A unit of area equal to
, abbreviated b or bn. The name derives from a humorous comparison
with a saying sometimes applied to those with poor aim, "you couldn't hit the broadside of a barn." The barn is
typically used to measure the cross section for nuclear reactions. For example, the elastic scattering cross section for
thermal neutrons on hydrogen is 20.47 barn.
© 1996-2007 Eric W. Weisstein
