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The Hardest Questions in Physics | World Science Festival

2026-05-29 Science & Technology
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What does it actually take to understand the universe at its deepest level, and what happens when the rules that govern it seem to contradict each other? Theoretical physicist Leonard Susskind joins Brian Greene for a conversation on black holes, the nature of reality, and what it means to spend a lifetime chasing the hardest questions in physics. Together they trace the ideas that have defined Susskind's career, from a Bronx childhood and early years as a plumber, to his decades-long battle with Stephen Hawking over whether information can ever truly be lost inside a black hole, and the idea that the universe itself might work like a hologram. Susskind and Greene also push into the messier, more human side of science that rarely makes it into textbooks. They discuss questions about why the biggest breakthroughs tend to start where two things that both seem true turn out to be impossible to reconcile, why being wrong never scared Susskind, and what it actually feels like to hold a conviction your entire field thinks is crazy. They take on the harder questions surrounding string theory like what it has and hasn't delivered, why experiments have gotten so difficult they now resemble building cathedrals, and whether a theory that hasn't made a confirmed prediction is still worth pursuing. It's a conversation with one of the most original thinkers in modern physics, and a reminder that the ideas that sound the craziest sometimes end up changing everything. This program is part of the Rethinking Reality series, supported by the John Templeton Foundation. Participant: Leonard Susskind Moderator: Brian Greene #worldsciencefestival #briangreene #leonardsusskind Don't miss a video! Subscribe NOW: https://www.youtube.com/worldsciencefestival?sub_confirmation=1 ABOUT WORLD SCIENCE FESTIVAL: The World Science Festival (WSF) is a multimedia organization bringing the most transformative ideas in science to global audiences. Through long- and short-form videos spanning physics, cosmology, quantum mechanics, biology, neuroscience, consciousness, medicine, space exploration, the dilemma of free will, artificial intelligence, engineering, robotics, and beyond. WSF gathers world-renowned scientists, artists, and thinkers for dynamic discussions, debates, lectures, performances, films, and immersive live experiences. Founded in 2008 and headquartered in New York City, the World Science Festival is a production of the World Science Foundation, a 501(c)(3) nonprofit organization. Our mission is to cultivate a public informed by science, inspired by its wonder, convinced of its value, and prepared to engage with its implications for the future. With live events reaching millions worldwide and hundreds of millions of digital views, WSF continues to expand its global impact through festivals, educational initiatives like World Science U, and digital content that explores the near and far future of our world. FOLLOW WORLD SCIENCE FESTIVAL: Website: https://worldsciencefestival.com/ Instagram: https://www.instagram.com/worldscifest/ TikTok: https://www.tiktok.com/@worldscifest X(Twitter): https://twitter.com/worldscifest Facebook: https://www.facebook.com/worldsciencefestival LinkedIn: https://www.linkedin.com/company/world-science-festival Chapters: 00:00 Introduction to The Physicist Who Helped Build String Theory 01:48 From Plumbing In The Bronx To Physics 04:42 The Moment Einstein Changed Everything 05:27 Why Engineering Almost Made Him Quit Science 06:34 The Professor Who Changed His Entire Life 07:48 Why Susskind Chases Big Questions Instead Of Calculations 09:04 The Physics Conflicts That Started Everything 09:46 Intuition Vs Mathematics In Science 10:53 Why Being Wrong Is Part Of Discovery 12:24 The Human Side Of Physics Nobody Talks About 13:49 Why Einstein Rejected Black Holes 16:07 Hawking’s Theory That Information Disappears Forever 17:39 The Fight Between Quantum Physics And Black Holes 19:57 The Birth Of The Holographic Principle 22:23 The Weird Hologram Story That Changed Physics 24:02 Why Scientists Thought Susskind Lost His Mind 25:38 How The Holographic Principle Took Over Physics 32:08 The Conflict That Created String Theory 34:49 How Vibrating Strings Changed Physics Forever 39:17 Why Quantum Gravity Refused To Work 42:23 Why Physicists Thought They Found The Final Theory 45:39 The Problem With Supersymmetry 51:02 Why Modern Physics Became So Hard To Test 55:32 Are There Infinite Universes Out There? 57:11 Why Physics Is Ultimately Just Fun For Susskind The Hardest Questions in Physics | World Science Festival https://www.youtube.com/channel/UCShHFwKyhcDo3g7hr4f1R8A

Top Comments (10)

@Hammeredprawn 2026-05-29

10:10 I found my love for physics and mathematics at the age of 36. I can’t get enough of it.

38 1 replies
@jamesbraun7484 2026-05-29

I've come to the conclusion that tireless searching in order to make sense of a mystery almost inevitably leads to a revelation, or a deep insight, which cannot be easily shared with someone else.

25 5 replies
@viewer3091 2026-05-30

Leonard Susskind is beginning to show his age and mortality = = Which is why it great to get these videos for the record. I mean this in the nicest possible way. Thanks Leonard and Brian.

17 1 replies
@javier.medrano 2026-05-30

Thank you, again, what a treat!

10
@jaiyinjing 2026-05-30

Susskind has a wonderful ability to explain things clearly, without leaving gaps that the novice will have difficulty understanding. Great video.

7
@sdepalan 2026-05-30

It's good to hear smart people discuss things, and trying to understand what they are saying

5 1 replies
@snarzetax 2026-05-30

Another great conversation! I've had so much fun with Dr. Greene and Susskind today! And again, many thanks to the host, guest, and WSF team!

5
@Jamesmahoney-r5d 2026-05-30

Great interview. Brian Greene handles the flow of the discussion with charm and skill. As a social scientist who follows physics in passing, I appreciate the comments on the role of intuition and the idea that breakthroughs emerge from trying to resolve two apparent truths that cannot both be right. I also liked how Dr. Susskind was inspired to think in terms of holograms by a visit to a museum. I find that my best insights often occur when I am not actively thinking about the material. Instead, after a deep-thinking session, they emerge when my mind is focused on something else. I am very grateful for these interviews.

4 1 replies
@jsalem343 2026-05-30

Magnanimous and captivating - two true treasures of this era

3
@marierausku9292 2026-05-30

Leonard is so well spoken no matter his age. Absolutely outstanding talk, thank you 🤗

2

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