As we mentioned earlier, our efforts to penetrate the Planck epoch are currently hampered by physicists' ignorance of how to incorporate the force of gravity into GUTs. No one has yet invented a "SuperGUT" that merges gravity and the grand unified force into a single, truly fundamental force at the energies characterizing the earliest part of the Planck epoch, although this is an area of very active research.

Many researchers feel that once we have in hand the proper description of quantum gravity, our understanding may automatically include a natural description of creation itself. It is even conceivable that the primal energy that formed the universe originally emerged from literally nothing. Even in a perfect vacuum—a region of space containing neither matter nor energy—virtual particle–antiparticle pairs are constantly appearing and disappearing within a time span too short to observe, causing natural quantum fluctuations to occur in empty space. We might be living in a sort of "self-creating universe" that erupted into existence spontaneously from just such a random quantum fluctuation! This sort of "statistical" creation of the primal cosmic energy from absolutely nothing has been dubbed "the ultimate free lunch."

Whether or not this scenario proves to be the correct description of the birth of the universe, it suggests a possible explanation for the original density fluctuations that eventually grew into today's large-scale structure. They might have been microscopic quantum fluctuations that existed naturally in the universe during the GUT epoch, then grew to macroscopic size during the inflationary epoch. The fluctuations predicted by this idea agree quite well with the requirements of several cold-dark-matter models.

If this view is correct, then our Galaxy, the Sun, Earth, even life itself, are direct consequences of a series of random events that occurred during an unimaginably short period of time some 10–15 billion years ago. Of course, these ideas are very speculative. In the strict sense, they are not really science at all, as they violate one of the central tenets of the scientific method: they are practically impossible to test experimentally. Still, whether or not you find them philosophically acceptable or intellectually pleasing, they do illustrate just how far the scope of physics and astronomy has expanded in the twentieth century. Astronomy is a subject that links the very big and the very small. Nowhere is that more evident than in our study of the most important question of all—the origin of the universe.