In early September 2015, Salvatore Vitale, who was then a research scientist at MIT, stopped home in Italy for a quick visit with his parents after attending a meeting in Budapest. The meeting had centered on the much-anticipated power-up of Advanced LIGO - a system scientists hoped would finally detect a passing ripple in space-time known as a gravitational wave.
Albert Einstein had predicted the existence of these cosmic reverberations nearly 100 years earlier and thought they would be impossible to measure. But scientists including Vitale believed they might have a shot with their new ripple detector, which was scheduled, finally, to turn on in a few days. At the meeting in Budapest, team members were excited, albeit cautious, acknowledging that it could be months or years before the instruments picked up any promising signs.
However, the day after he arrived for his long-overdue visit with his family, Vitale received a huge surprise.
"The next day, we detect the first gravitational wave, ever," he remembers. "And of course I had to lock myself in a room and start working on it."
Vitale and his colleagues had to work in secrecy to prevent the news from getting out before they could scientifically confirm the signal and characterize its source. That meant that no one - not even his parents - could know what he was working on. Vitale departed for MIT and promised that he would come back to visit for Christmas.
"And indeed, I fly back home on the 25th of December, and on the 26th we detect the second gravitational wave! At that point I had to swear them to secrecy and tell them what happened, or they would strike my name from the family record," he says, only partly in jest.
With the family peace restored, Vitale could focus on the path ahead, which suddenly seemed bright with gravitational discoveries. He and his colleagues, as part of the LIGO Scientific Collaboration, announced the detection of the first gravitational wave in February 2016, confirming Einstein's prediction. For Vitale, the moment also solidified his professional purpose.
"Had LIGO not detected gravitational waves when it did, I would not be where I am today," Vitale says. "For sure I was very lucky to be doing this at the right time, for me, and for the instrument and the science."
A few months after, Vitale joined the MIT faculty as an assistant professor of physics. Today, as a recently tenured associate professor, he is working with his students to analyze a bounty of gravitational signals, from Advanced LIGO as well as Virgo (a similar detector in Italy) and KAGRA, in Japan. The combined power of these observatories is enabling scientists to detect at least one gravitational wave a week, which has revealed a host of extreme sources, from merging black holes to colliding neutron stars.
"Gravitational waves give us a different view of the same universe, which could teach us about things that are very hard to see with just photons," Vitale says.
Random motion
Vitale is from Reggio di Calabria, a small coastal city in the south of Italy, right at "the tip of the boot," as he says. His family owned and ran a local grocery store, where he spent so much time as a child that he could recite the names of nearly all the wines in the store.
When he was 9 years old, he remembers stopping in at the local newsstand, which also sold used books. He gathered all the money he had in order to purchase two books, both by Albert Einstein. The first was a collection of letters from the physicist to his friends and family. The second was his theory of relativity.
"I read the letters, and then went through the second book and remember seeing these weird symbols that didn't mean anything to me," Vitale recalls.
Nevertheless, the kid was hooked, and continued reading up on physics, and later, quantum mechanics. Toward the end of high school, it wasn't clear if Vitale could go on to college. Large grocery chains had run his parents' store out of business, and in the process, the family lost their home and were struggling to recover their losses. But with his parents' support, Vitale applied and was accepted to the University of Bologna, where he went on to earn a bachelor's and a master's in theoretical physics, specializing in general relativity and approximating ways to solve Einstein's equations. He went on to pursue his PhD in theoretical physics at the Pierre and Marie Curie University in Paris.
"Then, things changed in a very, very random way," he says.
Vitale's PhD advisor was hosting a conference, and Vitale volunteered to hand out badges and flyers and help guests get their bearings. That first day, one guest drew his attention.
"I see this guy sitting on the floor, kind of banging his head against his computer because he could not connect his Ubuntu computer to the Wi-Fi, which back then was very common," Vitale says. "So I tried to help him, and failed miserably, but we started chatting."
The guest happened to be a professor from Arizona who specialized in analyzing gravitational-wave signals. Over the course of the conference, the two got to know each other, and the professor invited Vitale to Arizona to work with his research group. The unexpected opportunity opened a door to gravitational-wave physics that Vitale might have passed by otherwise.
"When I talk to undergrads and how they can plan their career, I say I don't know that you can," Vitale says. "The best you can hope for is a random motion that, overall, goes in the right direction."
High risk, high reward
Vitale spent two months at Embry-Riddle Aeronautical University in Prescott, Arizona, where he analyzed simulated data of gravitational waves. At that time, around 2009, no one had detected actual signals of gravitational waves. The first iteration of the LIGO detectors began observations in 2002 but had so far come up empty.
"Most of my first few years was working entirely with simulated data because there was no real data in the first place. That led a lot of people to leave the field because it was not an obvious path," Vitale says.
Nevertheless, the work he did in Arizona only piqued his interest, and Vitale chose to specialize in gravitational-wave physics, returning to Paris to finish up his PhD, then going on to a postdoc position at NIKHEF, the Dutch National Institute for Subatomic Physics at the University of Amsterdam. There, he joined on as a member of the Virgo collaboration, making further connections among the gravitational-wave community.
In 2012, he made the move to Cambridge, Massachusetts, where he started as a postdoc at MIT's LIGO Laboratory. At that time, scientists there were focused on fine-tuning Advanced LIGO's detectors and simulating the types of signals that they might pick up. Vitale helped to develop an algorithm to search for signals likely to be gravitational waves.
Just before the detectors turned on for the first observing run, Vitale was promoted to research scientist. And as luck would have it, he was working with MIT students and colleagues on one of the two algorithms that picked up what would later be confirmed to be the first ever gravitational wave.
"It was exciting," Vitale recalls. "Also, it took us several weeks to convince ourselves that it was real."
In the whirlwind that followed the official announcement , Vitale became an assistant professor in MIT's physics department. In 2017, in recognition of the discovery, the Nobel Prize in Physics was awarded to three pivotal members of the LIGO team, including MIT's Rainier Weiss. Vitale and other members of the LIGO-Virgo collaboration attended the Nobel ceremony later on, in Stockholm, Sweden - a moment that was captured in a photograph displayed proudly in Vitale's office.
In 2022, he was promoted to associate professor. In addition to analyzing gravitational-wave signals from LIGO, Virgo, and KAGRA, Vitale is pushing ahead on plans for an even bigger, better LIGO successor. He is part of the Cosmic Explorer Project , which aims to build a gravitational-wave detector that is similar in design to LIGO but 10 times bigger. At that scale, scientists believe such an instrument could pick up signals from sources that are much farther away in space and time, even close to the beginning of the universe.
Then, scientists could look for never-before-detected sources, such as the very first black holes formed in the universe. They could also search within the same neighborhood as LIGO and Virgo, but with higher precision. Then, they might see gravitational signals that Einstein didn't predict.
"Einstein developed the theory of relativity to explain everything from the motion of Mercury, which circles the sun every 88 days, to objects such as black holes that are 30 times the mass of the sun and move at half the speed of light," Vitale says. "There's no reason the same theory should work for both cases, but so far, it seems so, and we've found no departure from relativity. But you never know, and you have to keep looking. It's high risk, for high reward."
