time: Quick Facts

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Oct. 3, 2026

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Alfred North Whitehead

Stone sculpture of the reclining Buddha with serene expression, carved into the wall of Ajanta Caves, Maharashtra, India.

The Greek philosopher Plato

Portrait of Charles Darwin with a full white beard and dark hat, wearing a cloak, standing beside a wall with climbing vines. Photo by Julia Margaret Cameron, 1881.

Engraved portrait of Sir Isaac Newton from 1856, showing him seated with long curly hair, wearing a brown coat and white cravat, gazing to the side.

relativity of simultaneity

Listen to physicist Sean Carroll explaining the connection between entropy and the second law of thermodynamics

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Explore three simple ways and three complicated ways of time traveling

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Topics

Planck time Hubble time simultaneity future hypertime rotational time proper time present past stopping time light electromagnetism gravity relativity chemical reaction antimatter molecular beam dark matter physical constant force

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Key People

Henri Bergson

Henri Bergson

French philosopher

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Ferdinand Berthoud

horologist and author

Italian physicist Guglielmo Marconi at work in the wireless room of his yacht Electra, c. 1920.

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Italian-born physicist Dr. Enrico Fermi draws a diagram at a blackboard with mathematical equations. circa 1950.

Physics and Natural Law