Please tell us about yourself
Twenty years before Interstellar turned gravity, wormholes, and black holes into mainstream fodder, then-graduate student Nergis Mavalvala had just learnt about gravitational waves from her advisor, Rainer Weiss, now a Nobel laureate.
She thought he was absolutely crazy. “Detecting these waves sounds like a nearly impossible mission,” she mused. But the seed of interest had been planted.
Now, Mavalvala is a celebrity in her own right. A celebrated physicist, Pakistani-born, openly queer, and a mother of two, she is a non-conformist, simply by the virtue of being herself.
Mavalvala and her collaborators are fashioning an ultrasensitive telescope designed to catch a glimpse of gravitational waves. Albert Einstein predicted the existence of these ripples in spacetime nearly a century ago, but they haven’t been observed directly yet. Theoretically a consequence of violent cosmic events—the collisions of black holes, the explosive deaths of stars, or even the big bang—gravitational waves could provide a brand new lens for studying the universe.
She holds the Kathleen and Curtis Marble Professor of Physics position at MIT and is one of the stalwarts in a long, arduous, and deeply human discovery of faraway perturbations rippling through the universe. For the past decade, her lab has focused on engineering high-precision laser beams using the principles of quantum physics to enhance the ability to detect signals from deep space.
How did you end up in such an offbeat, unconventional and groundbreaking career?
She attended the Convent of Jesus and Mary before going to the US as a teenager where she graduated with a BA in physics and astronomy from the Wellesley College in 1990.
During her graduation and PhD at the Massachusetts Institute of Technology (MIT) she started working on gravitational waves – which would lead her to one of the biggest discoveries of the century. But the tale was not so simple.
Mavalvala, who came to this country as a teenager to attend Wellesley College in Massachusetts, has a natural gift for being comfortable in her own skin. “Even when Nergis was a freshman, she struck me as fearless, with a refreshing can-do attitude,” says Robert Berg, a professor of physics at Wellesley.
While many professors would like to treat students as colleagues, Berg observes, most students don’t respond as equals. From the first day, Mavalvala acted and worked like an equal. She helped Berg, who at the time was new to the faculty, set up a laser and transform an empty room into a lab. Before she graduated in 1990, Berg and Mavalvala had co-authored a paper in Physical Review B: Condensed Matter.
Her parents encouraged academic excellence. She was by temperament very hands-on. “I used to borrow tools and parts from the bike-repair man across the street to fix my bike,” she says. Her mother objected to the grease stains, “but my parents never said such skills were off-limits to me or my sister.” So she grew up without stereotypical gender roles. Once in the United States, she did not feel bound by U.S. social norms, she recalls.
Her practical skills stood her in good stead in 1991, when she was scouting for a research group to join after her first year as a graduate student at MIT. Her adviser was moving to Chicago and Mavalvala had decided not to follow him, so she needed a new adviser. She met Rainer Weiss, who worked down the hallway.
“What do you know?” Weiss asked her. She began to list the classes she had taken at the institute—but the renowned experimentalist interrupted with, “What do you know how to do?” Mavalvala ticked off her practical skills and accomplishments: machining, electronic circuitry, building a laser. Weiss took her on right away.
In the early 1990s, Weiss, a pioneer in the measurement of the cosmic microwave background, maneuvered his research group into a new field: the detection of gravitational waves. Advances in laser technology made it plausible, but big practical challenges remained. Gravitational waves stretch and compress spacetime, subtly distorting objects they pass through. If they pass through a pair of objects, the distance between the objects changes. Up till now, those changes have been imperceptible.
In principle, a laser interferometer, with its two equally spaced mirrors, can use the change in interference patterns to register the passage of gravitational waves. The displacement of its mirrors would be tiny, however, roughly the equivalent of a thousandth of a proton’s radius. And just about anything can move the mirrors by much larger amounts: a car speeding in the distance, a seismic tremor, a clap of thunder. Even the distortion caused by the laser beam itself would need to be accounted for after the system had been shielded against all those external disturbances.
Please tell us about your work
In graduate school, Mavalvala worked on proof-of-principle interferometers at tabletop scale. An actual detector would be huge: The greater the initial distance between the mirrors, the greater the change in distance and the better the chance of measuring a displacement. Size, however, brings its own complications. Two mirrors 4 kilometers apart would have to be aligned precisely with the incoming laser. “If there is misalignment, the beam could just walk off into the desert instead of hitting its partner,” she says. To ensure this doesn’t happen, Mavalvala devised an automatic alignment system for the complex interferometer.
Her thesis work was incorporated in the design of the Laser Interferometer Gravitational-Wave Observatory (LIGO), which is run by MIT and the California Institute of Technology (Caltech) with funding from the National Science Foundation (NSF). In 1997, Mavalvala began a 3-year postdoc at Caltech. When the observatory went up in Washington state (there is also one in Louisiana), she stayed in the high-altitude desert in Hanford for days at a stretch to get the detector ready for data runs. In 2000, she joined the team as a staff scientist.
How does your work benefit the society?
A decade into LIGO’s existence, no gravitational wave has been detected. But the Advanced LIGO (aLIGO), which should be functional within 3 years, is on the horizon. With aLIGO, researchers hope to detect waves from more-distant sources. “The farther out you can look, the more galaxies, and hence more gravitational wave sources, are visible to you,” Mavalvala says.
“Making the mirrors stay still,” she says, “is something we devote a lot of attention to.” Using lasers to study a tiny displacement means having to contend with the momentum of photons impinging the mirror. There is also jostling from the thermal energy of atoms in the mirror and the suspending wires. Five years ago, her group demonstrated a novel technique to optically trap and cool a coin-sized mirror, bringing it to within a degree of absolute zero (0.8 K).
With that result, Mavalvala found herself at the forefront of an emerging field: quantum optomechanics. Typically, very small things obey quantum mechanics; classical mechanics governs macroscopic objects. But near zero Kelvin, even large objects should show quantum behavior. By exploring this blurring of boundaries, researchers in the new discipline hope to achieve theoretical insights with practical applications such as designing quantum information processors or building a more sensitive LIGO detector.
Mavalvala says that although it may not be immediately apparent, she is a product of good mentoring. From the chemistry teacher in Pakistan who let her play with reagents in the lab after school to the head of the physics department at MIT, who supported her work when she joined the faculty in 2002, she has encountered several encouraging people on her journey.
In the 10 years since, she has passed on her infectious enthusiasm for the LIGO project to many of her graduate students. “That is exactly what we were hoping for,” says Stanley Whitcomb, LIGO chief scientist at Caltech. “When she speaks to reviewers from NSF, or casual visitors to the observatory, she always made it a point to present technical details clearly. At the same time, she conveys that the work is fun.” The skill and desire to reach out to a broader audience, he remarks, is not a common trait among researchers.