The Day We Found the Universe (25 page)

What de Sitter assumed was that the universe contained no matter. He discovered that Einstein's equation could be solved if he imagined that the universe was both stable and
empty
. On the face of it, this seemed like a ludicrous assumption, but de Sitter wondered if cosmic densities were so low that the universe could be considered essentially barren. By making this conjecture he was able to construct a model of spacetime in which “the frequency of light-vibrations diminishes.” That is, light waves get longer (more red) with increasing distance from their source. The unique properties of spacetime that arose in his solution demanded it. Einstein was not up on the latest astronomical news, but de Sitter was. In fact, he would soon be director of the Leiden Observatory, in the Netherlands. He was very aware that V. M. Slipher, at the Lowell Observatory, had recently discovered some spiral nebulae seemingly racing away from the Milky Way—and at very high velocities as measured by their redshifts. De Sitter was one of the few at the time who was sure that the spiral nebulae being sighted by astronomers in ever greater numbers were probably “amongst the most distant objects we know,” indisputably located beyond the Milky Way. And he surmised that their tendency to display appreciable redshifts could be proof of his model. In his paper, he suggested that the nebulae might only appear to be moving outward because their light waves were getting longer and longer (hence redder and redder) as the light traveled toward Earth. This set up the illusion of movement.

On the other hand, there was another way to interpret the effects in de Sitter's universe: Any bit of matter dropped inside its spacetime would immediately fly off. That was another possible reason for the redshifts Slipher was noticing. Eddington liked to say that “Einstein's universe contains matter but no motion and de Sitter's contains motion but no matter.”

Before the publication of his bizarre yet fascinating solution, de Sitter exchanged a number of letters with Einstein arguing over its details. Einstein was clearly flummoxed by de Sitter's quirky take on the universe. It “does not make sense to me,” he wrote. Where was the “world material” in his cosmos, where were the stars? It didn't seem based in reality. In Einstein's eyes, de Sitter's solution was physically impossible. The properties of space could not be determined, he believed, without the presence of matter.

Albert Einstein and Willem de Sitter working out a problem
at the Mount Wilson Observatory's Pasadena headquarters in 1932
(Associated Press)

De Sitter was certainly making a huge assumption by considering a cosmic density so low that the universe could be regarded as devoid of matter. But what was exciting about his model was that it was testable. If distances to the spiral nebulae could be measured precisely, then astronomers would be able to see if the redshifts truly increased “systematically,” as de Sitter noted in his paper. That is, the more distant a spiral, the larger its redshift. But in 1917 carrying out such rigorous measurements was a pipe dream. At that time astronomers were still not settled on what a spiral was, much less able to figure out its exact distance.

Besides, few astronomers were paying attention to Einstein's theory as yet. World War I had kept Einstein's work from being widely circulated outside Germany, and when astronomers did hear of it, they weren't quite sure what to make of its unconventional and perplexing view of gravity. George Hale, like many astronomers at the time who were trained to observe rather than to tinker with mathematical equations, said he feared “it will always remain beyond my grasp.” All of that changed, though, once the findings of a British solar-eclipse expedition in 1919 transformed the name of Einstein, the former Swiss patent clerk, into a synonym for genius.

At the time Einstein was working on general relativity, he had early on suggested a specific test that astronomers could perform to confirm his predicted curvatures in spacetime: Photograph a field of stars at night, then for comparison photograph those same stars when they pass near the Sun's limb during a solar eclipse. A beam of starlight passing right by the Sun would be gravitationally attracted to the Sun and get bent, making it appear that the star has shifted its standard position on the celestial sky, the position it would have if the Sun were in another part of the heavens. In 1911 he computed a bending of 0.83 arcseconds, the same arising from Newton's laws alone. But a few years later, once his final theory was in place, Einstein doubled his predicted bending. The extra contribution, Einstein figured out, occurs due to the Sun's enormous mass warping spacetime. He calculated that a stellar ray just grazing the Sun would get deflected by 1.7 arcseconds (a thousandth the width of the Moon).

Three solar-eclipse expeditions were launched prior to 1919 to detect this light bending but were unsuccessful due to either bad weather or the ongoing war. The results of a fourth effort, an American endeavor led by Lick astronomers W. W. Campbell and Heber Curtis, were plagued by data comparison problems and so were never published. That was a fortunate turn of events for Einstein. The shaky American results went against him, and some of the other expeditions were carried out when his theory, not yet fully developed, was predicting that smaller, incorrect deflection.

That's why scientists paid keen attention to British astronomers when they announced they would give it a try in 1919 during a favorable solar eclipse whose path crossed South America and continued over to central Africa. The eclipse was taking place against a particularly rich background of stars, the Hyades cluster, which offered excellent opportunities to detect a star's shift. Sir Frank Dyson, Great Britain's astronomer royal, first pointed out this fortunate occurrence more than two years earlier. “This should serve for an ample verification, or the contrary, of Einstein's theory,” he noted at the time. And as the victors in World War I, the British had the necessary funding to organize and carry out the intricate venture.

On the evening before sailing, Eddington and his eclipse companion, E. T Cottingham, joined Dyson in his study. The discussion turned to the amount of deflection expected from classical Newtonian theory compared to Einstein's predicted value, which was twice as great. “What will it mean,” asked Cottingham playfully, “if we get double the Einstein deflection?” Dyson replied, “Then Eddington will go mad and you will have to come home alone!”

