The Joy of Why
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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 , 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 , 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 https://podcasts.apple.com/us/podcast/the-joy-of-why/id1608948873, Spotify https://open.spotify.com/show/2FoxHraQSKwxV2HgUfwLMp, TuneIn https://tunein.com/podcasts/Science-Podcasts/The-Joy-of-Why-p1653040/ or your favorite podcasting app, or you can stream it from Quanta https://www.quantamagazine.org/tag/the-joy-of-why.
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 https://cee.mit.edu/people_individual/elfatih-eltahir/ has spent decades developing complex models https://eltahir.mit.edu/ to understand how climate change affects vulnerable regions like the Nile Basin and Singapore. In this episode of , 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 https://podcasts.apple.com/us/podcast/the-joy-of-why/id1608948873, Spotify https://open.spotify.com/show/2FoxHraQSKwxV2HgUfwLMp, TuneIn https://tunein.com/podcasts/Science-Podcasts/The-Joy-of-Why-p1653040/ or your favorite podcasting app, or you can stream it from Quanta https://www.quantamagazine.org/tag/the-joy-of-why.
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 , 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.
What links a Möbius strip, brain folds and termite mounds? The answer is Harvard University’s L. Mahadevan, whose career has been devoted to using mathematics and physics to explore the form and function of common phenomena. Mahadevan, or Maha to his friends and colleagues, has long been fascinated by questions one wouldn’t normally ask — from the equilibrium shape of inert objects like a Möbius strip, to the complex factors that drive biological systems like morphogenesis or social insect colonies. In this episode of , Mahadevan tells co-host Steven Strogatz what inspires him to tackle these questions, and how gels, gypsum and LED lights can help uncover form and function in biological systems. He also offers some provocative thoughts about how noisy random processes might underlie our intuitions about geometry.
For decades, string theory has been hailed as the leading candidate for the theory of everything in our universe. Yet despite its mathematical elegance, the theory still lacks empirical evidence. One of its most intriguing, yet vexing, implications is that if all matter and forces are composed of vibrations of tiny strands of energy, then this allows for a vast landscape of possible universes with different physical properties, varieties of particles and complex spacetimes. How, then, can we possibly pinpoint our own universe within a field of almost infinite possibilities? Since 2005, Cumrun Vafa(opens a new tab) https://www.physics.harvard.edu/people/facpages/vafa at MIT has been working to weed out this crowded landscape by identifying which hypothetical universes lie in a ‘swampland’ with properties inconsistent with the world we observe. In this episode of , Vafa talks to co-host Janna Levin about the current state of string theory, why there are no more than 11 dimensions, how his swampland concept got an unexpected lift from the BICEP array https://www.quantamagazine.org/bicep2-telescope-detects-possible-gravitational-waves-20140317/, and how close we may be to testable predictions.
Geometry is one of the oldest disciplines in human history, yet the worlds it can describe extend far beyond its original use. What began thousands of years ago as a way to measure land and build pyramids was given rigor by Euclid in ancient Greece, became applied to curves and surfaces in the 19th century, and eventually helped Einstein understand the universe. Yang-Hui He sees geometry as a unifying language for modern physics, a mutual exchange in which each discipline can influence and shape the other. In the latest episode of , He tells co-host Steven Strogatz how geometry evolved from its practical roots in ancient civilizations to its influence in the theory of general relativity and string theory — and speculates how AI could further revolutionize the field. They also discuss the tension between formal, rigorous mathematics and intuition-driven insight, and why there are two types of mathematicians — “birds” who have a broad overview of ideas from above, and “hedgehogs” who dig deep on one particular idea.
Large language models (LLMs) are becoming increasingly more impressive at creating human-like text and answering questions, but whether they can understand the meaning of the words they generate is a hotly debated issue. A big challenge is that LLMs are black boxes; they can make predictions and decisions on the order of words, but they cannot communicate the reasons for doing so. Ellie Pavlick https://cs.brown.edu/people/epavlick/ at Brown University is building models that could help understand how LLMs process language compared with humans. In this episode of The Joy of Why, Pavlick discusses what we know and don’t know about LLM language processing, how their processes differ from humans, and how understanding LLMs better could also help us better appreciate our own capacity for knowledge and creativity.
