Now I don't have to delete all those important ^#$#*&# PMs ...
yet... Thank you Magister!!! Helium II is a superfluid, a
quantum mechanical state of matter with strange properties . The
thermal conductivity of helium II is greater than that of any
other known substance, a million times that of helium I and
hundred of times that of copper. This is because heat conduction
occurs via a quantum mechanism. Second sound is a quantum
mechanical phenomenon in which heat transfer occurs by wave-like
motion, rather than by the usual mechanism of diffusion. Heat
takes the place of pressure in normal sound waves. This leads to
very high thermal conductivity. It's known as "second sound"
because the wave motion of heat is similar to the propagation of
sound in air. Sound waves are fluctuations in the density of
molecules in a substance; second sound waves are fluctuations in
the density of phonons. Second sound can be observed in any
system in which most phonon-phonon collisions conserve momentum.
This occurs in superflui