Come with us on a visit to the home of the prime meridian for a conversation with the curator of the Royal Observatory, Greenwich about the race to create a practical means for determining longitude. It’s a dramatic story of precision astronomy and clock making, told by the Curator of the Observatory to Mat Kaplan as they examined the timepieces that helped revolutionize navigation. Bill Nye is on vacation, but we’re joined by Emily Lakdawalla with hazy news from Pluto, and Bruce Betts’ explanation of the plutonium that just passed its namesake planet.