The Hunt for Vulcan Read online

  Copyright © 2015 by Thomas Levenson

  Illustrations on this page, this page, this page, this page, this page, and this page copyright © 2015 by Mapping Specialists, Ltd.

  All rights reserved.

  Published in the United States by Random House, an imprint and division of Penguin Random House LLC, New York.

  RANDOM HOUSE and the HOUSE colophon are registered trademarks of Penguin Random House LLC.

  ISBN 9780812998986

  eBook ISBN 9780812988291

  randomhousebooks.com

  Book design by Simon M. Sullivan, adapted for eBook

  Cover design: Nick Misani

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  Contents

  Cover

  Title Page

  Copyright

  PREFACE

  PART ONE: NEWTON TO NEPTUNE (1682–1846)

  1. “THE IMMOVABLE ORDER OF THE WORLD”

  2. “A HAPPY THOUGHT”

  3. “THAT STAR IS NOT ON THE MAP”

  INTERLUDE: “SO VERY OCCULT”

  PART TWO: NEPTUNE TO VULCAN (1846–1878)

  4. THIRTY-EIGHT SECONDS

  5. A DISTURBING MASS

  6. “THE SEARCH WILL END SATISFACTORILY”

  7. “SO LONG ELUDING THE HUNTERS”

  INTERLUDE: “A SPECIAL WAY OF FINDING THINGS OUT”

  PART THREE: VULCAN TO EINSTEIN (1905–1915)

  8. “THE HAPPIEST THOUGHT”

  9. “HELP ME, OR ELSE I’LL GO CRAZY”

  10. “BESIDE HIMSELF WITH JOY”

  POSTSCRIPT: “THE LONGING TO BEHOLD…PREEXISTING HARMONY”

  Dedication

  ACKNOWLEDGMENTS

  NOTES

  BIBLIOGRAPHY

  ILLUSTRATION CREDITS

  By Thomas Levenson

  About the Author

  Preface

  November 18, 1915, Berlin.

  A man is on the move, coming into the center of town from the western suburbs. Usually a bit disheveled—his shock of hair would become almost independently famous—today he’s fully presentable, girded for public performance. He enters Unter den Linden, the grand avenue that pierces the Brandenburg Gate on the way east to the River Spree. He walks up to number 8, the entrance to the Prussian Academy of Sciences, and steps inside.

  On this Thursday in the second autumn of what was already being called the “Great War,” the members of the Academy settle themselves in for a lecture, the third of four in a row by one of their newest colleagues. That still-young man makes his way to the front of the room. He takes up his notes—just a few pages—and begins to speak.

  —

  Albert Einstein’s talk that day and its sequel, presented the following week, completed the greatest individual intellectual accomplishment of the twentieth century. We now call that idea the general theory of relativity: at once a theory of gravity and the foundation for the science of cosmology, the study of the birth and evolution of the universe as a whole. Einstein’s results mark the triumph of a lone thinker, battling the odds, the doubts of his peers, and the most famous scientist in history, Sir Isaac Newton.

  For all the grand sweep of his theory, though, when he spoke on the 18th, Einstein focused on something much more parochial: Mercury, the smallest planet then known, and—at an even finer grain of detail—a tiny, unexplained hitch in its orbit, a wobble, barely measurable, for which there was (until he spoke) no adequate explanation.

  By 1915, Mercury’s misbehavior had been recognized for over sixty years. Throughout that time, astronomers had gone to greater and greater lengths to come up with some explanation for this errant behavior within the conventional framework of Newton’s centuries-old account of gravity—the crowning victory in the Scientific Revolution. The first and seemingly most obvious idea imagined a whole new planet hidden in the glare of the sun, which could provide enough of a gravitational tug to haul Mercury out of its “correct” orbit.

  As a hypothesis, conjuring a planet out of an orbital glitch was perfectly reasonable. Indeed, there was precedent, and at first it seemed not just logical, but right. Almost as soon as Mercury’s plight became public knowledge, amateur and professional astronomers alike spotted and identified an object lurking within the concealing glare of the sun. It would be seen again, over and over, more than a dozen times over two decades. Its own orbit would be calculated; its history recovered in old records of unexplained sightings; it would even receive a name.

  There was only one problem:

  The planet Vulcan was never there.

  —

  This book tells Vulcan’s story: its ancestry, its birth, its odd, twilit journey in and out of the grasp of eager would-be discoverers, its time in purgatory, and finally, on the 18th of November, 1915, its decisive end at the hands of Albert Einstein.

  At first blush, this may seem something of a burlesque, a tale of nineteenth-century astronomical follies, Victorian gentlemen chasing a mistake. But there’s more here than a comedy of errors. The story of Vulcan suggests something much deeper, an insight that gets to the heart of the way science really advances (as opposed to the way we’re taught in school).

  The enterprise of making sense of the material world turns on a key question: what happens when something observed in nature doesn’t fit within the established framework of existing human knowledge? The standard answer is that scientific ideas are supposed to evolve to accommodate new facts. After all, science is a uniquely powerful way of figuring things out precisely because all of its claims, even its most beloved, are subject to the ultimate test of reality. In our common description of the scientific method, any empirical result that refuses to conform to the demands of a theory invalidates that theory, and requires the construction of a new one.

