The life’s work that proved Einstein right
CAMBRIDGE — Long before he designed the detector that proved Einstein right, Rai Weiss climbed out of the subway on his first day at MIT and ran smack into a suffocating stench.
He had applied to the school without visiting and thought suddenly that he had made a mistake, unprepared for the acrid byproducts of mayonnaise, chocolate, and soap manufacture that belched from the smokestacks of East Cambridge.
When he found a seat in a crowded auditorium, he heard an imposing figure command the freshmen to look left, then right: One out of every three would be gone by graduation.
“Holy sh--,” thought Weiss, a streetwise New York City kid who had never taken calculus. “That’s me!”
And he was right. He hung on for two years before flunking out, losing his way while pursuing a girl he met on a ferry.
It was a failed experiment of sorts — and one Weiss can laugh about now, a venerated physicist who did much more than find his way back to the Massachusetts Institute of Technology, where he still works six days a week as a professor emeritus at 83.
Weiss is the cheerfully cursing, relentlessly curious experimenter who dreamed up and helped will into fruition the massive antennae that captured the “chirp heard round the universe” — the first detection of gravitational waves rippling toward Earth from a cataclysm in a distant galaxy, two black holes that collided a billion light-years away.
That discovery, made secretly last fall and revealed in February, would have made a splash if it had simply been the first recording of gravitational waves, something Einstein initially conceived a century before.
But it also marked the first detection of black holes in pairs — orbiting each other before colliding to form a more massive black hole — a cataclysmic event more common than theorists ever dreamed.
For Weiss, it was the culmination of a half-century of work that began with a “thought experiment” he proposed during his one and only semester teaching general relativity. He was just groping for a tangible way to help his students understand what Einstein was talking about without getting lost in his elegant and exceptionally complicated mathematics.
What seemed at the time like a fanciful idea — build a device so sensitive it could detect faint, invisible ripples in space-time — became a professional obsession.
By the early 1970s, Weiss had drawn blueprints for detectors that would split and bounce laser beams back and forth between mirrors hanging freely inside long vacuum-tube arms, a way, he hoped, to record fleeting distortions caused by passing gravitational waves.
Back then, Weiss’s MIT colleagues considered him a starry-eyed flake. But in persevering, he eventually won federal support for the construction of two L-shaped observatories known together as LIGO — one carved into a Louisiana loblolly forest, the other resting in the high desert of Eastern Washington — so finely tuned they did just what Weiss dreamed.
The laser interferometer gravitational-wave observatories measured a wave that briefly squeezed and stretched their 2.5-mile arms by just 1/1,000th of a proton’s width.
It was a rare discovery that crossed over into pop culture even as it wowed science. This month, Weiss and his team won both the $500,000 Gruber Cosmology Prize and the $3 million Special Breakthrough Prize in Fundamental Physics. Many predict a Nobel Prize will follow.
But the detection of the waves is merely the beginning. As the LIGO equipment becomes more sensitive, and as more observatories are built, scientists in the newly minted field of gravitational-wave astronomy expect to unlock more messages from the unseen universe.
Because he has opened a window — an ear — to space, some have likened Weiss to Galileo.
But even that comparison may not do justice, said Kip Thorne, a decorated theoretical physicist. Galileo refined the telescope and pointed it at the sky, but he did not invent it. Weiss is both LIGO’s intellectual father and its chief mechanic, Thorne said.
“He really is, by a large margin, the most influential person this field has seen,” said Thorne, a longtime collaborator with Weiss. “And will see.”
Weiss does not just dismiss such talk; he all but covers his ears and hums.
“Complete crap,” he said, quick to cite the 1,000 scientists and engineers in 15 countries who brought LIGO to life — a team he has insisted on sharing prize money with — and worried that Thorne, whom he admires, has gone “completely insane.” But Thorne is hardly the only one who feels that way. Nergis Mavalvala, a MacArthur “genius grant” recipient who trained under Weiss and has devoted her career to LIGO, speaks of Weiss in the same breath as Einstein.
Though Weiss has devoted 100,000 hours to searching for gravitational waves, he also found time to advance the atomic clock and contribute to the discovery of cosmic microwave background radiation, the leftover light lingering from the Big Bang.
“He’s worked on three different things, and every one of them has changed the way we understand physics and the universe,” said Mavalvala, an MIT professor.
