Are you one of those people who enjoyed science at school or college, but ended up with a different career, still wondering what makes the Universe tick? Maybe you subscribe to Scientific American, follow news stories about black holes, and read reviews of science books in WSJ without quite finding enough meat to satisfy you. If so, The Theoretical Minimum is the book for you. The subtitle “what you need to know to start doing physics” sets out the authors’ stall, and the “minimum” referred to in the title is the minimum amount of knowledge you need about classical physics (that is, everything except quantum mechanics) to proceed to “the next level”, which would be freshman physics at university.
Leonard Susskind is a Professor of Physics at Stanford University, and more widely known as the author of The Black Hole War and The Cosmic Landscape. George Hrabovsky got sidetracked from a possible career in science, but even without a science degree ended up running a technological research center, Madison Area Science and Technology.
Their book grew out of a course taught by Dr Susskind at Stanford University, for local people in what he calls “the nonacademic community”. He found that these students, eager to learn but with no need to worry about grades or exams, wanted “the real thing -- with equations”. And he gave it to them. But don’t be scared by that word “equations”. If you understand stock market derivatives or futures trading there is nothing here to worry about -- provided you start at the beginning and follow the story methodically.
That is where Susskind, aided by Hrabovsky, is so good. Their relationship began when Hrabovsky viewed Susskind’s lectures online, and sent Susskind an email suggesting that the course should be turned into a book. The resulting collaboration between master and pupil follows the structure of the lectures themselves, and is perfect for getting the message across. The beginning is disarmingly simple. It doesn’t start with anything as complicated as a coin toss, but with a coin glued to the table so that it always shows the same face uppermost. What could be simpler? But by the end, the committed reader will be familiar with Maxwell’s equations of electricity and magnetism, and have a thorough understanding of the force of gravity and its influence on planetary orbits, the work for which Isaac Newton is justly famous. Along the way you get beautifully clear explanations of famously “difficult” things like differential and integral calculus, what physicists mean by symmetries, and conservation laws. In spite of the emphasis here on classical physics, this actually takes the reader to the edge of an introduction to quantum mechanics; we can only hope that this will be the theme of the team’s next book.
More subtly, along the way the authors expound what might be called the philosophy of science, making it clear why physics contains deep truths about the Universe. The job of classical mechanics, they say, “is to predict the future,” which it does with far more success than alternatives such as astrology or the I Ching. They explain what scientists mean by terms such as “system” and “reversibility”, and are not afraid to spell out the limits of precision. Even if some of the equations do pass over the heads of some readers, this is a powerful exposition of why science is “real”, and a counter to the kind of wishful thinking employed by people who, for whatever reason, reject the scientific world view.
At the heart of this book, both physically and metaphorically, is the principle of least action, the most important idea in physics. It can be summed up in the phrase “the Universe is lazy”, and among many other things, the principle underpins the reason why light moves in straight lines, and how light “knows” which angle to turn through when it moves from one medium (such as air) to another (such as glass). It can be used to describe the parabola followed by a thrown baseball, and indeed, to derive Newton’s laws. If I had my way, all of physics would be taught starting with the principle of least action and working outwards from there; The Theoretical Minimum comes close to realising my dream.
Which brings me to the audience for the book. It most definitely hits the spot for the kind of mature, committed “nonacademic” that the authors have in mind. Equally, it is certainly not for the dilettante science watcher happy with the kind of “pop science” accounts” that deal as far as possible in words and images without worrying about the equations -- not that I am knocking that kind of book; I write them myself. But it is also just the right book for a much younger audience than the mature people with careers behind them who filled the classes at Stanford. It is spot on for any young student of science to read up before heading off to university to study physics seriously, and I shall certainly be recommending it in that connection. It should also be required reading for our politicians and lawmakers -- but that is probably hoping for too much.
This review first appeared in a slightly different form in the Wall Street Journal.