Do we live in a perfect liquid?

[quantumirage]

I'm a physics newbie, so forgive me if I'm ignorant sometimes, but I've been trying to learn physics on my own and understand things for the past couple of years, and I'm proud to say that I've come a long way - still got a long way to go.

There was an article posted last week about perfect liquids, and the fact that if one stirs a spoon in that liquid, the spoon will keep stirring forever. And it made me think about how everything on the quantum and grand-scale level (planets and stars) is also spinning forever in what is labeled as "angular momentum" in physics. What does that indicate? And what exactly is a perfect liquid and its connection to angular momentum?

There are lots and lots of questions in my head, but I'll start here. Thanks for helping me answer those questions and get to know the real nature of life and everything we live in.

 

[alxm]

Welcome to PF.

A 'perfect liquid' or superfluid is a liquid(-ish) state of matter that has no viscosity, or 'internal friction'. Which is why it will continue moving in a circular pattern forever when you stir it. (In a similar vein, a superconductor has no 'internal friction' in the form of electrical resistance, and a current set in motion in a closed loop in a superconductor will also continue perpetually)

It's got nothing to do with angular momentum, really, other than the example happened to use that. Angular momentum is a conserved property, as is linear momentum and energy. As long as a physical system isn't exchanging these things with the outside world (it's isolated), then those quantities will remain the same. An ordinary, viscous, fluid will slow down eventually if you stir it, but doesn't lose any angular momentum in the process; it merely became redistributed on the molecular scale. The difference is that this redistribution doesn't happen in a superfluid, not that angular momentum is conserved - that's always the case.


Not to discourage you, but if you've been learning on your own for several years, you might need to find a good curriculum or course plan to follow. The above, save for the specifics of superfluids, is pretty basic classical physics. You need to know that well if you want to have any hope of understanding the more advanced concepts. (There's a reason university-level physics is taught in the order it is!) Reading popular-scientific books about physics and cosmology is fine, but they don't really teach physics any more than reading a restaurant review teaches cooking.

 

[quantumirage]

Thanks Alxm for your response. The fact that angular momentum exists as a property within each system (whether it's a single atom or a whole planetary system) makes me believe that each of these systems behaves as a perfect liquid on its own.
You're probably right that I need to cover the Physics basics more extensively but I also appreciate the fact that I can think more "outside the box" than what you can find in textbooks.