Explain Luis Alvarez's asteroid impact theory.
That was a fascinating project. We were looking for a way to explain the sudden disappearance of dinosaurs and other species at the end of the Cretaceous period. My son, Walter, and I noticed a strange iridium layer in geological strata all over the world. Iridium is rare on Earth's surface but common in meteorites. So, the hypothesis was that a large asteroid, about ten kilometers across, hit the Earth. This impact would have thrown up enormous amounts of dust and debris, blocking sunlight and causing a global catastrophe. It's a classic case of observation leading to a testable theory.
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