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On Oct 17, 2024, at 5:23 PM, Paul Nord via Phys-l <phys-l@mail.phys-l.org> wrote:
That's the origin of that lie then?
Motion does not cease at 0ºK. But we can say nothing about what the motion
is. It will be in the minimum state allowed by quantum mechanics. This is
not rest. It does not interact with other matter since a collection of
particles at this temperature has no energy to give up in an interaction
with other particles. Vibrational modes in atomic bonds will be at their
ground state, but they are still vibrating.
I heard Douglas Osheroff talk about this once. He claims partial
responsibility for the myth. He was being interviewed for part of a PBS
documentary where he was asked to explain what happens at absolute zero.
After attempting several explanations, the producer was frustrated with his
responses. He asked what answer he wanted. And the producer just said,
"Just say that all motion stops." He obliged, and that's the only sound
bite that made it into the show. But he knew it was wrong at the time.
Paul
On Thu, Oct 17, 2024 at 1:36 PM Prof. Keith S. Taber via Phys-l <
phys-l@mail.phys-l.org> wrote:
This is from a popular science book by the physicist George Gamow:_______________________________________________
“If we heat the liquid the wild dance of tiny particles suspended in
it becomes more violent; with cooling the intensity of the motion
noticeably subsides. This leads no doubt that we are actually
watching here the effect of the hidden thermal motion of matter, and
that what we usually call temperature is nothing else but a
measurement of the degree of molecular agitation. *By studying the
dependence of Brownian motion on temperature, it was found that at
the temperature of -273˚ C *or -459˚ F, thermal agitation of matter
completely ceases, and all its molecules come to rest.”
Leaving aside the sense of observations leaving 'no doubt' about a
theoretical interpretation (rather counter to the idea of theory always
being underdetermined by observation) I was very surprised to read that
absolute zero had been found from studies of Brownian motion rather
than, say, change in volume/pressure of a gas or some other method.
I would have thought 'well, I never knew that', but I am not sure how
reliable Gamow is. (Elsewhere in the same book he has neutrons decaying
to protons AND protons decaying to neutrons
<
https://science-education-research.com/glossary/proton-decays-into-a-neutron/>,
in both cases emitting neutrinos and electrons/positrons, which to my
mind could have solved our power supply issues - if it had been
correct.) Is Gamow right about Brownian motion? I thought Brownian
motion was only well understood after Einstein in 1905, well after
absolute zero was estimated?
Keith
--
“The main point to realise is that all knowledge presents itself within
a conceptual framework adapted to account for previous experience and
that any such frame may prove too narrow to comprehend new experiences"
<https://science-education-research.com/commonplace/>
Dr. Keith S. Taber
https://science-education-research.com
<https://science-education-research.com>
Emeritus Professor of Science Education
University of Cambridge
http://www.educ.cam.ac.uk/staff/taber.html
Senior Member
Homerton College, Cambridge
Editor-in-Chief, Royal Society of Chemistry Book Series:
/RSC Advances in Chemistry Education/
<https://science-education-research.com/advances-in-chemistry-education/>
<https://science-education-research.com/advances-in-chemistry-education/>
_______________________________________________
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