### The Overview

The convention in physics books written for lay audiences is to minimize the amount of mathematics directly presented on the page. The problem with this, of course, is that in the realm of theoretical physics especially, the language of discovery is mathematics. So trying to explain physics without bringing the math to the forefront is difficult for physicists ... and, frankly, a bit disingenuous. You really cannot do physics without these equations, so why not put the equations in the books?

This appears to be the view taken by Dr. Leonard Susskind in his new book, *The Theoretical Minimum: What You Need to Know to Start Doing Physics*. He eschews conventional wisdom and anecdotal discussions to get into the meat of the subject, walking non-physicist readers through a broad swath of conventional physics topics with mathematical rigor, so that any reader should be able to understand basic concepts like motion, energy (and the conservation of energy), momentum (and its conservation, as well), electric and magnetic forces, and even the motion of the planets can be basically understood. This book will not make the reader a physics expert, of course, but you'll gain a far deeper understanding of the way that physicists view the natural world and the laws that govern it.

So, if you're not intimidated by mathematics and really do want to understand the basis of physics, this book definitely will be good for you. If you're at all squeamish about dealing with equations, however, I'd recommend a different primer for you.

### The Good

I really enjoyed *The Theoretical Minimum*, because I've spent a long time reading books that avoid mathematics and try to present advanced theoretical physics topics from a very high, conceptual level. (I even wrote one.) This book doesn't suffer from that problem. It actually teaches people how physicists approach problems, complete with the mathematics that they use, such as vector mathematics, and it explains how that mathematics guides physicists to understand different physical situations.

I get e-mails all the time from people for whom a book like this would be perfect. They clearly have a strong mathematical background, but they just haven't ever taken a physics course and need to figure out a way to assimilate the information that physicists gain in the ordinary course of study. Many of the amateur physicists in the world could definitely benefit from exposure to this book. For those out there who *think* they understand physics, this will be a stark wake-up call and a challenge to add significantly more rigor to your scientific work.

Of particular interest to many readers should be the understanding of the Lagrangian, the Hamiltonian, and the Principle of Least Action ... concepts which are critical to understanding physics, but which are often overlooked in popular accounts of the subject.

### The Bad

The above having been said ... I do have serious reservations about this book. For anyone who is not comfortable with a fairly high level of mathematical discussion, I'm concerned that the book will be largely inscrutable. Susskind doesn't provide a lot of concrete physical examples about what's going on and the absence of diagrams of physical system is noticeable. For example, if you're going to discuss angular momentum, it's usually a good idea to have a diagram that shows the various forces acting on an object, just to give the mind something to anchor to. These sort of helping illustrations are typically missing from this book.

Overall, I felt that this wasn't so much a problem with the book as a problem with the billing for the book ... specifically the subtitle: "What You Need to Know to Start Doing Physics." It gives the impression that this is the sort of a book that a true novice could pick up and get up to speed on physics from. I just don't feel that it quite lives up to that billing. I rather suspect that if I'd picked this book up as a starry-eyed high-school graduate trying to figure out what field to study, it would have turned me off of science. It matches too much with the stereotype of physics - nothing but math - with very little of the cool conceptual stuff that tends to drive people into the sciences in the first place.

I would say that to really make sense of this book, a reader would need, at minimum, two years of college-level mathematics. Calculus and a year beyond calculus is preferred. So it's a great book for mathematicians and engineers who want a better physics foundation ... but for your average initiate, I wouldn't recommend it.

This is not the book that you want to hand to a high school student who is thinking that maybe they might want to go into physics ... it's the book that you hand to the college sophomore physics student who is still trying to figure out how all of the ideas from his first couple of years' worth of courses fit together.

### Notable Quotes

*One often learns that there are many forms of energy (kinetic, potential, heat, chemical, nuclear, ... ) and that the sum total of all of them is conserved. But when reduced to the motion of particles, classical physics really has only two forms of energy: kinetic and potential.*

*Aristotle's mistake was to think that a net "applied" force is needed to keep an object moving. The right idea is that one force--the applied force--is needed to overcome another force--the force of friction. An isolated object moving in free space, with no forces acting on it, requires nothing to keep it moving. In fact, it needs a force to stop it. This is the* law of inertia.