Fermi (unit)

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The fermi is a non-SI unit of length that is internationally recognised and equivalent to the SI-recognised femtometre. The symbol for both the fermi and the femtometre is fm. The unit was named in honour of Enrico Fermi and is often encountered in nuclear physics as a characteristic of this scale.

[edit] Definition

1 fermi = 1.0 x 10^–15 metres = 1 femtometre = 0.001 picometre = 1000 attometres

1,000,000 fermis = 1 nanometer

For an example of lengths in this unit, the radius of a gold nucleus is approximately 8.45 fermis.

[edit] History

The fermi is named after the Italian physicist Enrico Fermi (1901–1954), one of the founders of nuclear physics. The term was coined by Robert Hofstadter in an 1956 paper published in the Reviews of Modern Physics journal. The term is widely used by nuclear and particle physicists.