Thursday, December 1, 2016

The search for gravitational waves as per Science AAAS


Physicists have sought to detect ripples in spacetime called gravitational waves ever since they realized Albert Einstein’s general theory of relativity predicted their existence. But only some of the most massive astrophysical events, such mergers of black holes and neutron stars, can produce gravitational waves strong enough to be detected on earth. Since the 1990s, two laser-based facilities in Washington and Louisiana, collectively known as LIGO, have tried to observe waves from such events. They finally detected the first gravitational wave last September, as announced on 11 February. The detection has made Rainer Weiss, the college dropout who invented the gravitational wave detector, a shoo-in for a Nobel Prize. Recent LIGO upgrades, including more sensitive instruments and incorporation of detectors around the world, should bring the detection of many more waves and open up a whole new way of viewing cataclysmic events in the universe.

Rainer Weiss at the LIGO testbed at MIT in Cambridge. He conceived the detector concept in 1972.
Meet the college dropout who invented the gravitational wave detector
By Adrian ChoAug. 4, 2016 , 9:00 AM
Nearly 50 years ago, Rainer Weiss dreamed up a way to detect gravitational waves—infinitesimal ripples in spacetime predicted by Einstein’s theory of gravity, general relativity. Last September, that dream came true as 1000 physicists working with the Laser Interferometer Gravitational-Wave Observatory (LIGO), two huge detectors in Livingston, Louisiana, and Hanford, Washington, sensed a pulse of waves radiated by two massive black holes as they spiraled into each other a billion light-years away. The discovery makes Weiss, a physicist at the Massachusetts Institute of Technology (MIT) in Cambridge, a sure bet to win a Nobel Prize, his peers say. Weiss, 83, acknowledges the prospect with some apprehension. “It will fuck me up for a year,” he predicts as he nimbly steers his silver Volkswagen Beetle ragtop through Cambridge traffic. “That’s what it did to John Mather.” The line is vintage “Rai,” his friends will tell you: blunt, irreverent, funny, and impatient with anything that gets in the way of his work.
By any measure, Weiss has led an extraordinary life. Born in 1932 in Berlin, he and his family fled the Nazis. He grew up in New York City, on Manhattan’s Upper West Side, a street-smart kid with a gift for tinkering who built and sold his own high fidelity (hi-fi) systems. As an MIT undergrad, Weiss flunked out, and he later struggled to get tenure there. Still, he established himself as a leading physicist and worked for more than 40 years on LIGO, one of the most audacious experiments ever attempted. He works on it even now. “He’s the best person I know with a soldering iron,” says David Shoemaker, a LIGO physicist at MIT.
Shoemaker adds that Weiss’s foremost quality is empathy. A college dropout, Shoemaker credits Weiss with getting him into graduate school at MIT without an undergraduate degree. “He sought ways to bring out the best in me,” Shoemaker says. “He also took a rather irregular path, and I think because of that and just his nature, he is really interested in helping people.”
Weiss is also known for speaking his mind. “He is absolutely 100% committed to honesty both in his physics and in life,” says Peter Saulson, a LIGO physicist at Syracuse University in New York, who worked with Weiss at MIT in the 1980s. Dirk Muehlner, a retired physicist in Alamo, California, and one of Weiss’s early graduate students, shares that sentiment. “He’s totally honest. There’s no bullshitting for Rai. There’s no performance.”
People say, 'I failed out of college! My life is over!' Well, it's not over.

