SUPERFLUID SOLID HYDROGEN; SOLVAY: THE MOVIE
Date: Friday, March 25, 2005 @ 19:30:33 GMT
Topic: Science


PHYSICS NEWS UPDATE - The American Institute of Physics Bulletin of Physics News, Number 724, March 25, 2005 by Phillip F. Schewe, Ben Stein

SUPERFLUID SOLID HYDROGEN. Quantum science allows for collective behavior that runs counter to human intuition. For example, at very low temperatures helium-4 atoms, in their wavelike manifestation, can begin to overlap. When this happens the atoms are indistinguishable and indeed constitute a single quantum state. In this state liquid helium-4 will flow without friction. Comparably chilled, quantum-condensed dilute gases (Bose-Einstein condensates, or BEC) also exhibit superfluid behavior.

What about solids? Can they "flow" without friction? Last year Moses Chan (Penn State) announced the results of an experiment in which solid helium-4 was revolved like a merry-go-round. It appeared that when the bulk was revolved at least part of the solid remained stationary. In effect part of the solid was passing through the rest of the solid without friction. Chan interpreted this to mean that a fraction of the sample had become superfluid (see www.aip.org/pnu/2004/split/669-1.html and www.aip.org/pnu/2004/split/699-2.html).

Now, Chan sees evidence for superfluid behavior in solid hydrogen as well. Speaking at this week's meeting of the American Physical Society (APS) in Los Angeles, Chan said that his hydrogen results are preliminary and that further checks are needed to be made before ruling out alternative explanations. The concept of what it means to be a solid, Chan said, needs to be re-examined.

SOLVAY: THE MOVIE. Arguably the most famous photograph of physicists is the group portrait taken at the 1927 Solvay Conference in Belgium. It turns out that a brief motion picture of that event also exists. In the course of this three-minute film, a dozen or more present and future Nobel laureates walk in and out of the frame, including Albert Einstein, Marie Curie, Niels Bohr, and Max Planck.

Forgotten or neglected for decades, the film was shown in public for the first time at the APS meeting by Nancy Greenspan, author of "The End of the Certain World," the first full biography of Max Born (http://www.maxborn.net). Born is credited with the insight that the wavefunction appearing in Erwin Schrodinger's famous equation provided not the exact location of an electron inside an atom but rather merely a statistical likelihood of the electron being at various locations.

This view of quantum reality would later take on the name of the "Copenhagen interpretation," in honor of Niels Bohr. Greenspan argues that Born has been underappreciated in histories describing the establishment of quantum science. Speaking at a press conference, APS president Marvin Cohen (Univ California, Berkeley) underscored this point. Max Born's group at the University of Gottingen, active over the period from 1922 to 1932, was, Cohen suggested, the most illustrious theoretical physics "school" of all time. The list of Born students or junior colleagues includes no less than Werner Heisenberg, Wolfgang Pauli, Enrico Fermi, Maria Goeppert-Mayer, Linus Pauling, Eugene Wigner, and Robert Oppenheimer.





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