Book Reviewed: Time Reborn: From the Crisis in Physics to the Future of the Universe by Lee Smolin

The cosmic evolution In this book, physicist Lee Smolin argues that time is a real phenomenon, and suggests that the laws of physics evolved over cosmic timescale, and the current laws came into existence because of cosmological natural selection like biological evolution. One of the principal reason is that this theory avoids the use of anthropic principle which claims that the universe came into existence with current laws that support living systems, but for Lee Smolin, since this idea is not scientifically falsifiable, therefore that it is not scientific. The book is philosophical than physics since it lacks scientific explanations as to why cosmos was born with different laws than we have at present. There are no scientific explanations except for ideas of an imaginative thinker. There is a conflict between relativity and quantum mechanics with regards to the concept of time. It is measured and malleable in relativity but remains as background (and not an observable) in quantum mechanics. Time emerges mainly from the second law of thermodynamics, a law that is statistical in nature which does not depend on the nature of individual particles but the behavior of a collection of particles. Time is not an irreducible element or concept required to construct physical reality. It is a human construct that differentiates present from our memories of the past. According to Einstein’s theory of relativity is that there is no absolute time, no absolute space, but everything is relative. This is a block universe, made of four-dimensional space-time (three space and one-time dimensions) structure where time is like space, in that every event has its own coordinates, or address, in spacetime. The malleability of space and time mean that two events occurring far apart might even happen in one order when viewed by one observer, and in the opposite order when viewed by another. Hence, time change really is an illusion according to relativity because there's nothing that's changing; it's all there, past, present, and future. But the laws of quantum physics are symmetric and reversible, hence that time could have moved in a backward direction or in the forward direction. For example, according to the ‘big crunch’ theory, the universe is expanding since its birth, but at some time in future it will stop expanding and starts contracting back in on itself. This will require time to flow backwards, and the cosmos will collapse into a big crunch into its initial state when big bang happened. Physicists like Sean Carroll, Andreas Albrecht, and John Polkinghorne believes that the flow and direction of time are real but do not claim that it permits the evolution of laws of nature over time. But physicists like Julian Barbour, Max Tegmark, Carlo Rovelli, and philosopher J. M. E. McTaggart are strong proponents of time being an illusion. Lee Smolin considers that space is an illusion and only time is real and paramount to the way the universe evolved to its current state.