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  Praise for

  For the Love of Physics

  “Fascinating. . . . A delightful scientific memoir combined with a memorable introduction to physics.”

  —Kirkus Reviews

  “MIT’s Lewin is deservedly popular for his memorable physics lectures (both live and on MIT’s OpenCourseWare website and YouTube), and this quick-paced autobiography-cum-physics intro fully captures his candor and lively teaching style . . . joyful . . . [this text] glows with energy and should please a wide range of readers.”

  —Publishers Weekly (starred review)

  “Lewin may be the only physics professor in the world who celebrates the beauty of Maxwell’s equations for electromagnetic fields by passing out flowers to his delighted students. As the hundreds of thousands of students who have witnessed his lectures in person or online can attest, this classroom wizard transforms textbook formulas into magic. Lewin’s rare creativity shines through . . . a passport to adventure.”

  —Booklist (starred review)

  “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. 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.”

  —The Boston Globe

  “Everyone knows that rainbows appear after a storm. But in his new book, Lewin reveals nature’s more unusual rainbows hiding in spray kicked up by ocean waves, in fog swirling around headlights, even in glass particles floating above construction sites. After more than thirty years of teaching undergraduate physics at MIT, Lewin has honed a toolbox of clear, engaging explanations that present physics as a way of uncovering the world’s hidden wonders. Quirky, playful, and brimming with earnestness, each chapter is a joyful sketch of a topic—from Newton’s laws to Lewin’s own pioneering discoveries in X-ray astronomy. Lewin’s creativity offers lessons both for students and for educators. . . . Throughout it all, his sense of wonder is infectious.”

  —Science News

  “Walter Lewin’s unabashed passion for physics shines through on every page of this colorful, largely autobiographical tour of science. The excitement of discovery is infectious.”

  —Mario Livio, author of The Golden Ratio and Is God a Mathematician?

  “In this fun, engaging, and accessible book, Walter Lewin, a superhero of the classroom, uses his powers for good—ours! The authors share the joy of learning that the world is a knowable place.”

  —James Kakalios, professor and author of The Physics of Superheroes and The Amazing Story of Quantum Mechanics

  Free Press

  A Division of Simon & Schuster, Inc. 1230 Avenue of the Americas

  New York, NY 10020

  www.SimonandSchuster.com

  Copyright © 2011 by Walter Lewin and Warren Goldstein

  All rights reserved, including the right to reproduce this book or portions thereof in any form whatsoever. For information address Free Press Subsidiary Rights Department, 1230 Avenue of the Americas, New York, NY 10020.

  First Free Press hardcover edition May 2011

  FREE PRESS and colophon are trademarks of Simon & Schuster, Inc.

  The Simon & Schuster Speakers Bureau can bring authors to your live event. For more information or to book an event contact the Simon & Schuster Speakers Bureau at 1-866-248-3049 or visit our website at www.simonspeakers.com.

  Book design by Ellen R. Sasahara

  Manufactured in the United States of America

  1 3 5 7 9 10 8 6 4 2

  Library of Congress Cataloging-in-Publication Data

  Lewin, Walter H. G.

  For the love of physics : from the end of the rainbow to the edge of time—a journey through the wonders of physics / by Walter Lewin with Warren Goldstein.

  p. cm.

  1. Lewin, Walter H. G. 2. Physicists—Massachusetts—Biography. 3. College teachers—Massachusetts—Biography. 4. Physics—Study and teaching—Netherlands. 5. Physics—Study and teaching—Massachusetts. I. Goldstein, Warren Jay. II. Title.

  QC16.L485A3 2011

  530.092—dc22

  [B] 2010047737

  ISBN 978-1-4391-0827-7

  ISBN 978-1-4391-2354-6 (ebook)

  For all who inspired my love for physics and art

  —Walter lewin

  For my grandson Caleb Benjamin Luria

  —Warren Goldstein

  CONTENTS

  Introduction

  1. From the Nucleus to Deep Space

  2. Measurements, Uncertainties, and the Stars

  3. Bodies in Motion

  4. The Magic of Drinking with a Straw

  5. Over and Under—Outside and Inside—the Rainbow

  6. The Harmonies of Strings and Winds

  7. The Wonders of Electricity

  8. The Mysteries of Magnetism

  9. Energy Conservation—Plus ça change…

  10. X-rays from Outer Space!

  11. X-ray Ballooning, the Early Days

  12. Cosmic Catastrophes, Neutron Stars, and Black Holes

  13. Celestial Ballet

  14. X-ray Bursters!

  15. Ways of Seeing

  Acknowledgments

  Appendix 1

  Appendix 2

  Index

  INTRODUCTION

  Six feet two and lean, wearing what looks like a blue work shirt, sleeves rolled to the elbows, khaki cargo pants, sandals and white socks, the professor strides back and forth at the front of his lecture hall, declaiming, gesturing, occasionally stopping for emphasis between a long series of blackboards and a thigh-high lab table. Four hundred chairs slope upward in front of him, occupied by students who shift in their seats but keep their eyes glued to their professor, who gives the impression that he is barely containing some powerful energy coursing through his body. With his high forehead, shock of unruly grey hair, glasses, and the trace of some unidentifiable European accent, he gives off a hint of Christopher Lloyd’s Doc Brown in the movie Back to the Future—the intense, otherworldly, slightly mad scientist-inventor.

