The Perfect Theory Read online

  Table of Contents

  Title Page

  Table of Contents

  Copyright

  Dedication

  Prologue

  If a Person Falls Freely

  The Most Valuable Discovery

  Correct Mathematics, Abominable Physics

  Collapsing Stars

  Completely Cuckoo

  Radio Days

  Wheelerisms

  Singularities

  Unification Woes

  Seeing Gravity

  The Dark Universe

  The End of Spacetime

  A Spectacular Extrapolation

  Something Is Going to Happen

  Acknowledgments

  Notes

  Bibliography

  Index

  About the Author

  Copyright © 2014 by Pedro G. Ferreira

  All rights reserved

  For information about permission to reproduce selections from this book, write to Permissions, Houghton Mifflin Harcourt Publishing Company, 215 Park Avenue South, New York, New York 10003.

  www.hmhco.com

  The Library of Congress has cataloged the print edition as follows:

  Ferreira, Pedro G.

  The perfect theory : a century of geniuses and the battle over general relativity / Pedro G. Ferreira.

  pages cm

  Includes bibliographical references and index.

  ISBN 978-0-547-55489-1 (hardback) ISBN 978-0-544-26408-3 (international pbk.)

  1. General relativity (Physics)—History—20th century. 2. Physicists—Biography. 3. Physics—History—20th century. 4. Science—Social aspects—History—20th century. 5. Science and civilization—History—20th century. I. Title.

  QC173.6.F47 2014

  530.11—dc23

  2013021741

  eISBN 978-0-547-55490-7

  v1.0214

  To Gisa, Bruno, and Mia

  Prologue

  WHEN ARTHUR EDDINGTON stood up at a joint meeting of the Royal Society and Royal Astronomical Society on November 6, 1919, his announcement quietly upended the reigning paradigm of gravitational physics. In a solemn monotone, the Cambridge astronomer described his trip to the small, lush island of Príncipe off the west coast of Africa, where he had set up a telescope and taken photographs of a total eclipse of the sun, being particularly careful to capture a faint cluster of stars scattered behind it. By measuring the positions of those stars, Eddington had found that the theory of gravity invented by British science’s patron saint, Isaac Newton, a theory that had been accepted as truth for over two centuries, was wrong. In its place, he claimed, belonged a new, correct theory proposed by Albert Einstein, known as the “general theory of relativity.”

  At the time, Einstein’s theory was already known as much for its potential to explain the universe as it was for its incredible difficulty. After the ceremony, as the audience and speakers milled around, ready to escape into the London evening, a Polish physicist named Ludwik Silberstein ambled over to Eddington. Silberstein had already written a book about Einstein’s more restricted “special theory of relativity” and had followed Eddington’s presentation with interest. Now he pronounced, “Professor Eddington, you must be one of the three persons in the world who understand general relativity.” When Eddington was slow to respond, he added, “Don’t be modest, Eddington.” Eddington looked at him firmly and said, “On the contrary, I am trying to think who the third person is.”

  By the time I first discovered Einstein’s general theory of relativity, Silberstein’s count could probably be adjusted upward. It was the early 1980s, and I saw Carl Sagan on the television series Cosmos talking about how space and time can shrink or stretch. I immediately asked my dad to explain the theory. All he could tell me was that it is very, very difficult. “Hardly anyone understands general relativity,” he said. I was not so easily deterred. There was something deeply appealing about this bizarre theory, with its warped grids of spacetime wrapping around deep, desolate throats of nothingness. I could see general relativity at work on old episodes of Star Trek when the starship Enterprise was kicked back in time by a “black star” or when James T. Kirk floundered around between different dimensions of spacetime. Could it really be so hard to understand?

  A few years later I went to university in Lisbon, where I studied engineering in a monolithic building of stone, iron, and glass, a perfect example of the Fascist architecture of the Salazar regime. The setting was apt for the endless lectures where we were taught useful things: how to build computers, bridges, and machines. A few of us escaped the drudgery by reading about modern physics in our spare time. We all wanted to be Albert Einstein. Every now and then some of his ideas would appear in our lectures. We learned how energy is related to mass and how light is actually made of particles. When it was time to study electromagnetic waves, we were introduced to Einstein’s special theory of relativity. He had come up with it in 1905, at the tender young age of twenty-six, just a few years older than us. One of our more enlightened lecturers told us to read Einstein’s original papers. They were little gems of concision and clarity compared to the tedious exercises we were being set. But general relativity, Einstein’s grand theory of spacetime, was not part of the menu.

  At some point I decided to teach myself general relativity. I scoured the library at my university and found a mesmerizing collection of monographs and textbooks by some of the greatest physicists and mathematicians of the twentieth century. There was Arthur Eddington, the Astronomer Royal from Cambridge; Hermann Weyl, the geometer from Göttingen; Erwin Schrödinger and Wolfgang Pauli, both fathers of quantum physics—all with their own take on how Einstein’s theory should be taught. One tome looked like a big black phone book, running more than a thousand pages, with flourishes and comments from a trio of American relativists. Another one, written by the quantum physicist Paul Dirac, barely made it to a sleek and spare seventy pages. I felt that I had entered a completely new universe of ideas populated by the most fascinating characters.

