160: Going back in time with Dr. Bottke

Dr. Bill Bottke  stops by the show to talk about ancient craters on the Moon and Earth. He tells us about how you can figure out crater ages by looking at the nearby rocks, and how that led him and his colleagues to figure out that the impact rate on Earth changes with time.  Image: The lunar crater  Daedalus , as imaged by the Apollo 11 astronauts.

Dr. Bill Bottke stops by the show to talk about ancient craters on the Moon and Earth. He tells us about how you can figure out crater ages by looking at the nearby rocks, and how that led him and his colleagues to figure out that the impact rate on Earth changes with time.

Image: The lunar crater Daedalus, as imaged by the Apollo 11 astronauts.