How Does Graph Theory Shape Our World?
The Joy of Why
Steven Strogatz, Janna Levin and Quanta Magazine
4.9 • 577 Ratings
🗓️ 26 June 2025
⏱️ 34 minutes
🧾️ Download transcript
Summary
Born in the 18th century when Leonhard Euler solved the puzzle of the seven bridges of Königsberg, graph theory has become a foundational tool in mathematics. It studies relationships through nodes (vertices) and the links (edges) that connect them, transforming the complexity of systems — from friendship networks to airline routes — into elegant abstractions that reveal underlying structure and interaction.
Maria Chudnovsky from Princeton University is a leading mathematician in the field. In this episode of The Joy of Why, Chudnovsky talks with co-host Janna Levin about how she got into graph theory, solved the decades-old perfect graph problem, and used it to plan her wedding seating chart. Chudnovsky also reflects on her appearance in commercials as a “superstar mathematician,” and how her background primed her for a discipline that transcends language, culture and time.
Transcript
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| 0:00.0 | I'm Jana Levin and I'm Steve Strogetz and this is The Joy of Why, a podcast from Quantum |
| 0:11.2 | Magazine exploring some of the biggest unanswered questions in math and science today. |
| 0:20.8 | Steve, hi. Hi there. How are you doing, Jana? Good. It's good to see you again. I have a mouth problem for you. Oh, love it. |
| 0:28.4 | So imagine you're visiting a city and has a river maybe, let's say, maybe it's an island like Manhattan. And there's little islands like Randall's Island or Roosevelt Island, |
| 0:41.9 | and they're connected by bridges. And you're a tourist. You want to cross every bridge, |
| 0:46.3 | but you don't want to over-exert yourself, so you're going to try to cross each bridge once. |
| 0:49.6 | Have you heard of this before? I haven't mentioned that of the problem. |
| 0:51.1 | You know I have. |
| 0:53.7 | Seed planted. |
| 0:54.8 | Yeah, yeah. |
| 0:58.3 | No, it's a classic problem sometime in the 1700s. |
| 1:00.5 | Leonard Euler was asked this question. |
| 1:06.5 | You know, a funny thing about it that I only recently learned is that when the mayor of that town, |
| 1:09.2 | Kernigsberg, asked him to think about this question, |
| 1:27.5 | Euler complained, what are you asking me for? This is not a math problem. Right. Isn't that interesting to him? Yeah. This was not math. That's really interesting. At the time, he founded a new branch of math in thinking about it, but he didn't see it as math at the time. So how did he get interested enough to mathematicallyize the problem, which is really what we're doing a lot of the times? I think it's just that Euler felt that it was a curious question worth thinking about |
| 1:33.1 | just because it involved, as he put it, reasoning. A puzzle. It was a puzzle. Yeah. Now, |
| 1:38.9 | Konigsberg is now the Russian city of Kaliningrad, if I've got that right. So can a visitor there |
| 1:43.8 | figure out how to go across, there's a river, there's a mainland, |
| 1:47.7 | there's two islands, and seven bridges? |
| 1:50.0 | Yeah, that's right. |
| 1:50.8 | And in that old problem, the townspeople used to go out on Sundays and take strolls, |
| 1:56.1 | and it was an amusement to see if they could walk across each bridge exactly once. |
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