Doing ‘Paleontology’ in the Outer Recesses of Space

Maximiliano Isi was a graduate student at the California Institute of Technology in 2014, when scientists there first detected gravitational waves—ripples in spacetime that Einstein had predicted nearly 100 years earlier, but that had never before been directly observed.

“The scientific attitude when you make a big discovery is to immediately understand what’s wrong with it—all the possible things that explain that it wasn’t an actual major discovery,” Isi said in a recent interview. “We even considered possibilities like that a hacker hacked into our computers and planted fake data.” In the months that followed, though, the data proved real, and, in September 2015, scientists from Caltech, MIT, and other institutions (including Columbia) announced that they had detected gravitational waves.

Since then, gravitational wave astronomy has blossomed, offering new insights into black holes, neutron stars, and the overall shape and scale of the universe. Columbia News caught up with Isi, who joined Columbia in July, to discuss his research and his life outside of work.

What makes gravitational waves so interesting to you?

Measuring and observing light is the primary way in which we understand the universe. Gravitational waves have some similarities to light, but instead of being in the electromagnetic field, they’re in the gravitational field. Gravitational waves travel at the speed of light and tend to travel unscathed through most things without being blocked. They are difficult to detect, but once you do you get a view into some of the most energetic processes out there in the universe that create these waves.

The primary source of gravitational waves are collisions of “compact objects,” which are objects that are denser than a normal star, like neutron stars and black holes. When two black holes encounter each other, they go in an orbit that starts shrinking as the black holes, drawn by gravity, move toward each other, and move faster and faster. When the black holes merge, in a fraction of a second, the process can pulverize the equivalent of three times the mass of a sun, and the energy released turns into gravitational radiation. There’s no light emitted in the merger. The only thing that is emitted is these gravitational ripples.

We’re now detecting these collisions roughly every other day, but our instruments are always improving.

What can gravitational waves tell us about the universe?

I think of it a bit like paleontology. When we look at gravitational waves, we also learn about the binary black holes that emitted them, and the stars that gave birth to those binary black holes. We also learn about the processes that regulate the life and death of stars and the environments in which stars live and their interactions with each other and the broader galaxy.

The other thing is that these signals are very loud. We can detect signals that typically traveled 1 billion light years or more before reaching us, so these gravitational waves give us access to the far universe, which is also the very old universe, since the universe is expanding away from us. That helps us answer questions like how far the universe is expanding.

There’s still a lot more for us to understand about how gravity works.

But that really was just the starting point. We keep uncovering new puzzles as to what these black holes that emit gravitational waves are doing and where they came from. It’s really rare to be at the start of a new field from the moment it gets started from zero, but that’s basically where I’ve had the luck to be.

Where did your interest in this field come from? Were you a stargazer as a kid?

I got into science through philosophy, in a way. I was a very curious kid always, and I just wanted to know how the world works. Like: What are we? What is this existence around us?

And so I was naturally inclined to think about these big, metaphysical questions, and that led me to philosophy. But then eventually I realized that to understand the world, we can’t just do it in abstraction. So to me, science, and astronomy in particular, is a way to explore.

Certainly the awe of the dark sky, that's, of course, propelling these questions. Just the sheer scale of it—like this sheer magnitude of where we find ourselves—puts humans into perspective, and that perspective can be both diminishing and scary, but at the same time, extremely thrilling and exciting, that we're like this beacon of self-awareness in this vast ocean. To me, it's like being an explorer out there and trying to make sense of what this all is. It's a big motivation for me, and it's always been, since I was a kid.

I wasn't out there building telescopes and stuff. I'm not a screwdriver kind of person. I'm more of, like, the nerdy book worm kind of person.

You have a dual appointment with the Simons Foundation, which is based in the Flatiron Building in Lower Manhattan. How does that work?

For the first three years of my time at Columbia, I’m based between Columbia and the Flatiron. After three years, I’ll be full-time at Columbia. It’s a nice set-up because there’s a lot of astrophysics happening down there, and other universities in the area have a similar set-up, so we can really bring these communities together.

What do you like to do when you aren’t hunting for gravitational waves?

I play very bad tennis, but I have a lot of fun doing it. I go to both Mets: The museum and the opera. I like Italian opera and contemporary opera. I’m also a big Formula One fan. I can watch it all weekend.