11

GREEK DRAMA

Searching the Stars: An Answer in the Hyades

Whether the theory ultimately proves to be correct or not, it claims attention as being one of the most beautiful examples of the power of general mathematical reasoning.

—Arthur Stanley Eddington, Report of the Relativity Theory of Gravitation, 1918

No one must think that Newton’s great creation can be overthrown in any real sense by this or by any other theory. His clear and wide ideas will forever retain their significance as the foundation on which our modern conceptions of physics have been built.

—Albert Einstein, Times of London, November 28, 1919

A QUESTION THAT might be asked is, What took them so long? Modern technology had caught up with Newton’s question by the turn of the twentieth century. Otherwise, Einstein and Freundlich would not have felt encouraged to send out a circular, in 1911, asking astronomers at large if usable plates from past eclipse expeditions might exist. Nor would Charles Perrine and William Campbell have gone back more than a decade to inspect their Vulcan plates. So light-detecting instruments did exist. There had been several successful eclipse expeditions for Campbell, Perrine, Dyson, Davidson, Crommelin, and numerous other astronomers in spots all over the world. In recounting just the expeditions for the Lick Observatory, one would need to name Chile, India, the United States, Sumatra, Spain, Egypt, and Flint Island. The Lick expeditions to those places (excluding Japan and Labrador, which were clouded over) returned with high-resolution images of the solar corona, the astronomers’ interest at the time. Why not light deflection in respect to Newton’s long-standing query?

Science is extraordinarily fragile. Until the right question is raised, in the right time and place, it’s often impossible to make progress. Scientists are just as human as any other man or woman in a different calling. There is no magical font of wisdom that pours down on the scientific community and guides it in pushing knowledge forward. It’s a chaotic playground, a jumbled and messy process with countless false leads and boondoggles, and even a good measure of quackery. But fortunately, the principles of science and the scientific method are powerful enough to overcome all these obstacles. In its wake, science produces the highest quality of accuracy within the human ability to understand nature at its deepest and most hidden levels.

So why did science wait so long to test Isaac Newton’s question? Had any astronomer done so successfully during those early eclipses, the glory would have been all theirs in verifying a new law of gravitation. There could be many reasons why no one considered the question urgent before Einstein came along. Being fallible like the rest of humanity, scientists cannot clearly see the future. At any given time, there are many provocative ideas that are worthy of support and that will stimulate research and advance knowledge. But there is rarely enough financial support to allow scientists to pursue more than a few of these projects at one time. Until Einstein raised the issue a hundred years after Johann Soldner did, it is likely that no astronomer understood that there was even an issue to be raised. Einstein’s persistence, and his pushing Freundlich forward, clearly had its personal incentive. It was his own theory. What greater need could there be for him to stay in the struggle for a verification of ideas that had occupied his brain for years? After all, this was Einstein’s baby.

THE MEETING AT BURLINGTON HOUSE

The special meeting for members of the Royal Society and the Royal Astronomical Society—the Joint Permanent Eclipse Committee—had been set for Thursday, November 6. Dyson, Crommelin, and Davidson would take the train from Greenwich. Eddington and Cottingham would come in from Cambridge. The day began as the month had, with a chilly wind blowing over London from the north. Rain was mixed with drizzle and occasional sleet as the taxicabs began arriving at Burlington House, on Piccadilly, in the heart of London. Wearing hats and bundled in heavy coats and some carrying umbrellas, the members hurried in from the cold, passing through doors that had welcomed many of the world’s greatest thinkers for generations. Isaac Newton was twenty-two years old in 1664, when construction first began on Burlington House, which was then a private mansion. It would be another forty years before Opticks was published, his book that had launched the famous question about the fundamental nature of light. Now the members were gathering in the East Wing, home to the Royal Society since 1873, to await the opening of the meeting.¹

Interest in the 1919 eclipse expeditions had built over the months. Upward of 150 scientists filled the pews and the anteroom. The brilliant Sir Joseph John Thomson, recipient of the 1906 Nobel Prize in physics for his work on the electron, had been president of the Royal Society since 1915. Known affectionately as “J. J.” to his colleagues, he opened the meeting by calling on the astronomer royal to give an account of the eclipse results. An expectancy fell over the audience as they waited for Dyson to speak. This was a world recovering from a long war, the ink still dripping like blood from the Treaty of Versailles, signed less than five months earlier. A week before, the German High Seas Fleet that had so plagued the North Sea was scuttled in Scotland, fifty-two of its finest ships going to rest on the ocean floor. If anyone needed proof that the Central Powers had lost the war, the sinking of this fleet would be it. On their way to Burlington House that afternoon, many Royal Society and RAS members, arriving by private autos or taxis, would have driven past the wood-and-plaster cenotaph that had been erected that July in Whitehall for the Peace Day Parade. The monument’s presence celebrated the end of the war and commemorated the dead who were buried in foreign soil. There would be a permanent memorial built of stone the following year. But for now, the memory of what had been lost still clung to the base of this wooden one, in the dried flowers and withered wreaths placed there that summer by a bereaved public. It was as if the world needed something remarkable just then to help lighten this burden of grief.

