At the Galileo Museum in Florence, there’s a dazzling collection of old scientific instruments, including the telescope Galileo used to discover new moons. Cosmologist Marcelo Gleiser explains how Galileo revolutionized the scientific worldview.

Astrophysicist Adam Frank says there’s an emerging science of “planetary intelligence,” which regards the Earth itself as sentient. It’s a radical idea, with far-reaching implications, and it may just help save the planet.