Why is syncing atomic clocks still one of the hardest problems in physics and engineering?

In this episode, we speak with Judah Levine—legendary NIST physicist and one of the key architects of modern timekeeping—about the invisible systems that hold the digital world together. Levine explains why synchronizing atomic clocks across the planet is far more complex than the clocks themselves, and why seemingly simple ideas like “round-trip delay” break down in real-world media such as fiber optics and the internet.

We explore how UTC is built from hundreds of atomic clocks, the difference between keeping time and *transferring* time, and the surprising challenges introduced by asymmetric delays, chromatic dispersion, and environmental noise. Levine walks us through the evolution of cesium clocks, the rise of optical clocks, and the technologies that make GPS, finance, power grids, and global communication possible.

Along the way, we discuss the history of time synchronization, from railroad schedules to radio frequencies to modern satellite systems; the ongoing debate over leap seconds; and why the future of precision timing depends not just on better clocks, but on better *engineering* to deliver those clocks’ performance to the real world.

Whether you’re curious about atomic clocks, relativity, fiber optics, GPS, the structure of time itself, or the hidden physics behind everyday technology, this conversation offers a rare look at how science, engineering, and careful statistical thinking keep modern civilization in sync—down to the nanosecond.

Follow us for more technical interviews with the world’s greatest scientists:

Twitter: https://x.com/632nmPodcast
Instagram: https://www.instagram.com/632nmpodcast?utm_source=ig_web_button_share_sheet&igsh=ZDNlZDc0MzIxNw==
LinkedIn: https://www.linkedin.com/company/632nm/about/
Substack: https://632nmpodcast.substack.com/

Follow our hosts!
Michael Dubrovsky: https://x.com/MikeDubrovsky
Misha Shalaginov: https://x.com/MYShalaginov
Xinghui Yin: https://x.com/XinghuiYin

Subscribe:
Apple Podcasts: https://podcasts.apple.com/us/podcast/632nm/id1751170269
Spotify: https://open.spotify.com/show/4aVH9vT5qp5UUUvQ6Uf6OR
Website: [https://www.632nm.com](https://www.632nm.com/)

Timestamps:
00:00 – Intro
01:03 – What is UTC?
05:50 – Timekeeping for Satellites
07:08 – How Radio Created Better Clocks
18:32 – From Astronomy to Atoms
25:25 – Why are there 24 Hours in a Day?
29:55 – Why Synchronizing Clocks is so Hard
47:09 – How did Judah get into Clocks?
53:29 – Is UTC Vulnerable to Hackers?
1:06:41 – Cesium vs Optical Atomic Clocks
1:11:23 – How Cesium Clocks Work
1:23:35 – Why Cesium Clocks are Imperfect
1:26:17 – Judah’s 3 Year Experiment
1:29:30 – Statistics with Clocks
1:33:40 – Is Time Real?
1:36:29 – Is the Universe Slowing Down?
1:40:29 – Atomic Time and General Relativity
1:42:17 – What’s Left for Atomic Clocks?
1:54:34 – What would Judah do with Unlimited Funding?
1:58:57 – Judah's Past in Programming
2:02:55 – Advice for Young Scientists

Why do civilizations rise, prosper, and then collapse? Here's what the math tells us.

In this episode, we sit down with Peter Turchin, complexity scientist and founder of the field of cliodynamics, which uses data and mathematical models to study the long-term cycles of history. Turchin explains his theory of elite overproduction, how societies generate too many ambitious, educated elites competing for too few positions, and why this dynamic reliably leads to polarization, inequality, and political turmoil.

We explore how his structural-demographic theory maps the recurring “boom and bust” rhythms that have shaped civilizations from ancient Rome to modern America, the role of military competition in driving cooperation and social complexity, and how new tools—from AI-assisted historical databases to ancient DNA and LiDAR—are transforming the study of the past.

Whether you’re drawn to history, sociology, complexity science, or the fate of modern democracies, this conversation reveals how Turchin’s quantitative approach offers a new way to understand—and maybe even forecast—the forces that make societies rise and fall.

