Like an onion, the Earth has layers. In this episode we’ll see if you can dig through those layers to get to the center of the planet. We’ll also hear about the Danish scientist who discovered more about Earth’s core by studying earthquakes. Plus, we investigate the phrase “dig a hole to China.” Children’s book author and illustrator Oliver Jeffers stops by to talk about the Earth’s crust. “Here We Are,” his book about our vast and wonderful planet, was just turned into a movie (you can find it on Apple TV+). And our Moment of Um answers the question: do fish have tongues? All that and a Mystery Sound in this very layered episode! This episode is sponsored by KiwiCo (kiwico.com/brainson) and Skylight Frame (skylightframe.com/brains). You can support the show at brainson.org/fans See omnystudio.com/listener for privacy information.