Quantum gravity is one of the biggest unresolved and challenging problems in physics, as it seeks to reconcile quantum mechanics, which governs the microscopic world, and general relativity, which describes the macroscopic world of gravity and space-time. Efforts to understand quantum gravity have been focused almost entirely at the theoretical level, but Monika Schleier-Smith at Stanford University has been exploring a novel experimental approach — trying to create quantum gravity from scratch. Using laser-cooled clouds of atoms, she is testing the idea that gravity might be an emergent phenomenon arising from quantum entanglement. In this episode of the Joy of Why podcast, Schleier-Smith discusses the thinking behind what she admits is a high-risk, high-reward approach, and how her experiments could provide important insights about entanglement and quantum mechanical systems even if the end goal of simulating quantum gravity is never achieved.
Quantum computing promises unprecedented speed, but in practice, it’s proven remarkably difficult to find important questions that quantum machines can solve faster than classical ones. One of the most notable demonstrations of this came from Ewin Tang https://ewintang.com/, who rose to prominence in the field as a teenager. When quantum algorithms had in principle cracked the so-called recommendation problem, Tang designed classical algorithms that could match them https://www.quantamagazine.org/teenager-finds-classical-alternative-to-quantum-recommendation-algorithm-20180731/. So began the approach of “dequantizing,” in which computer scientists look at quantum algorithms and try to achieve the same speeds with classical counterparts. To understand the ongoing contest between classical and quantum computing, co-host Janna Levin spoke to Tang on The Joy of Why podcast. The wide-ranging conversation covered what it was like for Tang to challenge the prevailing wisdom at such a young age, the role of failure in scientific progress, and whether quantum computing will ultimately fulfill its grand ambitions.
At first, life on Earth was simple. Cells existed, functioned and reproduced as free-living individuals. But then, something remarkable happened. Some cells joined forces, working together instead of being alone. This transition, known as multicellularity, was a pivotal event in the history of life on Earth. Multicellularity enabled greater biological complexity, which sparked an extraordinary diversity of organisms and structures. How life evolved from unicellular to multicellular organisms remains a mystery, though evidence indicates that this may have occurred multiple times independently. To understand what could have happened, Will Ratcliff at Georgia Tech has been conducting long-term evolution experiments on yeast in which multicellularity develops and emerges spontaneously. In this episode of podcast, Ratcliff discusses what his “snowflake yeast” model could reveal about the origins of multicellularity, the surprising discoveries his team has made, and how he responds to skeptics who question his approach.
How did complex life evolve? Where did space-time come from? Will computers ever understand language like we do? How did geometry create modern physics? These are just a few of the big and bold questions that we’ll be exploring in the latest season of ’s interview podcast, “The Joy of Why,” starting March 20, and released every other Thursday.
We have identified thousands of planets just in our neighborhood in the Milky Way, mostly from the way they impact their host stars. Basic calculations suggest that there are countless more across the galaxy, and that billions of them could potentially support life. But what kind of life they host, and how we would be able to detect the presence of those biological processes from Earth, remain big questions in the world of exoplanets and astrobiology. What technologies might lie ahead to help us answer the question of whether we are alone in the universe? Lisa Kaltenegger, an astrophysicist and astrobiologist at Cornell University, talks to Janna Levin about that search, the atmospheric fingerprints of life, and why an advanced alien civilization might decide not to talk to us.
Death might seem like a pure loss, the disappearance of what makes a living thing distinct from everything else on our planet. But zoom in closer, to the cellular level, and it takes on a different, more nuanced meaning. There is a challenge in simply defining what makes an individual cell alive or dead. Scientists today are working to understand the various ways and reasons that cells disappear, and what these processes mean to biological systems. In this episode, cellular biologist Shai Shaham talks to Steven Strogatz about the different forms of cell death, their roles in evolution and disease, and why the right kinds and patterns of cell death are essential to our development and well-being.