  Ideas, though, are hard to relinquish, none more so than those of Isaac Newton. For decades, the old understanding of gravity was so powerful that observers on multiple continents risked their retinas to gaze at the sun in search of Vulcan. And, contrary to the popular picture of science, a mere fact—Mercury’s misplaced motion—wasn’t nearly enough to undermine that sturdy edifice. As Vulcan’s troublesome history reveals, no one gives up on a powerful, or a beautiful, or perhaps simply a familiar and useful conception of the world without utter compulsion—and a real alternative.

  —

  Einstein wrote Vulcan out of history on the third Thursday in the second November of the war. It had taken him the better part of a decade to develop what became his radical new picture of gravity: how matter and energy mold space and time; how space and time fix the paths that matter and energy must take. As presented to his colleagues that Thursday afternoon, Einstein showed how Mercury’s “wobble” turned out to be just its natural path, the one it has to take in a universe in which relativity is true. That result emerged at the end of a chain of mathematical reasoning, the inevitable outcome of subjecting matter to number.

  In that context, Vulcan’s fate provided the first test of general relativity, proof that Einstein had managed to capture something true about how our universe works. But to get to that point, to follow the radical strangeness of general relativity all the way to its conclusion took both boldness and exquisitely subtle reasoning: hard labor sustained over the eight years it took Einstein to dispatch the ghost planet. That part of the story shows how powerful a thinker it took to clamber past accepted wisdom to achieve what he, alone of all his peers, was able to do.

  Einstein, usually a fairly phlegmatic man, felt this one to the bone. When he completed the calculation of the orbit of Mercury and saw exactly the right number fall out of the long chain of pure reasoning, he told friends that he felt “beside himself with excitement.” Seeing Mercury’s motion simply fall ou
t of his equations pierced him to his heart, he said. He felt palpitations, a sensation “as if something had burst within him.”

  —

  Vulcan is long gone, almost completely forgotten. It may seem today to be merely a curiosity, just another mistake our ancestors made, about which we now know better. But the issue of what to do with failure in science was tricky right at the start of the Scientific Revolution, and it remains so now. We may—we do—know more than the folks back then. But we are not thus somehow immune to the habits of mind, the leaps of imagination, or the capacity for error that they possessed. Vulcan’s biography is one of the human capacity to both discover and self-deceive. It offers a glimpse of how hard it is to make sense of the natural world, and how difficult it is for any of us to unlearn the things we think are so, but aren’t.

  And, in the end, it is a tale of the joy that accrues when we do.

  “THE IMMOVABLE ORDER OF THE WORLD”

  August 1684, Cambridge.

  Edmond Halley had suffered a sad and vexing spring. In March, his father disappeared under suspicious circumstances—a not-altogether-unusual fate in the political turmoil that shot through the last years of the Stuart dynasty’s rule. He was found dead five weeks later. He’d left no will, which forced the younger Halley to spend the next few months dealing with the resulting mess: the twelve pounds owed to his father by a local rector; the three pounds a year promised as an annuity to a woman as part of a real estate transaction; rents to collect and trustees to satisfy. That miserable business consumed him into the summer, and ultimately required a trip to Cambridgeshire to handle face to face those details that couldn’t be resolved from London.

  There was nothing happy about the first part of that journey, but once he’d dealt with the legal issues, one unexpected pleasure came his way. In January, before his troubles began, Halley had produced a clever bit of celestial analysis, a calculation that suggested that whatever force held the planets on their paths around the sun grew weaker in proportion to the square of each object’s distance from the sun. But that prompted an immediate question: could that particular mathematical relationship—called an inverse square law—explain why all celestial objects moved down the paths they’d been observed to follow?

  The best minds in Europe knew what was at stake in that seemingly technical issue. This was the decisive climax in what we’ve come to call the Scientific Revolution, the long struggle through which mathematics supplanted Latin as the language of science. On the 14th of January, 1684, following a meeting of the Royal Society, Halley fell into conversation with two old friends: the polymath Robert Hooke and the former president of the Society, Sir Christopher Wren. As their talk moved on to astronomy, Hooke claimed he’d already worked out the inverse square law that guided the motions of the universe. Wren didn’t believe him, and so offered both Halley and Hooke a prize—a book worth roughly $300 in today’s money—if either of them could present a rigorous account of such a universal law within two months. Halley swiftly acknowledged that he couldn’t find his way to such a result, and Hooke, for all his bravado, failed to deliver a written proof by Wren’s deadline.

  There the matter stuck until, at last, Halley escaped from the wretchedness of postmortem wrangles with his surviving family. His business had taken him east from London anyway—why not detour to the university at Cambridge, there to gain at least an afternoon’s respite in talk of natural philosophy? Coming into town he made his way to the great gate of the College of the Holy and Undivided Trinity. A left onto the college grounds, then right and almost immediately up the stairs would have brought him to the rooms occupied by the Lucasian Professor of Mathematics, Isaac Newton.

