Katie Mack is a theoretical astrophysicist who examines a range of questions in cosmology, the study of the universe from beginning to end. She is the Hawking Chair in Cosmology and Science Communication at the Perimeter Institute for Theoretical Physics, where she investigates dark matter and the early universe, while also making physics more accessible to a wider audience.
Mack is the author of the book The End of Everything (Astrophysically Speaking), which The New York Times called “engrossing” and “elegant,” and The Economist listed among the top science books of 2020. Mack has written for a number of popular publications, such as Scientific American, Slate, BBC Science Focus, Sky & Telescope, and Cosmos Magazine.
You can find her on X as @AstroKatie, Instagram and TikTok as @astrokatiemack, and Bluesky as @astrokatie.com.
In this Q&A with FirstPrinciples, she shares her zest for the “really, really deep physics that governs how everything works."
FirstPrinciples: What compels you to tackle fundamental questions for which the answers are so elusive?
Katie Mack: I think it's part of human nature to be curious about the world. For me, I like the big questions because they're fundamental to how the universe works and, in a sense, how we fit into that. I like the idea of getting insight into the really, really deep physics that governs how everything works. The fact that the answers might not come easy (or might not come at all) doesn't bother me – it's still very worthwhile to try.
FP: Why do you focus specifically on astrophysics?
KM: One of the things that limits what we can learn with particle physics experiments is the constraints involved in building the experiments themselves. But the universe is performing experiments for us, all the time.
Studying the universe means learning not only about our cosmic environment, but also about the basic laws that govern how things work both on Earth and in the cosmos.
FP: What do you find most surprising or amazing about our universe?
KM: I think the thing I find most amazing about the universe is how much about it we can understand.
Relativity gives us the ability to literally look back in time and see how the universe has evolved over the billions of years of its existence. I love that we can see the early universe and use our knowledge of it to better understand fundamental physics.
FP: What keeps you up at night?
KM: The thing I always worry about is whether I'm approaching a problem the right way, or if I might have missed something important. There's no guidebook on how to approach a research problem, and you can never be sure that you didn't miss an important paper that might contain information crucial to the problem you're trying to solve.
The best you can do is to try to stay engaged with the community and do what you can to keep up with the research.
FP: What discovery or advance do you hope to witness (or be part of) in your lifetime?
KM: I'd really love to know what dark matter is!
I hope we get some solid information about that soon. We have a lot of really interesting models for what dark matter might be but, so far, we don't have strong evidence in support of any specific one.
I hope we can solve that mystery. And I hope that my work will contribute to that project.
FP: How do you cope with the “cosmic vertigo" that comes with examining the universe in all its dizzying hugeness?
KM: I think the universe is just too big to possibly comprehend in any intuitive way. In some cases, trying to hold that vastness in your mind leads to something like fear and, in some cases, just awe.
For me, it's mostly awe.
FP: Why did you get a pilot's license? Does flying help you see scientific problems differently?
KM: I started flying because it was something I'd always been curious about, but never had an opportunity to try. At the time I started my training, it was late 2020, so most things were shut down and I was doing everything else remotely. Going out and actually doing something extremely non-virtual in the world was a big draw. But aside from the distraction and the way it got me out of the house, after a lesson or two, I knew it was going to be my new obsession.
It's great to get up into the sky and get a new perspective on the world, but I think it mostly appeals to me because it's technical and challenging and it has this very physical component as well.
I don't think it helps me see scientific problems differently, really, but it does make me think about how to approach new and unfamiliar problems and how to learn complicated things.
