This was disturbing news, and suddenly Lemaître had Einstein’s full attention. He had been able to push aside Friedmann by declaring that the unknown Russian’s calculations were just some mathematical sleight of hand, with no astronomical facts to back them up. But now here was another scientifically trained man telling him that there was valid evidence that the universe was expanding.
Lemaître’s explanation was necessarily rushed, for Piccard’s laboratory wasn’t too far away. He talked about the graduate work he’d recently done in the United States, at Harvard and MIT, where he’d learned remarkable things about a type of star called a Cepheid variable. He didn’t know who had done the first work on those stars, he explained, but they had the ability to grow and shrink in brightness, and thus provide definite information about what was happening in distant space. That research seemed to show—the evidence was fragmentary, but ah, the Professor should recognize how significant this might be—that distant star clusters were speeding away.
Einstein wasn’t rude, but Lemaître sensed that he was distracted. “He didn’t seem at all well informed about astronomical facts,” the Belgian remembered later. The taxi stopped; Einstein got out. Lemaître had no idea whether his message had gotten through.
It had, and it hadn’t. Five years before, in 1922, Einstein had dismissed Friedmann’s paper by saying that his work was just mathematics. Now, in 1927, when Lemaître went further and said he had data to back up the vision of an expanding universe—exactly what Einstein had asked for from Friedmann—Einstein dismissed that, too, as being physically unacceptable. Einstein knew that Lemaître hadn’t been entirely clear in what he’d explained, and Einstein was acting as if he didn’t really want to hear more, as if the fact that the findings Lemaître spoke of were incomplete and not from the most famous astronomers meant they could be ignored.
Clearly, something else was going on—and a famous social psychology experiment at Harvard suggests what it might have been. The study’s organizers had a group of students briefly shown a sequence of playing cards. The experimenters had, however, reversed the colors on the cards, so that the hearts and diamonds were black, and the spades and clubs were red.
It was a study of perception. When the cards were shown slowly, the students easily saw what was wrong. When the cards were flicked very quickly—too fast to recognize any details—the students had no idea anything was wrong and also were at ease. But when the cards were displayed at an intermediate speed—that is, the subjects could just about make out what was shown but didn’t have time to fully analyze it—the results were different. Many of them felt terribly uncomfortable. They complained of being dizzy, said they were suddenly very tired, or—without knowing why—said they just wanted to get out of the room. They wanted the experiment to end.
That was the situation Einstein was in after hearing about Friedmann’s work and now about Lemaître’s even more detailed developments. Their ideas preyed on him. He didn’t entirely understand all the details yet, but he could sense the underlying truth: something was wrong, and he wanted that feeling to end.
EINSTEIN’S DILEMMA WASN’T going to be solved simply. His aversion to confronting it was too strong, and his investment in adding the lambda to his G=T equation was too great. He would need someone with more authority than an unknown Belgian priest or a Russian mathematician to move him. And in the world’s astronomical community of 1927, the man at the opposite extreme—renowned above almost all others—was the director of the famed observatory on top of California’s Mount Wilson, Edwin Powell Hubble.
Hubble was a man’s man who in his youth, reputedly, had been such a tough boxer that Chicago promoters had sounded him out to see if he would go up against the world heavyweight champion, the powerful Jack Johnson. Hubble had turned them down and gone on to become a combat officer, serving in some of the most desperate battles near the end of the Great War in France.
Hubble didn’t like to talk about the war too much, but occasionally, late at night, he would admit to awed grad students that “the hardest thing was to see wounded men fall, but yet go forward without stopping to help them.” He also told of having been knocked out by shell bursts (which would explain his injured right elbow) and even of being trapped in a swaying observation balloon: terrified, of course, yet somehow finding what some people called the courage—but which he knew as simple common sense—to keep observing the battlefield below, drawing charts of the enemy’s positions.
It was the story of a remarkable life—and it was far from accurate. For one thing, while Hubble was a tall man, and fit, he had done only one term of boxing as an undergraduate at the University of Chicago—a fine academic institution, but not one especially known for the ferocity of its students. No promoter could possibly have considered a relatively inexperienced student for a bout against the world heavyweight champion.
