Solution to the Grandfather Paradox | Sleep on Science

How physicists actually solved the grandfather paradox is stranger than the movies: killing your grandfather looked like an airtight proof that time travel is impossible, yet the leading physicists found the universe never forbids the trip — it quietly guarantees you can never change a single thing once you arrive. From the pulp-magazine letter columns where the paradox was born, to Gödel's rotating universe, to wormholes and time loops built from light, the past turns out to be read-only. In this documentary, we trace the century-long attempt to solve the grandfather paradox, exploring closed timelike curves, Gödel's 1949 rotating universe, tilted light cones and the chronology-violating region, the Tipler cylinder, Gott's cosmic strings, van Stockum's rotating dust, traversable wormholes and the exotic matter and Casimir effect they demand, Novikov's self-consistency principle, Polchinski's billiard ball, Deutsch's quantum fixed-point resolution, and Hawking's chronology protection conjecture. We also explore the Queensland photon experiment, Lloyd and Maccone's postselection model, the philosopher David Lewis's answer, and the eerie Jinn that circulate in loops with no origin. Throughout, we separate what popular culture invented from what the documented record actually shows. New here? Snoozable Wonders is long-form science history for sleep — if tonight's episode helps you drift off, a like or a subscribe genuinely helps a small channel get found. Thank you so much for your support! ❤️ It truly means the world to me! Resources: Closed Timelike Curves, Singularities and Causality: A Survey – arXiv – https://arxiv.org/pdf/2101.08592 Wormholes, Time Machines, and the Weak Energy Condition – Physical Review Letters – https://link.aps.org/doi/10.1103/Phys... Quantum Mechanics Near Closed Timelike Lines – Physical Review D – https://link.aps.org/doi/10.1103/Phys... Experimental Simulation of Closed Timelike Curves – Nature Communications – https://www.nature.com/articles/ncomm... Chronology Protection Conjecture – Physical Review D – https://link.aps.org/doi/10.1103/Phys...