Though Weiss lights up about the way gravitational waves have sparked the public’s imagination, he has no stomach — or time — for exultation.
“Don’t tell me what Nergis said!” Weiss protested. “I don’t want to know! It just gets worse and worse.”
LIGO’s success hinges on tuning out “noise” — a falling tree, a seismic rumble — that could obscure the quiver of a gravitational wave.
As a boy, Weiss wanted to eliminate another kind of noise: the hiss and scratch of a stylus on the shellac records of the late 1940s.
By 12, he was repairing AC radios that blew out from being plugged accidentally into DC outlets, skipping school to read textbooks in the public library and scour the city for parts. By 16, he was building hi-fi systems from scratch so good that his parents’ friends lined up to buy them.
All they heard was vivid sound. But Weiss heard something else, especially in the music’s quiet passages, and remained obsessed with doing something about “that record scratching that drove me absolutely crazy.”
It wasn’t as if he came from a technical family. Born in Germany in the last heady days of the Weimar Republic, Rainer
As the Nazis rose to power, the Weisses fled to Prague and eventually New York City, toting Rai and baby sister Sybille. For years, they bounced among shabby apartments, Weiss’s mother supporting them with odd jobs until his father regained his footing, becoming a psychoanalyst.
Free to roam the city, Weiss became a teenage hi-fi pioneer. “I could’ve made a real killing, because I was there at the beginning,” he said. “But I was never a businessman.”
Obsessed with that hiss, he tried to invent a smart circuit with varying bandwidth, to capture the full range of fast, loud sounds while narrowing whenever a record grew slow and quiet. He didn’t quite succeed. “It made me madder than hell,” Weiss said. Though his grades were spotty, a teacher who saw his promise and technical ingenuity guided him to MIT.
Intending to major in electrical engineering, Weiss was deterred by a curriculum geared more to heavy-equipment design than acoustics. He switched to physics — simply, he says, because it had fewer requirements.
And then he met a girl on the ferry during a brief trip to Nantucket, a piano student at Northwestern. He decamped for Chicago, taking up folk dancing and piano in a Hail Mary courtship, returning in time for exams.
“I flunked the girl. I flunked out,” Weiss said. “Every way possible, I flunked.”
Unenrolled and casting about, Weiss wandered one day through MIT’s “Plywood Palace,” a ramshackle complex erected a decade earlier as temporary World War II laboratory space.
Overhearing an argument, Weiss peered through the grill on a lab door and saw what looked like a torpedo. One guy was seated on top, manipulating knobs; another guy barked frustrated instructions as he watched a light flicker on a galvanometer across the room.
Weiss offered to help these experimental physicists, using his electronics know-how to wire the controls and make their life easier. Soon, he had a full-time job, joining a salty-tongued crew of technicians who had previously fixed gunsights and repaired radar in the wartime Pacific. He loved it.
Weiss’s evident intellectual curiosity caught the attention of Jerrold Zacharias, the influential professor who ran the lab and was trying to develop an atomic clock, convinced that tracking the regular oscillations inside atoms could provide more precise measurements of time.
He cleared a path for Weiss to return to MIT and to stay on as his grad student. “Given my lousy record, it was sort of amazing,” Weiss said.
Zacharias thrilled Weiss with talk of using the clock to test a wild slice of general relativity, that time would appear to speed up or slow down in varying forces of gravity. He wanted to put one clock atop a mountain and another in a valley to test if they ran at different speeds.
They built a small version — now in the Smithsonian — that would become the world’s first commercial atomic clock. Zacharias left the lab to lead a national effort to reform science education, but Weiss kept toiling, hoping to perfect the even bigger, more precise clock needed for the mountaintop experiment.
Though he never quite got there, he helped advance the design of the most precise atomic clocks in the world.
Weiss was in no hurry to finish his doctorate until he married, beginning a family with Rebecca, a Radcliffe student. After stints at Tufts and Princeton, he returned to MIT as an assistant professor in 1964.
Soon after, the department head asked Weiss to teach relativity — just once, until they hired a theorist who knew it better.
But that was long enough for Weiss to engage the students with his hypothetical notion of how to detect gravitational waves. At the time, some still doubted whether they existed, let alone could be measured. Einstein himself had wavered about the former and died doubting the latter.
