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# Physics/thermodynamics

Question
Dear Prof Nelson
"The net flow in and out of each piece  of material is equal, and by the zeroth law of thermodynamics that makes all pieces of the system in thermal equilibrium."
I can not accept this. If we have macroscopic circulation of a current, locally we have simply a macroscopic current. And this is contradict with a statement that no macroscopic currents are present in equilibrium stste.
In magnetic domain you have nonzero electric current as a consequence of spontaneous magnetization and Maxwell laws, look at the texbook of Feynmann. If we have magnetization, we have also density of circulating electric current! The current itself is macroscopic (because atomic moments are oriented) and of microscopic and quantum origin.
And this make me troubles in understanding the statement.
You may also consider superfluid circulation. There is macroscopic current of matter.
All these phenomena have quantumorigin as collective states, which can not be destroyed by thermal fluctuations.
Do you accept this point?

NET macroscopic currents.  The net macroscopic current around a closed loop is zero.  The magnetic field situation you mention falls under the same category.  Same with superfluid circulation, there's not NET macroscopic current.  That means there's not a flow from one part that's not equaled exactly by the flow from another part, that's the basic definition.

I don't know who made this "statement" that you're so strongly against, but you're misinterpreting their words to mean "any" macroscopic current instead of a net macroscopic current (where you must add up all currents in and out).  And I'm done answering this question with more statements of the same.

Physics

Volunteer

#### Dr. Stephen O. Nelson

##### Expertise

I can answer most basic physics questions, physics questions about science fiction and everyday observations of physics, etc. I'm also usually good for science fair advice (I'm the regional science fair director). I do not answer homework problems. I will occasionally point out where a homework solution went wrong, though. I'm usually good at explaining odd observations that seem counterintuitive, energy science, nuclear physics, nuclear astrophysics, and alternative theories of physics are my specialties.

##### Experience

I was a physics professor at the University of Texas of the Permian Basin, research in nuclear technology and nuclear astrophysics. My travelling science show saw over 20,000 students of all ages. I taught physics, nuclear chemistry, radiation safety, vacuum technology, and answer tons of questions as I tour schools encouraging students to consider careers in science. I moved on to a non-academic job with more research just recently.

Education/Credentials
Ph. D. from Duke University in physics, research in nuclear astrophysics reactions, gamma-ray astronomy technology, and advanced nuclear reactors.