The Milky Way looks permanent from our place inside it, a great band of stars stretching across the night sky. But new research suggests our galaxy may once have been oriented in a completely different direction, perhaps reorienting by more than 90 degrees during its violent youth.

This episode explores the evidence for the Milky Way's possible ancient flip and, even more remarkably, how astronomers could possibly reconstruct something that happened around ten billion years ago. Using stellar motions measured by Gaia, the debris of the ancient Gaia-Enceladus merger, cosmological simulations, and even the inferred shape of the Milky Way's invisible dark-matter halo, astronomers are learning to read our galaxy's history from the fossils it left behind.

We also follow up on the August 5 rocket-body impact on the Moon, and discover why an ...