In this talk I will describe constraints from causality and unitarity on
2ā2 graviton scattering in four-dimensional weakly-coupled effective
field theories. Together, causality and unitarity imply dispersion
relations that connect low-energy observables to high-energy data. Using
such dispersion relations, I will explain how to derive two-sided bounds
on gravitational Wilson coefficients in terms of the mass M of new
higher-spin states. Such bounds imply that gravitational interactions
must shut off uniformly in the limit Gā0, and prove the scaling with M
expected from dimensional analysis. In addition they demonstrate the
gravity must be weakly coupled at all scales below Planck. Time
permitting, I will comment on the experimental implications of the
bounds.