Cosmic Considerations

Abstract

The significance of reduction to initial state and evolution for the Universe as a whole is considered. Since we have access to only a single universe, that reduction is problematic. How symmetry of the laws of nature might fit into the picture is considered as well. Symmetry of the Universe is discussed, with the conclusions that the Universe as a whole cannot possess exact symmetry, and for the Universe as a whole, undifferentiability of degrees of freedom means their physical identity. A discussion of big-bang cosmological schemes that have the Universe evolve through a number of eras, starting with a “quantum era,” leads to these conclusions: (1) Cosmological schemes cannot involve perfect symmetry for the Universe as a whole. (2) Cosmological schemes cannot involve fundamentally undifferentiable, yet still somehow different, degrees of freedom of the Universe. (3) Cosmological schemes with phase transitions between eras cannot involve symmetry breaking. (4) High-energy physics cannot be expected to reflect precisely the situation that prevailed during earlier cosmic eras that evolved into the present era via phase transitions, although it might be indicative. Specifically, any symmetry emerging at high energies cannot have been a feature of such earlier eras. However, if the evolution of the Universe occurred in a continuous manner, instead of via (discontinuous) phase transitions, then an approximate symmetry for the Universe in some era could have worsened in a later era, and high-energy physics in our era might indeed reveal the situations that prevailed in earlier cosmic eras. Finally, the chapter speculates on the nature of the quantum era that presumably served as the first in the sequence of eras forming the evolution of the Universe and considers what The Beginning of that evolution could have been.