knudsen (08/06/82)
I'm not sure whether empty space is "physically real" or not, BUT: it does have two well-known, precisely measured qualities: "mu", the magnetic permitivity of free space, and "epsilon" its electrostatic dielectric constant (which determines the capacitance between two metal plates in air, or more ideally in a vacuum). Both these natural constants show up in Maxwell's equations, I think. Now, of course, the philosophical debate: Are these constants properties that "belong" to space itself, or do they just "belong" to our universe, along with the speed of light and Planck's constant, etc? For that matter, does speed of light "belong" to space (Albert E. didn't hear me say that). --mike knudsen ihnss!knudsen