Archive for DARPA You are browsing the archives of DARPA. You
are browsing the archives of DARPA. There a lot of great stuff
going on: On the absolute temperature scale that is used by
physicists, the Kelvin scale, one cannot go below zero—at least
not in the sense of getting colder than zero Kelvin. Physicists
of the Ludwig-Maximilians University Munich and the Max Planck
Institute of Quantum Optics, Garching, Germany, have now created
an atomic gas in the lab that has nonetheless negative Kelvin
values. These negative absolute temperatures lead to several
striking consequences: Although the atoms in the gas attract
each other and give rise to a negative pressure, the gas does
not collapse, a behavior that is also postulated for dark energy
in cosmology. Also supposedly impossible heat engines can be
realized with the help of negative absolute temperatures, such
as an engine with a thermodynamic efficiency above 100 percent.
In order to bring water to the boil, energy needs to be added to
the water. During h