  Understanding their ideas wasn’t easy. I had to teach myself to think in a completely new way, relying on what initially seemed like elusive geometry and abstruse mathematics. Decoding Einstein’s theory required mastering a foreign mathematical language. Little did I know that Einstein himself had done the same as he tried to figure out his own theory. Once I learned the vocabulary and grammar, I was blown away by what I could do. And so began my lifelong love affair with general relativity.

  It sounds like the ultimate overstatement, but I can’t resist it: the reward for harnessing Albert Einstein’s general theory of relativity is nothing less than the key to understanding the history of the universe, the origin of time, and the evolution of all the stars and galaxies in the cosmos. General relativity can tell us about what lies at the farthest reaches of the universe and explain how that knowledge affects our existence here and now. Einstein’s theory also sheds light on the smallest scales of existence, where the highest-energy particles can come into being out of nothing. It can explain how the fabric of reality, space, and time emerges to become the backbone of nature.

  What I learned during those months of intense study is that general relativity brings space and time alive. Space is no longer just a place where things exist, nor is time a ticking clock keeping tabs on things. According to Einstein, space and time are intertwined in a cosmic dance as they respond to every single speck of stuff imaginable, from particles to galaxies, weaving themselves into elaborate patterns that can lead to the most bizarre effects. And from the moment he first proposed his theory, it has been used to explore the natural world, revealing the universe as a dynamic place, expanding at breakneck speed, filled with black holes, devastating punctures o
f space and time, and grand waves of energy, each carrying almost as much energy as a whole galaxy. General relativity has let us reach further than we ever imagined.

  There was something else that struck me when I first learned general relativity. Although Einstein took just under a decade to develop it, it has remained unchanged ever since. For almost a century, it has been considered by many to be the perfect theory, a source of profound admiration to anyone who has had the privilege of coming across it. General relativity has become iconic for its resilience, as a centerpiece of modern thought and as a colossal cultural achievement along the lines of the Sistine Chapel, the Bach cello suites, or an Antonioni film. General relativity can be encapsulated succinctly in a set of equations and rules that are easy to summarize and write down. And they are not just beautiful—they also say something about the real world. They have been used to make predictions about the universe that have since been proved by observation, and there is a firm belief that buried in general relativity there are more deep secrets about the universe that remain to be exposed. What more could I want?

  For almost twenty-five years, general relativity has been part of my daily life. It has been at the heart of much of my research and underpinned so much of what my collaborators and I are trying to understand. My first experience with Einstein’s theory was far from unique; I have come across people from all over the world who have been hooked by Einstein’s theory and have devoted their lives to uncovering its mysteries. And I really do mean all over the world. From Kinshasa to Kraków, and from Canterbury to Santiago, I am regularly sent scientific papers whose authors are trying to find new solutions or even possible changes to general relativity. Einstein’s theory may be difficult to grasp but it is also democratic; its very difficulty and intractability mean that much remains to be done before all its implications are exposed. There is opportunity here for anyone with a pen and paper and stamina.

  I have often heard PhD supervisors telling their students not to work on general relativity for fear of becoming unemployable. To many it is far too esoteric. Devoting one’s life to general relativity is definitely a labor of love, an almost irresponsible calling. But once you have been bitten by the bug, it can be all but impossible to leave relativity behind. Recently I met one of the leading lights in modeling climate change. He is a real pioneer in the field, a fellow of the Royal Society, an expert in making predictions of weather and climate in what is still a fiendishly difficult area of research. He hasn’t always done this for a living. In fact, as a young man in the 1970s, he studied general relativity. That was almost forty years ago, yet, when we first met, he told me with a wry smile, “I am, in fact, a relativist.”

  A friend of mine left academia quite a while back, having worked on Einstein’s theory for almost twenty years. He now works for a software company, developing and installing mechanisms for storing large amounts of data. His week is spent flying all over the world to set up these highly complex and expensive systems in banks, corporations, and government offices. Yet when we meet, he always wants to quiz me about Einstein’s theory, or share with me his latest thoughts on general relativity. He can’t shake it.

  One thing about general relativity that has always puzzled me is how, despite being around for almost a century, it continues to yield new results. I would have thought that, given the phenomenal brain power that has been devoted to it, the theory would have been done and dusted decades ago. The theory might be difficult, but surely there is a limit to how much it can give us? Aren’t black holes and an expanding universe more than enough? But as I’ve continued to grapple with the ideas that come out of Einstein’s theory and met many of the brilliant minds that have worked on it, it has dawned on me that the story of general relativity is a fascinating and magnificent narrative, maybe as complicated as the theory itself. The key to understanding why the theory is, well, so alive is to follow its travails throughout its century of life.

