When Galileo turned a rudimentary telescope of his own invention to the sky some 400 years ago, it was a paradigm-shifting moment—not necessarily because of what he saw, but because of how. Suddenly, humans could access more of the universe than was visible to the naked eye, and in the ensuing years, scientists devoted themselves to building bigger and better telescopes to probe the universe in greater and greater detail. Yet one category of celestial curiosities eluded them: objects like black holes and neutron stars that are so dense they don’t give off any light at all, deeming them invisible to even the most powerful telescopes.
Then, in 2015, the paradigm shifted once again—scientists successfully captured two black holes colliding by detecting the gravitational waves produced by the impact. In the thick of a discovery that can only be described as monumental was an unlikely player: a Pakistani-American, openly gay, female astrophysicist named Nergis Mavalvala ’90, who began working on the Laser Interferometer Gravitational-Wave Observatory (LIGO) project as a Ph.D. student at Massachusetts Institute of Technology, and quickly established herself as a leader in the field.
What was it like as the discovery unfolded? “Crazy. Completely crazy,” Mavalvala recalls. “Our first reaction when we saw the signal was, ‘Oh, this is a mistake or a glitch in our instrument, but not something real.’ There was this frenzy of everyone checking their own work and then others cross-checking their work.” The excitement mounted over weeks and months as the scientists determined that indeed, for the first time, LIGO had detected gravitational waves from a celestial object: ripples in the space-time continuum produced when such an object accelerates through space. The findings confirmed Einstein’s Theory of Relativity, which had predicted that massive objects in space would give off gravitational waves.
The researchers announced their findings six months later, and science would never be the same. “A hundred years from now, people won’t really remember that LIGO was the first to see these colliding black holes,” Mavalvala posits. “It will really be the paradigm shift that now, instead of only being able to see things that are bright, we can also see the dark universe.”
So how did Mavalvala end up on leading edge of one of the most significant and complex research efforts of the modern era? Her journey starts growing up in Karachi, Pakistan, where she recalls being intrigued by the origins of the universe, yet completely dissatisfied by religious and social explanations. “I remember, from early childhood, thinking, the various narratives of genesis didn’t hang together with even simple scientific observations about the age of the solar system,” she says. “I think I was trying to make sense of these opposing narratives, and to me, the scientific ones seemed more testable.”
At the same time, Mavalvala was cultivating her natural aptitude for math and science in school while spending her free time pursuing her interest in building and fixing: making things out of spare parts, repairing bicycles. Not realizing that she could have a career as a scientist, she assumed she would become an engineer.
That all changed at Wellesley, where she spent three years conducting research with physics professor Robbie Berg. “That was my first taste for working in a physics lab, and I remember thinking this was the most fun thing anyone could ever do—I could be here day in and day out, and it felt just right,” she recalls. Her research focused on understanding the properties of a relatively unknown but promising semiconductor called aluminum gallium arsenide by looking for defects in its crystalline structure.
Of course, it wasn’t always smooth sailing. One of the first things Mavalvala did was break a laser … sort of. Charged with cleaning the mirrors on the instrument, Mavalvala enthusiastically removed all of them at the same time, rather than one at a time per the protocol. It took a week to get the laser working again, but Mavalvala learned a valuable lesson: “I always tell my students, you’re not at the cutting edge if you also aren’t breaking something.”
Wellesley, however, was about more than just research for Mavalvala. She honed her competitive edge on the varsity squash team, spending so much time at the sports center that the women at the front desk became concerned if she missed a day. She also found a home away from home at the Slater International Center, and developed a habit of riding her bike back and forth between Wellesley and MIT for class, too impatient to deal with the bus. “I think a lot of my identity, even today, kind of gelled there,” she says.
After graduating from Wellesley with a double major in astronomy and physics, Mavalvala headed to MIT for her Ph.D. “I knew I wanted to do physics. I wasn’t so wedded to what part of physics, and in fact LIGO was nowhere on my radar,” she recalls. “When I first heard of it was more or less the day I joined.”
That day came in 1991, after Mavalvala’s original advisor departed MIT, leaving her shopping for a lab. She met with Rainer Weiss, now an emeritus professor of physics at MIT, and a Nobel laureate for his contributions to LIGO. During the meeting, she recalls, Weiss had his feet up on his desk and a pipe in his mouth and asked her, “Well, what do you know?” As Mavalvala rattled off a list of advanced physics coursework, Weiss stopped her and clarified, “But what do you know how to do?” Mavalvala then told him about repairing bicycles growing up, and building electronics and using a machine shop at Wellesley, at which point he invited her to join his lab. “I was both amused and perplexed,” Mavalvala says. Weiss, for his part, had a simple reason for making the offer: “I could see that she was determined, and she was zippy, and that makes all the difference in the world.”
As Weiss pitched Mavalvala the LIGO project, which was still squarely in its startup phase, “I actually thought it was completely insane—I didn’t think anybody could make such a measurement with this level of precision,” she says. “But I thought about it the whole day after that, and I felt that if you could do it, it would be amazing, not just as a technical feat, but in terms of the science of being able to look at the universe with gravity instead of light.”
