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It’s ridiculous to attempt to lay out the conceptualization of time throughout recorded thought, to present a primer on the physics (including but not limited to quantum theory and a large part of Einstein’s career) behind theories of time, and to give an account of the ways one’s thoughts on time evolve throughout a career in physics and relate to personal achievements. But this is what Muller attempts, and though it’s an admirable project, it rather predictably fails in thoroughness.
His thinking style is engaging, but his writing does not keep up with his rapid-fire jumps from topic to topic. His summaries of complex quantum theory for pedestrian non-physicist rubes like myself are obviously well-intentioned, but didn’t quite do the trick for me; all the same I appreciated the intention to explain rather than dismiss material as too complex for the common audience. I’d agree with other reviewers that his actual addressing of the topic of “Now,” postponed until the last 6 pages of the book, was inadequate.
The most significant part of the book, the idea on which he built his ideas of experiencing “now,” was the work he had done at Berkeley. He observed precisely identical particles behaving differently, and deduced that because statistical and quantum physics cannot predict different behaviors for identical particles, they cannot predict the full future, and free will is therefore possible. His history of the philosophical and scientific analyses of time were interesting, and could have been expanded into an interesting book in their own right. This also would’ve provided a more solid foundation for the last two chapters, which explain his personal views on free will, which seemed a bit out of place after several hundred pages on specific physics theories. ( )

Interesting up until the point where it goes all whiny about how free will must exist because we really want it to exist. Have you considered the alternative of not believing in it and yet acting as if you believed in it? Because it works for many other problems where something isn't true which we wish it was. Like living forever, life being fair etc.. Just because you want it so doesn't make it so but you can still act as if it did. In fact it's advantageous to do so. ( )

Now: The Physics of Time is quite thorough in its scope. Written by Richard A. Muller, the book discusses his personal theories of why time possesses a direction. The question is harder than it seems at first since you must define all of your terms. For instance, what is the past? Why do we remember what has happened rather than what has not happened? This might seem elementary, but it almost requires a tautology to explain. We don’t remember what hasn’t happened because it hasn’t happened yet.

Along the way, Muller talks about Relativity and Quantum Physics. Einstein thought of something we take for granted, namely time and simultaneity and threw that notion out the window. According to Relativity, there is no such thing as a universal frame of reference that allows for two events to occur simultaneously under all reference frames. Einstein even had to explain what he meant by “Now,” but he found that difficult as well. How do you explain the concept of Now and not sound like you are talking to a five-year-old?

In the main portions of the arguments Muller makes, he points out that a lion’s share of physics contains equations that don’t have a preferred direction in time. You may say that time plays a role in the equations and I would not argue with you there, but think of simple mechanics. If you throw a baseball from the top of a tall building, aren’t there technically two solutions? One doesn’t make sense only because of the frame of the problem. We don’t accept negative time. Many physicists argue that this is because Time is an intrinsic quality of the universe and point to the idea of entropy and how it can only increase.

Entropy for those of you not in the know is a concept that I am only familiar with because I read a few books on Statistical Mechanics and Thermodynamics. Even so, I don’t entirely get the idea of Entropy, so I will turn to a dictionary definition. In Thermodynamics, Entropy is a quantity representing the unavailability of a system’s thermal energy for conversion into mechanical work. Basically, you take gasoline and use it to run an engine. You get waste products from that simple combustion that equal the masses of the gasoline and oxygen put into the system. This is the first law of thermodynamics. The second law states that the process of this is irreversible. Things tend toward disorder and chaos. So many physicists point this out and use this to say that this is why time has an arrow.

Professor Muller disagrees though. He comes up with some alternative theories and tells us that Entropy does not determine the arrow of time, it is the other way around. Muller then begins to discuss ideas outside of science, which I found to be fascinating. I have heard of a lot of these arguments before, so none of it was really new to me. Take the idea of teleportation. There is nothing in physics to rule it out as a possibility, but doing so would destroy your original body. Even our perceptions are beyond the realm of physics. Muller illustrates this by talking about how people perceive the color blue. Is my blue your blue? To be more convoluted and precise, is my perception of the color blue the same as yours? It is a question that goes beyond physics. It is like “What is it like to be a bat?” We don’t know how our perceptions would change as a bat. I mean, you can think about what it would be like to have echolocation and fly around eating mosquitoes and other insects but that isn’t the same as having a Chiropteran brain.

The final part of the book is a set of six appendices that add to the background of the theories and ideas. The book is really quite enjoyable and interesting, at least to me. I don’t know if it is right or wrong, but the idea is rather compelling. ( )

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 “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.

Muller, on the other hand, has a definite concept of time that he wants to impart; but 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 concept of free will, intertwined with the laws of 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. However, he occasionally inserts sentences like:

"Energy is the canonically conserved quantity corresponding to the absence of explicit time dependence in the Lagrangian."

and

"Entropy is the logarithm of the number of quantum states accessible to a system."

Well, if you already knew that, you can probably skip much of the first two thirds of the book.

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. Spoiler Alert! Muller argues that the cause of the flow of time lies “not in the concept of entropy, but in the physics of cosmology.” [Entropy is a property of physical systems. It is often calibrated in joules per Kelvin, that is, energy divided by temperature. It is a measure of the extent of disorder of the system.]

The concept of time permeates classical physics in subtle ways. For example, Emmy Noether proved that the law of the conservation of energy could be derived from the principle of time invariance. Emmy Noether was a German female mathematician known for her landmark contributions to abstract algebra and theoretical physics. Time invariance means the laws of physics don’t change with time. But then Einstein (who referred to Noether as one of the most significant and creative mathematicians of all time) showed that time itself varies with relative velocity.

