‘A New Window to the Universe’: Radcliffe Institute Reflects on Scientific History of Gravitational Waves

Dean of the MIT School of Science Nergis Mavalvala – one of the astrophysicists who first directly detected gravitational waves – gave a lecture on the scientific history of gravitational waves Tuesday at an event hosted by Harvard’s Radcliffe Institute for Advanced Study.

The lecture, called “Gravitational Waves: A New Window to the Universe,” was part of Radcliffe’s annual Kim and Judy Davis Dean’s Lecture in the Sciences series.

Radcliffe Dean Tomiko Brown-Nagin kicked off the lecture with her own perspective on the groundbreaking discovery, which came in 2015.

Gravitational waves are ripples in space-time caused by high-energy cosmic events like the merging of black holes. Even though scientists like Albert Einstein theorized about gravitational waves as early as 1916, they dismissed them as very faint and therefore undetectable.

“Indeed, our desire for new and deeper understanding has driven path-breaking discoveries throughout history,” Brown-Nagin said. “Few subjects have captured our curiosity more than the cosmos itself.”

Mavalvala explained at the start of her lecture that before the discovery of gravitational waves, astrophysicists relied on light, which she referred to as a “natural messenger,” to study the universe.

However, while working with the Laser Interferometer Gravitational-Wave Observatory, which has locations in Livingston, La. and Hanford, Wash., Mavalvala and her colleagues detected gravitational waves for the first time.

During Tuesday’s lecture, which took place on Zoom, Mavalvala described her and her colleagues’ methodology.

“The L in LIGO stands for laser. It is the light source that made it possible,” she said. “When you’re trying to make a really precise measurement, you need a really, really good ruler.”

The detectors consisted of four-kilometer long tunnels with extremely precise lasers and mirrors that constantly searched for a signal from a gravitational wave rippling through space, she said.

“If you had a really precise clock you measure the light travel time, and if a gravitational wave comes through, that light travel time would change because the gravitational wave is shrinking and stretching the space between the laser and the mirror,” Mavalvala explained.

Upon first seeing the signal in September 2015, Mavalvala and her colleagues were in disbelief. According to Mavalvala, they shook their heads and said, “No, that can’t be real.” Their historical observation, she said, was “as beautiful as the astrophysical story because it has made us confront the smallest, most fundamental forces in nature at the quantum level.”

Despite the groundbreaking success achieved by Mavalvala and her team, they faced challenges, Mavalvala said in an interview after the lecture.

“When you’re trying to do something of this precision that’s never been done before, there’s almost nothing you can just buy off the shelf,” she said. “We had to invent solutions for just about every technology that we used.”

Mavalvala stressed that scientific achievements should not end conversations but should in fact start new ones.

“We’ve turned on this completely new way to sense the universe, but this moment in history won’t be remembered for these particular discoveries but for the paradigm shift where we can now use gravity alone or gravity with light as a new tool for unimagined discovery,” she said during the lecture.

Currently, Mavalvala and her team are trying to improve how astrophysicists detect gravitational waves through using a quantum light source instead of an ordinary laser.

—Staff writer Jorge O. Guerra can be reached at jorge.guerra@thecrimson.com. Follow him on Twitter @jorgeoguerra_.

—Staff Writer Christie K. Choi can be reached at christie.choi@thecrimson.com.