7 Willard Libby 7of its Institute of Geophysics and Planetary Physics (from
1962) until his death. He was the recipient of numerous
honours, awards, and honourary degrees.
During the late 1950s, Libby and physicist Edward
Teller, both committed to the Cold War and both promi-
nent advocates of nuclear weapons testing, opposed Nobel
chemistry and peace laureate Linus Pauling’s petition for
a ban on nuclear weapons. To prove the survivability of
nuclear war, Libby built a fallout shelter at his house, an
event that was widely publicized. The shelter and house
burned down several weeks later, however, which caused
physicist and nuclear testing critic Leo Szilard to joke,
“This proves not only that there is a God but that he has a
sense of humor.”
While associated with the Manhattan Project (1941–45),
Libby helped develop a method for separating uranium
isotopes by gaseous diffusion, an essential step in the
creation of the atomic bomb. In 1946 he showed that
cosmic rays in the upper atmosphere produce traces of
tritium, the heaviest isotope of hydrogen, which can be
used as a tracer for atmospheric water. By measuring tri-
tium concentrations, he developed a method for dating
well water and wine, as well as for measuring circulation
patterns of water and the mixing of ocean waters.
Because it had been known since 1939 that cosmic
rays create showers of neutrons on striking atoms in the
atmosphere, and because the atmosphere contains about
78 percent nitrogen, which absorbs neutrons to decay
into the radioactive isotope carbon-14, Libby concluded
that traces of carbon-14 should always exist in atmospheric
carbon dioxide. Also, because carbon dioxide is contin-
uously absorbed by plants and becomes part of their
tissues, plants should contain traces of carbon-14. Since
animals consume plants, animals should likewise contain