We consider a heavy external object moving in an ideal gas of light
particles. Collisions with the gas particles transfer momentum to the object,
leading to a force that is proportional to the object's velocity but in the
opposite direction. In an ideal classical gas at temperature T, the force
acting on the object is proportional to Tβ. Quantum statistics causes a
deviation from the Tβ-dependence and shows that the force scales with
T2 at low temperatures. At T=0, the force vanishes in a Bose gas but is
finite in a Fermi gas.Comment: 11 pages, 4 figures; This material has been submitted to/accepted by
the American Journal of Physics. After it is published, it will be found at
(https://pubs.aip.org/aapt/ajps