The density of the firmament relates to several fundamental physical constants. For our purposes it will suffice to write down the density of the firmament, D, in terms of these physical constants:
where
In these equations h is 1.054573 x 10-27 erg-sec (Planck's constant), c is the speed of light, and G is the gravitational constant. L is the Planck length (1.62 x 10-33 cm) which is the size of the grains which make up the firmament (heretofore called Planck particles). Finally, D, the Planck density, is 3.6 x 1093 gm/cm3.
For several decades the Planck particles have been regarded as nothing more than fluctuations in a vacuum caused by the Heisenberg uncertainty principle. These particles were believed to pop into existence, exist for about 5.39 x 10-44 seconds, and then vanish back out of existence only to pop up again a brief instant later. Because of this, some have looked to this medium as an explanation of the origin of the big-bang, assuming that the latter started at that density. Furthermore, there is nothing vacuous about the firmament, and so it is more reasonable to conclude that it is a pervasive medium which, on nuclear scales, the universe can only suspect but of whose existence it can never be certain. This, then, is the firmament. This is also the view of Roger Penrose.
Notes and References
Note 4
J. A. Wheeler and C.M. Patton, 1977. "Is Physics Legislated by Cosmogony?" in R. Duncan and M. Weston-Smith, eds., The Encyclopedia of Ignorance. (Elmsford: Pergamon Press), pp. 19-35.