CAN a pendulum swing in space? It might if it is quantum powered, a fact that could be exploited to build tiny timepieces that run off the quantum fluctuations that occur in a vacuum.
Habibollah Razmi and Mah Abdollahi from the University of Qom, Iran, envisaged a tiny pendulum made with a string of 30 atoms attached to a conducting plate at one end. They calculated that the Casimir-Polder force - which arises from the exchange of the "virtual" photons that pop in and out of existence in a vacuum - would attract the nanostring towards the plate. Before it touched the plate, however, the forces between its atoms would force it back. The cycle would repeat, causing the nanostring to swing like a pendulum (Physics Letters A, DOI: 10.1016/j.physleta.2008.09.040).
Traditional pendulums rely on gravity to regulate their swing, but gravity varies with position in space. The Casimir-Polder ...
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