Liquid helium belongs to a class of fluids known as quantum fluids, as distinct from classical fluids.

The quantum Newton's cradle is just like a classical Newton's cradle, except that it's more perfectly one-dimensional and instead of five balls there are hundreds. Also, because it's a quantum system, the atoms often just go right through each other, which never happens with the executive desk toy. Another difference is that you can't buy the quantum Newton's cradle on the Internet.

Classical mechanics gave us a deterministic view of the world. Quantum mechanics, conversely, gives us a probabilistic view instead. According to Newton, if you know the cause af an event, you can predict the outcome. According to M.Born, you can only predict how likely that outcome will be.

Modern low temperature physics began with the liquefaction of helium by Kamerlingh Onnes and the discovery of superconductivity at the University of Leiden in the early part of the 20th century.

These guys are a great class,

To have it come this late is really challenging. We've been through half the admitted class already, and now we have to stop everything and review those students who were affected.