These Georgia Tech physicists helped prove Einstein right

Physics professors Deirdre Shoemaker and Laura Cadonati thrive in a male-dominated field
Deirdre Shoemaker and Laura Cadonati
Georgia Tech physics professors Deirdre Shoemaker (left) and Laura Cadonati

Photograph by Josh Meister

Deirdre Shoemaker has known from the time she was a 12-year-old science fiction fan that she wanted to spend her life studying black holes. But when she came to Georgia Tech in 2008 as a founding faculty member of the university’s Center for Relativistic Astrophysics, she found few other female postgraduates.

“You see women in biology, life sciences, and even math, but physics is still lagging for whatever reason,” says the bubbly Shoemaker, who in 2013 became director of the center, which researches cosmic mysteries like dark matter and particle physics.

This past February, Shoemaker and Laura Cadonati, a veteran researcher who joined Tech last year, were part of the international team that confirmed the existence of gravitational waves, a long-elusive cosmic feature first predicted a century ago by Albert Einstein’s theory of relativity.

A few days after the scientific breakthrough made headlines around the world, the two women delivered a presentation on the findings during a Sunday afternoon event sponsored by the Atlanta Science Tavern. Before an improbably standing-room-only crowd at the Decatur Recreation Center, they explained that the first gravitational waves ever to be detected had come from the collision and merger of two black holes—each about 30 times the mass of the sun—that occurred 1.3 billion years ago.

“The gravitational wave discovery,” Cadonati says, “has opened up new ways to study the universe” because the waves can be used to collect data about distant objects like neutron stars and cosmic events like the Big Bang.

Both Shoemaker and Cadonati are part of the Laser Interferometer Gravitational-Wave Observatory (LIGO), a global collaboration of more than 1,000 scientists working to detect the waves Einstein predicted in 1916. Students of general relativity—and fans of the movie Interstellar—know that gravity is produced when a mass distorts the universe’s underlying space time, which is why time slows near a source of gravity.

Gravitational waves are essentially ripples in space time radiating at the speed of light and can be observed as they sweep by and momentarily change the distances between objects. But the effect is too small to be detected unless the waves are especially strong, such as those emanating from a cataclysmic event like a black hole mashup, and even then the measuring tools must be extraordinarily precise.

On September 14, 2015, LIGO scientists working at identical four-kilometer-long laser detectors—located 2,400 miles apart in Washington State and Louisiana—recorded the telltale signature of a gravitational wave washing over Earth from deep space. The signal appeared seven milliseconds later in Washington, telling observers that it had come from somewhere in the southern sky. After months quietly spent corroborating the findings, the LIGO team made its historic announcement on February 11.

As chair of LIGO’s Data Analysis Council, Cadonati oversees the verification of all experimental results, including the September 14 signal. Shoemaker’s team at Tech crafted hundreds of binary black hole simulations. Their calculations helped establish that the detected wave had to have come from that long-ago collision.

Cadonati has found that an important part of her role in LIGO involves brokering agreement among smart, highly competitive researchers. She now jokes that her experience has prepared her for a career in politics.

A native of Italy, Cadonati, 45, earned her PhD at Princeton and taught at UMass-Amherst. She became hooked on experimentation during a year at Italy’s Gran Sasso National Laboratory, where she studied the properties of neutrinos, nearly imperceptible particles emitted by the sun.

Even though Cadonati holds a high post in LIGO, men fill nearly all of the other leadership positions. She believes the scarcity of women physicists in the tops ranks of academia is due to female students’ lack of self-confidence and perhaps subtle discouragement along the way. But the numbers are ticking upward: About one in five physics doctorates are currently held by women, up from one in 10 in 1990.

“I don’t see hurdles when I look back at my career, and I’ve enjoyed support from colleagues,” she says. “But I’ve also noticed an intangible bias against women in physics.”

Her daughter, she says proudly, is in a high school honors program for math.

Shoemaker, 44, who earned her doctorate at the University of Texas in Austin, likewise says she always felt people wanted her to succeed in her chosen field of theoretical astrophysics, but concedes that female scientists often aren’t taken as seriously as their young male counterparts. “I’m goofy and friendly, so that may have worked against me, but I was never discouraged,” she says. “Most people thought [my interest in science] was cute and that I would grow out of it.”

Three times a week, she takes part in a LIGO-related teleconference. About half her research time is devoted to the project, which reported the second detection of a gravitational wave in mid-June. The LIGO research, which is funded by the National Science Foundation, is considered a shoo-in for a Nobel Prize­—at least for the group’s founders at Caltech and MIT. Still, Shoemaker and Cadonati believe that involvement with LIGO will benefit and inspire their female students and junior colleagues as well.

“It’s pretty astounding that the data that LIGO has collected has so closely aligned with Einstein’s theory,” Shoemaker says, pointing out that the supercomputers that performed the calculations proving his predictions didn’t exist during his lifetime. As a bonus, gravitational waves have given scientists additional observational evidence for the existence of Shoemaker’s beloved black holes, another Einsteinian prediction.

As faculty advisor to Tech’s Women in Physics undergraduate social group, Shoemaker has been encouraged to see that about a third of the department’s incoming grad students are women. Recently promoted to full professor, she’s now one of the few senior women in academic physics. “It’s lonely up here,” she says.

This article originally appeared in our September 2016 issue.