On The Gist, guest host Jeffrey Lewis fills in for Mike and talks about trying to solve big problems.

Regulating space is tough because it surrounds the whole world, and people can't even agree where the Earth's atmosphere stops and space begins. Jonathan McDowell, astrophysicist at the Harvard-Smithsonian Center for Astrophysics, thinks he has the definitive answer to where that line is. McDowell recently published "The Edge of Space: Revisiting the Karman Line" in Acta Astronautica.

In the Spiel, North Korea and nuclear weapons.

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