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

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.

In 1997, 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 second measurement was produced by Mohideen & Roy in 1998. The method used in this instance was somewhat different to that used by Lamoreaux, and has been much repeated in measurements carried out after 1998. This experiment (shown above) also used a sphere/plate setup, but the sphere was a 200 micron gold plated polystyrene ball, mounted on the tip of a cantilever.

A very precise measurement of this 'vacuum force' was made in 2013 and the graph above shows the strength of this force as you increase the separation beteen the plates. This recent study, published online on Sept. 27 in the Nature Communications, breaks new ground in the standard measurements of the Casimir effect known to scientists. The experiment used nanostructured (micro-ridged) metallic plates to suppress the force to a much lower rate than ever recorded previously, said Ricardo Decca, Ph.D., professor of physics at IUPUI. Read more at: https://phys.org/news/2013-10-casimir-lowest.html#jCp

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.