4 ms·

A femtobarn, see https://en.m.wikipedia.org/wiki/Barn_(unit) https://en.m.wikipedia.org/wiki/Barn_(unit)

• FeepingCreature 6y ago
  Quoting: > During Manhattan Project research on the atomic bomb during World War II, American physicists at Purdue University needed a secretive unit to describe the approximate cross-sectional area presented by the typical nucleus (10^−28 m2) and decided on "barn". They considered this a large target for particle accelerators that needed to have direct strikes on nuclei, and the American idiom "couldn't hit the broad side of a barn" refers to someone whose aim is very bad. ... > Other related units are the outhouse (1 μb, or 10^−34 m^2) and the shed (10^−24 b (1 yb), or 10^−52 m^2), although these are rarely used in practice.
  • Already__Taken 6y ago
    > needed a secretive unit > American idiom "couldn't hit the broad side of a barn" It's being clever like that what got the Germans in WWII in trouble, I particularly like Wotan -https://en.wikipedia.org/wiki/Code_name#German_code_names https://en.wikipedia.org/wiki/Code_name#German_code_names Were as the brits made up a random code for this purpose - https://en.wikipedia.org/wiki/List_of_Rainbow_Codes https://en.wikipedia.org/wiki/List_of_Rainbow_Codes
    • mhh__ 6y ago
      RV Jones's book is a great read about scientific intelligence of WW2. Also, the NRO have previously given away classified orbits of spy satellites on their mission patches.