Rainer Weiss
Yet getting a fix on Weiss isn’t easy. An inveterate storyteller, he has clearly told his tales many times, smoothing the edges and burnishing the details. As he conjures up his past, little clues—loose threads, differing versions—suggest he’s not quite an open book. In fact, for Weiss, storytelling itself seems to serve some more subtle purpose.
In his modest office at MIT, on the second floor of a brick building resembling an old warehouse, Weiss settles behind a small wooden desk with a gaping hole in the top. Before the advent of flat-panel displays, Weiss took a saw to the desk so that he could tilt back bulky computer monitors. In a staccato New York accent, he tells his tale.
Rainer Weiss was born of a tryst between Frederick Weiss, a neurologist and scion of a wealthy German-Jewish family, and Gertrude Loesner, a stage and radio actress. While Gertrude was pregnant, Frederick, an ardent Communist, got into trouble by testifying in court against an incompetent Nazi doctor. The Nazis abducted him, and Gertrude’s family had to pull strings to get him released. The couple, who wed in 1933, soon fled to Prague, then in Czechoslovakia, where Weiss’s sister was born in 1937. Weiss says he was a happy, headstrong child. “I was probably an egotistical little bastard,” he says.
The family soon had to flee again, when U.K. Prime Minister Neville Chamberlain signed an accord ceding parts of Czechoslovakia to Germany. They heard the news on the night of 30 September 1938, while on vacation in the Tatra Mountains in Slovakia. As Chamberlain’s address blared from the hotel’s massive radio, 6-year-old Rainer stared in fascination at the glowing array of vacuum tubes inside the cabinet. The hotel emptied overnight as people fled to Prague.
The family immigrated to New York City in January 1939, 2 months before Hitler’s Weh rmacht rolled into Prague. “It was a miracle,” Weiss says. Unable to pass the medical board exams because of the language barrier, Frederick set up a practice as a counselor and eventually became a noted psychoanalyst. Gertrude worked in department stores, as a housekeeper, and at odd jobs. It was an unhappy household. “My father was a dictator in the true German sense,” Weiss says. “He suppressed my mother.” Both parents blamed Hitler for their marriage, he says.
Weiss says he grew up in an environment of benign neglect. “My parents were singularly uninterested in me,” he says. “My father was too self-centered and too busy with his own practice to pay a lot of attention to me, and my mother was probably deflected more by my sister.” He attended the prestigious Columbia Grammar and Preparatory School on a scholarship—“My mother went over and pleaded for them to take me,” Weiss says—but he sometimes cut classes, and teachers compared him unfavorably with his older schoolmate Murray Gell-Mann, who went on to win the Nobel Prize in Physics in 1969.
As a teenager, Weiss developed two passions: classical music and electronics. Snapping up army surplus parts, he repaired radios out of his bedroom. He even made a deal with the local toughs: If they left him alone as he lugged radios to and from the subway, he’d fix theirs for free. “They would steal things and I would have to fix them,” he says. “It wasn’t a good deal.”
Weiss’s sister, playwright Sybille Pearson, confirms that Weiss spent as much time as possible out of the unhappy home. But, as the only son, he was still something of a prince in his family, she says. For example, whenever the family moved to a new apartment, Weiss got the biggest bedroom to himself, she recalls. “He was adored.”
Nor was he a laggard at school, Pearson says. “He was bright and interested in everything and very smart.” Michael Wallach, Weiss’s classmate at Columbia Grammar, agrees. “Rai’s scientific abilities were widely recognized at school,” says Wallach, a psychologist retired from Duke University in Durham, North Carolina, although he adds that Weiss really was a street-smart kid and once broke his leg in some sort of a tangle.
If Weiss did cut classes, it wasn’t to hang out on the corner, says his son, Benjamin Weiss, a historian and curator at Boston’s Museum of Fine Arts. “He was going to piano recitals at Town Hall.” At the same time, Benjamin speculates, Weiss was drawn to tinkering partly as a reaction to his family’s cerebral atmosphere. “This is a German-refugee kid with very self-consciously cultured parents, and he’s rebelling against them by doing things with his hands,” Benjamin says. “But he’s surely not rejecting doing things with his head.”
If Weiss skipped cheerfully through his youth, he stumbled in early adulthood. He applied to MIT to study electrical engineering so that he could solve a problem in hi-fi—how to suppress the hiss made by the shellac records of the day. But electrical engineering courses disappointed him, as they focused more on power plants than on hi-fi. So Weiss switched to physics—the major that had, he says, the fewest requirements.
Then, in his junior year, Weiss flunked out of school entirely. He fell for a woman he met on a ferry from Nantucket to Boston. “She taught me about folk dancing and playing the piano,” he says. Weiss followed her when she moved to Evanston, Illinois, abandoning his classes in midterm. But the affair fizzled. “I fell in love and went crazy,” he says, “and of course she couldn’t stand to be around a crazy man.” Weiss returned to MIT hoping to take his finals only to find he’d flunked out.
Weiss says he was unfazed. “People say, ‘I failed out of college! My life is over!’ Well, it’s not over. It depends on what you do with it.” He took a job as a technician in MIT’s legendary Building 20, a temporary structure erected during the war, working for Jerrold Zacharias, who studied beams of atoms and molecules with light and microwaves and developed the first commercial atomic clock. Under Zacharias’s tutelage, Weiss finished his bachelor’s degree in 1955 and earned his Ph.D. in 1962.
Other physicists say Zacharias’s approach to research—using high-precision measurements to probe fundamental physics— inspired Weiss’s. But Weiss says he owes Zacharias a larger personal debt. “He got me back into school, then he got me into graduate school, all with a very bad record,” he says. “I think that extends all the way up to tenure.” A photograph of Zacharias hangs on Weiss’s office wall.
After a postdoc at Princeton University developing experimental tests of gravity under physicist Robert Dicke, Weiss returned to MIT in 1964. As a junior faculty member, he says, he published little and didn’t worry about advancing his career. MIT’s Shoemaker says Weiss probably got tenure only for his teaching—and wouldn’t get it today. Bernard Burke, an emeritus physicist at MIT, agrees that early on Weiss was a “happy gadgeteer” who “wasn’t likely to get tenure unless he did something that did something.” But, Burke says, Weiss soon turned things around.
Burke suggested that Weiss turn his attention from gravity to measurements of so-called cosmic microwave background (CMB) radiation, an all-pervading fuzz of radio waves that had been discovered in 1965 and that had been tentatively identified as the afterglow of the big bang, stretched to longer, cooler wavelengths by the unrelenting expansion of the universe.
In the late 1960s that connection remained tenuous, however. Radiation from the big bang should have a “thermal spectrum” with a lopsided peak indicating the radiation’s temperature. At long wavelengths, several groups had observed a climbing spectrum consistent with a temperature of 3°C above absolute zero. But in 1968, rocket measurements found high amounts of shorter wavelength radiation that clashed with a thermal spectrum and threatened the big bang hypothesis.