  But this is not Doc Brown’s garage—it’s the Massachusetts Institute of Technology, the preeminent science and engineering university in the United States, perhaps even the world, and lecturing at the blackboard is Professor Walter H. G. Lewin. He halts his stride and turns to the class. “Now. All important in making measurements, which is always ignored in every college physics book”—he throws his arms wide, fingers spread—“is the uncertainty in your measurements.” He pauses, takes a step, giving them time to consider, and stops again: “Any measurement that you make without knowledge of the uncertainty is meaningless.” And the hands fly apart, chopping the air for emphasis. Another pause.

  “I will repeat this. I want you to hear it tonight at three o’clock in the morning when you wake up.” He is holding both index fingers to his temples, twisting them, pretending to bore into his brain. “Any measurement that you make without knowledge of its uncertainty is completely meaningless.” The students stare at him, utterly rapt.

  We’re just eleven minutes into the first class of Physics 8.01, the most famous introductory college physics course in the world.

  The New York Times ran a front-page piece on Walter Lewin as an MIT “webstar” in December 2007, featuring his p
hysics lectures available on the MIT OpenCourseWare site, as well as on YouTube, iTunes U, and Academic Earth. Lewin’s were among the first lectures that MIT posted on the Internet, and it paid off for MIT. They have been exceptionally popular. The ninety-four lectures—in three full courses, plus seven stand-alones—garner about three thousand viewers per day, a million hits a year. Those include quite a few visits from none other than Bill Gates, who’s watched all of courses 8.01, Classical Mechanics, and 8.02, Electricity and Magnetism, according to letters (snail mail!) he’s sent Walter, reporting that he was looking forward to moving on to 8.03, Vibrations and Waves.

  “You have changed my life,” runs a common subject line in the emails Lewin receives every day from people of all ages and from all over the world. Steve, a florist from San Diego, wrote, “I walk with a new spring in my step and I look at life through physics-colored eyes.” Mohamed, an engineering prep school student in Tunisia wrote, “Unfortunately, here in my country my professors don’t see any beauty in physics as you do see, and I’ve suffered a lot from this. They just want us to learn how to solve ‘typical’ exercises to succeed in the exam, they don’t look beyond that tiny horizon.” Seyed, an Iranian who had already earned a couple of American master’s degrees, writes, “I never really enjoy of life until I have watched you teach physics. Professor Lewin you have changed my life Indeed. The way you teach it is worth 10 times the tuition, and make SOME not all other teachers bunch of criminals. It is CAPITAL CRIME to teach bad.” Or Siddharth from India: “I could feel Physics beyond those equations. Your students will always remember you as I will always remember you—as a very-very fine teacher who made life and learning more interesting than I thought was possible.”

  Mohamed enthusiastically quotes Lewin’s final lecture in Physics 8.01 with approval: “Perhaps you will always remember from my lectures that physics can be very exciting and beautiful and it’s everywhere around us, all the time, if only you have learned to see it and appreciate its beauty.” Marjory, another fan, wrote, “I watch you as often as I can; sometimes five times per week. I am fascinated by your personality, your sense of humor, and above all by your ability to simplify matters. I hated physics in high school, but you made me love it.”

  Lewin receives dozens of such emails every week, and he answers each one.

  Walter Lewin creates magic when he introduces the wonders of physics. What’s his secret? “I introduce people to their own world,” he says, “the world they live in and are familiar with, but don’t approach like a physicist—yet. If I talk about waves on water, I ask them to do certain experiments in their bathtubs; they can relate to that. They can relate to rainbows. That’s one of the things I love about physics: you get to explain anything. And that can be a wonderful experience—for them and for me. I make them love physics! Sometimes, when my students get really engaged, the classes almost feel like happenings.”

  He might be perched at the top of a sixteen-foot ladder sucking cranberry juice out of a beaker on the floor with a long snaking straw made out of lab tubing. Or he could be courting serious injury by putting his head in the path of a small but quite powerful wrecking ball that swings to within millimeters of his chin. He might be firing a rifle into two paint cans filled with water, or charging himself with 300,000 volts of electricity with a large contraption called a Van de Graaff generator—like something out of a mad scientist’s laboratory in a science fiction movie—so that his already wild hair stands straight out from his skull. He uses his body as a piece of experimental equipment. As he says often, “Science requires sacrifices, after all.” In one demonstration—captured in the photo on the jacket of this book—he sits on an extremely uncomfortable metal ball at the end of a rope suspended from the lecture hall’s ceiling (what he calls the mother of all pendulums) and swings back and forth while his students chant the number of swings, all to prove that the number of swings a pendulum makes in any given time is independent of the weight at its end.

