In 1983, scientists proposed that the dinosaur extinction at the K-T boundary was triggered by a cosmic impact, and the skeptics had one simple demand: show us the crater. At almost exactly the same time, petroleum crews drilling in Mexico’s Yucatan Peninsula punched through half a kilometer of limestone and pulled up something unexpected, a dense, green, glass-like vitrified material unlike anything volcanic. American researchers caught wind of it, ran subsurface surveys, and found a giant circular structure buried beneath that limestone, the unmistakable signature of a massive impact crater. The vitrified rock was limestone melted by superheated impact temperatures, and subsequent research turned up the remnants of gigantic tsunamis washed as far north as Louisiana and Texas. The crater the skeptics demanded had been sitting under the Yucatan the whole time.