Einstein’s special and general theories of relativity imply many counterintuitive aspects of time without explicitly defining it. The first startling idea from the special theory of relativity is that not just velocity, but time itself, depends on the reference frame. Observers in relative motion perceive time differently, but they agree on how it would be perceived in the other’s reference frame.

Muller provides the most lucid explanation of the famous Twin Paradox that I have ever seen. Why does Twin #1, Mary, who takes off in rocket and travels at very high speed, age more slowly and return to earth at a younger age than Twin #2, John, who remains on earth? After all, both were moving at high speed relative to one another? The flippant answer often given is that Mary had to accelerate (change speed) to return to earth. I never understood why that mattered until I saw Muller’s answer (provided in the Appendix) that actually does the math and provides an insightful graph showing how the two actually age at different rates.

A key transition takes place when Mary must stop and turn around to return to earth. While she has stopped (even if only instantaneously), her reference frame makes a discrete jump and becomes the same reference frame as that of John because the two of them are no longer in relative motion. So, if one has been traveling at great speed and suddenly stops, her proper time frame jumps to a different reference frame and so does the time of a distant event, namely what is happening back on earth!

Unfortunately, Einstein failed to account for the fact that time moves. Arthur Eddington observed that the second law of thermodynamics was the only principle of physics that operates in only one direction of time. Under the second law, in the absences of outside forces, physical systems unavoidably evolve from less probable (more ordered) states to more probable (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, Eddington concluded that the second law caused the motion of time in the direction of what is called “time’s arrow.”

But Muller thinks Eddington got things backward — Muller argues that time’s ineluctable forward movement is the cause of the Second Law, not vice versa. He points out that Eddington’s “theory” makes no predictions that would make it falsifiable. It merely explains. Moreover, Muller contends that if increasing entropy caused the direction of time, shouldn’t the rate of time passage change locally when there is a local decrease in entropy, as when the entropy of the Earth’s surface decreases at night?

Muller’s concept of time fits in nicely with modern cosmology and the Big Bang theory. Astronomers infer from the red shift in starlight that galaxies are all moving rapidly apart, the greater the distance, the more rapid the velocity difference. The observable universe is expanding. In the standard formulation of Einstein’s general relativity and the Big Bang theory, the galaxies are not so much moving through pre-existing space as the three dimensions of space itself are expanding. 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.

Muller also discusses some of the counterintuitive aspects of quantum physics, not so much because of their relevance to the physics of time but because they affect other issues he raises later in the book. He describes the wave function that characterizes atomic particles as “ghostlike.” He says the wave function of an electron:

"…isn’t really the electron. It is the amplitude, the spirit of the electron, its apparition, its soul."

[Muller likes the concept of souls. He employs it later in his discussion of free will.]

In what was a revelation to me, he also shows that Heisenberg’s uncertainty principle follows from the fact that particles display wave-like properties:

"Virtually all waves will have some uncertainty in both their velocity and their position….The math of the Heisenberg uncertainty principle follows exactly the math of classical waves….The mathematical statement of Heisenberg’s principle…is identical (except for the multiplication by Planck’s constant h) to the equation that describes classical waves, including water waves, sound waves, and radio waves."

Despite its title (and subtitle), Now isn’t only about the physics of time. I’m guessing that in Muller’s mind, his most important points are his thoughts about free will and the incompleteness of physics. He agrees with Immanuel Kant, of whom he says:

"[Kant] felt that he had nonphysics knowledge, true knowledge, of ethics and morality and virtue. Given his certainty of this knowledge, free will must indeed exist….But it would take advances in physics, particularly in understanding its quantum aspects, to see the true compatibility between physics and Kant’s thoughts on free will."

As an example of an issue beyond physics, he asks, “What does blue look like?”

Muller attacks what he calls “physicalism,” a belief that science says all that can be said. Physicalism reaches its extreme when it asserts that all nonquantifiable assertions are illusions. He takes on deterministic philosophers and atheists like Richard Dawkins:

"Dawkins makes a fundamental error in his unstated but implicit postulate that logic requires us to ignore nonphysics reality."

After discussing the uncertainty principle in quantum physics, Mueller says:

"The philosophers’ key assumption that the past completely determines the future is not supported in modern physics. Their arguments that free will does not exist were based on a false premise. We can’t conclude that free will exists, but we can conclude that nothing in science rules it out."

Muller proposes his own test to determine whether free will exists:

"If humans always follow the laws of probability, then free will does not exist. If humans regularly do highly improbably things, things that are not predictable based on external influences, then such behavior constitutes free will."

As a physicist, Muller perceives improbable acts as decreasing entropy, at least locally. As you can imagine, he argues forcefully in favor of free will. You may ask, “What does all this have to do with the physics of time?” My guess is that Muller might answer that the importance of now is that it:

"…is the only moment when we can exercise influence, the only moment when we can direct the increase the increase in entropy away from ourselves so that we can orchestrate local entropy to decrease."

Muller concludes with some musings about the human soul, free will, and personal responsibility. As he says, “Free will can be use to break a teacup or to make a new one. It can be used to start a war, or to seek peace.” 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 a lucid 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 incomplete in the way Gödel showed us all logical systems were incomplete. 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 wasn’t offended by his statement of belief, but I wonder what it has to do with the physics of time, besides perhaps motivating an interest in answering the big questions about existence. Nonetheless, this book was good enough to pique my interest in reading Muller’s Physics for Future Presidents.

(JAB) ( )