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Researcher Challenges Supersolid Helium Theory - 7/23/2010
The theory that helium becomes a frictionless supersolid when it reaches extreme cold temperatures has been held in popular belief by scientists since the 1970s. Now, John Reppy, the John Wetherall professor of physics emeritus at Cornell University, is challenging that theory.
Reppy’s report in Physical Review Letters challenges the results of a 2004 experiment that claims evidence of supersolid helium. In that study, researchers placed solid helium cooled to near absolute zero in an oscillator. As the helium got colder, the scientists observed a change in the rate of oscillation, leading them to believe that the helium particles had taken on supersolid qualities and were moving in a frictionless state. Reppy argues that helium does not become a harder solid at low temperatures, but rather it becomes softer at high temperatures. Reppy’s theory refutes the appearance of a low-temperature phenomenon of supersolid helium. Instead, he says, the phenomenon occurs with a hardening of helium at high temperatures.
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