What links certain mathematical models of traffic flow, shallow-water waves, and quantum particle scattering? The surprising answer lies in a corner of the algebraic combinatorics world that goes by the name of positive Grassmannian. In simple terms, the positive Grassmannian is a shape that classifies other shapes. Remarkably, pieces of the positive Grassmannian can be reassembled in forms that reveal shared structures in these and many other seemingly unrelated mathematical systems.

That we know the positive Grassmannian crops up in many real-world settings is largely down to the theoretical work of Lauren Williams at Harvard University. In this latest episode of The Joy of Why, Williams talks to co-host Steven Strogatz about her work, how she realized the surprising pervasiveness of the positive Grassmannian, and how she has made a career of finding connections among fields that don’t at first sight seem connected. The conversation then switches to another project Williams is working on, called First Proof, which is trying to measure objectively how good AI systems are at coming up with proofs of research-level mathematical statements, and which leads to an exploration of whether AI may or may not take over mathematics.

Note: Since this conversation was recorded, results from the First Proof, Second Batch project were released on June 10 2026.

One of the most surprising and remarkable discoveries in recent scientific history has been CRISPR. Short for Clustered Regularly Interspaced Short Palindromic Repeats, CRISPR is a form of immune system that evolved in bacteria more than a billion years ago to defend against persistent viral threats. Under attack, bacteria can snip a small fragment of a virus’s DNA, store it in the CRISPR region of their genome, and then use it to recognize and destroy the same virus if it returns. The CRISPR-Cas9 system, to give it its longer name, consists of a short strand of guide RNA that identifies where to cut the DNA and a protein that acts as the molecular scissors.

What made this system truly revolutionary was the demonstration in 2012 that it could be reprogrammed with different pieces of guide RNA to edit virtually any genome in any species, and at a level of precision and ease that far surpassed existing gene-editing tools. Since then, the editing capability of CRISPR has been tested on everything from developing disease treatments to engineering drought-resistant crops to resurrecting genes of extinct species. The possibilities have expanded so rapidly that researchers, ethicists, and regulators have found themselves struggling to keep up.

One person acutely aware of the power of CRISPR is Jennifer Doudna, co-developer of the technology. Doudna, who received the Nobel Prize in Chemistry in 2020 with Emmanuelle Charpentier for this pioneering work, has been a prominent voice not only for its vast potential but also for its responsible and ethical use. In this episode of The Joy of Why, Doudna tells co-host Janna Levin how her early, “rebellious,” decision to study RNA led her on a serendipitous path to one of biology’s most transformative discoveries. They also discuss the breakthroughs, barriers, and frontiers that will define CRISPR’s true impact.

What is the future of gene editing with CRISPR? Has AI changed mathematics forever? Will we find other civilizations in the universe? What if we’ve been wrong about dark energy all along? These are just a few of the big, bold questions we’ll be exploring in the new season of The Joy of Why.

Mathematician Steven Strogatz and physicist Janna Levin are back as your hosts for these and other conversations that explore the frontiers of basic science and mathematics. Each episode features an in-depth conversation in which Steven or Janna sits down with a leading scientist or mathematician to unpack one big idea or area of research. The two hosts also chat together throughout each episode, sharing their own thoughts, reactions, and questions.

Birds are not merely descendants of dinosaurs — they are dinosaurs. For Yale evolutionary biologist and ornithologist Richard Prum, birds have been a lifelong passion and a window into some of evolution’s most intriguing mysteries.

In a wide-ranging conversation with co-host Janna Levin, Prum traces the deep evolutionary origins of feathers, which he argues first emerged not for flight but for insulation, camouflage and display. Their colors — often invisible to the human eye — come into sharp focus under birds’ ultraviolet vision, suggesting a sensory world far richer than our own.

Prum also explains why he champions Darwin’s once-marginalized theory of sexual selection, which proposes that traits such as the peacock’s tail evolved not for survival, but simply because they were attractive. Beauty, in other words, may shape life as powerfully as utility.

Every time data travels — from smartphones to the cloud, or across the vacuum of space — it relies on a silent but vigilant guardian in the form of error-correcting codes. These codes, baked into nearly every digital system, are designed to detect and repair any errors that noise, interference or cosmic rays might inflict.

In this episode of The Joy of Why, Stanford computer scientist Mary Wootters joins co-host Steven Strogatz to explain how these codes work, and why they matter more than ever. Wootters discusses the evolving list of codes that keep modern communication resilient, and the frontiers in which error correction may have a crucial role, including distributed cloud systems, quantum computing and even DNA-based data storage.

Most cosmologists agree that our universe had a beginning. But the finer details about the Big Bang remain a mystery. A history of everything would explain all, or so theoretical physicists hoped. In his final years, Stephen Hawking working with Thomas Hertog proposed a striking idea: The laws of physics were not precisely determined before the Big Bang; they evolved as the universe evolved.

In this episode of The Joy of Why, Hertog speaks with co-host Janna Levin about his work and partnership with Hawking. Hertog, now at KU Leuven in Belgium, explains why they rejected the popular multiverse theory and instead explored the idea that the universe’s properties are a result of cosmological natural selection. According to Hertog and Hawking, these properties must be viewed through the lens of human observers, who are also the consequence of natural selection.

So, how could the universe have created the conditions needed for life to emerge? Listen to the episode below to find out.

Listen on Apple Podcasts, Spotify, TuneIn or your favorite podcasting app, or you can stream it from Quanta.

Climate models have changed the way we view the world. While effective, these models are imperfect, and scientists are constantly looking at ways to improve their accuracy and predictability.

MIT professor Elfatih Eltahir has spent decades developing complex models to understand how climate change affects vulnerable regions like the Nile Basin and Singapore. In this episode of The Joy of Why, Eltahir tells co-host Steven Strogatz how growing up near the Nile in Sudan helped him realize that climate change doesn’t occur in isolation. To better understand climate-related impacts and to create more effective adaptation strategies, Eltahir says we need regional models that incorporate contextual data like disease spread and population growth. Eltahir also discusses his “Equation of the Future of Africa,” and he introduces the concept of “outdoor days,” which he hopes can improve public perception about climate change.

Listen on Apple Podcasts, Spotify, TuneIn or your favorite podcasting app, or you can stream it from Quanta.

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.