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The Earth and Moon are twins! A discovery that explains their origin

Part 3 of the TED Radio Hour episode Doppelgangers.

Everything in the solar system is made of different rocks and materials, except the Earth and Moon. They're like twins. It's a mystery that planetary scientist Sarah T. Stewart set out to solve.

About Sarah T. Stewart

Sarah T. Stewart is a Professor in the Department of Earth and Planetary Sciences at UC Davis. A planetary scientist and MacArthur Fellow, she specializes in the study of collisions in the solar system and directs the Shock Compression Laboratory, which uses light gas guns to study shock waves in planetary materials. Stewart is best known for proposing a new model for the origin of the moon.

This segment of the TED Radio Hour was produced by Matthew Cloutier and edited by Sanaz Meshkinpour and Manoush Zomorodi. You can follow us on Facebook @TEDRadioHour and email us at

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Manoush Zomorodi is the host of TED Radio Hour. She is a journalist, podcaster and media entrepreneur, and her work reflects her passion for investigating how technology and business are transforming humanity.
Matthew Cloutier is a producer for TED Radio Hour. While at the show, he has focused on stories about science and the natural world, ranging from operating Mars rovers to exploring Antarctica's hidden life. He has also pitched these kinds of episodes, including "Through The Looking Glass" and "Migration."