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Why Syncing Atomic Clocks is Virtually Impossible | Judah Levine on UTC

Nov 26, 2025 · 2h 4m

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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…