In this talk, I will present recent work on the properties of radiation from a one-dimensional electron liquid. Because of the large mismatch between the speed of light and the Fermi velocity, radiation serves as a direct test of spectral weight of the system which is far `off-shell'. In the Luttinger liquid model, excitations of the electron liquid are described by non-interacting bosons and this spectral weight vanishes. Thus, radiation offers a direct test of behavior which is beyond the Luttinger liquid paradigm. I will discuss several examples of systems for which such radiation can be observed.