In this highly acclaimed book, first published in 2011, Adam Frank traces the changing perception of time and shows how man’s experience of time in social and cultural life shapes his understanding of the cosmos. Much of the discussion centers on the nature of the Big Bang and the supposed beginning of time, with astrophysicists arguing about numerous hidden dimensions and huge amounts of invisible “black matter” needed to satisfy their complex mathematical speculations. The Big Bang, which has long been part of popular scientific knowledge, is now being called into question. And perhaps most surprising of all to the lay reader is to discover that physicists are still preoccupied with the nature of time, to the point that some even doubt its existence.

Since their discovery, Newton’s laws, which treat time as a fourth dimension, have been applied so successfully that they guided the Apollo missions to the moon. Einstein had already shown that time varies with the speed of the observer, decreasing to zero at the speed of light, but the effect was negligible at the relatively modest speed of a Saturn rocket. The same cannot be said for astronomical bodies, galaxies and stars, which move much faster and at speeds at which the effect on time cannot be ignored. There is no doubt that the universe is expanding and, at an increasing rate, the still unanswered question is how did it all start? Is time tied to the physical dimensions of the universe, beginning at the same instant in the Big Bang, or does it have an independent existence? Was there a before of our present universe and will there be an after?

Some physicists reasoned that the Big Bang was just one of a series of repeating universes. Teachers used to tell their students that only one physical law was true: the second law of thermodynamics. This law, expressed simply as entropy tends to increase, implies that order will degenerate into disorder and temperature differences will disappear leaving everything at a uniform low temperature. When applied to the possibility of repeated cycles of expanding universes, the second law has the effect of increasing the duration of each successive cycle. Going back, the cycle length is reduced to zero, so, as Frank says, “entropy forces a start even for a cyclical universe.”

Despite much thought, manipulation of equations, and introduction of hidden dimensions, physicists have not been able to find a complete explanation for the beginning of the universe. Some theories suggest that multiple universes coexist, each with different physical laws, and that our universe has the right conditions to support life. That our universe exists is true, and that is the conclusion of Frank’s argument: “Always and again we have been the co-creators of a time and a cosmos that exist together with us.” For Frank, it is the process of discovery that does not matter its imagined end and is likely to continue for a long time.