The Joy of Why

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, a pioneering roboticist at the Massachusetts Institute of Technology, talks to host 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 talks with computer scientist Boaz Barak about the cryptographic techniques that keep information confidential, and why “security through mathematics” beats “security through obscurity.”

Common sense rules our world. This fundamental, sometimes trivial knowledge is inherent to how humans interpret language. Yet, some of these simple human truths are so obvious that they're rarely put into words. And without the data of common sense to train on, large language models such as ChatGPT have bizarre, often humorous blind spots.Yejin Choi, professor and the chair of computer science at the University of Washington, calls common sense the “dark matter” of intelligence. In this week’s episode of “The Joy of Why,” Choi talks with co-host Steven Strogatz about decoding the interstitial glue of language and comprehension. Together, they explore the question: Should we program more humanity into the next generation of artificial intelligence?

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, co-host Janna Levin speaks with mathematician Natalie Priebe Frank on the subject of 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.

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 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 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.

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.

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, a neuropharmacologist at the Yale School of Medicine, tells Steve Strogatz about the new findings in mental health research that are revolutionizing psychiatric medication.

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, a condensed-matter physicist at the University of Cambridge, gives co-host Janna Levin the details about why high-temperature superconductors remain so stubbornly out of reach.

Milk is more than just a food for babies. Breast milk has evolved to deliver thousands of diverse molecules including growth factors, hormones and antibodies, as well as microbes. Elizabeth Johnson, a molecular nutritionist at Cornell University, studies the effects of infants’ diet on the gut microbiome. These studies could hold clues to hard questions in public health for children and adults alike. In this episode of “The Joy of Why” podcast, co-host Steven Strogatz interviews Johnson about the microbial components that make breast milk one of the most wondrous biofluids found in nature. You can read the transcript for this episode and see the image of the micrograph Johnson references on our website.

Nothing escapes a black hole… or does it? In the 1970s, Stephen Hawking described a subtle process by which black holes can “evaporate,” with some particles evading gravitational oblivion. This phenomenon, now dubbed “Hawking radiation,” seems inherently at odds with general relativity, but it gets weirder still: If particles can escape, do they preserve some information about the matter that was obliterated? Leonard Susskind, a physicist at Stanford University, found himself at odds with Hawking when it came to answering this question. In this episode, co-host Janna Levin speaks with Susskind about the “black hole war” that ensued and the powerful scientific lessons that have radiated from one of the most famous paradoxes in physics.

Birds flock. Locusts swarm. Fish school. In these chaotic assemblies, order somehow emerges. Collective behaviors differ in their details from one species to another, but they largely adhere to principles of collective motion that physicists have worked out over centuries. Now, using technologies that only recently became available, researchers have been able to study these patterns of collective animal behavior more closely than ever before. These new insights are unlocking some of the secret fitness advantages of living as part of a group rather than as an individual. The improved understanding of swarming pests such as locusts could also help to protect global food security. In this episode, co-host Steven Strogatz interviews the evolutionary ecologist Iain Couzin about  how and why animals exhibit collective behaviors, and the secret advantages that arise from them.

Quantum teleportation isn’t just science fiction; it’s entirely real and happening in laboratories today. But teleporting quantum particles and information is a far cry from beaming people through space. In some ways, it’s even more astonishing. John Preskill, a theoretical physicist at the California Institute of Technology, is one of the leading theoreticians of quantum computing and information. In this episode, co-host Janna Levin interviews him about entanglement, teleporting bits from coast to coast, and the revolutionary promise of quantum technology.

Time seems linear to us: We remember the past, experience the present and predict the future, moving consecutively from one moment to the next. But why is it that way, and could time ultimately be a kind of illusion? In this episode, the Nobel Prize-winning physicist Frank Wilczek speaks with host Steven Strogatz about the many “arrows” of time and why most of them seem irreversible, the essence of what a clock is, how Einstein changed our definition of time, and the unexpected connection between time and our notions of what dark matter might be.

