The Joy of Why

People may think of soil as just dirt, but it is anything but inert. Beneath your feet, a vast network of mycorrhizal fungi is hard at work, trading minerals with plant roots. This trading system helps enrich the soil, and it sequesters 13 billion tons of atmospheric carbon dioxide each year — roughly equivalent to one-third of the world’s fossil-fuel emissions. Scientists know that these fungi form partnerships with 80...

We know all about how things exist in the three dimensions of length, width, and height. Physicists often talk about time as a fourth dimension, but what if there were a fourth spatial dimension — another direction entirely? How on earth would we picture that?

Mathematicians use topology to visualize abstract spaces in higher dimensions. Maggie Miller at the University of Texas at Austin explores what happens when knots encou...

Quantum mechanics may be one of the most precisely tested paradigms in science, but there’s still no universally accepted interpretation of what it tells us about reality. How do we get from the wave-like behavior of quantum systems to the solid, macroscopic world of objects and the universe at large?

Jonathan Halliwell, a professor of theoretical physics at Imperial College London, has spent his career probing the foundation...

Mathematicians are witnessing a profound shift in their field. AI systems are now producing proofs, spotting connections between distant fields, and, in a few cases, solving problems that had stumped mathematicians for decades. The pace of progress over the past several months has raised challenging questions: What can AI systems actually do? And what happens to the more human, creative aspects of the field once machines can match ...

When an LLM answers a question, is it reasoning like humans, or just producing text that looks like reasoning? The distinction isn’t just philosophical, this determines what we can trust AI to do, how closely we need to supervise it, and ultimately what its real-world impact will turn out to be.

Melanie Mitchell at the Santa Fe Institute argues that we lack adequate methods for measuring machine cognition, and that AI is...

Pain and pleasure seem like simple facts of life, but they are far from it. Neuroscientists still cannot say why physical pain differs from psychological pain, for instance, nor why a loved one’s touch soothes while a stranger’s touch repels.

To explore the science behind these sensations, Janna Levin talked to Ishmail Abdus-Saboor, a neuroscientist at Columbia University’s Zuckerman Institute. Their conversa...

One of the biggest mysteries in cosmology seems to keep getting bigger. Astronomers have known since the 1930s that the universe is expanding, but in the 1990s, the discovery that this expansion is accelerating rather than slowing down came as a huge shock to the field. Something had to be driving that acceleration, and dark energy was proposed as the cause. What began as a seismic shock in cosmology eventually led to a Nobel ...

Does intelligent life exist elsewhere in the universe? The question has captivated us for centuries, but despite decades of searching it remains frustratingly unanswered. Every so often a curious signal appears — fossilized structures in a meteorite, say, or an unusual gas in an exoplanet’s atmosphere — and for a moment it seems possible that we are not alone before the excitement gives way to a more mundane expla...

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 ...

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 ...

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 f...

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...

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 St...

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, Herto...

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 h...

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 Chudn...

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 comp...

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, var...

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...