The Cosmic Cookbook entry for an inflationary universe, on the other hand, looks as simple as meringue. In this case, the natural starting time would be the onset of inflation -- just a fraction of a second after the Big Bang. In contrast to the standard big bang recipe, the inflationary version calls for only a single ingredient: a region of false vacuum (see "The False Vacuum," page 56). And the region need not be very large. A patch of false vacuum 10-26 centimeter across might be all the recipe demands. While the mass required for the previous recipe was 1032 solar masses, the mass in this case is only an ounce: about the mass of a slice of bread. So, in the inflationary theory the universe evolves from essentially nothing at all, which is why I frequently refer to it as the ultimate free lunch. Does this mean that the laws of physics truly enable us to create a new universe at will? If we tried to carry out this recipe, unfortunately, we would immediately encounter an annoying snag: Because a sphere of false vacuum 10[sup -26] centimeter across has a mass of one ounce, its density is a phenomenal 10[sup 80] grams per cubic centimeter. For comparison, the density of water is 1 gram per cubic centimeter, and even the density of an atomic nucleus is only 10[sup 15] grams per cubic centimeter. If the mass of the entire observed universe were compressed to false-vacuum density, it would fit in a volume smaller than an atom. The mass density of a false vacuum is not only beyond the range of present technology, it is beyond the range of any conceivable technology. As a practical matter, therefore, I would not recommend buying stock in a company that intends to market do-it-yourself universe kits. Nevertheless, I will dismiss the gargantuan mass density of the false vacuum as a mere engineering problem, boldly assuming that some civilization in the distant, unforeseeable future will be capable of creating such densities.