CYCLES OF TIME

Award-winning physicist Penrose (The Road to Reality: A Complete Guide to the Laws of the Universe, 2006, etc.) challenges current theoretical models of the Big Bang.

The author reprises the discovery of the Doppler shift by Edwin Hubble, which established the fact that our universe was expanding at an increasing rate, and he explains how this allowed astronomers to extrapolate backward to a moment approximately 14 billion years ago “when the matter of the universe would have to have been all together at its starting point.” In 1964, the observation of the cosmic background radiation allowed scientists to elaborate a detailed model of the evolution of the universe, beginning in the fraction of a second after an explosive Big Bang. Penrose points out that this picture is problematic because it appears to violate the Second Law of Thermodynamics. Except for minor violations, entropy—a measure of disorder—always increases over time. At the instant of the Big Bang, entropy would be extremely high, then energy would be decreased as the universe entered its expansionary phase, elementary particles formed and gravity kicked in. The author suggests that what is called the Big Bang was not an explosion but a transition point from an earlier cycle of the universe. To resolve this theoretical conundrum, he suggests that in the far-distant future, stars and galaxies will be compressed into tremendously massive black holes that will clump together and ultimately disappear leaving only cosmic radiation in their wake, after which a new expansionary cycle will begin. A controversial but intriguing theory that will challenge readers but is well worth the effort.