Note: This review is by my husband Jim.
Richard A. Muller is a professor of physics at the University of California, Berkeley. For years, he taught a course entitled “Physics for Future Presidents” to undergraduates. Much of that course was condensed into a highly regarded and favorably reviewed book of the same name.
Muller has employed his formidable explication skills in a new book, Now, subtitled, The Physics of Time. In it, he sets forth his theory of why time – the fourth dimension – flows, proceeds, or progresses inexorably into the future. The extremely elusive concept of NOW is how we perceive time. Early on, Muller refers to the concept of “now” as considered to be “indescribable.” He even reprises Supreme Court Justice Potter Stewart’s famous [to lawyers] bon mot: “I can’t define [it] . . . but I know it when I see it.” Stewart was trying to define “obscenity,” but his sentiment aptly characterizes most efforts to define time.
But Muller has a different concept of time that he wants to impart; however, before he does so, he wants to bring the reader “up to speed” with a crash course in modern physics. He then segues into his personal musings on the “timeless” philosophical mysteries that he thinks cannot be answered by physics.
The first 250 pages of the book might serve as a pretty decent undergraduate Physics 101 course for liberal arts majors who aren’t afraid of a little algebra. Most of it is very comprehensible, even to those with no affinity for math.
Muller begins by summarizing what physicists know about time before he speculates about the definition of and nature of now and why time seems to flow. Specifically, Muller argues that, contrary to what most physicists contend, the cause of the flow of time lies “not in the concept of entropy.”
Generally, entropy has been thought of as causing time to move in one direction only. Entropy is described by the Second Law of Thermodynamics, which states that, in the absence of outside forces, physical systems unavoidably evolve from more ordered states to less ordered states, not the other way around. Think of getting older (alas) or the shattering of a tea cup dropped on the floor. We do not get younger and broken tea cups do not reassemble themselves. Physicists characterize these phenomena as increases in entropy. From those facts, physicists concluded that the second law caused the motion of time in the direction of what is called “time’s arrow.”
Muller contends that physicists got the arrow of time explanation backwards, arguing that time’s ineluctable forward movement is the cause of the Second Law, not vice versa. In Muller’s view, time is a fourth dimension, expanding right along with the other three. Now is the leading edge of that expansion — the furthest extent of the dimension of time.
[As science writer Ethan Siegel explains, ordinarily, when we conceptualize how we can move through the Universe, we immediately think of three different directions. Left-or-right, forwards-or-backwards, and upwards-or-downwards: the three independent directions of a Cartesian grid. But time also describes a location: where you are right now, as opposed to an hour ago, yesterday or ten years from now. Thus time is also a dimension that we “move” through, the same as any of the spatial dimensions.]
But as indicated above, Now isn’t only about the physics of time. [Or even, about the physics aspect of the perception of time. Think of how “fast” time seems to move when you’re having fun, and how slow it seems to go when you are unhappy or sick, for example.]. I’m guessing that in Muller’s mind, his most important points are his thoughts about the incompleteness of physics vis-a-vis the big philosophical questions.
Muller attacks what he calls “physicalism,” a belief that science says all that can be said about knowing. Physicalism reaches its extreme when it asserts that all non-quantifiable assertions are illusions.
About free will (a preoccupation of physics because of its inviolable laws), he states: “We can’t conclude that free will exists, but we can conclude that nothing in science rules it out.”
Muller ends with some musings about the human soul and personal responsibility. In his sixth, and final, appendix, he cites several quotations from leading physicists expressing their personal beliefs in God.
Evaluation: Now can be viewed as two books in one. The first is an adept presentation of issues in modern physics dealing with the notion of time. Muller’s writing is comprehensible for the nonphysicist-lay-mathphobe, and in the Appendix he includes real equations (quite a lot of them) for the adventurous who seek a deeper understanding. This first “book” is exceptionally well done and pretty much incontrovertible.
The second is more controversial. Muller is highly critical of physicalism, and he argues that physics is an incomplete way of knowing. Although he is careful not to espouse any religious beliefs in the main body of the book, he sets forth his own semi-religious beliefs, a mild sort of deism, in the final Appendix. I preferred the first half of the book to the second, but nonetheless the book was good enough to pique my interest in reading Muller’s Physics for Future Presidents.
Published by W.W. Norton & Company, 2016