The Casimir effect

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.

Only toroidinos of a certain size (wave length) can exist between the plates. The formation of toroidinos outside the plates is unrestricted, resulting in a net force that pushes the plates together. This is the Casimir effect.

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.

Only conditions of practically no wind but with waves on the sea would result in the phenomenon occurring and then the force was so small that the ships could be pulled out of danger by rowing boats.

I had first hand experience of this in 1998, while waiting for our start in the sailing regatta for the New South Wales Hood championships on Sydney Harbour. We had conditions of no wind but a lot of waves caused by everything from power boat and ferry wakes to waves made by arriving and departing float planes. Much to the mirth of the rest of the crew, I made the prediction that, because of the conditions and the Casimir effect, the waiting boats would drift together. Within minutes that's exactly what had happened and we had to continually fend off from boats that literally drifted together into clusters. A firm push was enough to separate the boats but we'd soon drift into another cluster.

So it seems that the Casimir effect applies at levels from sub-nuclear to at least the human scale. I believe that future experiments will show that the Casimir effect operates at all levels from sub-nuclear to cosmological scales.

The Casimir effect causes the toroidinos to move towards the zone of highest concentration, and, therefore, the greatest restriction to the formation of toroidinos, which in this case is to the left of the drawing.