What is a superfluid, or perfect fluid?


What is a superfluid, or perfect fluid?

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All fluids are subject to “Viscosity”, which is basically akin to friction within the fluid which acts against flowing. Think of pouring water vs. pouring honey, it’s a resistance to flow.

A way to visualize this resistance would be putting a marble on U shaped channel and letting it go. It’ll go back and forth, back and forth, but each time it’ll climb a little less high and eventually come to rest at the bottom of the U, that’s all due to friction resisting the motion.

A superfluid has absolutely zero resistance to flow which means it’ll flow forever. In the ball in the marble example, it would just keep going back and forth forever. If you put in a cup and stirred it with a spoon, the liquid would circle around and around forever. It’s “perfectly fluid”.

It’s kind of hard to get a superfluid in the real world at least in our daily lives. You can create a superfluid in a laboratory though under some pretty extreme conditions.