A unit of length equal to one femtometer (10^-15 meters), used especially in nuclear physics to measure nuclear distances. noun
    The radius of a proton is approximately 0.84 to 0.87 fermis.
    Nuclear physicists often use the fermi to describe the size of atomic nuclei.
  2. Named after Enrico Fermi, an Italian-American physicist known for his work on the development of the first nuclear reactor and contributions to quantum theory, nuclear and particle physics, and statistical mechanics. noun
    The Fermi paradox questions why, given the vastness of the universe, we have not yet encountered extraterrestrial life.
    Fermi's contributions to science were recognized with the naming of the Fermi Gamma-ray Space Telescope.