In today's Crash Course Astronomy, Phil takes a look at the explosive history of our cosmic backyard. We explore how we went from a giant ball of gas to the system of planets and other celestial objects we have today.

Once it was determined that the Earth is round, the next step was to decipher the geometry of the solar system. Does everything rotate around the Earth, like in the geocentric model of Ptolemy? We thought so for thousands of years, but...

The moon as seen from earth or Hubble telescope, zoom in to the Aristarchus Crater and then to Shroters Valley. NASA/Goddard Space Flight Center Scientific Visualization Studio Additional credit to Zoltan G. Levay (STScI)