Subject: MERCURY-GLASS CONTACT LIGHT DISCHARGE
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Click: http://scienceweek.com/ January 30, 1998
5. AN EXPLANATION FOR MERCURY-GLASS CONTACT LIGHT DISCHARGE
The term "barometer light" refers to an optical discharge discovered in
1670 by Picard, the discharge being produced by the swirling of liquid
mercury in an evacuated glass flask. In mechanics, "stick-slip" motion
is motion involving two surfaces that are alternately at rest and in
motion with respect to each other. ... ... Budakian et al (4 authors at
Univ. California Los Angeles, US) revisit the "barometer light"
phenomenon, and report that repetitive emission of light from mercury
moving over glass is accompanied by the collective picosecond transfer
of large numbers of electrons, the glass acquiring a net charge. The
electrical interaction can drag mercury against gravity, and when the
mercury slips relative to the glass, a picosecond electrical discharge
and flash of light are produced. The repetitive build-up and discharge
of static electricity thus gives rise to stick-slip motion.
QY: S.J. Putterman, Univ. of Calif. Los Angeles,
Dept. Physics 310-825-3164 (Nature 15 Jan 98)