The years around 1600 saw tremendous changes in astronomy. Tycho Brahe's precision in measuring planetary positions partly fueled Johannes Kepler's astronomical discoveries. Kepler's desire to find the hidden harmonies in the planetary system provided a basis for modern celestial dynamics. About the same time, Galileo turned a new instrument, the telescope, on the heavens and saw amazing things never before seen by man. This lecture examines these characters, their context, their work and their impact.