I will discuss potential new science arising from atomic clock technology deployed on Earth and in space. For space-based clocks, I will focus on higher order relativistic effects for a satellite that orbits a planet, and describe their potential to learn about the planet's internal structure. On the ground, a global optical clock network would provide local, continuous monitoring of the geoid on continents. Portable optical clocks could combine their measurements with those of gravimeters and gradiometers to potentially resolve underground substructure of the order of a kilometer.