Others were just starting to try. A Maryland physicist named Joseph Weber had made a splash by claiming he had designed sensor-laden aluminum bars that rang whenever gravitational waves passed. When other scientists tried to replicate that experiment, though, they heard nothing.
It spawned a fierce dispute that tarnished the whole field; a pioneer, Weber quickly became a pariah. But Weiss was fascinated. Instead of following the few who continued testing Weber’s bars, Weiss wondered if he could design a device sensitive enough to do it by tracking the movement of laser light between floating objects.
Weiss proposed taking an existing device called an interferometer, which splits and times the travel of a light beam, and adding critical innovations — lasers, miles-long vacuum arms, and freely hanging mirrors.
The idea was that the mirrors would float as if in space, sensitive enough to be jiggled by a gravitational wave. Beams would traverse the long tubes many times, bouncing back and forth between the mirrors, simulating a beam long enough to make a minuscule change detectable.
In a 1972 article published in an MIT bulletin, he laid out the basic design for a laser interferometer gravitational-wave observatory (the future “LIGO”), while identifying noise sources that would obscure the signal and ways to suppress them.
The project electrified him. But at MIT, where prominent faculty did not believe in gravitational waves or black holes, Weiss garnered mostly skepticism. He started building a prototype about a yard and a half long, but he had to pursue it on the side.
Still, he wrote a proposal to the National Science Foundation in 1974 for a grant to keep building his tiny prototype, his laser-interferometer dream. He got rejected.
Then the Germans called. The uproar that had tainted the gravitational-wave search hadn’t extended across the Atlantic. Some experimenters at the Max Planck Institute for Astrophysics had seen a copy of Weiss’s failed NSF proposal and were intrigued.
They asked if they could build a prototype. Without hesitation, thrilled that they might advance the field, Weiss encouraged them. Jolted by the German interest, he again appealed to the NSF for money — around $50,000 — and this time succeeded.
Meanwhile, NASA in 1975 asked Weiss to run a Washington committee examining what the agency might do to advance cosmology and gravitation, and he invited a rising talent named Kip Thorne to testify. But Thorne, who had become a full Caltech professor at 30, failed to book a room for his visit.
Forced to bunk together, the physicists stayed up until dawn. Though Thorne was a theorist, he had Caltech’s backing to start a lab on the cutting edge of gravitation research. He had also co-written an influential textbook that included a line dismissing the tracking of split light beams as a dead end for finding gravitational waves.
In the hotel, Weiss began scribbling on scrap paper. “I explained to him that night where they had it wrong,” he said.
Indeed, the conversation proved “quite momentous,” as Thorne put it. He returned to Pasadena eager to build a prototype, persuading Caltech to hire experimenters and throw its weight behind the project. Weiss was not in position to move West, but suggested a Scottish experimenter named Ron Drever with a reputation for brilliance.
While the Germans and Caltech advanced test models large enough to fill a hall, Weiss retreated to MIT and dreamed of building “the big one” — or two, rather.
He knew multiple observatories were needed to determine whether signals were caused by a gravitational wave rippling past Earth and not, say, a truck backfiring.
Knowing a project of that magnitude would require collaboration, Weiss partnered with Thorne and Drever. With a second NSF grant, he also developed a blueprint and cost estimates for full-scale construction.
In 1986, the NSF urged them to go for it and to hire a director who could help them as they moved from tabletop experiment to “Big Science.”
But over the next several years, the project would nearly derail amid a funding battle with other researchers. Every observatory in history had used telescopes that used the electromagnetic spectrum to see the universe. LIGO was completely different, a detector made to hear invisible waves. Astronomers feared it was a pipe dream that might siphon funding from a limited supply.
“Feuding Scientists: ‘Leggo my LIGO!’ ” one newspaper headline put it.
Two directors, Rochus Vogt and then Barry Barish, helped Weiss and Thorne keep pressing the case. Lawmakers eventually approved the money sought by NSF and LIGO, providing $1 billion for design, construction, and operations over 20 years.
At the same time, a culture change at MIT — new administrators, younger professors — elevated Weiss and his project. He was able to work on it full-time, while helping graduate students earn their doctorates from this experiment alone.
Everything about LIGO pushed existing limits. Some particle accelerators had longer vacuum tubes, but those were skinny as a straw.
