A century ago, astronomers were locked in a debate about the scope of our universe. Were we it? The answer is no. There are other galaxies beyond the Milky Way, and they are speeding away from us. Answering that question left astronomers with an even bigger puzzle. Why is everything sprinting away from us and what does that mean for the center of the universe? Today, Scientist in Residence Regina G. Barber brings back astronomer Dr. Vicky Scowcroft for the final episode in our series on cosmic distances and humanity's place in the universe. It's a big one: The mystery of our expanding universe. If you haven't heard the other two episodes in the series yet, check them out here:- Venus And The 18th Century Space Race- The Stars that Settled The Great DebateCurious about other intergalactic goings on? Tweet us @NPRShortWave or email us at shortwave@npr.org.