Of all the souls made famous by YouTube — Justin Bieber, those wedding entrance dancers, that guy who loses his mind while videotaping a double-rainbow — none is more deserving than MIT physics professor Walter Lewin. Lewin taught introductory physics at the university for more than three decades, and his lectures were intense, elegant, and perfectly orchestrated tributes to the harmonies of the physical world.
Lewin is 6 feet 2, silver-haired, and speaks with a Dutch accent. In the videos of his lectures he lopes energetically in front of his chalkboards and makes pronouncements like “Now, I’m going blow your minds!” You can watch him shoot bullets through paint cans, ride a bike with a rocket attached to the back, or make a battery with trash cans and water.
“For me physics is a way of seeing,” Lewin says, “the spectacular and the mundane, the immense and the minute — as a beautiful, thrillingly interwoven whole.”
The professor’s sense of wonder is on full display in a new book: “For the Love of Physics: From the End of the Rainbow to the Edge of Time — A Journey Through the Wonders of Physics.’’ Why is a rainbow an arc and not a straight line? Why can we typically see auroras only if we’re close to the North or South pole?
If you’ve ever been interested in learning — or relearning — the answers to these and a hundred other fascinating questions, Lewin’s book is for you. He’s a straightforward writer, fond of using simple analogues (soda straws, tire irons, tuning forks) to explain concepts like Bernoulli’s flight principle or wave resonance.
So why read Lewin, rather than watch videos of his lectures? The videos are popular and engaging, no doubt. But the book is more personal, more rambling, more inviting. Although it is primarily about getting readers excited about classical physics, “For the Love of Physics’’ is also a memoir.
Lewin writes, for example, about his love for modern art and how his grandmother’s technique for drying wet lettuce got him thinking about centripetal forces. He describes poignantly, how much of his family was murdered in concentration camps, and how the German occupation of Holland dismantled the dignity of his Jewish father.
What you ultimately get from the book is a window into the professor’s humility. “The absolute last thing you want to do is make [your students] feel they’re stupid and you’re smart,” he concludes, and you leave “For the Love of Physics’’ feeling blessed, reminded of the tiny miracles happening all around you.
Another major star in the physics firmament has a new book out this month: Roger Penrose, the well-known author and mathematics professor at the University of Oxford.
For almost 50 years now, we’ve known that the universe is suffused with a low-level background glow. Scientists call it the cosmic microwave background radiation, and little fluctuations in its uniformity offer strong support for the Big Bang theory — the idea that 13.7 billion years ago a primeval, zero-sized, unfathomably hot kernel rapidly expanded to produce everything. You and me, space and time.
Penrose’s dense new book, “Cycles of Time: An Extraordinary New View of the Universe,’’ tries to answer the question: What came before the Big Bang?
Before positing his own theory, Penrose looks closely at the nooks and crannies of the Second Law of Thermodynamics, the one that says that disorder increases with the passage of time. How, wonders Penrose, could the Big Bang, which had to be a moment of incredible heat and massive entropy, fulfill the Second Law? Can disorder really have increased since then? In a prologue, he puts it like this: “A thing like a big walloping explosion doesn’t sound like something organized.”
In the dense and bristling second half of his book, Penrose advances his theory: conformal cyclic cosmology. What he suggests is that the universe endlessly succeeds itself. That is, in the ultradistant future, our universe will start to look like the universe just before the Big Bang. Black holes will grow, removing the entropy from the system, and the universe will restart at a moment of high organization. Space and time are continually reborn in endless repetition.
Penrose has never shied away from including mathematics in his texts, and kudos to his publisher for honoring that wish. That said, the second half of “Cycles of Time’’ offers some seriously hard sledding. Lewin’s book took me two days to read; Penrose’s took me two weeks. If you’ll forgive a skiing metaphor, “Cycles of Time’’ is a black diamond of a book.
But like all steep slopes, sometimes you take a moment from your struggles and look up, and in front of you is an utterly gorgeous view.
Anthony Doerr, author of the story collection ”Memory Wall,” can be reached at adoerr@ cableone.net. 
