From Max Wallis
Detecting the Casimir force at submicron scales in the 1990s was hugely
important in establishing a continuum between atomic and macroscopic scales. It
was also important in demonstrating that the “vacuum” is full of zero-point
fields.
But it is unlikely that the force could account for the aggregation of dust
grains in space
(20 October, p 61).
Hendrik Casimir predicted the force in 1948,
not the 1920s, but it was later found that it doesn’t always obey an inverse
fourth law of distance. Casimir himself derived the inverse fourth law of
attraction for ideal parallel plates, but for a sphere close to a plane plate,
theory and experiment show that the Casimir force obeys a repulsive inverse cube
law. And the force between two halves of a spherical shell is also predicted to
be repulsive, so Casimir probably doesn’t explain gravity at the microscopic
scale.
Cardiff
