The weird quantum world can occasionally be glimpsed in the ordinary world. Take, for example, the phenomenon
of superfluidity.
Helium is the second simplest atom after hydrogen, and is a very light gas. In 1908, Dutch physicist Heike
Kamerlingh Onnes
succeeded in cooling helium to a temperature of -268.9ºC (absolute temperature of 4.2 K), at around
which point it becomes a liquid. If this liquid helium is further cooled to -271ºC (or, more precisely,
2.2 K), it starts showing some very strange behavior.
Helium cooled to 2.2 K is known as helium-II, a "superfluid" that shows no viscosity, and can amazingly climb
up the sides of a container spontaneously and escape (it can also climb into a container). Helium-II can penetrate
through the tiniest of spaces, and will escape even a capped container unless it is sealed very tightly. This
is called superfluidity.
This phenomenon occurs when there is helium-II outside the container, and there is a difference in the height
of the helium inside and out. When the height of helium-II inside and outside the container becomes the same,
the movement ceases. It's as if there were an invisible siphon at work.
This is a truly odd phenomenon, which is said to occur as a result of helium-II's quantum-like properties.
