A Proclivity for the Unknown

In the Review’s July 1, 2021 issue, astrophysicist Priyamvada Natarajan reviews three new books about matter: Katia Moskovitch’s Neutron Stars, which addresses the composition of the incredibly dense remains of collapsed stars; Katie Mack’s The End of Everything, on what may happen during the universe’s inevitable demise, and Franck Wilczek’s Fundamentals, about the basic physical laws of reality as we currently understand them. 

Natarajan explains that one simple but powerful law, first theorized by the fifth-century-BCE Greek philosophers Leucippus and Democritus, runs through the long history of inquiry into the makeup of the world around us, from medieval alchemy to nuclear physics: that all things are made of small, indivisible particles. However, after recent discoveries about the behavior of subatomic particles and the apparent existence of large amounts of dark matter and energy, scientists are finding matter more and more mysterious. It is in these murky edges of the map that Natarajan has made her career, as she told me this week via e-mail: “My research work focuses on the dark side of the universe—mysterious entities like dark matter, black holes and dark energy—whose presence we can only indirectly infer from observational data.”

This suits her well: she enjoys the Holmesian hunt, and it’s an exciting time intellectually in her field. “The connection of abstract models, mathematics and computation to data is what I enjoy playing with,” she said, “and I feel so fortunate to be working at the cutting edge of these topics at this very special time, when the confluence of ideas, instruments and computation are leading rapidly to radical and transformative discoveries.” New data from the Chandra and Hubble Space Telescopes facilitated her research modeling black holes and mapping the detailed distribution of dark matter throughout the cosmos.

A proclivity for the unknown as a child helped bring Natarajan to astrophysics. She grew up in an academic environment in Delhi—both her parents are professors, and the house was full of books, as well as maps, “both celestial and terrestrial,” which she became obsessed with. Naturally curious, she was drawn to scientific inquiry. “I was an avid experimenter, and would dive into the shallow tanks that stored water in our garden for watering plants,” she said. “I would take various toys with me to see which ones sunk and which floated. In addition to satisfying my curiosity, I was often dripping wet and had to have my clothes changed.” Perhaps trying to redirect her scientific enthusiasm out of the water, her parents bought her both a telescope and microscope. “It was a clear-cut choice for me—the unreachable, distant, and untouchable was far more fascinating. I was always attracted by the cosmos—the night sky and the deep, dark mysteries it held have always seduced me.”

In high school, she got her first taste of research by doing a project with the director of the Nehru Planetarium, using a Commodore 64 computer that she had learned to program to make a sky map of Delhi, plotting the monthly positions of visible planets and constellations, which ended up being published in a national newspaper. She followed this with a project on sunspots, but despite this strong start in astronomy, her interests remained broad. She moved to the US to attend MIT as an undergraduate, enjoying classes in anthropology and other areas of the humanities, especially in the history and philosophy of science. She decided she wanted to do two doctorates, deferring graduate study in Physics for a PhD in MIT’s Program in Science, Technology & Society, hoping to bridge the cultural divide between the disciplines. “I wanted to be a consummate insider in science working at the research frontier while also being able to interrogate my work as an outsider and witness,” she said. She left partway through the degree (though she got a masters) to study astrophysics at the University of Cambridge, where she was elected the first woman fellow in the discipline in the history of Trinity College. She was offered a faculty position at Yale, and has worked there ever since.

Though her academic career ultimately focused on hard science, where she is recognized for her seminal contributions to mapping dark matter, the formation of the first black holes, and tracing the growth of supermassive black holes, Natarajan continues to write for a general audience, in publications such as The New York Times and The Wall Street Journal, in addition to her work in our pages, and in a 2017 book, Mapping the Heavens, which explained the greatest cosmological discoveries of the last century. She is attracted to the history of ideas—a particularly long history, in the case of astronomy. “I am sure that since humans first stood upright and gazed up at the stars, they began to wonder what was going on in the skies and what role they had to play in this cosmic stage,” she told me. “The evolution in our explanations for phenomena encode important insights into how we as humans have made sense of the world.”

For her part, she hopes to demystify the scientific process, which she sees as a fundamentally creative, human endeavor:

In the United States, more than anywhere else, there is troubling, rampant disbelief in science, and in my opinion this stems from a lack of understanding not of the content of science but the practice of science. I wanted to demonstrate the passions that drive us scientists, the rivalries both intellectual and personal that underlie our grand quests. This in my opinion makes science more relatable and accessible to the non-scientist.

Of course, the human element can have its downsides. I wondered if she had ever felt marginalized in a male-dominated discipline. “It is challenging to work in a field where one is an outlier in many ways—gender, race, life choices, culture, and temperament,” she said. “I want to do my part to level the playing field for those who come behind me—the younger generation of scientists. I would love for them to have fewer obstacles and barriers than I experienced.”

But the thrill of discovery has maintained her enthusiasm over the years. Given what we know now, I asked, is it time to revise our old assumption about the fundamental atomism of our world? Things had changed even since she wrote her article for the Review, Natarajan replied—new analysis of measurements of neutron stars from the NICER (Neutron Star Interior Composition Explorer) experiment aboard the International Space Station had found that “the internal structure of neutron stars is quite different from our speculations.” As she describes in the article, it was thought that in the unbelievable pressure inside of neutron stars, neutrons might be crushed and turn into a liquid of quarks, the smallest known subatomic particle. However, it turns out that “the universe has surprised us yet again and it seems to be that it is neutrons all the way—that they remain intact right down to the core! The pace of scientific discovery is so hectic right now, that our understanding of many astrophysical phenomena is rapidly evolving. It is a very heady time.”

I wondered how spending most of her workday pondering these cosmological mysteries affected her day-to-day life. “I don’t particularly fancy our messy, inequitable, unjust, and unfair world, so the cosmos offers me an escape,” she said. “One benefit of being an astrophysicist dealing with these vast physical scales and long timescales on a daily basis is that one naturally defaults to a long cosmic view.” The drawbacks seemed limited.

The peril is that I am much more comfortable and have better intuition dealing with solar masses than ounces—which is not particularly helpful when trying to follow a recipe!