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 $\sqrt{ T}$. Quantum statistics causes a deviation from the $\sqrt{ T}$-dependence and shows that the force scales with $T^2$ at low temperatures. At $T=0$, the force vanishes in a Bose gas but is finite in a Fermi gas.
Categories: physics.gen-ph