Created by P.T. Barnum in 1871 and named “The Greatest Show on Earth,” Ringling Bros. and Barnum & Bailey Circus shut down in 2017. But now this American institution is being reimagined for a new age, and is relaunching with a two-year tour, featuring aerial acts, a new take on clowns, and no animals (except for a robot dog named Bailey). Correspondent Martha Teichner reports on how the circus is catapulting into the future.