Cycles of time

Roger Penrose claims to have found evidence in the Cosmic Microwave Background (CMB) radiation to support his iconoclastic theory of Conformally Cyclic Cosmology.

To recall, Penrose claims that the universe consists of an endless chain of aeons. It is claimed that each aeon begins and ends with a population of massless particles, and because such particles are unable to provide physical standards of length and time, the apparently hot and dense manner in which our universe began, can be identified with the cold and rarefied manner with which the previous aeon ended.

Penrose claims, however, that the gravitational radiation emitted by the collision of supermassive black holes towards the end of one aeon, leave an imprint on the CMB of the next. The CMB radiation is characterised by a temperature distribution over a fixed two-dimensional sphere, and the pulse of gravitational radiation emitted by a black hole collision can be thought of as an expanding spherical shell, which intersects the CMB surface along a circle. The variation in the temperature of the CMB along such a circle would be less than that of a random distribution, and working with Vahe Gurzadyan, Penrose claims to have found just such low-variance circles in the CMB.

A more leisurely explanation of Penrose's theory, and its observational consequences, can be found in his excellent recent publication, Cycles of time. As ever, Penrose is an engaging writer, and his hand-drawn diagrams are simply exquisite. The one qualification to mark, however, is that Penrose expects a level of mathematical readiness from his audience that many readers will be unable to supply. Banished from the pages of magazines such as Scientific American and New Scientist, there are things called equations in this book. The intelligent, non-specialist reader will be able to discern their meaning from context, but there are gaps in the exposition which those without a prior knowledge of relativity and cosmology will be unable to fill.