Change The Game COOKING UP A COSMOS Will our descendants create a universe in a laboratory? YOU DON’T HAVE TO BE A MASTER CHEF TO MAKE meringue. Simply combine egg whites and sugar in a large bowl and beat vigorously until the mixture is light and fluffy. Spread in a pan and put in an oven preheated to 300 degrees F. Bake for 40 to 45 minutes and voile! Could it be just as easy to make a universe? Since the big bang theory implies that the entire observed universe can evolve from a tiny speck, it’s tempting to ask whether a universe can in principle be created in a laboratory. Given what we know of the laws of physics, would it be possible for an extraordinarily advanced civilization to create new universes at will? The first thing to think about is the list of necessary ingredients. Curiously, scientific theories continue to offer an enormous range of answers to the question of what the universe was made from. One of the most dramatic differences between the standard big bang theory (without inflation) and the inflationary universe theory is the answer that each gives to this fundamental question.
If the recipe for the standard big bang universe were written in a Cosmic Cookbook, how would it read? To begin the universe at an age of one second, the ingredient list would include 10[sup 89] photons, 10[sup 89] electrons, 10[sup 89] positrons, 10[sup 89] neutrinos, 10[sup 89] antineutrinos, 10[sup 79] protons, and 10[sup 79] neutrons. The ingredients should be stirred vigorously to produce a uniform batter, which should then be heated to a temperature of 10[sup 10] kelvins. After heating, the total mass/energy of the mix would be about 10[sup 65] grams, or 10[sup 32] solar masses. This number, by the way, is about 10 billion times larger than the total mass in the visible universe today. So, to produce a universe by the standard big-bang description, one must start with the energy of 10 billion universes! Since a chefs first task is to assemble the ingredients, this recipe looks formidable enough to discourage anybody.
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. Is it possible, given what we know of the laws of physics, that someday our descendants might produce new universes by slicing pieces of false vacuum? On the darker side, does the physics of the false vacuum create the possibility of an ultimate doomsday machine? Is our universe imperiled by the threat that a super-advanced civilization in some remote galaxy might create a cancerous patch of false vacuum that would engulf us all? The first step in trying to fabricate a laboratory universe is to create a patch of false vacuum. How exactly this can be achieved depends on the details of physics at extremely high levels of energy (more than a trillion times higher than modern particle accelerators), which at present we have no way of knowing. This part of the problem, therefore, will be left for our descendants to solve. At present, we can say that our current theories offer several possibilities. In many theories, the desired false vacuum can be created by heating a region of space to enormous temperatures (perhaps 10[sup 29] kelvins), and then rapidly cooling it.
The region would then supercool into the false vacuum, exactly as we imagine that the early universe may have done. Once a patch of false vacuum is created, its evolution does not depend on how it was created. The false vacuum is characterized by having a huge energy density and a huge but negative pressure. Through the equations of general relativity, these properties alone determine how space-time is distorted by a region of false vacuum. Because the false vacuum creates a strong gravitational repulsion, we expect that the region of false vacuum will grow. However, if the false vacuum bubble wall is to move outward, there must be a force pushing it that way. The pressure outside the bubble is zero, and the pressure inside is negative. The pressure is therefore higher outside than inside, so the pressure difference will push inward on the bubble wall.
One might guess that the gravitational repulsion of the false vacuum would push outward on the bubble wall, so if this repulsion were strong enough, the bubble would start to grow. Not so, however, say the equations of general relativity. The gravitational repulsion causes the false vacuum to swell, but the repulsion does not extend beyond the false vacuum. Objects outside the bubble wall are attracted toward the bubble, and the gravitational force on the bubble wall is inward. Because bot …