Book Review written for* Home Education Magazine*

Leonard Susskind and George Hrabovsky

The Theoretical Minimum

New York: Basic Books, 2013

238 pp.

Thanks to various findings such as the long-awaited Higgs Boson, and the award-winning television sitcom “Big Bang Theory,” key concepts in physics have acquired a coolness factor that launches them into the popular imagination with regular frequency. So it is great time for physicists to lecture and write for a public that is eager to understand more about forces, particles, energy, matter, light, dark, time and space.

The Theoretical Minimum was inspired by a Continuing Studies course that Leonard Susskind taught at Stanford University. He first taught the course feeling that it would be fun “for one academic quarter,” but kept teaching it after he found that, in contrast to undergraduates, night school students were lively and asked questions:

These students were there for only one reason: Not to get credit, not to get a degree, and not to be tested, but just to learn and indulge their curiosity.

It was one such student, George Hrabovsky, who suggested that Susskind “turn the lectures into a book,” and became its co-author.

The book begins with a simple explanation of spaces of states and systems, laying the groundwork for understanding basic concepts in physics. The opening chapter, called “The Nature of Classical Physics” takes us behind the scenes, to a law that governs neither matter nor energy but information – namely, the law of conservation of information.

From the next chapter, the book turns more mathematical. The nice thing is that the basic vector analysis, trigonometry and calculus needed for physics are introduced. However, although the book aims to help readers who are prepared to do more math than what most of the currently available body of popular physics literature involves, it may have gone too far and used much more math than required to explain physical concepts, and in the process lost some of the clarity one expects from science books.

There is also some confusion in the notations used in the book that may throw the uninitiated reader off-track. The subscript “i” is at first associated with the x, y, and z coordinates of a single particle. For example on page 39: “The three coordinates x, y, z are collectively denoted by x_i…” Later on, however, the same subscript “i” is used to identify a particle amongst several particles, rather than the coordinates. For example on page 87: “In this set of equations…..the force on the ‘i th’ particle…” On page 91 the confusion is even greater since the two different meanings of “i” are used one after the other on the same page. On that page the equation for momentum of the “i th” particle is “p_i = m_i v_i”, while the phase space is given by “x_i, p_i” where “i” refers to the x, y, z coordinates of a single particle.

Perhaps the book could have chosen to focus the mathematics on fewer things rather than apply it to a wide range of situations making the notations more complicated and confusing.

In comparison, Richard Feynman, known for The Feynman Lectures, uses vivid imagery and provides physical intuition to take his physics undergraduate student audience deep into the theoretical foundations of heat, energy, momentum and even quantum mechanical concepts. He uses mathematics to supplement his explanations, rather than as the basis of the arguments.

More recently, Brian Greene, Stephen Weinberg, Lawrence Krauss and others have written about the latest frontiers in physics for general audiences. What this book aims to do differently, is to include enough math to probe more deeply into the subject. As a concept, is is fair enough. But the execution leaves this reader wondering if it has indeed delivered on its promise, and more fundamentally, whether it could have done more with less.

**For students or for teachers?**

I had all but concluded that this book would be more useful for physicists and those eager to use the book to help them teach physics, rather than readers seeking to learn physics — until I found the lectures. Video recordings of the lectures from Professor Susskind’s course are available on this website: http://theoreticalminimum.com/courses/.

What you can understand from a live presentation is somewhat more and somewhat less than from a book that you read on your own. Each chapter of the book opens with a casual snippet of conversation between the co-authors, sometimes including a joke, which gave this reader the feeling that you had to be there.

In combination with the online lectures, The Theoretical Minimum provides the student who is proficient in algebra, trigonometry and calculus a thorough introduction to theoretical physics. Homeschoolers and other independent students looking for a path to approach theoretical physics may also wish to look at the guide that Gerard t’Hooft has published on his website: http://www.staff.science.uu.nl/~hooft101/theorist.html. Starting from basic mathematics it contains links to material that will help you learn what you need to know at each step of way towards theoretical physics. Though there may in many cases be better resources for learning the specific material on his outline, the very existence of the outline inspires confidence that we can work our way along the path. And *The Theoretical Minimum*, both the book and the lectures, are worthwhile stops along the way.

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