In the 1970s, Rainer Weiss made his name studying the cosmic microwave background with balloons.
In the 1970s, Rainer Weiss made his name studying the cosmic microwave background with balloons.
Massachusetts Institute of Technology

To probe the matter, Weiss and his graduate student Muehlner built a device that would fly on a weather balloon and measure the microwave spectrum to shorter wavelengths. In 1973, after three flights and a rebuild, they had solid data that fit a thermal spectrum and for the first time revealed the telltale peak. “It completely destroyed the rocket result,” Burke says. “Among those interested in the microwave background, [Weiss] was suddenly one of their stars.”
Robert Birgeneau, chancellor emeritus at the University of California, Berkeley, who was at MIT from 1975 to 2000, says that Weiss’s work won respect within the MIT physics department, too. “He liked to have the affectation of going to a working-class bar and stuff like that,” Birgeneau says. But “people looked up to him broadly at MIT. They respected his passion and his courage in going after really important physics.”
The CMB study not only secured tenure for Weiss, but also propelled him to a leading role in the broader scientific community. In 1976, NASA began work on its Cosmic Background Explorer (COBE) satellite, and the project’s scientific working group elected Weiss chair. Launched in 1989, COBE measured the spectrum of the microwaves with exquisite precision, proving beyond doubt that the CMB has a thermal spectrum. It also sensed tiny 1-part-in-100,000 variations in the CMB’s temperature from point to point on the sky—traces of infinitesimal quantum fluctuations in the newborn universe that are essential to the standard model of cosmology. In 2006, Americans John Mather and George Smoot shared the Nobel Prize in Physics for, respectively, measuring the spectrum and detecting the fluctuations.
Some physicists say Weiss should have shared that award. “It was a near miss,” Syracuse’s Saulson says. Nevertheless, Weiss’s contributions to COBE show he excelled in a role for which he says he’s badly suited: leader of a large scientific effort. “He’s a good collaborator,” says Mather, who works at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “He’s also good at deciding who should do what and making sure that people get the credit they deserve.”
Long before COBE, during his wayward untenured days, Weiss hatched the idea that would become LIGO. In the late 1960s, the MIT physics department asked him to teach a graduate course on general relativity. “I couldn’t tell them that I didn’t know any general relativity,” he says. So, striving to stay one step ahead of his students, Weiss focused on experimental tests of gravity.
Weiss’s students asked him to discuss experiments in which Joseph Weber, an engineer at the University of Maryland, College Park, was trying to detect gravitational waves using aluminum cylinders the size of a footlocker. General relativity states that massive objects—such as two black holes—spiraling together should radiate ripples in spacetime. Weber argued that those ripples— gravitational waves—would stretch his cylinders and make them vibrate like tuning forks. In 1969, he would claim a discovery of the waves, which others couldn’t reproduce.
Weiss couldn’t grasp Weber’s method, so he invented his own, based on an L-shaped device called an interferometer. It splits a laser beam and sends the two beams down perpendicular “arms.” The beams reflect off mirrors and race back to the beam splitter. If the arms are precisely the same length, the light waves return in sync and recombine so that light flows back toward the laser. But if the arms differ by a sliver of the light’s wavelength, then the out-of-kilter overlap sends some light leaking out a perpendicular “dark port.” Weiss realized that output could reveal a passing gravitational wave, which generally would stretch the arms by different amounts. He let the class chew on the idea in homework and wrote a 23-page report in the quarterly newsletter of MIT’s Research Laboratory of Electronics. LIGO sprouted from that document.

