Welcome To The Quantum World! Your Host: Helium Superfluid

Submitted by: Essen 1 month ago in Science


Everything you need to know about helium and its awesome powers of awesomeness. (The superfluidity stuff starts at about 3:50.)

There are 20 comments:
Male 18,342
Even after reading the Wikipedia page, I still do not intuitively understand superfluidity
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Male 1,203
Draculya When you make that shit cold enough, parts of it no longer contribute to the entropy or heat capacity. That means its thermal conductivity rises a lot. It also means that those parts can do things that would otherwise increase the entropy -- like climbing up walls.

They effectively become similar to Bose-Einstein condensates, and quantum effects become observable macroscopically.
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Male 269
Draculya This is quantum mechanics. There is no intuitiv understanding. But For me at least the key point is:
1) instant transport of information (and I mean instant)
2) Due to this fact will quantum fulctuations be amplified
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Male 18,342
Essen please explain in detail. Serious request. Why does it creep uphill? Why does it pour through thick ceramic and flass bowls? Why do perpetual localised vortices form? Why does the fluid itself superconduct heat?
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Male 282
Draculya How exactly is a rainbow made? How exactly does a sun set? How exactly does a posi-trac rear-end on a Plymouth work? It just does.
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Male 18,342
I had to google the last answer, but it turns out that posi-trac is a limited slip differential. A LSD differs from an open diff by adding a passive clutch pack in line with the drive shaft. A wheel experiencing more traction will apply more compression on the clutch pack and receive more torque.

... also googling revealed you are quoting Joe Dirt.

My point is all these questions are easy to answer, because they make sense. A stopped learning physics at 18, and all the quantum experiments like laser diffraction etc. was just explained by ooh, that's spooky quantum shit. I hated that explanation, because it's a bit like when Bill O'Reilly said you can't explain tides. Or someone using god to explain evolution, or fairies to explain the changes of the seasons, or kids are delivered by the stork. It basically means "I don't know or don't want to explain."

Since then, I've watched countless videos and documentaries about what quantum particles there are and the spooky shit that happens for quantum reasons, but nobody ever fully explains why the spooky shit happens.

It turns out that in every case, either nobody really knows why or they have to use math to explain it and the math is so involved that I'll never understand it.

Go on, google "Why quantum entanglement happens". You'll get a description of the phenomena, but you won't be able to describe why it happens.
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Male 18,342
tisk A sunset happens because as the earth rotates, the sun sets lower in the sky. The red cast is because blue light is bent more and doesn't reach the viewer.
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Male 18,342
tisk 

Optical atmospheric phenomena are easy to understand as long as you know that refraction happens when higher frequency light bends more when it enters a solid at an angle because light moves slower through a solid than air or a vacuum.

A rainbow happens when light coming from the sun hits enters raindrops, gets refracted as it goes in, reflected off the back of the raindrop like a catseye road reflector and then dispersed backwards. In aggregate, they form a ring which is usually seen as an arc because the ground gets in the way. 

That's why rainbows always form after rain, where the sun is at the back of your head, why it's an arc, why red is on the outside, why blue is on the inside. 

https://waterstories.nestle-waters.com/environment/how-does-a-rainbow-form/
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Male 269
Draculya Unfortunately it is mathematics that makes it easy to understand. So I have to use anecdotes to explain it.
As you know every particles exact position is uncertain (this uncertainty is very small but not negligeble in quantum sizes) you can think of it as something shaking very fast in its place.

Since there is space between every atom/molecule these random shakes does not give rise to any significant variation in our observation of matter. (like a glass of water that is still but the molecules are moving in RANDOM direction with high speeds)

Now what happens to these molecules when you cool them? They get closer and closer and in the end attach to each other (freezing). But helium does not freeze. So these atoms are attached to each other yet the whole thing is fluid/movable.

Now if one of these heliums start to vary its position all the other helium atoms will also change their position in a NONE RANDOM way. This is due to their attachement to each other.

So finally these small varations become amplified and thus observable.

This is a really short description and not exact (again due to the lack of mathematics and other fundemental physics basics)

Fun fact this thing happens in neutron stars where the particles are actually touching each other. You get among others pulsars. (IMO very neat)
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Male 1,203
Essen

"Unfortunately it is mathematics that makes it easy to understand. So I have to use anecdotes to explain it."

Feynman disagrees, as do I. We should be able to describe it easily to a child otherwise we do not understand it.

"you can think of it as something shaking very fast in its place."

This seems to posit a known, albeit, fast oscillating position. Are you referencing Zitterbewegung

"This is a really short description and not exact (again due to the lack of mathematics and other fundemental physics basics)"

Yes, it is a challenge to explain without mathematics. But this is our burden as physicists.

"Fun fact this thing happens in neutron stars where the particles are actually touching each other."

You mean the degenerate energy among fermions? They are not understood to be "touching" each other physically -- how could that (via QED) even happen? You mean to say that their energy values overlap. This is not the same as photons positionally stacking in, say, a laser. 
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Male 269
BuckeyeJoe I agree with you on the explanation point. But for explaining to a child you do need to use anecdotes and simplifications.
PS. I am not a fan of Feynman. Specially how he held the introductory physics course (make it harder as a test of students)

I ment simply Heisenbergs undertainty principle and Brownian motion roled in one. When you cool helium (or anything) they loose "degrees of freedom" (thermodynamics). When it happens the number of available quantum states for a given energy-level is decreesed. Thus fermions have to keep a minimum distance from each other. This coupling of particle will give you the extremely fast heat/information transfer.

In neutron stars this phenomenon (quantum coupling) happens due to gravitational forces. 


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Male 1,203
Essen Well, we must agree to differ regarding Feynman. There was a lot more to him than his introductory course pedagogy.

"I ment simply Heisenbergs undertainty principle and Brownian motion roled in one. When you cool helium (or anything) they loose "degrees of freedom" (thermodynamics). When it happens the number of available quantum states for a given energy-level is decreesed. Thus fermions have to keep a minimum distance from each other. This coupling of particle will give you the extremely fast heat/information transfer."

Well, that is not quite right is it? What you mean to say is that cooper pairs must keep a minimum distance. You get two fermions per spin eigenstate. They act like a boson condensate. 

But these are technical details. I see what you are saying. It is basically impossible to explain things accurately and accessibly. 

I maintain that we still must try.

"In neutron stars this phenomenon (quantum coupling) happens due to gravitational forces."

I would offer that the EOS is a better tool. A relativistic mean field theory description of isovector scalar meson-nucleon couplings form a better theoretical basis for understanding the rotons that result. 
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Male 269
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Male 1,203
Essen Well, I would offer that you might want to consider offering more. 

But we all applaud your wit, I'm sure.
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Male 18,342
Essen thanks. I appreciate your effort
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Male 269
Draculya You are very welcome. I enjoy explaining science to people who are (at least some what) interested.
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