We often talk about evolution as the survival of the fittest. But if it is, then where did the widespread (and widely admired) impulse to help others even at great cost to ourselves come from? In this episode, host Janna Levin speaks with Stephanie Preston, a professor of psychology and head of the Ecological Neuroscience Lab at the University of Michigan, about the evolutionary, neurological and behavioral foundations for altruism.

We tend to think of mathematics as purely logical, but the teaching of math, its usefulness and its workings are packed with nuance. So what is “good” mathematics? In 2007, the mathematician Terence Tao wrote an essay for the “Bulletin of the American Mathematical Society” that sought to answer this question. Today, as the recipient of a Fields Medal, a Breakthrough Prize in Mathematics and a MacArthur Fellowship, Tao is among the most prolific mathematicians alive. In this episode, he joins Steven Strogatz to revisit the makings of good mathematics.

Tune in to the new season of ‘The Joy of Why,’ a podcast from Quanta Magazine and PRX. This season, new co-host cosmologist Janna Levin and mathematician Steven Strogatz will be joined by guests including Terence Tao, the mathematician and Fields Medalist, and Frank Wilczek, the Nobel Prize-winning physicist. New episodes premiere every other Thursday.

Even empty space is bubbling with a form of energy, according to quantum mechanics - and that fact affects almost every facet of physical reality. The theoretical physicist Isabel Garcia Garcia explains to Steven Strogatz why it's so important in modern physics to understand what a true vacuum is.

Abnormal waves of electrical activity can cause a heart's muscle cells to beat out of sync. In this episode, Flavio Fenton, an expert in cardiac dynamics, talks with Steve Strogatz about ways to treat heart arrhythmias without resorting to painful defibrillators.

Jellyfish and other aquatic creatures embody solutions to diverse problems in engineering, medicine and mathematics. John Dabiri, a fluid dynamics expert, talks with Steven Strogatz about what jellyfish can teach us about going with the flow.

Once dismissed as myths, monstrous rogue waves that tower over ships and appear without warning are real. Wave-science researcher Ton van den Bremer and Steven Strogatz discuss how rogue waves can form in relatively calm seas and whether their threat can be predicted.

Consciousness, our experience of being in the world, is one of the mind's greatest mysteries, but as the neuroscientist Anil Seth explains to Steven Strogatz, research is making progress in understanding this elusive phenomenon.

Several areas of physics suggest reasons to think that unobservable universes with different natural laws could lie beyond ours. The theoretical physicist David Kaplan talks with Steven Strogatz about the mysteries that a multiverse would solve.

A new state of matter called a "time crystal," recently created on a quantum computing platform, can bend our expectations of thermodynamics. The physicist Vedika Khemani talks with Steven Strogatz about counterintuitive quantum behavior.

All infinities go on forever, so how is it possible for some infinities to be larger than others? The mathematician Justin Moore discusses the mysteries of infinity with Steven Strogatz.

Should Covid-19 vaccines be judged by how well they prevent disease or how well they prevent death? Anna Durbin, a public health expert and vaccine researcher, talks with Steven Strogatz about the science behind vaccines.

Can mathematics handle things that are essentially the same without being exactly equal? Category theorist Eugenia Cheng and host Steven Strogatz discuss the power and pleasures of abstraction.

By genetically instructing cells to perform tasks that they wouldn't in nature, synthetic biologists can learn deep secrets about how life works. Steven Strogatz discusses the potential of this young field with researcher Michael Elowitz.

"The Joy of Why" is a podcast about curiosity and the pursuit of knowledge from Quanta Magazine. The acclaimed mathematician and author Steven Strogatz interviews leading researchers about the great scientific and mathematical questions of our time.

As The Joy of Why podcast returns for a second season, producer Polly Stryker and host Steven Strogatz invite listeners to join them and their brilliant new guests on another voyage of discovery.

Dreams are subjective and fleeting, but laboratories have developed ways of getting into the minds of people while they are dreaming. In this episode, Steven Strogatz speaks with sleep researcher Antonio Zadra about how new experimental methods have changed our understanding of dreams.