Rainer Weiss in his lab in MIT’s Building 20 in the late 1970s, working on radiation detectors called bolometers.
Rainer Weiss in his lab in MIT’s Building 20 in the late 1970s, working on radiation detectors called bolometers.
Massachusetts Institute of Technology

Weiss insists the concept of an interferometric detector was already “floating around.” But others say he was the first to spell out that the detector would have to be kilometers long and to describe how to deal with the various types of noise—from seismic vibrations to the pinging of individual photons on the mirrors—that could drown out the elusive waves.
Making the experiment a reality required mind-boggling technological feats. The twin LIGO interferometers have arms 4 kilometers long. To detect a gravitational wave, physicists must compare the arms’ lengths to within 1/10,000 the width of a proton. Approval to build the $300 million project did not come until 1994, 22 years later (see sidebar, p. 534).
In the meantime, Weiss became a fixture in Building 20, identifiable by the corncob pipes he smoked until he suffered a mild heart attack in 1995. He would work until 2 a.m., says Nergis Mavalvala, a LIGO physicist at MIT who was Weiss’s graduate student from 1990 to 1997, and would stay even later to help a student. When Mavalvala failed her qualifying exams, Weiss had her attend “reform school” in his office every Saturday for weeks. “He didn’t give a damn about the exams,” Mavalvala says. “But he knew that I had to get past them.”
Weiss earned a reputation for lending nontraditional students a helping hand. In 1983, Lyman Page, who had been out of school for 5 years and had spent 2 years sailing around the world, walked into Weiss’s lab and asked whether he could work for him. “He said ‘I can’t pay you, but you can work in the lab,’” Page says. “So I worked as a carpenter during the day and in the lab at night.” Page, now a cosmologist at Princ eton, credits Weiss for giving him a chance that others did not.
A functioning workaholic, Weiss enjoyed a full life outside the lab, too. In 1959, he married Rebecca Young, a recently graduated biology student working at the Harvard University Herbaria. The two frequented the same diner, says Rebecca, a retired children’s librarian. “One evening he asked me to pass the salt and we started having this big conversation about photosynthesis,” she says. “After we had been married for years it occurred to me that he never puts salt on anything.”
Rebecca says she was often a “physics widow,” especially in the 1960s and 70s, when Weiss would travel to Palestine, Texas, to launch his balloon experiments. Still, she says, he was a devoted husband and father. Even when he was away “there was always a lifeline,” she says. On Sundays Weiss would take his children to the lab, says Sarah Weiss, the couple’s daughter, now an ethnomusicologist at Yale-NUS College in Singapore. “I never felt that I didn’t have the access that I needed or hoped for,” she says.
Through it all, Weiss has had music. “Music is a big factor in his life,” Rebecca says. Weiss says he started playing the piano at 20, when the woman he failed to win started teaching him. He plays for an hour every evening, favoring classical composers such as Mozart, Beethoven, and Schubert, on a Steinway baby grand in the living room of the couple’s two-story Victorian in Newton, Massachusetts. “He goes in there at 8 o’clock and he shuts all the doors,” Rebecca says. “He thinks I can’t hear him.”
Weiss insists that even after 63 years of practice, he isn’t very good. “My technique sucks,” he says. “You will recognize the piece I play, but you won’t be satisfied.”