The astronomer royal arranged the pages before him. There was a wave of nervous coughs until the room fell silent. Dyson began his address.

“The purpose of the expedition,” he said, “was to determine whether any displacement is caused to a ray of light by the gravitational field of the sun, and, if so, the amount of the displacement.” The listeners waited. Even Isaac Newton seemed to be waiting. His three-quarter-length likeness hung from the wall behind Thomson’s chair. This was not the younger Newton in his full-bottom wig of cascading curls and ruffles at his throat. At eighty-three, his white hair was thinning. Wearing a long and open brown coat, with a white neck cloth and wide white cuffs, he bore an unsmiling, even grim, expression. Newton had served for over two decades as president of the Royal Society, from 1703 until his death in 1727. Now, from his stern gaze, he seemed tired of all the hoopla surrounding his life. He would be dead a year after the sitting.

After giving the main details of the Greenwich expedition—the planning, the travel, the astrographic instruments taken—Dyson turned to the task at hand. “Einstein’s theory predicted a displacement varying inversely as the distance of the ray from the sun’s centre, amounting to 1″.75 for a star seen just grazing the sun.” He went on to recount that Einstein’s theory had already explained the perihelion of Mercury, the mystery that Campbell and Perrine had hoped to solve during several total eclipse expeditions in search of Vulcan. This was the ghost planet that had been “discovered” beneath the pencil lead of Urbain Le Verrier. In 1908, and in doing what science does best, Campbell and Perrine had thrown the hypothetical planet into the dustbin. It didn’t exist. And then, Einstein’s new theory had shown why.

Dyson then told the scientists that previous photographic plates obtained during past eclipses were of too large a scale to show enough stars. Or the scale was too small to test the delicate accuracy necessary for light deflection. He described how the measurements of the Sobral plates had come about, being undertaken by Davidson and Furner, both men independently evaluating each plate twice. The plates taken with the four-inch telescope loaned to the expedition by the Royal Irish Academy—it was plain good luck that Father Cortie suggested taking it to Sobral when the Jesuit was forced to back out—showed good results. Dyson ended his opening remarks with an assessment that would not have pleased many members in the room on that rainy afternoon. “After a careful study of the plates I am prepared to say that there can be no doubt that they confirm Einstein’s prediction,” said the astronomer royal. “A very definite result has been obtained that light is deflected in accordance with Einstein’s law of gravitation.”²

LAW VERSUS THEORY

One can only imagine the impact those words had that day, especially for the scientists who might not have read the paper submitted a week earlier. Crommelin spoke briefly, mostly to thank Morize and his staff, the interpreter, and the Booth Steamship Company. He was grateful to the party’s gracious host, Colonel Saboya, for his house with its constant supply of water, “no small boon in a time of drought, and of great importance in the photographic work.” Then it was Eddington’s turn. This audience of his peers would have been waiting for him. He was the man who had been so vocal in England, in his papers and lectures, in support of the general theory. Dyson might have been the one to point out that a perfect eclipse was coming on May 29, 1919, and decided to send expeditions. But it was only after Eddington had laid the beauty of Einstein’s theory at the astronomer royal’s door. After sharing details of his and Cottingham’s expedition to Príncipe, Eddington addressed Dyson’s earlier announcement.

“The simplest interpretation of the bending of the ray is to consider it as an effect of the weight of light,” Eddington said. “We know that momentum is carried along on the path of a beam of light. Gravity in acting creates momentum in a direction different to that of the path of the ray and so causes it to bend.” The audience listened carefully. A half effect would mean that England’s own Sir Isaac Newton would maintain his scientific throne. A full effect, and gravity would, as Dyson had just professed, obey the law of Albert Einstein, the native son of Germany, their recent enemy. “This is one of the most crucial tests between Newton’s law and the proposed new law,” Eddington continued. “Einstein’s law had already indicated a perturbation, causing the orbit of Mercury to revolve. That confirms it for relatively small velocities. Going to the limit, where the speed is that of light, the perturbation is increased in such a way as to double the curvature of the path, and this is now confirmed. This effect may be taken as proving Einstein’s law rather than his theory.”