LIGO’s four vacuum arms, stretching 10 combined miles, are wide enough for a child to walk through — yet achieve an absence of atmosphere approaching interstellar space. Inside, the laser beams set a new standard for stability; the mirrors, the most flawless made, are suspended by silica fibers less than a millimeter wide.
The first-generation LIGO began searching for real in 2002, while work started in 2008 on “Advanced LIGO,” a project to upgrade the components and achieve greater sensitivity.
Amid a sprawling collaboration, Weiss earned a reputation for trouble-shooting down to the smallest detail; at one point he ventured through dank tunnels to pinpoint a vacuum leak — caused by a mouse family whose urine had broken down molecules in the steel.
Finally, last summer, Advanced LIGO neared the sensitivity needed to begin its first official run. They were still in test mode on Sept. 14, when a brief chirp played through speakers in the control room of the Louisiana observatory at 2:50 a.m., a sound like a hand abruptly brushing up the left half of a piano. Seven milliseconds later, the same thing happened in Washington.
The constant tiny movements of LIGO’s mirrors feed data to continuous graphs. If and when a wave hit, they expected the differences on the graph to be so minute they could only be distinguished from noise by a computer. But this one was so big it jumped off the screen, with the same waveform at both sites.
Weiss was in Maine, vacationing with family. As he does daily, he rose early to check
LIGO’s overnight logs. “Holy mackerel!” Weiss shouted. His wife and son came running, thinking something was wrong. So did Weiss. The signal was so strong. It must be a mistake, a hack.
The LIGO collaborators spent five months parsing the findings and preparing a paper, and by then there was no doubt: The signal represented the final movements of two black holes that combined were about 65 times as massive as our sun.
But when they slammed together, they formed a single black hole about 62 times as massive — with the balance radiating out as gravitational waves, ripples through the universe that took 1 billion years to reach Earth.
At a press conference that streamed live around the globe, an elegant animation demonstrated the collision of the black holes and the way LIGO found them.
When it was Weiss’s turn, he stepped forward as if from central casting, a professor in tortoise-shell glasses and tweed, producing from his pocket a simple section of mesh. He stretched and squeezed it, explaining how the ripple moved through space-time — his arms waving with excitement, an index finger in the air.
In the weeks ahead, he couldn’t believe how the finding grabbed people — even referenced in a New Yorker cartoon. Some might have relished a victory tour, but Weiss longed to disappear back into LIGO, whose components were still not as sensitive as he hoped.
“I mean, we were lucky!” Weiss admitted in April at an invitation-only workshop for 75 physicists, astronomers, and cosmologists around the launch of a Black Hole Initiative at Harvard. Though LIGO was not quite ready to detect the less powerful waves that theorists had predicted, the wave from the black-hole collision was so strong it couldn’t be missed. “That’s the big discovery,” Weiss said, that black holes exist, they exist in pairs, “and there seem to be about one of them a month that we can detect.”
“Did you say one a month?” said Avi Loeb, the theoretical physicist behind the Harvard initiative, as others repeated it.
“Yes,” Weiss said.
“Rai!” said Vicky Kalogera, a Northwestern professor who is part of the LIGO collaboration, which has not yet published that particular finding. “You’re being recorded!”
“That’s all right,” Weiss said. Laughter erupted.
Afterward, Loeb called Weiss’s candor a sign of “his young, free-spirited approach to science.” He said too few experimenters aim big, because long-shot projects are at odds with the publishing pressure of the job market.
“I love listening to Rai speak because it reminds me why doing science is so thrilling,” he added. “Forty years ago, mainstream astronomers were laughing at Rai’s hope to measure gravitational waves. His story illustrates how taking the path not taken can pay great dividends.”
Indeed, as Weiss made his way toward the exit, a Harvard theorist named Cumrun Vafa asked Weiss if he thought LIGO’s innovations could have benefits for other projects, like the Large Hadron Collider.
Weiss wasn’t sure. But with a child’s gusto, he turned to a blackboard nearby. In an instant, he was filling the surface with calculations, a small crowd gathering around him.
A voice in back called out, “Stephen is coming” — Stephen Hawking, surrounded by cameras — and the room parted as the most celebrated figure in world physics rolled to the front. Weiss hardly seemed to notice, engrossed as ever in finding an answer.