Hubble’s army experience was also not quite what he described. He had been called up, but his units had never seen combat. His military discharge record has categories for battles, medals, and wounds—and the word “none” is neatly inked after each one. The elbow injury may have been incurred while playing softball during a brief stint teaching high school in Kentucky.
The advantage of Hubble’s tall tales was that having Walter Mitty dreams could be a wonderful motivation for real achievements. Hubble did study astronomy and wanted to be very good at it. He ended up director of the observatory on Mount Wilson. His predecessor had been skilled at extracting money from wealthy benefactors, including a businessman named John D. Hooker, and the rugged mountain now housed the world’s most powerful telescopes, including the massive 100-inch Hooker telescope. It weighed so much that the sleek iron girders and counterweights that kept it in the proper position made the inside of its curved dome look like a set from Fritz Lang’s 1927 futuristic film Metropolis. Hubble was further motivated to succeed by a competitor with the disconcerting habit of seeing through his mannerisms. For despite the extreme English accent that Hubble put on—his conversation full of expressions such as “By Jove” and “Jolly good”—he’d actually been born on a farm in the Ozarks in Missouri. So, too, had Harlow Shapley, America’s other leading astronomer. Shapley was suspicious of Hubble’s affectations, and like Hubble he too wanted acclaim and success.
Hubble dressed in a quilted jacket for cold nighttime observations, 1937
The rivalry between Hubble and Shapley made them both keen to use their positions to spread ideas that they liked to say were their own. In 1924, for example, a Swedish mathematician had written to the Harvard observatory saying that news had reached the Continent of Professor Leavitt’s stunning work on using Cepheid variables to measure distance. Could Leavitt please get back in touch to provide details on her achievement?
Normally, a communication like that from Sweden would be taken as a sign that there was at least some interest in nominating an individual for a Nobel Prize. Shapley by then had taken over from Pickering as the director of the observatory. He wrote back to explain that, sadly, Miss Leavitt was deceased (he knew that Nobel Prizes are never given posthumously) and it turned out that he, Shapley, had actually done the main work on Cepheids, while Miss Leavitt, far from being a professor, had been little more than a passive tool under his direction.
This was the opposite of the truth, but since Shapley was now keen to broadcast news of what Leavitt had told him, her findings about Cepheid variable stars received a wider audience. This helped Hubble, still on Mount Wilson, take Cepheids the next step forward.
Astronomers at the time knew that there were a great number of stars floating nearly stationary in our Milky Way galaxy, but no one was sure whether there was anything beyond it. A few strange wisps of light called nebulae had been found that didn’t fit in any obvious classification scheme, but those were generally assumed to be clouds of gas existing here and there among the Milky Way’s many stars.
The 100-inch telescope on Mount Wilson was so powerful that Hubble and astr
onomer Milton Humason were able to take extremely detailed pictures of what was taking place in those wispy nebulae. Some of them didn’t seem to be gas at all, but rather clusters of stars. The question became: how far away were they?
If these nebulae were relatively near, they’d be just more stars within our Milky Way, and the belief that the universe was composed of one unchanging island galaxy—our own—would be confirmed. If the mysterious nebula wisps were, however, much farther away, maybe we weren’t as alone in the universe as we’d believed.
Hubble was a diligent worker, for as the gap between his stories and the reality of his life widened, he knew he had to achieve something substantive, and quickly, or he really would be caught out. He was good with his hands, but Humason was even better. An exceptionally careful, sensible man, he’d begun as a teenage mule driver on the mountain, helping lug materials for the observatory’s construction over rough, winding trails amidst the scrubland and forests. He had trained himself, with the help of a handful of generous astronomers, to operate the heavy machinery and sensitive photographic units.
