28:45 Welcome to Planet Earth
30:09 to 36:42 Eratosthenes
39:36 to 50:04 Library of Alexandria
50:04 Kepler
51:25 Timekeeping permitted exploration
51:52 The Earth was all explored.  Hubble, galaxies.  1920s.  Expansion of galaxy.  Age of universe.
52:48 Cosmic Calendar [big bang intro]
53:05 Cosmic Calendar [calendar itself]