On Aug. 21, a total solar eclipse will trace a line stretching from Oregon to South Carolina. A similar event happened in July of 1878, which helped astronomers of the day to better understand our solar system. David Baron joins us to tell the story of the scientists who chased the eclipse, which he writes about in “American Eclipse: A Nation’s Epic Race to Catch the Shadow of the Moon and Win the Glory of the World” (Liveright Publishing).