ABSTRACT
In this Chapter we will discuss some of the most interesting, profound, and topical speculations about the earliest moments of the Universe: those concerning the Planck epoch, t ≲ 10–43 sec. Up to this point our discussion of the very early Universe (t ≪ 10–2 sec) has been based upon highly speculative, but nevertheless well formulated, ideas about the nature of the fundamental interactions at energies well beyond 1 TeV. For instance, the existence of a grand unified theory of the strong and electroweak interactions is speculation, but the construction of a spontaneously broken, Yang-Mills gauge theory based upon a specific gauge group is well understood. In contrast to our discussions of the post-Planck epoch, even the most promising ideas about the Planck epoch are based upon ideas that have yet to reach the stage of being well formulated theories. Because the underlying physics is still cloudy, it is not clear how (or even whether) one should approach the Planck time. In spite of the fact that the physics is not well formulated, we will attempt to give the reader a taste for some of the most exciting and potentially important research being pursued at present. The reader should understand that we are fishing in murky waters, and that the ideas we shall discuss here are both highly speculative and not yet unambiguously formulated. The faint-hearted reader may wish to skip to the Finale.