Follow us for more technical interviews with the world’s greatest scientists:

Twitter: https://x.com/632nmPodcast
Instagram: https://www.instagram.com/632nmpodcast?utm_source=ig_web_button_share_sheet&igsh=ZDNlZDc0MzIxNw==
LinkedIn: https://www.linkedin.com/company/632nm/about/
Substack: https://632nmpodcast.substack.com/

Follow our hosts!
Michael Dubrovsky: https://x.com/MikeDubrovsky
Misha Shalaginov: https://x.com/MYShalaginov
Xinghui Yin: https://x.com/XinghuiYin

Subscribe:
Apple Podcasts: https://podcasts.apple.com/us/podcast/632nm/id1751170269
Spotify: https://open.spotify.com/show/4aVH9vT5qp5UUUvQ6Uf6OR
Website: https://www.632nm.com

Timestamps:

00:00 - Intro
01:48 - Overproduction of Elites
10:56 - Did Models Predict the Rise of Trump?
20:43 - Is Russian History Repeating in the US?
26:48 - How Competition Stabilizes Societies
32:14 - What Data Goes into Cliodynamic Models?
38:13 - How New Technologies Shaped Archaeology
43:28 - Can Historians Build Mathematical Intuitions?
47:59 - What Questions can be Answered with Cliodynamics?
52:23 - Does the NYC Mayoral Race Fit into Turchin's Theory?
56:37 - Is Fear of China Bringing Us Together?
58:29 - Do Historians Reject Turchin’s Work?
1:00:03 - Trends in Civilizations and Outliers
1:03:29 - Calvary and the Evolution of Societies
1:10:03 - Is Evolution via Natural Selection a Suitable Analog for History?
1:15:16 - Could Turchin's Ideas Be Misinterpreted Dangerously?

You can’t copy a qubit. So how do quantum computers remember anything?

In this episode, we sit down with Mikhail Lukin, Harvard physicist and co-director of the Harvard Quantum Initiative, whose lab is building quantum computers from arrays of individually trapped atoms. Lukin explains the paradox of quantum error correction—how you can safeguard quantum information even though it can’t be copied or measured directly—and why this breakthrough may be the key to making large-scale quantum computers possible.

We dive into the strange logic of superposition, entanglement, and “small cat states,” explore what makes quantum evolution inherently analog, and learn how Lukin’s team uses optical tweezers and Rydberg interactions to engineer stable, reconfigurable qubits—atoms literally held and moved by light.

Whether you’re fascinated by quantum mechanics, computing, Schrödinger’s cat, or the future of information, this conversation reveals how physicists are turning the weirdness of quantum physics into working technology—and why building a fault-tolerant quantum computer is one of the hardest and most exciting challenges in science today.

Follow us for more technical interviews with the world’s greatest scientists:
Twitter: https://x.com/632nmPodcast
Instagram: https://www.instagram.com/632nmpodcast?utm_source=ig_web_button_share_sheet&igsh=ZDNlZDc0MzIxNw==
LinkedIn: https://www.linkedin.com/company/632nm/about/
Substack: https://632nmpodcast.substack.com/

Follow our hosts!
Michael Dubrovsky: https://x.com/MikeDubrovsky
Misha Shalaginov: https://x.com/MYShalaginov
Xinghui Yin: https://x.com/XinghuiYin

Subscribe:
Apple Podcasts: https://podcasts.apple.com/us/podcast/632nm/id1751170269
Spotify: https://open.spotify.com/show/4aVH9vT5qp5UUUvQ6Uf6OR
Website: https://www.632nm.com

Timestamps:
00:00 - Intro
01:32 - Fundamentals of Quantum Computers
04:09 - Transistors vs Quantum Gates
10:07 - What is Quantum Error Correction?
14:23 - State of the Art QEC
22:19 - Quantum Research Before Lukin
27:35 - Lukin’s Breakout Work
31:10 - From Quantum Optics to Quantum Computing
36:59 - Working with Neutral Atoms
48:17 - Funding Quantum Computers
50:00 - Transverse Gate Operations
58:22 - Is Quantum Computing All Hype?

#quantumcomputing #quantumerrorcorrection #mikhaillukin #qubits #schrodingerscat #entanglement #superposition #quantumphysics