So what did Eddington mean? Physicists are rather like storytellers who use mathematics to weave narratives that, when finished, are often called a theory. The audience for any theory, the readership, is always nature. Because most theories are incorrect from inception, a physicist must be in constant conversation with the fundamental laws of nature. This process, this communication, is called, quite simply, experimentation. It becomes nature’s job to sort through each mathematical story to decide what’s correct and to toss out what isn’t. Physics is not a search for the truth, but a search for accuracy. Like all of science, physics can never be 100 percent certain of anything. This uncertainty places a burden on the understanding between scientists and the public. Because the public is accustomed to thinking in certainty, scientists often have difficulty explaining their approach.

Imagine human beings who lived a few thousand years ago. They would have had a sense of what we might call the Law of the Sunrise. They understood that each day began when the sun rose. They had witnessed this event hundreds of times over the years. In science, a law is a summary of observations that yield the same result when carried out repeatedly. A law is found to be accurate and valid each time it’s tested by observation. What, then, would be the Theory of the Sunrise? Perhaps the sun rises when Helios, the Greek god, drives his golden chariot across the heavens, pulled by fiery steeds. Or the theory is that the Egyptian god Ra floats through the sky each day in his sun boat. A theory is the reason behind why a law is valid. The Theory of the Sunrise has long been proven. We understand now that the sun doesn’t rise at all. It maintains its position at the center of our solar system. It only appears to rise because of the earth’s rotation every twenty-four hours on its axis. Those two older “theories” have been rejected, just as Vulcan was for causing that glitch in Mercury’s orbit.

But Einstein’s theory was not home yet. Since his final paper in 1915, he had insisted that the theory must stand up to three tests: (1) the perihelion of Mercury, (2) the deflection of light at 1.7 arc seconds, and (3) the redshift, an example of the Doppler effect that enables astronomers to determine the chemical composition of far-off objects in the universe. This triumvirate was the entire mathematical superstructure and foundation on which the general relativity theory rested. His equations had earlier predicted and explained Mercury’s wobble in its orbit around the sun. The expedition results had just proven that not only does light have weight, but it has double the weight Newton anticipated. What Einstein needed now to quell his naysayers was the full proof of his theory, the third test. The predicted shift of the spectrum lines would need to be obtained. If so, the theory of general relativity would provide an accurate and new description of how the universe works.

Astronomers had been hard at work on the redshift problem, especially Charles St. John, at Mount Wilson, and John Evershed, director of the Kodaikanal Observatory in India. That St. John, with some of the best equipment in the world, was dubious of the shift had haunted Eddington for many months. As early as January 1918, Eddington had written to a colleague about these doubts: “St. John’s latest paper has been giving me sleepless nights—chasing mare’s nests to reconcile the relativity theory with the results, or vice-versa. I cannot make any headway.”³ Now, at the Burlington House meeting, Eddington stated that a failure of the redshift to be confirmed would not affect Einstein’s law, but that his equations that buoyed up the theory, the “views on which the law was arrived at,” would be wrong. A blackboard with neatly written equations had been prepared. On it were two sets:

“I think the second expression may be accepted as corresponding to Newton’s law,” Eddington said. “At any rate, it gives no motion of perihelion of Mercury and the half-deflection of light.”⁴

General relativity would not be an easy theory to sell. Who but its creator, Einstein, and its foremost spokesman, Eddington, could understand it? The four pioneering mathematicians who had provided Einstein with the rigorous mathematics he needed to encode his theory had died long before Einstein was born: Carl Frederick Gauss in 1855, Nikolai Lobachevsky in 1856, János Bolyai in 1860, and Bernhard Riemann in 1866. His colleague, the brilliant astronomer and physicist Karl Schwarzschild, who had helped him with his field equations from the battlefield, had died in 1916 from the illness he had contracted on the Russian front. Among the living who could comprehend Einstein’s theory would be the German mathematician David Hilbert, who was already being falsely credited by Einstein’s detractors as having published the theory first. And there would be others, of course, but it would be a select group.⁵

THE AUDIENCE REACTS

Sir J. J. Thomson, from the chair, was ready to open the floor for discussion. But first, obviously impressed with the overwhelming magnitude of this announcement, Thomson, who had once been Dyson’s revered professor, shared his thoughts with the members:

If the results obtained had been only that light was affected by gravitation, it would have been of the greatest importance. But this result is not an isolated one; it is part of a whole continent of scientific ideas affecting the most fundamental concepts of physics. It is difficult for the audience to weigh fully the meaning of the figures that have been put before us.… [T]his is the most important result obtained in connection with the theory of gravitation since Newton’s day, and it is fitting that it should be announced at a meeting of the Society so closely connected with him. [If the theory passed the third test,] then it is the result of one of the highest achievements of human thought.