It’s fair to say that enjoyment of a podcast would be severely limited without the human capacity to create and understand speech. That capacity has often been cited as a defining characteristic of our species, and one that sets us apart in the long history of life on Earth. Yet we know that other species communicate in complex ways. Studies of the neurological foundations of language suggest that birdsong, or communication among bats or elephants, originates with brain structures similar to our own. So why do some species vocalize while others don’t? In this episode, Erich Jarvis, who studies behavior and neurogenetics at the Rockefeller University, chats with Janna Levin about the surprising connections between human speech, birdsong and dance.
Scientists routinely build quantitative models — of, say, the weather or an epidemic — and then use them to make predictions, which they can then test against the real thing. This work can reveal how well we understand complex phenomena, and also dictate where research should go next. In recent years, the remarkable successes of “black box” systems such as large language models suggest that it is sometimes possible to make successful predictions without knowing how something works at all. In this episode, noted statistician Emmanuel Candès and host Steven Strogatz discuss using statistics, data science and AI in the study of everything from college admissions to election forecasting to drug discovery.
The “species” category is almost certainly the best known of all the taxonomic classifications that biologists use to organize life’s vast diversity. It’s a linchpin of both conservation policy and evolutionary theory, though in practice biologists have struggled to find a definition that works across the natural world. In this episode, Kevin de Queiroz, a zoologist and evolutionary biologist, talks with host Janna Levin about the variety of ways to conceive of a species, and ways to understand the relationships among living things.
When we think about medicine’s war on cancer, treatments such as surgery, radiation and chemotherapy spring to mind first. Now there is another potential weapon for defeating tumors: statistics and mathematical models that can optimize the selection, combination or timing of treatment. Building and feeding these models requires accounting for the complexity of the body, and recognizing that cancer cells are constantly evolving. In this episode, host Steven Strogatz hears from Franziska Michor, a computational biologist, about how our understanding of evolutionary dynamics is being used to devise new anticancer therapies.
If instruments do someday detect evidence of life beyond Earth, whether it’s in this solar system or in the farther reaches of space, astrobiologists want to be ready. One of the best ways to learn how alien life might function can be to study the organisms called extremophiles, which live in incredibly challenging environments on or in the Earth. In this episode, Penelope Boston https://astrobiology.nasa.gov/nai/directory/boston-penelope/, a microbiologist who has worked for many years with NASA, speaks with Janna Levin https://barnard.edu/profiles/janna-levin about the bizarre life found in habitats such as caves, how it would be possible to detect life beyond our solar system and what it would mean for humanity if we do.
The principles of thermodynamics are cornerstones of our understanding of physics. But they were discovered in the era of steam-driven technology, long before anyone dreamed of quantum mechanics. In this episode, the theoretical physicist Nicole Yunger Halpern https://quics.umd.edu/people/nicole-yunger-halpern talks to host Steven Strogatz https://math.cornell.edu/steven-strogatz about how physicists today are reinterpreting concepts such as work, energy and information for a quantum world.
Observations of the cosmos suggest that unseen sources of gravity — dark matter — tug at the stars in galaxies, while another mysterious force — dark energy — drives the universe to expand at an ever-increasing rate. The evidence for both of them, however, hinges on assumptions that gravity works the same way at all scales. What if that’s not true? In this episode, theoretical physicist Claudia de Rham explains her work on an alternative explanation called “massive gravity” to host Janna Levin.
Within just a few years, artificial intelligence systems that sometimes seem to display almost human characteristics have gone from science fiction to apps on your phone. But there’s another AI-influenced frontier that is developing rapidly and remains untamed: robotics. Can the technologies that have helped computers get smarter now bring similar improvements to the robots that will work alongside us? In this episode, Daniela Rus https://www.csail.mit.edu/person/daniela-rus, a pioneering roboticist at the Massachusetts Institute of Technology, talks to host Steven Strogatz https://math.cornell.edu/steven-strogatz about the surprising inspirations from biology that may help robots rise to new levels.
