|In 1948 Hendrik B G Casimir of the Philips Research Laboratories in the Netherlands, proposed an experiment to measure what has become known as the Casimir effect. |
Based on the idea that the 'vacuum' of space is actually a seething foam of quantum fluctuations of different frequencies, Casimir proposed that if two electrically conducting, but uncharged parallel plates were mounted a small distance apart in a vacuum, they would tend to be drawn together. An important point is that the plates carry no electrical charge so that any interaction between the plates must come from some other source.
Assuming that the plates are completely surrounded by quantum fluctuations, we can see from the drawing that the fluctuations between the plates will be restricted to those that will fit between the plates, whereas outside the plates they will be unrestricted. This means that there will be a greater variety and therefore more fluctuations outside the plates than between them, resulting in a net force that will tend to push the plates together.
Casimir predicted the value of this force and in 1996 Steve K Lamoreaux, then at Washington University, measured the force to within an accuracy of five per cent of Casimir's prediction for that configuration of plate separation and geometry.
Over the range measured the force is directly proportional to the area of the plates and inversely proportional to the fourth power of their separation.
As far as I know only a very limited number of experiments have been carried out over a very limited range of plate separations, so it is only possible to conclude that the force is inversely proportional to the fourth power of the plate separation for a very limited range of separations. It may be possible to show that, depending on the shape of the quantum fluctuation, the force may appear to be proportional to the inverse fourth power of the separation at one distance but proportional to some other ratio at a greater or smaller distance.
Whatever the magnitude of the Casimir effect, its very existence indicates that the 19th-century idea of the classical vacuum is fundamentally wrong.
Link to Scientific American article.
DEMONSTRATION OF THE CASIMIR FORCE IN THE 0.6 TO 6 µM RANGE. S. K. Lamoreaux in Physical Review Letters, Vol. 78, No. 1, pages 5--8; January 6, 1997.
Large scale Casimir effects
In the 8 June 1996 issue of New Scientist magazine an article entitled Physics unpicks a sailor's yarn, by Paul Guinnessy, reported on the phenomena noticed in the days of the square rigged sailing ships that, under certain sea conditions, ships lying close together would be mysteriously drawn together until there was a danger of their riggings clashing.
Dutch physicist, Sipko Boersma found that a rolling ship absorbs power from the waves and re-emits it as secondary waves from its hull. If the secondary waves radiated by two ships are out of phase they will cancel, reducing the wave energy between the ships. This is similar to the reduction in radiation energy between atoms or the plates used to measure the Casimir effect. The result is that the ships will be pushed together by the outside wave energy.