Much of Lord Rayleigh's research concerned the behavior of all
sorts of waves. One of the waves produced by earthquakes is
named for him. In 1871 he explained why the sky is blue, because
of the preferential scattering of short wavelength blue sunlight
in the atmosphere. The phenomenon is known as Rayleigh
scattering today. As previously noted, Rayleigh's Nobel Prize-
winning work was in the discovery of the element argon. In his
home laboratory, he discovered that nitrogen prepared from air
was slightly heavier than nitrogen prepared from nitrogen-
containing compounds. With the chemist William Ramsay, he found
that the reason for this was an unknown gas that makes up
approximately 1% of the atmosphere. They named the gas argon,
from the Greek word for "inert", because they found that it
would not react with anything. Ramsay then went on to find most
of the noble gases, such as neon ("new"), krypton ("hidden"),
and xenon ("stranger"), as well as isolating helium on earth,
which previously had been known only f