Milton Humason, around 1940
In 1925 Humason and Hubble compared several photographs of a particular nebula in the constellation Andromeda and saw that there was one star that oscillated just like one of the Cepheid variables Leavitt—or was it Shapley?—had so carefully analyzed. This particular star had a period of about thirty-one days, which was so long that Leavitt’s charts showed it should be extremely bright. Yet even with the enormous magnification of the 100-inch telescope, it was very, very dim.
How could something so intrinsically bright appear dim to the observers’ eyes? There was only one answer. The brilliant light this star gave out must have been diminished by its flight over enormous distances to earth. Hubble did the calculations. Astronomers often use a unit of distance called a light-year. (Despite the confusing label, this is not a measure of time, but simply how far light travels in one year. It comes to about 6 trillion miles.) Our Milky Way galaxy is perhaps 90,000 light-years across, and most astronomers at the time would have agreed that was the extent of all important matter in the universe. But the Cepheid in Andromeda worked out to be nearly 1,000,000 light-years away.
Hubble’s finding could mean only one thing: our galaxy was not alone. That wisp wasn’t a tiny cloud of interstellar gas or a nearby cluster of a few stars. Instead, it had to be another complete galaxy: huge, glorious, floating far away from ours, no doubt part of a flotilla in the heavens that stretched farther than anyone had imagined.
Even better than this discovery of a new galaxy was the fact that there was a way to measure how quickly it and any other distant galaxies were moving. This could be done using a variation of the well-known Doppler effect. That phenomenon initially concerned sound: if an ambulance whirs past you on the street, the sound of its siren appears to shift from a high pitch as it’s approaching to a suddenly lower pitch as it speeds away. So in a sense it is also with light, although here it’s not the sound that changes, but aspects of its color. A spaceship that’s heading toward you will appear a little bit bluer than it would if it were stationary; if it’s moving away, it will appear a little bit redder. The effect is slight at low velocities but becomes more noticeable as the spaceship speeds up.
Several astronomers had already begun to measure the shifting colors of different clusters of stars in the sky, and that’s what Lemaître had used in the rough early data that he’d tried to explain to Einstein in the taxi in Brussels. The farther away groups of stars were, the redder their color became. Whatever was on the outer reaches of space really was speeding away from us.
Humason and Hubble were simply working out Lemaître’s discoveries about the movement of stars in greater detail. Lemaître hadn’t had such accurate information on distances as they did. No one had. Mount Wilson’s great telescope was allowing them to identify pulsating Cepheids in galaxies so distant that these details would have been invisible to the telescopes Freundlich had lugged to the Crimea or Eddington had traveled with to Principe. The data being acquired at Mount Wilson also—and, oh, was this pleasing for Hubble to contemplate—could scarcely be detected by the once mighty 24-inch telescope at the Harvard research station in Arequipa that Shapley in Boston sent instructions to. Humason’s telescope had a mirror 100 inches across, which could concentrate far more light than Shapley’s instrument. Hubble, accordingly, couldn’t resist taking a few digs at his nemesis, writing to Shapley that “in the last 5 months [I] have netted nine novae and two variables . . . Altogether, the next season should be a merry one.”
By 1929 Hubble and Humason were done. Humason, easygoing as he was, didn’t mind ace boxer and war hero Hubble publishing the work under just his name (though giving credit to loyal support from his “assistant” Milton Humason). The paper had a neat chart showing how far away twenty-four different galaxies were and the best evidence about how fast they were moving based on shifts in their color. There was a bit of scatter in the data, but the main thrust was clear. Galaxies were speeding away from us, and the more distant they were, the faster they sped.
The evidence presented in the paper was more complete than anyone else’s, and that fact—combined with Hubble’s majestic voice and skillful use of publicity—ensured that his findings traveled more widely and far more quickly than those in the Annales de la Société scientifique de Bruxelles could.
The news crossed the Atlantic, reaching Einstein in Berlin. And, finally, he couldn’t hold out against the evidence any longer.
Einstein let it be known that lambda was now dead. Hubble had killed it—or at least he had amplified and added authority to findings showing that it was no longer needed. Einstein’s original equation was restored, in all its beautiful simplicity, but his psyche would never recover.
