I saw a panel discussion about time from the World Science Festival on YouTube. The panel was composed of several physicists and a few other people. One of the non-physicists was so disturbed by the fact that neither the math nor the physics requires that time pass in a single direction that he made up a whole different version of math that does require that time flows in one direction. While I admire the effort, it seems to me that when the science disagrees with our intuition we should abandon our intuition rather than come up with a science that does agree. Humans evolved in order to survive and reproduce, not in order to grasp the microscopic details of the universe.

This book presents the current physics of time in a way that lay people can understand, which is good because the science of time is radically different from how we perceive it. While we perceive time as flowing in one direction, in physics equations work the same regardless of which direction time flows in. While we assume that time flows at a constant speed everywhere in physics time is only consistent locally. In short, the way we perceive time seems to be an illusion created by our brains. The only real factor that determines which direction time flows in is the transfer of heat and increasing entropy.

This was an amazing, if brief, book that provides a clear and understandable overview of what we actually know about time, and I am thankful to Mr Rovelli for having written it.