He was educated at Caltech and Princeton University, after which he held NASA postdoctoral fellowships. His speciality is in the dynamics of planetary systems, both in their formative stages and in today's observations. He has developed and tested theories of why some gas-giant planets hug their host stars in tight orbits, showed how interactions between observed planets cause their orbital periods to vary and thereby reveal their masses and probed their origins through the architectures of these systems.