  To most of his contemporaries, Newton in the summer of 1684 was something of an enigma. London’s natural philosophers knew him as a man of formidable intelligence, but Halley was among very few who counted him as an acquaintance, much less a friend. The public record of Newton’s work was slim. His reputation rested on a handful of exceptional results, mostly transmitted to the secretary of the Royal Society in the early 1670s, but he was irascible, proud, swift to anger, and agonizingly slow to forgive, and an early dispute with Hooke left him unwilling to risk grubby public wrangling. He kept much of his work secret for the next decade—so much so that, as his biographer Richard Westfall put it, had he died in the spring of 1684, Newton would have been remembered as a very talented and rather odd man, and nothing more. But those who made it so far as to be welcome in the rooms on the northeast corner of Trinity’s Great Court would find someone capable of real warmth—and a mind whose power no learned man in Europe could match.

  Fashionable portraitist Godfrey Kneller painted the earliest known likeness of Isaac Newton in 1689.

  Much later Newton told the story of Halley’s visit that summer day to another friend, and if the old man’s memory wasn’t playing tricks, the two men chatted about this and that for a while. But eventually Halley got down to the question troubling him since January: what about that inverse square relationship? What curve would the planets in their orbits trace, “supposing the force of the attraction towards the sun to be reciprocal to the square of their distance to it?”

  Edmond Halley, painted by Thomas Murray around the time Principia was published

  “An ellipse,” Newton said instantly.

  Halley, “struck with amazement and joy,” asked how his friend knew that answer so surely.

  “I have calculated it,” Newton recalled telling his companion, and when Halley asked to see his workings, fumbled among his notes. On that day he claimed he couldn’t find them, and promised to dig them up and send the result to Halley in London. Here, Newton almost certainly lied. The calculation was later found in his papers—and, as Newton may have recognized while Halley waited eagerly in his rooms, it contained an error.

  No matter. Newton reworked his sums that fall, and then pressed on. In November, he sent Halley nine pages of dense mathematical reasoning, titled De motu corporum in gyrum—“On the Motion of Bodies in an Orbit.” It proved that what would become known as Newton’s law of gravitation—an inverse square relationship—requires that given certain circumstances, an object in orbit around another must trace out an ellipse, just as the planets of our own solar system were known to do. Newton went further, sketching the beginnings of a general science of motion, a set of laws that could, deployed properly, describe the how, the where, and the when of every bit of matter on the move anywhere—everywhere—in the cosmos.

  —

  The pamphlet was more than Halley had expected when he first goaded Newton into rethinking old thoughts. Once he read it, though, he understood immediately its larger significance: Newton hadn’t just solved a single problem in planetary dynamics. Rather, Halley grasped, his friend had sketched something much greater, a newly rigorous science of motion of potentially universal scope.

  Newton too grasped the opportunity before him. He was famously reticent, and he had published almost nothing for more than a decade. But this time he surrendered to Halley’s encouragement, and began to write with the explicit intention of telling the world what he knew. For the next three years he developed a description of nature based on quantitative laws, applying those ideas to a whole range of problems of motion. As he completed each of the first two parts, he forwarded the manuscript to Halley, who took on the heroic double duty of preparing the dense mathematical texts for the printer while continually prodding Newton to get on with it, to deliver what he already knew would be the book of the age. Finally, in 1687, Halley received Newton’s conclusion, the third section of the work, immodestly and accurately titled “On the System of the World.”

  This was the main event, nothing less than Newton’s demonstration that his new science could encompass the universe. He took all the equations, the geometrical demonstrations, all the proofs he’d worked out to describe motion and produced a detailed, mathematically precise account of the behavior of the night sky, beginning with an analysi
s of the moons of Jupiter. He worked his way through the solar system, eventually returning home, to the surface of the earth. There he revealed a gloriously elegant result, an account of the way the gravitational tugs of the moon and sun produced the seemingly intractably complex action of the tides, turning the rise and fall of the sea into rigorous, calculable, scientific order.

  He could have stopped there. It would have made sense, leading readers to rest at the natural end of one of the greatest stories ever told: an odyssey through the heavens above (those tiny, naked-eye-invisible motes circling Jupiter) to the earth below, our home, with every vista along the way accounted for by the workings of a handful of simply expressed laws.

  There was, however, one more matter Newton chose to address before the last leaves of his manuscript could be released into Halley’s hands. Comets had first brought Halley and Newton together: they had met after both had chased the bright comet of 1682—the one we now know as Halley’s.*1 But in the last months of his work on Principia, a different object held Newton’s attention: the Great Comet of 1680, discovered by the German astronomer and calendar maker Gottfried Kirch.

  Kirch’s comet was itself something of a milestone within the scientific revolution. On the night of November 14, 1680, Kirch had begun his regular night’s work looking for something else entirely, mapping stars as part of a long-running observing program. That evening, he pursued his usual sequence: guiding his telescope to the first object of the night, taking notes, tracing the familiar patterns. Then his telescope shifted a little and something new appeared: “a sort of nebulous spot, of an uncommon appearance.” He held on the stranger, tracking it long enough to be sure. It was no star. Rather, he’d found a vagabond, a comet—the first to be discovered using that icon of scientific discovery, the telescope.