Does the physical vacuum produce a pressure that can be measured?

Yes.

The effect was observed in the curious behavior of the van der Waals inter-atomic force by Hendrick Casimir and Dik Polder in 1948 and is called the quantum 'Casimir Effect'. Later, they realized that this effect could also be directly observed when you put two parallel conducting plates about 1 micron apart inside a vacuum vessel: a weak attractive force is produced.

Recently, physicist Steven Lamoreaux of Los Alamos national Labs ( see Science, 10 January 1997 page 158) performed this very delicate experiment using state of the art sensors and not only confirmed that this vacuum force does exist but that its strength and behavior with plate separation matches the predictions of quantum electrodynamics to better than 5 percent. The infinite zero-point energy of the vacuum outside the plates overpowers the infinite but slightly smaller vacuum energy between the plates, and forces them together. Between the 1-micron plates, a force of 1 billionth of a Newton was detected.

The measurement of this effect only confirms that at the quantum scale, the universe is a very strange place. When the universe itself was 'as large as an atom' this Casimir Effect operating in the vacuum may have had many other spectacular effects, and supports the idea that something like an Inflationary Phase may have happened.


Copyright 1997 Dr. Sten Odenwald

Return to Ask the Astronomer.