Particles of Thought

What does it feel like to make one of the biggest discoveries in physics? Adam Riess knows — because his work revealed that the universe isn’t just expanding, it’s accelerating. In this episode, the Nobel Prize–winning astrophysicist takes us behind the scenes of the moment that changed cosmology forever. How did his team use exploding stars as “standard candles” to measure the cosmos? Why did the data point to a mysterious force now called dark energy, making up nearly 70% of the universe? And what’s behind today’s biggest cosmic puzzle: the Hubble tension? Plus, Adam shares what new telescopes could uncover — and why the next decade might rewrite the laws of physics all over again. Learn more about NOVA and subscribe to our YouTube channel. —————————Guest Bio: Adam Riess is an astrophysicist, professor at Johns Hopkins University, and a distinguished astronomer at Space Telescope Science Institute. In 2011, he was named as a co-winner of the Nobel Prize in Physics for his contributions to the discovery that the expansion rate of the universe is accelerating. Since then, he has continued refining measurements of cosmic expansion and the Hubble constant, aiming to find and measure the most distant type Ia supernovae known, to probe the origin of cosmic acceleration.Timestamps(00:00:00) Introduction(00:03:16) What Is a Type Ia Supernova? (00:10:52) The Discovery of Dark Energy(00:44:39) What Is the Hubble Tension?(00:58:59) Winning a Nobel Prize(01:15:32) Credits

The universe isn’t adding up—and it’s creating a crisis in cosmology. Nobel Prize winner Adam Riess explains why measurements of the universe’s expansion rate from its earliest light and from nearby galaxies don’t match, and how this growing gap threatens the foundations of our standard model of the cosmos.For more, check out the extended interview with Adam RiessLearn more about NOVA and subscribe to our YouTube channel. 

Adam Riess, an esteemed astrophysicist and Nobel Prize winner, shares the thrilling yet nerve-wracking journey of discovering dark energy. He reflects on the harrowing checks and team confirmations that led to the paradigm-shifting realization of the universe's accelerating expansion. Riess explains Einstein's lambda and the infamous 'biggest blunder', illustrating how negative pressure drives repulsive gravity. With evidence solidifying towards 2025, he shares insights into the cosmic relevance of this dark force.

Fame can hijack the brain like a drug—activating the same reward circuits that fuel a relentless chase for dopamine highs. Neuroscientist Heather Berlin reveals the antidote—and why even social media fame can trigger this cycle.For more, check out the extended interview with Heather Berlin.Learn more about NOVA and subscribe to our YouTube channel. 

Fossilization isn’t luck - it’s geology. Paleobotanist Kirk Johnson explains how fossils only form in certain conditions, the tricks to finding them, and why one fossil leaf can lead to thousands more. For more, check out the extended interview with Kirk Johnson.Learn more about NOVA and subscribe to our YouTube channel. 

Speech is rare in the animal kingdom because it requires a very specific brain architecture. Neuroscientist Erich Jarvis explains how duplicating neural pathways for movement unlocked language, dancing, and even advanced problem-solving in more than just humans.For more, check out the extended interview with Erich Jarvis. Learn more about NOVA and subscribe to our YouTube channel. 

How does evolution invent entirely new things, like limbs, wings, and venom? Evolutionary biologist Sean B. Carroll joins us to reveal the hidden rules behind nature’s creativity and the genetic toolkit that makes it possible. Carroll explains how the same set of genes can build wildly different creatures — from fruit flies to lobsters — simply by rewiring their genetic circuits. Discover why developmental biology holds the key to understanding evolution, how snake venom evolved, and why medicines like GLP-1 drugs and statins trace their origins to nature’s own innovations. Plus, what the emergence of new species tells us about life’s future and the surprising power of evolution to repurpose old parts in new ways. Learn more about NOVA and subscribe to our YouTube channel. —————————Guest Bio: Sean B. Carroll is a renowned evolutionary biologist and author whose work has inspired a deeper public understanding of evolution and the natural world. He is an Investigator at Howard Hughes Medical Institute (HHMI), where he was formerly Head of HHMI Tangled Bank Studios, and led the Department of Science Education from 2010-2023. He is also a Professor of Biology at the University of Maryland. His research focuses on genes that influence the evolution of animal diversity.Timestamps(00:00:00) How Does A New Species Evolve?(00:12:54) The Process of Speciation: Use It or Lose It(00:36:22) Development: What the Fruit Fly Taught Us(00:55:37) The Evolution of Defense Mechanisms & Developing Medications(01:19:55) The Role of Chance in Evolution(01:24:22) Credits

From legs on heads to missing eyes, fruit fly mutations exposed the genetic toolkit that builds all animals. Evolutionary Biologist Sean B. Carroll shows how these discoveries rewrote our understanding of evolution.For more, check out the extended interview with Sean B. Carroll.Learn more about NOVA and subscribe to our YouTube channel. 

From snakes to jellyfish, venom is one of evolution’s most lethal inventions. Evolutionary Biologist Sean B. Carroll reveals how this deadly innovation emerged—and the new science behind antivenom inspired by nature’s own defenses.For more, check out the extended interview with Sean B. Carroll.Learn more about NOVA and subscribe to our YouTube channel. 

The edge of a black hole isn’t what you think. Astrophysicist Janna Levin dives into the event horizon, the one-way transition where space and time warp so much that escape becomes as impossible as reversing the clock.For more, check out the extended interview with Janna Levin.Learn more about NOVA and subscribe to our YouTube channel.