Quantum field theory may be the most successful scientific theory of all time, but there's reason to think it's missing something. Steven Strogatz speaks with theoretical physicist David Tong about this enigmatic theory.

Everybody gets older, but not everyone ages in the same way. In this episode, Steven Strogatz speaks with Judith Campisi and Dena Dubal, two biomedical researchers who study the causes and outcomes of aging, to understand how age works - and what scientists know about postponing or even reversing the aging process.

Just as scientists test hypotheses, mathematicians prove or disprove conjectures. But what makes a proof stronger than a guess? What does evidence look like in the world of mathematics? Hear Melanie Matchett Wood, professor of mathematics at Harvard University, explain how probability helps to guide number theorists toward certainty.

Artificial intelligence has bested humans at problem-solving tasks including games like chess and Go. Is mathematics research next? Steven Strogatz speaks with Kevin Buzzard, professor of pure mathematics at Imperial College London, to learn about the ongoing multidisciplinary effort to translate math into language that computers understand.

Without a good definition of life, how do we look for it on alien planets? Steven Strogatz speaks with Robert Hazen, a mineralogist and astrobiologist, and Sheref Mansy, a chemist, to learn more.

How did life arise on Earth? It's one of the greatest and most ancient mysteries in all of science - and the clues to solving it are all around us. Steven Strogatz speaks with Jack Szostak, a Nobel Prize-winning biologist, and Betül Kaçar, a paleogeneticist and astrobiologist, to explore our best understanding of how we all got here.

With the December 2021 launch of the James Webb Space Telescope, one of the most expensive and ambitious scientific initiatives ever attempted commenced operations. Now that the telescope has been successfully deployed in its unique position in space, its advanced instruments will be able to gather data on questions that scientists once could only dream of answering. Is there life on other planets? How do supermassive black holes mold the mass in their galaxies? JWST may soon be able to tell us. In this episode, host Steven Strogatz speaks to two researchers leading JWST's observations of our universe: Marcia Rieke, the principal investigator of the telescope's Near-Infrared Camera, and Nikole Lewis, an astrophysicist studying planets outside of our solar system. (For more on the JWST and the history of its construction and launch, read Natalie Wolchover's article, "The Webb Space Telescope Will Rewrite Cosmic History. If It Works," which was recently honored with a 2022 Pulitzer Prize for Explanatory Reporting.)

Einstein's description of gravity as a curvature in space-time doesn't easily mesh with a universe made up of quantum wavefunctions. Theoretical physicist Sean Carroll (of the "Mindscape" podcast) tells Steven Strogatz about the mind-bending implications of the quest for quantum gravity.

We've heard a lot about the immune system during the COVID-19 pandemic, but of course our immune system fights off much more than the coronavirus. And while the immune system protects us brilliantly from countless pathogens every day, sometimes it can also attack our own bodies, causing harmful and even deadly inflammation. In this episode, host Steven Strogatz speaks with Shruti Naik, an immunologist and assistant professor of biological sciences at NYU's Langone Medical Center, to learn why the immune system works so well - and how that effectiveness can backfire.

Everyone knows what a knot is. But they have special significance in math and science because their properties can help unlock hidden secrets like the biochemistry of DNA or the geometry of three-dimensional spaces. In this episode, Steven Strogatz explores the mysteries of knots with the mathematicians Colin Adams and Lisa Piccirillo.

Why do we need sleep? In the search for answers, scientists have uncovered more thought-provoking mysteries central to what sleep is, how it evolved and the benefits that it provides. In this episode, the mathematician and science communicator Steven Strogatz speaks with Dragana Rogulja, an assistant professor of neurobiology at Harvard Medical School who recently discovered how sleep deprivation causes death in fruit flies, and Alex Keene, a neurogeneticist at Texas A and M University studying cave fish to understand sleep's evolutionary history.

An introduction to the new Quanta Magazine podcast The Joy of Why, in which noted mathematician and author Steven Strogatz talks with experts about some of the greatest scientific questions of all time.