  This book is the biography of general relativity. Einstein’s idea of how space and time are put together has taken on a life of its own, and throughout the twentieth century it was a source of delight and frustration among some of the world’s most brilliant minds. General relativity is a theory that has constantly thrown up surprises, outlandish insights into the natural world that even Einstein found difficult to accept. As the theory has been passed from mind to mind, new and unexpected discoveries have come up in the strangest situations. Black holes were first conceived on the battlefields of the First World War and came of age in the hands of the pioneers of both the American and Soviet atom bombs. The expansion of the universe was first proposed by a Belgian priest and a Russian mathematician and meteorologist. New and strange astrophysical objects that have played a crucial role in establishing general relativity were discovered by chance. Jocelyn Bell discovered neutron stars in the Cambridge Fens using chicken wire strung out over a rickety structure of wood and nails.

  The general theory of relativity was also at the heart of some of the major intellectual battles of the twentieth century. It was the target of persecution in Hitler’s Germany, hounded in Stalin’s Russia, and disdained in 1950s America. It has pitted some of the biggest names in physics and astronomy against each other in a battle for the ultimate theory of the universe. They slugged it out over whether the universe started with a bang or has always been eternal and what the fundamental structure of space and time really is. The theory also brought distant communities together; in the midst of the Cold War, Soviet, British, and American scientists joined to solve the problem of the origin of black holes.

  The story of general relativity is not all about the past. Over the past ten years, it has become apparent that if general relativity is correct, most of the universe is dark. It is full of stuff that not only doesn’t emit light but doesn’t even reflect or absorb it. The observational evidence is overwhelming. Almost a third of the universe seems to be made up of dark matter, heavy, invisible stuff that swarms around galaxies like a cloud of angry bees. The other two-thirds is in the form of an ethereal substance, dark energy, that pushes space apart. Only 4 percent of the universe is made of the stuff that we are familiar with: atoms. We are insignificant. That is, if Einstein’s theory is correct. It may just be possible that we are reaching the limits of general relativity and that Einstein’s theory is beginning to crack.

  Einstein’s theory is also essential to the new fundamental theory of nature that has theoretical physicists at each other’s throats. String theory, which attempts to go even further than Newton and Einstein and unify everything in nature, relies on complicated spacetimes with strange geometrical properties in higher dimensions. Far more esoteric than Einstein’s theory ever was, it is hailed by many as the final theory and railed against by others as romantic fiction, not even science. Like a breakaway cult, string theory wouldn’t exist if not for the general theory of relativity, yet it is looked at with skepticism by many practicing relativists.

  Dark matter, dark energy, black holes, and string theory are all progeny of Einstein’s theory, and they dominate physics and astronomy. While giving talks at various universities, attending workshops, and participating in meetings of the European Space Agency, responsible for some of the world’s most important scientific satellites, I have come to realize that we are in the midst of a momentous transformation in modern physics. We have talented young scientists looking at general relativity with an expertise that is built on a century of geniuses. They are mining Einstein’s theory with unparalleled computational power, exploring alternative theories of gravity that might dethrone Einstein’s, and looking for exotic objects in the cosmos that could confirm or refute the fundamental tenets of general relativity. The wider community of scientists is simultaneously being galvanized to build colossal machines to look farther and more clearly into space than we ever have done before, satellites that will set out to search for the outlandish predictions with which general relativity seems to have burdened us.

  The sto
ry of general relativity is magnificent and overarching and needs to be told. For, well into the twenty-first century, we are facing up to many of its great discoveries and unanswered questions. Something important really is going to happen in the next few years, and we need to understand where it all comes from. My suspicion is that if the twentieth century was the century of quantum physics, the twenty-first will give full play to Einstein’s general theory of relativity.

  Chapter 1

  If a Person Falls Freely

  DURING THE autumn of 1907, Albert Einstein worked under pressure. He had been invited to deliver the definitive review of his theory of relativity to the Yearbook of Electronics and Radioactivity. It was a tall order, to summarize such an important piece of work at such short notice, especially since he could do so only in his spare time. From 8:00 a.m. to 6:00 p.m. Monday through Saturday, Einstein could be found working at the Bern Federal Office for Intellectual Property in the newly built Postal and Telegraph Building, where he would meticulously pore over plans for newfangled electrical contraptions and figure out if there was any merit in them. Einstein’s boss had advised him, “When you pick up an application, think that everything the inventor says is wrong,” and he took his advice to heart. For much of the day, the notes and calculations for his own theories and discoveries had to be relegated to the second drawer of his desk, which he referred to as his “theoretical physics department.”

  Einstein’s review would recap his triumphant marriage of the old mechanics of Galileo Galilei and Isaac Newton with the new electricity and magnetism of Michael Faraday and James Clerk Maxwell. It would explain much of the weirdness that Einstein had uncovered a few years before, such as how clocks would run more slowly when moving, or how objects would shrink if they were speeding ahead. It would explain his strange and magical formula that showed how mass and energy were interchangeable, and that nothing could move faster than the speed of light. His review of his principle of relativity would describe how almost all of physics should be governed by a new common set of rules.