Exploring Earth and Space with Atomic Clocks
I will discuss potential applications of atomic clocks. For the first time, the accuracy and stability of the best frequency standards and related technology permits the use of general relativity as a tool. In space, both the trajectory of a space-craft and the light signals it sends towards Earth are affected by the curvature of the space-time. The magnitude of the relativistic effects can be used to constrain the spin and moment of inertia of the planet that the satellite orbits. Any two separate frequency standards also act as a gravitational wave detector. Such a detector is sensitive to a frequency range between that of pulsar timing arrays and approved space-based interferometric detectors. I will also mention potential applications to geophysics. Frequency standards measure geopotential differences providing the most direct measurement of the geoid, which is the equipotential surface of the Earth that corresponds to the mean sea level. They can monitor the underground (e.g., track the water level, the solid Earth tide in areas where hydraulic fracturing is performed, etc), add detail and calibrate satellite maps.