Can you keep a secret? Modern techniques for maintaining the confidentiality of information are based on mathematical problems that are inherently too difficult for anyone to solve without the right hints. Yet what does that mean when quantum computers capable of solving many problems astronomically faster are on the horizon? In this episode, host Janna Levin https://barnard.edu/profiles/janna-levin talks with computer scientist Boaz Barak about the cryptographic techniques that keep information confidential, and why “security through mathematics” beats “security through obscurity.” Listen on Apple Podcasts https://podcasts.apple.com/us/podcast/the-joy-of-why/id1608948873, Spotify https://open.spotify.com/show/2FoxHraQSKwxV2HgUfwLMp, TuneIn https://tunein.com/podcasts/Science-Podcasts/The-Joy-of-Why-p1653040/ or your favorite podcasting app, or you can stream it from https://www.quantamagazine.org/tag/the-joy-of-why.
Ask a question of ChatGPT and other, similar chatbots and there’s a good chance you’ll be impressed at how adeptly it comes up with a good answer — unless it spits out unrealistic nonsense instead. Part of what’s mystifying about these kinds of machine learning systems is that they are fundamentally black boxes. No one knows precisely how they arrive at the answers that they do. Given that mystery, is it possible that these systems in some way truly understand the world and the questions they answer? In this episode, the computer scientist Yejin Choi https://homes.cs.washington.edu/~yejin/ of the University of Washington and host Steven Strogatz https://math.cornell.edu/steven-strogatz discuss the capabilities and limitations of chatbots and the large language models, or LLMs, on which they are built. Listen on Apple Podcasts https://podcasts.apple.com/us/podcast/the-joy-of-why/id1608948873, Spotify https://open.spotify.com/show/2FoxHraQSKwxV2HgUfwLMp, TuneIn https://tunein.com/podcasts/Science-Podcasts/The-Joy-of-Why-p1653040/ or your favorite podcasting app, or you can stream it from https://www.quantamagazine.org/tag/the-joy-of-why.
In the tiling of wallpaper and bathroom floors, collective repeated patterns often emerge. Mathematicians have long tried to find a tiling shape that never repeats in this way. In 2023, they lauded an unexpected amateur victor. That discovery of the elusive aperiodic monotile propelled the field into new dimensions. The study of tessellation is much more than a fun thought exercise: Peculiar, rare tiling formations can sometimes seem to tell us something about the natural world, from the structure of minerals to the organization of the cosmos. In this episode, Janna Levin https://barnard.edu/profiles/janna-levin speaks with mathematician Natalie Priebe Frank https://www.vassar.edu/faculty/nafrank about these complex geometric combinations, and where they may pop up unexpectedly. Specifically, they explore her research into quasicrystals — crystals that, like aperiodic tiles, enigmatically resist structural uniformity.. Listen on Apple Podcasts https://podcasts.apple.com/us/podcast/the-joy-of-why/id1608948873, Spotify https://open.spotify.com/show/2FoxHraQSKwxV2HgUfwLMp, TuneIn https://tunein.com/podcasts/Science-Podcasts/The-Joy-of-Why-p1653040/ or your favorite podcasting app, or you can stream it from https://www.quantamagazine.org/tag/the-joy-of-why.
