It seems tailor-made for us, but how common are planets like Earth in the galaxy? We’re discovering alien worlds by the thousands, but none so far reminds us of our own blue-green home. We may yet find one… but maybe we should also ask ourselves just how Earth-like a planet has to be to be like Earth. Join for this talk (broadcast from NIST Boulder campus) featuring Phil Plait, The Bad Astronomer. Phil is author of The Bad Astronomy Blog that covers the entire Universe, from subatomic particles to the Big Bang itself. This talk was recorded March 8th, 2019.