Superfluid Helium Climbs Up Walls

 SUPERFLUID HELIUM DEFIES GRAVITY

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Don't worry about a soft drink spontaneously overflowing its rim or shooting up and out of the straw from which you're trying to drink because it's nothing like the superfluid helium shown in this video. 

Like plenty of other experiments that make you go, "huh?", superfluidity flows from the counterintuitive rules of quantum mechanics.

A superfluid is a state of matter in which the matter behaves like a fluid with zero viscosity and zero entropy. Helium is the only gas that makes a good superfluid because it has weak intermolecular forces. Helium has the unique ability to remain liquid at absolute zero temperature (-273.15° C), the temperature at which atoms theoretically stop moving. When most liquids are cooled, the attraction between atoms in the fluid finally begins to overcome heat vibrations and the particles arrange themselves in a regular fashion, that is, a solid. But helium atoms are so light and weakly attracted to each other that they never settle into the solid state.

Superfluid helium climbs up walls 

Helium condenses to a liquid at 4.2K and turns into a superfluid at 2.17K. The point at which it becomes superfluid is called the critical point, or lambda point. At that point a remarkable discontinuity in heat capacity occurs, liquid density drops, and a fraction of the liquid becomes a zero viscosity. Superfluidity arises from the fraction of helium atoms which has condensed to the lowest possible energy by a process called Bose-Einstein condensation, a condition in which individual particles overlap until they behave like one big particle, and atoms acting in unison don't behave like individual atoms.

Liquid Helium

Cool liquid helium is able to do things that other fluids can't, like dribble through molecule thin cracks, climb up and over the sides of a dish, and remain motionless when its container is spun. In superfluid helium, the frictionless film slithers over the whole container creating a sort of arena through which it can flow. If the liquid has somewhere to fall after it climbs out, it drips from the bottom of the container until it siphons out all the superfluid.

John Beamish, an experimental physicist at the University of Alberta in Edmonton says, "If you set a cup with a liquid circulating and you come back 10 minutes later, of course, it'd stop moving". This is because atoms in the liquid will collide with one another and slow down. "But if you did that with helium at low temperature and came back a million years later, it would still be moving", he says. And the reason lies in the fact that helium has now become a superfluid that flows without friction.

There is a famous demonstration called the superfluid fountain, in which superfluid rapidly shoots out of an open, heated glass tube packed with fine power at the bottom. This occurs because the superfluid outside the tube rushes in to cool down the superfluid that has been warmed by the inside of the tube. Watch this video for better understanding.