There are two LIGO detectors in the United States, the Hanford Observatory in Washington State and the Livingston Observatory in Louisiana. Each is shaped like an L, with each “arm” of the L extending 4 kilometers (roughly 2.5 miles.) At the end of each arm is a 35-centimeter diameter, 40-kilogram mirror that is perfectly aligned to face a similar mirror at the corner of the L. Laser beams are used to continually compare the distance between the two mirrors on each arm. As gravitational waves produced by celestial objects like black holes pass through the earth, the distance between the mirrors on each arm changes by 10^-19 meters—one ten-thousandth the width of a proton—which the laser beams can then detect.
A major challenge of the project is to detect the almost imperceptible movements of the mirrors caused by the gravitational waves while ensuring that the mirrors aren’t misaligned or moving due to some other force. For her Ph.D., Mavalvala developed a system to sense the orientations of the mirrors, and perfectly align them. “It’s one of the most difficult of all the problems we have in LIGO, how to get all the mirrors aligned so they’re all pointing in right direction.” Weiss says. “You have to do that automatically with enormous precision.” Malvalvala’s system is still used in the detectors today.
While advising her, Weiss came to realize that Mavalvala possesses two traits he considers critical for any successful scientist. “She has good ideas, but also has the persistence to make it happen,” he says. “When something’s not right, she finds out what’s wrong and she fixes it. And she doesn’t give up—she is as stubborn as a mule.”
After finishing her Ph.D. in 1997, Mavalvala carried her technical savvy and gritty, hands-on work ethic to the California Institute of Technology where she continued working on LIGO, first as a postdoctoral researcher, and later as a staff scientist. There, she helped build the LIGO detectors, spending some 25 days a month on site in Washington or Louisiana. “That was perhaps one of the most fun times of my life, because we were building something from scratch, and we were doing something that had never been done before, so we were inventing,” she says. “I felt like there was tremendous room for trying out ideas, because we were doing something that was so difficult.”
During that time, she worked closely with Stanley Whitcomb of Caltech, a chief scientist for LIGO. “I could see immediately that she had a liveliness and a sparkle that was going to take her a long way,” he recalls. “I grew to have an enormous respect for not only her technical ability, but also her ability to work with people of all levels. Nergis was the first person that anybody on the site would go to if they needed to have something explained to them about how the detectors work—she was more accessible and could explain things better than most anybody else.”
In 2002, as the detectors got up and running and the project expanded to include thousands of scientists all over the world, Mavalvala accepted a faculty position at MIT, where she has continued working on LIGO while leading a team of graduate students and postdoctoral researchers. Unable to spend as much time at the sites, she carved out a piece of the project related to quantum mechanics to tackle in the lab. Quantum mechanics is a fundamental theory of physics that attempts to describe nature at its smallest scale. Quantum uncertainty, a principle of quantum mechanics, states that we cannot know the exact location of microscopic particles like electrons and protons due to their natural jittering.
However, even though the LIGO mirrors are quite large, “it turns out that when you try to make measurements at that precision, quantum mechanics is important,” Mavalvala explains, since quantum uncertainty means that the laser light used to measure the microscopic changes in the distances between the mirrors jitters ever so slightly, thus limiting the precision of the measurements. (Mavalvala describes it as trying to measure a piece of paper with a ruler where the tick marks are continuously shaking.)
“In our group here at MIT, we’ve been doing something called quantum engineering: We’re developing light sources that perform better than just an ordinary laser by using ideas of quantum engineering,” Mavalvala says.
One of the group’s major developments is “squeezed light”: laser light that overcomes the limitations of quantum uncertainty in measuring the distance between the mirrors. To do this, the laser light becomes extremely precise in one property that the researchers are interested in measuring—namely the arrival rate of the high-energy photons that make up the laser beam—by sacrificing precision in another property the researchers don’t need to quantify—specifically, the total number of photons in the beam.
“Even as we speak, our students are installing the first of these squeezed light sources on LIGO, so when it comes back after this present shutdown for improvements, it will be a quantum enhanced detector,” Mavalvala says, adding that her work also has implications for other quantum measurement systems such as quantum computing. In fact, Mavalvala won a MacArthur Fellowship (a “genius grant”) in 2010 for her research, and Weiss credits her with launching a new field called the quantum physics of macroscopic objects.
With an illustrious scientific career spanning some three decades, it is no surprise that Mavalvala has become a role model for the groups she represents, including women in science and the queer and immigrant communities. And while Mavalvala is not entirely comfortable with the idea, she appreciates that she can have a positive impact simply by living her life openly and without reservation, the only way she knows how. “Somehow, by just being who I am, it can make a difference to people in terms of inspiring them be who they want to be, and that’s a wonderful thing,” she says. Mavalvala, who lives in Arlington, Mass., with her partner and two boys, says that these days, her life largely revolves around work and family. Though she doesn’t find much time for squash, she still bikes everywhere, hearkening back to her days at Wellesley.
As for her scientific aspirations, Mavalvala has no intention of slowing down on her quest to discover whatever the universe may still be concealing just out of sight. “Nature gives us signals, and they are what they are, so our job is to always be thinking about, how do we measure these?” Mavalvala explains. “What I love is thinking about instruments that can tease out these secrets of nature—how you design an experiment that will tell you something new about how nature works.”