  His son, Emanuel (Chuck) Lewin, has attended some of these lectures and recounts, “I saw him once inhale helium to change his voice. To get the effect right—the devil is in the details—he typically gets pretty close to the point of fainting.” An accomplished artist of the blackboard, Lewin draws geometrical figures, vectors, graphs, astronomical phenomena, and animals with abandon. His method of drawing dotted lines so entranced several students that they produced a funny YouTube video titled “Some of Walter Lewin’s Best Lines,” consisting simply of lecture excerpts showing Lewin drawing his famous dotted lines on different blackboards during his 8.01 lectures. (You can watch it here: www.youtube.com/watch?v=raurl4s0pjU.)

  A commanding, charismatic presence, Lewin is a genuine eccentric: quirky and physics obsessed. He carries two devices called polarizers in his wallet at all times, so that at a moment’s notice he can see if any source of light, such as the blue sky, a rainbow, or reflections off windows, is polarized, and whoever he might be with can see it too.

  What about those blue work shirts he wears to class? Not work shirts at all, it turns out. Lewin orders them, custom made to his specifications, of high-grade cotton, a dozen at a time every few years, from a tailor in Hong Kong. The oversize pocket on the left side Lewin designed to accommodate his calendar. No pocket protectors here—this physicist-performer-teacher is a man of meticulous fashion—which makes a person wonder why he appears to be wearing the oddest brooch ever worn by a university professor: a plastic fried egg. “Better,” he says, “to have egg on my shirt than on my face.”

  What is that oversize pink Lucite ring doing on his left hand? And what is that silvery thing pinching his shirt right at belly-button level, which he keeps sneaking looks at?

  Every morning as Lewin dresses, he has the choice of forty rings and thirty-five brooches, as well as dozens of bracelets and necklaces. His taste runs from the eclectic (Kenyan beaded bracelets, a necklace of large amber pieces, plastic fruit brooches) to the antique (a heavy silver Turkmen cuff bracelet) to designer and artist-created jewelry, to the simply and hilariously outrageous (a necklace of felt licorice candies). “The students started noticing,” he says, “so I began wearing a different piece every lecture. And especially when I give talks to kids. They love it.”

  And that thing clipped to his shirt that looks like an oversize tie clip? It’s a specially designed watch (the gift of an artist friend) with the face upside down, so Lewin can look down at his shirt and keep track of time.

  It sometimes seems to others that Lewin is distracted, perhaps a classic absentminded professor. But in reality, he is usually deeply engaged in thinking about some aspect of physics. As his wife Susan Kaufman recently recalled, “When we go to New York I always drive. But recently I took this map out, I’m not sure why, but when I did I noticed there were equations all over the margins of the states. Those margins were done when he was last lecturing, and he was bored when we were driving. Physics was always on his mind. His students and school were with him twenty-four hours a day.”

  Perhaps most striking of all about Lewin’s personality, according to his longtime friend the architectural historian Nancy Stieber, is “the laser-sharp intensity of his interest. He seems always to be maximally engaged in whatever he chooses to be involved in, and eliminates 90 percent of the world. With that laserlike focus, he eliminates what’s inessential to him, getting to a form of engagement that is so intense, it produces a remarkable joie de vivre.”

  Lewin is a perfectionist; he has an almost fanatical obsession with detail. He is not only the world’s premier physics teacher; he was also a pioneer in the field of X-ray astronomy, and he spent two decades building, testing, and observing subatomic and astronomical phenomena with ultrasensitive equipment designed to measure X-rays to a remarkable degree of accuracy. Launching enormous and extremely delicate balloons that skimmed the upper limit of Earth’s atmosphere, he began to uncover an exotic menagerie of astronomical phenomena, such as X-ray bursters. The discoveries he and his coll
eagues in the field made helped to demystify the nature of the death of stars in massive supernova explosions and to verify that black holes really do exist.

  He learned to test, and test, and test again—which not only accounts for his success as an observational astrophysicist, but also for the remarkable clarity he brings to revealing the majesty of Newton’s laws, why the strings of a violin produce such beautifully resonant notes, and why you lose and gain weight, be it only very briefly, when you ride in an elevator.

  For his lectures, he always practiced at least three times in an empty classroom, with the last rehearsal being at five a.m. on lecture day. “What makes his lectures work,” says astrophysicist David Pooley, a former student who worked with him in the classroom, “is the time he puts into them.”

  When MIT’s Physics Department nominated Lewin for a prestigious teaching award in 2002, a number of his colleagues zeroed in on these exact qualities. One of the most evocative descriptions of the experience of learning physics from Lewin is from Steven Leeb, now a professor of electrical engineering and computer science at MIT’s Laboratory for Electromagnetic and Electronic Systems, who took his Electricity and Magnetism course in 1984. “He exploded onto the stage,” Leeb recalls, “seized us by the brains, and took off on a roller-coaster ride of electromagnetics that I can still feel on the back of my neck. He is a genius in the classroom with an unmatched resourcefulness for finding ways to make concepts plain.”

  Robert Hulsizer, one of Lewin’s Physics Department colleagues, tried to excerpt some of Lewin’s in-class demonstrations on video to make a kind of highlight film for other universities. He found the task impossible. “The demonstrations were so well woven into the development of the ideas, including a buildup and denouement, that there was no clear time when the demonstration started and when it finished. To my mind, Walter had a richness of presentation that could not be sliced into bites.”