The next day Eddington and his assistant began their journey to the tiny isle of Principe, situated 140 miles off the coast of West Africa, a favorable site in the path of the eclipse. And to improve the venture's chances for a clear-weather view, two other astronomers traveled to the village of Sobral in the Amazon jungle of northern Brazil. On the day of the eclipse, May 29, a violent morning rainstorm almost doomed the Principe crew's operations. But by noon, the deluge ended and an hour and a half later they got their first glimpse of the Sun, already partially covered by the Moon. Too busy changing plates during totality, Eddington had only one chance, halfway through, to view the Sun's dark visage. “We are conscious only of the weird half-light of the landscape and the hush of nature, broken by the calls of the observers, and beat of the metronome ticking out the 302 seconds of totality,” he later recalled of the adventure.

The astronomers in Sobral were more fortunate. There they had two instruments and better weather. With their astrographic telescope they clicked off sixteen photos, and eight more were taken with a 4-inch scope. On Principe, Eddington and Cottingham, too, took sixteen photographs, but most ultimately turned out useless because of the intervening clouds. For several days after the eclipse, Eddington spent the daytime hours taking a first stab at measuring the star images on the plates that did turn out well. Upon examining the preliminary results, he turned to his colleague and exclaimed, “Cottingham, you won't have to go home alone.” He saw evidence that the streams of starlight had indeed bent around the darkened Sun according to Einstein's rules.

At a dinner soon after his return to England, Eddington entertained some fellow astronomers with a poem in the style of the Rubáiyát. “One thing is certain, and the rest debate—light-rays, when near the Sun, DO NOT GO STRAIGHT” was his rousing finale. In November the results of the expedition were officially reported at a special joint meeting in London of the Royal Society and the Royal Astronomical Society. Dyson spoke on behalf of the participants and behind him, almost like a stage setting, hung a picture of Isaac Newton, whose historic law of gravitation was undergoing its first modification. The best results supporting Einstein came from the Sobral 4-inch telescope. From its plates, the Britishers measured a starlight deflection of 1.98 arcseconds, a little on the high side of Einstein's prediction. The poorer images from Principe suggested a bending of 1.61 arcseconds, just below what Einstein calculated. Viewed together, though, Einstein was deemed a winner. These were the results that Eddington and Dyson stressed in their reports, which were widely hailed in newspaper headlines worldwide, turning Einstein into an overnight celebrity. “LIGHTS ALL ASKEW IN THE HEAVENS, Men of Science More or Less Agog Over Results of Eclipse Observations… Stars Not Where They Seemed or Were Calculated to be, but Nobody Need Worry,” blared the
New York Times
. Suddenly the public's attention was riveted to all things relative. Awed by the contributions scientists had made in the war effort, the public was highly receptive to hear more from the physics frontier—at least until their attention was diverted by the tomb of a young Egyptian pharaoh named Tutankhamen (“King Tut”) found a few years later almost completely intact.

Often neglected in the recountings of the famous 1919 solar-eclipse expedition was the team's largest data set from the Sobral astrographic telescope, which indicated a deflection of 0.93 arcseconds, in favor of Sir Isaac Newton. Because of various technical problems with the Sobral scope, including a blurring of its images, the British team decided to downplay that instrument's results. Eddington admitted he was unscientifically rooting for Einstein, but his instincts to reject the astrographic telescope results turned out to be good in the end. Campbell headed up another solar-eclipse expedition in 1922, which arrived at similar results and further confirmed Einstein's theory. When asked what he had been expecting, Campbell replied in all seriousness, “I hoped it would not be true.” Relativity's thoroughly new vision of space and time, coupled with its complexity, made even several leading scientists reluctant to accept its predictions. Those primarily trained in classical physics were quite leery of general relativity's strange outlook on the force of gravity and wondered if the light-bending was actually a refraction effect in the Sun's atmosphere or perhaps was due to a physical distortion of the photographic plate from imaging the hot solar corona. Heber Curtis, who met Einstein during his first visit to the United States, was certainly no fan of relativity. “We met in quick succession Their Eminences, the Prince of Monaco, Dr. Einstein and President Harding, and were photographed in a group on the White House lawn,” Curtis wrote Campbell soon after the meeting. Curtis, who was still convinced he had proven Einstein wrong with his flawed 1918 expedition results, would have been glad to see someone join him in overturning Einstein. “He surely looks like the fourth dimension!” joked Curtis about the German phenom. “Face is somewhat sallow and yellowish, redeemed by very keen bright eyes. But wears his hair a la [Polish pianist Ignacy] Paderewski in narrow greasy curls of small diameter and four or five inches long.”

Even a full decade after general relativity was introduced, many scientists were still resisting Einstein's new view of the universe. At the National Academy of Sciences meeting in Washington in 1925, physicist Dayton Miller of the Case School of Applied Science in Cleveland announced he had seen evidence of an “ether drag,” the speed of light changing with the motion of Earth. According to one conference attendee, this report was a “bombshell…which quite blew up the meeting of the Academy and
got more applause
than anything that happened…[disturbing] the relativists in general.”

Einstein supporters were enraged that doubts over relativity still lingered at all. “I am really getting pretty tired of the fundamentalist's attitude of the opponents of relativity,” said Henry Norris Russell in response to Miller's bolt from the blue. “Their psychology seems to me to be exactly similar to that of the most conservative theologians.” In time, though, Miller's experiments proved faulty, and astronomers would eventually have to face up to the new cosmic order.