Do you, for example, think the past exists, but the future doesn’t? Perhaps, if pressed, you might say the present is real, but the past is gone and the future is yet to come. Or maybe, like Albert Einstein, you think all moments are equally real and we simply move through them.
If pondering such deep questions is your kind of thing, then physicist and broadcaster Jim Al-Khalili’s latest book might be for you. A word of warning, though. On Time: The physics that makes the universe tick (UK | US) is a book you should read if you want to understand more or less everything there is to know about time.
But if you just want to dip your toe into the subject, then there are easier places to start. Al-Khalili begins with a rundown of the many interwoven strands that thinking about time involves, separating them into two categories. First, there are the problems of manifest time, or time as we experience it.
These include questions like: why do we feel time flowing, why does that flow feel continuous like a river, and what exactly is the difference between the past and the future? Second, we have the problems of physical time, which are to do with the different ways various fields of physics interpret time and the efforts to resolve the tensions these produce. For instance, some equations in physics treat time as a label, writes Al-Khalili, while Einstein’s general theory of relativity tells us it is a dimension, and thermodynamics paints it as an arrow.
So, what is time, really? How do we reconcile all these contradictory views? And can the problems of physical time help us with the problems of manifest time?
General relativity tells us time is a dimension, and thermodynamics paints it as an arrow. I found the early part of the book that disentangles these questions supremely helpful. As a New Scientist editor, I have read plenty about the mysteries of time in my, er, time, but Al-Khalili sets it all out with great skill and clarity.
Extract — continue reading at the source.
