A CLOUD of lithium atoms has broken the record for the coolest atomic gas on
Earth. By chilling the atoms to less than a quarter of a millionth of a degree
above absolute zero, scientists have seen the gas develop “Fermi
pressure”—a strange quantum effect that stops superdense stars collapsing
completely.
Fermi pressure only occurs in a gas of fermions, the class of particles that
includes electrons and neutrons. Fermions obey a quantum rule that forbids them
from occupying exactly the same energy states. So at extremely low temperatures
or at enormous densities, the particles simply jam up all…