Not everyone in the audience agreed. There were probably cynics who wanted no part of a grand idea conceived by a German, but others believed that Einstein was simply wrong. The charismatic Sir Oliver Lodge, who had just that year retired as the first principal of Birmingham University, was expected to speak. The Royal Society had presented him with its Rumford Medal in 1898 for his studies of the relationship between matter and ether. The members would be curious to hear his comments. It was well known that Lodge had been busy trying to contact his son, Raymond, through the help of mediums after the boy had died in battle in France. According to the grieving father, ether was needed in the afterlife as well as in space. A committed “ether man” of the older school of physicists—Einstein’s special theory of relativity had invalidated ether in 1905—Lodge had addressed the Royal Society earlier that year as the expeditions were preparing to leave England. He had conjectured that ether, “responsible for the velocity of light,” might be affected by gravity and thus cause a refraction. If so, he would prefer Newton’s value over Einstein’s. After Thomson was finished heaping praise on these new results, Lodge rose and left the meeting.

One of the next men to speak was H. F. Newall, an astrophysicist and the director of the Solar Physics Institute at Cambridge. “I feel that the Einstein effect holds the day,” he said, “but I do not yet feel that I can give up my freedom of mind in favour of another interpretation of the effects obtained.” He extended his heartiest congratulations to the astronomer royal and the eclipse observers. Newall had been on at least as many eclipse expeditions as had anyone else in the room that day, beginning in 1898, when his pianist wife had gone with him to India. In 1900, Newall was at the Algiers Observatory a short distance away from where Crommelin stood on the rooftop of the Hôtel de la Régence. In 1914, he waited next to Perrine and Mulvey in the Crimean hillside vineyard, watching clouds float in from the mountain at Staryi Krym. “I prefer to keep an open mind about interpretation,” Newall told his colleagues.⁶

It wasn’t that the scientists seated at this meeting didn’t have a right to be skeptical or at least ambivalent. There were a few weak areas in the evidence presented. There had been problems with the larger telescope in Sobral, some of the plates were troublesome at both places in the warm temperatures, the statistical evidence had been gleaned from a small number of stars, and Eddington had thrown out one of the measurements. But this uncertainty was the nature of observation and experimentation. As a case in point, in the paper Dyson and his coauthors Eddington and Davidson had submitted a week earlier, they conceded that this observation, being of such magnitude in discovery, should be repeated at future eclipses even if they would not be as star-rich as the May 29 eclipse for many years. Moreover, Dyson also offered to send exact copies of the original glass plates to any astronomers who wished to make their own measurements. This was science in the making.

Drama was also in the making. When Ludwik Silberstein took his turn to weigh in, so to speak, he rebuked the high praise that Thomson had leveled on the results. “There is a deflection of the light rays,” he said, “but it does not prove Einstein’s theory.” Silberstein would become a steady nuisance that Einstein would have to endure in the upcoming years. He then brought up the failure of both St. John and Evershed to obtain the predicted shift of the spectrum lines: “The discovery made at the eclipse expedition, beautiful though it is, does not, in these circumstances, prove Einstein’s theory.” Dyson and especially Eddington had made this quite clear: the law, not the theory. At this, Silberstein pointed at the portrait of Isaac Newton, who seemed to be eavesdropping from behind Thomson’s chair. “We owe it to that great man,” he said theatrically, “to proceed very carefully in modifying or retouching his Law of Gravitation.”⁷

In the audience that day was Alfred North Whitehead, the esteemed British philosopher and mathematician who had attended the meeting as a member of the Royal Society. Whitehead was then professor of applied mathematics at Imperial College, London. “The whole atmosphere of intense interest was exactly that of the Greek drama,” Whitehead wrote. “We were the chorus commenting on the decree of destiny as disclosed in the development of a supreme incident. There was dramatic quality in the very staging:—the traditional ceremonial, and in the background the picture of Newton to remind us that the greatest of scientific generalisations was now, after more than two centuries, to receive its first modification. Nor was the personal interest wanting: a great adventure in thought had at length come safe to shore.”⁸

It’s the job of Greek drama, after all, to comment on a world-changing event. Einstein was forcing every scientist in the room that afternoon to fundamentally re-conceptualize the universe in which they existed: not only did the earth rotate, mixing time and space, but time and space were also warped. Eddington stood to address Silberstein in what might be taken as a polite dressing-down. “When a result that has been forecasted is obtained,” Eddington said, “we naturally ask what part of the theory exactly does it confirm. In this case it is Einstein’s law of gravitation.” The special meeting was over.