TRAVEL WAS HARDER in the interwar period than it is today, and it wasn’t until nearly two years after Hubble’s 1929 finding that Einstein could make it to California, by a long steamship journey that took him first to New York and then west through the Panama Canal. There he would pay homage in person. When he and Elsa arrived in December 1930, their ship was met by thousands of excited locals, numerous photographers, and even a band that struck up a specially composed Einstein song.
If Hubble had been happy before, merely pretending that he had been a war hero and boxing champion, now in 1931, with the world’s greatest scientist in attendance, his pride knew no bounds. He sent out invitations for Einstein’s visit to almost everyone who counted in the American astronomical community. Elsa had already brought her husband to a great number of Hollywood dinners, for which she had an efficient if not especially polite selection procedure. As invitations poured in, she accepted them all, then at the last minute would decide which one her husband would appreciate most and cancel the others. Invitations from Hollywood royalty were always accepted, and Einstein attended the Hollywood premiere of the movie City Lights alongside its star, Charlie Chaplin, surrounded by photographers and crowds.
Einstein with Charlie Chaplin at the City Lights premiere in Los Angeles, January 1931. When Einstein asked him what all the attention meant, Chaplin replied, “It means nothing.”
Hubble knew his own invitation was one the Einsteins were not going to cancel. On the great day itself, Thursday, January 29, 1931, Hubble dressed carefully: his shoes polished just so; his best Oxford-style plus fours (trousers bunched below the knees); his pipe; his favorite tweed jacket—perhaps a final check of the tie—and then he was ready.
The vehicle that usually trundled visitors to the top of Mount Wilson was an old, muffler-rattling truck. For Einstein’s presence, Hubble hired a sleek Pierce-Arrow touring sedan instead. The photographers and newsreel cameramen who pushed close to record Einstein and his wife inside the car saw beside him, on the great man’s right, a beaming, exuberant, utterly content Edwin Powell Hubble.
Hubble stuck close to Einstein on the twenty minutes of hairpin turns going up the mountain, and also while the
y inspected the 150-foot-high tower where a solar imaging telescope was housed (only briefly—and anxiously—staying behind when Einstein proceeded to the top in the single-passenger open elevator, pulled along the fifteen-story ascent by a slender cable). Once Einstein was safely back down from the tower—and headlines of WORLD’S GREATEST GENIUS KILLED BY INCOMPETENT ASTRONOMER averted—Hubble didn’t let go. He stuck to Einstein when they went into the main lodge and the other telescope buildings, and when it came time to enter the huge dome where the 100-inch giant was housed, as soon as the nimble Einstein started clambering up to the exposed catwalk at the very top—a terrifying view of Los Angeles sometimes visible in the distance, far, far below—Hubble clambered right up beside him. Photographers stood beneath them, clicking away. “He sort of wormed or muscled his way in,” one colleague later recorded. “That’s where he wanted to be photographed, with the great man.”
After dinner, when the sun finally went down and the stars came out, Hubble escorted Einstein back to the 100-inch telescope, this time not for photo opportunities, but to look through the eyepiece and examine the planets, nebulae, and stars. Whether Hubble’s greatest pleasure was in hosting Einstein or in knowing that Shapley would have to read about it in the newspapers in the following days (for Shapley’s was one invitation Hubble had somehow forgotten to send) has not been recorded.
Hubble loved glory, but he wasn’t selfish—at least not entirely so—and he knew it would only be fair if Humason was part of the day. When he told Einstein that this was the jolly good man who’d performed the actual recordings to get the redshifts—the data that proved how fast the galaxies were moving—Einstein settled down with Humason in one of the observatory’s offices to examine the original plates. Einstein had spent years in the Patent Office in Bern and had always liked to build things. His father and uncle had, of course, been immersed in engineering throughout his youth. He respected solid, practical skills. Humason had the gnarled hands of the laborer he’d been in his youth. It was clear to Einstein, as the two men went through the images, that Humason had taken no shortcuts in his work. The shifts were unquestionable. Entire galaxies were hurtling away, at ever increasing speed.
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