Lex Fridman Podcast full episode: • Sara Walker: Physics of Life, Time, Comple…
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Sara Walker is an astrobiologist and theoretical physicist. She is the author of a new book titled \.
Since gravitational waves were first detected in 2015, instruments including LIGO, Virgo and KAGRA have picked up a steady stream of signals from colliding black holes, building a catalog that now numbers in the hundreds. Yet despite this wealth of data, a fundamental question has remained stubbornly unresolved: How do these black holes actually form?
Now, two independent research teams have used fresh theoretical approaches to comb through the data, and both arrived at a similar conclusion: Merging black holes don’t form a single uniform group, but instead separate into distinct subpopulations, each bearing the fingerprints of different formation mechanisms. Both studies have been published in Physical Review Letters.
Source: Ashtekar A, Paraizo DE, Shu J (2026). “Thermodynamics of Black Holes, Far from Equilibrium.” Physical Review Letters. DOI 10.1103/3c1r-v8f1. Published June 24, 2026. Selected as Editor’s Suggestion. Penn State University. ScienceDaily, July 13, 2026. Quotes: Abhay Ashtekar, Penn State. Video.
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Scientists at Nanyang Technological University, Singapore (NTU Singapore) have found a much simpler way to produce unusual light structures known as optical skyrmions by reviving a classic optics experiment that dates back more than 200 years.
Optical skyrmions are tiny, stable swirling patterns formed within the properties of light. Their structure has often been compared to the spines of a hedgehog. Because they can potentially encode and store information, researchers see them as promising building blocks for future data storage, communications, and computing technologies.
Instead of relying on expensive, highly engineered metamaterials that have traditionally been needed to generate optical skyrmions, the NTU team created them by shining a laser at a small circular disc. The approach provides a far simpler way to produce, study, and control these complex light structures.
Cornstarch can thicken soup or serve as a base for a DIY shampoo, but there’s more to the humble pantry staple. Given the right conditions, it seems to defy the laws of physics. Mixing cornstarch with water creates “oobleck”—a shape-shifting substance classified as a non-Newtonian fluid that changes states when subjected to a force.
Leave it alone, and it oozes like liquid. Stir it up, and it gets more viscous before locking into a solid. Under certain conditions, if it’s punctured, it can even fracture, according to Northeastern University researchers. The thickening phenomenon is known as the oobleck effect.
Back in 1949, Seuss made oobleck famous as the “green goo” wreaking havoc on a fictional kingdom that a boy named Bartholomew endeavors to rescue. But today, Northeastern mechanical and industrial engineering scientist Xiaoyu Tang and Ph.D. student Boqian Yan are using the same mix of ingredients for a different purpose.
For over a century, the accepted value for a firefly’s brightness has mostly stood, tracing its origins to experiments carried out in 1912. Through rigorous new analysis published in the American Journal of Physics, David Silver of Remiza AI in New York has discovered that this value has likely been vastly overestimated. His results provide a stark reminder of what can happen when widely accepted older measurements are converted into modern standard units.
Out of the hundreds of species of animals, fungi and bacteria that produce their own light, fireflies are the most widely studied. In the 1880s, experiments revealed that their flashing bioluminescence emerges from a catalyzed reaction between an organic compound named luciferin and an enzyme named luciferase.
In 1912, the brightness of these flashes was measured for the first time by William Coblentz—one of the founders of modern radiometry. “Coblentz reported that the flash of the firefly Photinus pyralis ranged from 1/50th to 1/400th the power of a candle, with 1/400 predominating,” Silver describes.
Each summer, lawns are marked by a familiar addition: “silly sprinklers,” whose loops and spirals spew water in creative ways. While seemingly frivolous in their construction, a team of mathematicians has used their design to address a long-standing mystery surrounding the laws of physics.
For decades, scientists have been trying to solve Feynman’s Sprinkler Problem: How does a sprinkler running in reverse—in which the water flows into the device rather than out of it—work? Through a series of experiments on custom-designed sprinklers with different shapes, the researchers arrived at a clear answer and, more generally, determined how flowing fluids exert forces and move structures.
“This work provides the experimental answer for Feynman’s Sprinkler Problem by showing, across several sprinkler types, how the angular momentum of water flows drives sprinklers’ rotation,” explains Leif Ristroph, an associate professor at New York University’s Courant Institute School of Mathematics, Computing, and Data Science and the senior author of the paper, which appears in the journal Proceedings of the National Academy of Sciences.
The mysterious substance that binds galaxies together could naturally be “in tune” with a hidden fifth dimension, according to a new University of Sheffield theory aiming to shed light on one of science’s biggest enigmas: dark matter.
Dark matter has been explored by scientists and science fiction writers for decades, inspiring everything from planet-destroying vortexes in “Star Trek” to the “dust” that sustains the multiverse in Philip Pullman’s “His Dark Materials” fantasy trilogy.
Yet it remains one of the greatest open problems in physics. While scientists are certain it exists because of its immense gravitational effect—acting as an invisible “cosmic glue” holding galaxies together—it has never been observed, and its true nature remains a mystery.
Darwin spent his life trying to find the law that governs evolution. He knew it existed — he just never found it. Stephen Wolfram thinks he has. And it explains a lot more than evolution.
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Stephen Wolfram is a mathematician, complexity theorist, and the mind behind Wolfram Alpha and Mathematica — someone who has spent his career finding the hidden rules underneath reality itself.
The same principle that explains why evolution never gets stuck, why you have free will despite living in a deterministic universe, and why the laws of physics are the way they are turns out to say something profound about what it means to be alive.
0:00 Intro.
1:08 Chapter 1: The limits of theoretical physics.
5:50 Chapter 2: A computational understanding of the world.
12:03 Rule 30: a simple program that outputs pure randomness.
15:48 Evolution and machine learning are the same trick.
18:19 What computational irreducibility means for science.
25:00 Chapter 3: A new kind of theory of everything.
31:36 The ruliad: every possible computation, in one object.
35:03 The second law, explained by the limits of our minds.
38:38 Why the universe exists isn’t the real question — why we do is.
42:53 Chapter 4: If the universe is a program, what is the meaning of life?
44:59 Free will as a side effect of computational irreducibility.
48:06 AI as a civilization we’re learning to coexist with.
In this exclusive, long-form interview, Turing Award laureate Geoffrey Hinton—often called the “Godfather of Deep Learning”—opens up about the promise and peril of advanced AI. Hinton explains why he left Google, how close we really are to artificial general intelligence (AGI), and what guard-rails governments, researchers, and ordinary citizens can put in place today to keep powerful neural networks from going off the rails.
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Watch the interview with Yann LeCun on AI and machine learning: • Father of AI: AI Needs PHYSICS to EVOLVE |…
Geoffrey Hinton is a British-Canadian cognitive psychologist and computer scientist best known as the “godfather of deep learning.” As a professor at the University of Toronto and co-founder of Google Brain, he pioneered modern neural networks—work that earned him the 2018 Turing Award alongside Yann LeCun and Yoshua Bengio. Since leaving Google in 2023, Hinton has focused on warning about the societal and existential risks of increasingly powerful AI systems.