LIGO has spotted just the type of source Rainer Weiss had hoped to see: black holes spiraling together.
LIGO has spotted just the type of source Rainer Weiss had hoped to see: black holes spiraling together.
© Matt Weber

Now, Weiss’s tranquil life seems sure to be upended, as physicists expect him to share the Nobel Prize, if not this year, then the next. Since the LIGO team announced their discovery in February, he and LIGO cofounders Kip Thorne of the California Institute of Technology (Caltech) in Pasadena and Ronald Drever, retired from Caltech, have already won several prizes: the Special Breakthrough Award, the Gruber Cosmology Prize, the Shaw Prize in Astronomy, and the Kavli Prize in Astrophysics. “To tell you the truth, these prizes give me the willies,” says Weiss, who adds that he plans to use 90% of the award money to help graduate students. Weiss’s humility, expressed in the many stories in which he is never the hero, is striking. “He’s a very modest person,” his friend Wallach says. “That’s part of his charm.” But Weiss’s compulsive storytelling also seems to serve some deeper purpose, as becomes clear in what he calls “this famous story”: how he fell in love and flunked out of college.
The conversation circles back to the incident a couple times. At first, it seems simple enough. Weiss falls in love, comes on too strong, and scares the girl away. On the second pass, however, Weiss says that he wasn’t more of a lover than the woman could handle, but less than she wanted. “I had made a goddess out of her, and you don’t touch a goddess,” he says. “She wanted something more.” But that version soon fades, too. Asked whether he was popular as a young man, Weiss responds, “I wasn’t unpopular. I didn’t have any trouble getting girls.” When it came to love, Weiss says, “I had the experience.”
Wallach remembers it all differently. When Weiss was in his early 20s he fell in love with his piano teacher, a woman in her 30s. Wallach recalls that Weiss spent most of his time at his teacher’s house. “She was, not surprisingly, very taken with him and wanted to marry him,” Wallach says. Too young to marry, Weiss broke it off, he says.
Weiss’s sister questions how much any of it had to do with his failing out of college. “At that age that’s rebellion,” Pearson says. “And from the family we came from, what’s the way to do it? You drop out of school.”
The specifics of the decades-old affair matter far less than the way Weiss tells the story. He revels in changing the details, revealing a little more each time. But he never explains exactly what happened, how he really felt, or why he tells the story in the first place. Perhaps that is the point.
LIGO, Weiss’s brainchild, proved beyond a reasonable doubt the existence of black holes, the intense gravitational fields left by stars that collapse to infinitesimal points. Within a certain distance of that point—beyond the event horizon—gravity grows so strong that nothing can escape, not even light. In telling his tales, Weiss seems to create his own personal event horizon, a charming screen of words and anecdotes behind which he conceals his deeper self. For all his storytelling, Weiss remains a deeply private person.
At the couple’s house, Rebecca explains how, tinkering as always, Weiss has rigged a computer monitor to magnify his sheet music to compensate for his weakening sight. At her insistence, Weiss shows how the system works. In the living room stands his aging Steinway baby grand, the gloss finish worn to matte, the wood showing through at the corners, the top piled with sheet music. A flatpanel screen on makeshift gimbaled mount displays the enlarged music—a Beethoven sonata?—the 16th notes running up and down like staircases. The keyboard beckons.
“No,” Weiss says. “I won’t play.”
*Correction, 26 August, 12:25 p.m.: The story has been updated to reflect that in the photo of Weiss at the lab bench, he is working on equipment for measurements of the cosmic microwave background.