The universe seems like it should be unfathomably complex. How then is science able to crack fundamental questions about nature and life? Scientists and philosophers alike have often commented on the “unreasonable” success of mathematics at describing the universe. That success has helped science probe some profound mysteries — but as the physicist Nigel Goldenfeld https://guava.physics.uiuc.edu/~nigel/ points out, it also helps that the “hard” physical sciences, where this progress is most evident, are in major ways simpler than the “soft” biological sciences. In this episode, Goldenfeld speaks with co-host Steven Strogatz https://math.cornell.edu/steven-strogatz about the scientific importance of asking the right questions at the right time. They also discuss the mysterious effects of “emergence,” the phenomenon that allows new properties to arise in systems at different scales, imposing unexpected order on cosmic complexity. Listen on Apple Podcasts https://podcasts.apple.com/us/podcast/the-joy-of-why/id1608948873, Spotify https://open.spotify.com/show/2FoxHraQSKwxV2HgUfwLMp, TuneIn https://tunein.com/podcasts/Science-Podcasts/The-Joy-of-Why-p1653040/ or your favorite podcasting app, or you can stream it from https://www.quantamagazine.org/tag/the-joy-of-why.
During traumatic periods and their aftermath, our brains can fall into habitual ways of thinking that may be helpful in the short run but become maladaptive years later. For the brain to readjust to new situations later in life, it needs to be restored to the malleable state it was in when the habits first formed. That is exactly what Gül Dölen, a neuroscientist and psychiatric researcher at the University of California, Berkeley, is working toward in her lab. What is her surprising tool? Psychedelics. In this episode, Dölen shares with co-host Janna Levin the surprising potential of psychedelics to change the lives of those grappling with addiction, depression and post-traumatic stress. Listen on Apple Podcasts https://podcasts.apple.com/us/podcast/the-joy-of-why/id1608948873, Spotify https://open.spotify.com/show/2FoxHraQSKwxV2HgUfwLMp, TuneIn https://tunein.com/podcasts/Science-Podcasts/The-Joy-of-Why-p1653040/ or your favorite podcasting app, or you can stream it from https://www.quantamagazine.org/tag/the-joy-of-why.
For decades, the best drug therapies for treating depression, like SSRIs, have been based on the idea that depressed brains don’t have enough of the neurotransmitter serotonin. Yet for almost as long, it’s been clear that simplistic theory is wrong. Recent research into the true causes of depression is finding clues in other neurotransmitters and the realization that the brain is much more adaptable than scientists once imagined. Treatments for depression are being reinvented by drugs like ketamine that can help regrow synapses, which can in turn restore the right brain chemistry and improve whole body health. In this episode, John Krystal https://medicine.yale.edu/profile/john-krystal/, a neuropharmacologist at the Yale School of Medicine, shares the new findings in mental health research that are revolutionizing psychiatric medication. Listen on Apple Podcasts https://podcasts.apple.com/us/podcast/the-joy-of-why/id1608948873, Spotify https://open.spotify.com/show/2FoxHraQSKwxV2HgUfwLMp, TuneIn https://tunein.com/podcasts/Science-Podcasts/The-Joy-of-Why-p1653040/ or your favorite podcasting app, or you can stream it from https://www.quantamagazine.org/tag/the-joy-of-why.
If superconductors — materials that conduct electricity without any resistance — worked at temperatures and pressures close to what we would consider normal, they would be world-changing. They could dramatically amplify power grids, levitate high-speed trains and enable more affordable medical technologies. For more than a century, physicists have tinkered with different compounds and environmental conditions in pursuit of this elusive property, but while success has sometimes been claimed, the reports were always debunked or withdrawn. What makes this challenge so tricky? In this episode, Siddharth Shanker Saxena https://www.phy.cam.ac.uk/directory/dr-siddharth-s-saxena, a condensed-matter physicist at the University of Cambridge, gives co-host Janna Levin https://barnard.edu/profiles/janna-levin the details about why high-temperature superconductors remain so stubbornly out of reach.. Listen on Apple Podcasts https://podcasts.apple.com/us/podcast/the-joy-of-why/id1608948873, Spotify https://open.spotify.com/show/2FoxHraQSKwxV2HgUfwLMp, TuneIn https://tunein.com/podcasts/Science-Podcasts/The-Joy-of-Why-p1653040/ or your favorite podcasting app, or you can stream it from https://www.quantamagazine.org/tag/the-joy-of-why.