Before closing, Thomson thanked his former student, Dyson, and Eddington “for bringing this enormously important discovery before us, and for taking such pains to make clear to us exactly where the problem stands.” If learned scholars of mathematics, physics, and astronomy had difficulties grasping the ramifications of what Einstein’s theory proposed or what the 1919 eclipse expeditions had actually verified, then how could the public possibly understand even a thread of what it meant? A report would be sent to the Times of London, giving an account of events at the meeting.

THE BRITISH RAISE A TOAST

The Royal Astronomical Society began as a dining club when fourteen astronomers met for dinner at the Freemasons’ Tavern in London’s West End. The year was 1820. During those early decades, when travel to and from monthly meetings could pose an inconvenience for many members, it became customary for them to enjoy a dinner discussion afterward and then to spend the night. Often, guests were invited. The once-yearly “Parish” dinners were more exclusive, with only members in attendance. At these annual gatherings, the astronomers sang songs over a dinner of marrowbones, which were eaten with long-handled scoops designed to extract the marrow. All these social gatherings were beloved by many RAS members, no one more than Dyson. The dinner that night would be memorable, given the special meeting earlier.⁹

The principal players were all there. It was a night for celebration mixed in with the usual songs and toasts. These dinners weren’t always devoid of serious conversation or even results. Once, when Dyson mentioned to Eddington that a formula was needed for correcting statistics in errors of observation, Eddington had reached into his pocket for a pen, flipped over his menu card, and soon handed the required formula back to his astonished colleague.¹⁰ As the toasts began, it was time for Dyson to launch the story that would live far longer than would anyone in the room that night. He rose to speak about the importance of the results that the expeditions had revealed. Then he proposed a toast to the four men who had sailed to those far-off continents. He told the members about that March night in his study, at Flamsteed House, the night before both expeditions left for Liverpool and the first leg of their journey. That cold evening by the fire, Cottingham had asked what would happen if the amount of deflection was twice what Einstein predicted. Dyson had informed Cottingham that he would have to come home alone because “Eddington will go off his head and commit suicide.” When the laughter had died down, he added, “Newton wanted 0.87 seconds of arc. Einstein wanted 1.7, but Cottingham wanted to double this amount!”

The story was given its foothold on that night of rain and drizzle in London. It was the kind of story that would keep the memory of flesh-and-blood men alive long after they had disappeared, more so than formulas on the backs of menu cards. With perfect timing, Cottingham, the clockmaker with a brilliance for astronomical timepieces, sheepishly stood to explain that while he had asked the question, he had never doubted the astronomer royal’s judgment or Professor Eddington’s sanity. And then he added, “All the same, I must confess I was very pleased when Eddington said to me one morning, after making a few plate measurements from those we developed on the island—‘Cottingham, you won’t have to go home alone.’”

Eddington, being a fan of light verse, had written a parody of the Rubaiyat of Omar Khayyam. He delivered several quatrains, such as this one:

Oh leave the Wise our measures to collate

One thing at least is certain, LIGHT has WEIGHT

One thing is certain, and the rest debate—

Lights rays, when near the Sun, DO NOT GO STRAIGHT.

That mention of “the rest debate” was likely the redshift, the final test to prove the theory. The dinner would end with Turner, the club “poet,” delivering a new drinking song he had penned to celebrate the expeditions:

The idea that light has mass, we got

From Newton, it’s bequeather,

They ‘waved’ aside his news as rot,

And filled all space with ether.

But once more comes a change of scene,

The ether’s swept away, Sir.

And space is emptied now as clean

As the bottle of yesterday, Sir.

We cheered the Eclipse Observers’ start

We welcome their return, Sir.

Right manfully they played their part,

And much from them we’ve learned, Sir.

No toils or pains they thought too great,

Nor left Einstein unturned, Sir.

Right cordially we asseverate

Their bottle a day they’ve earned, Sir.¹¹

The lively RAS dinner was over. The members made their way home or to where they were being housed. It had been an exciting day, followed by a dinner of good cheer and camaraderie. Most of England would go to bed that night never having heard the name Albert Einstein.