Precision cosmological measurements, especially measurements of the CMB from Planck, have allowed a determination of the basic ingredients (energy densities) of the universe at per-cent level precision. The overall picture strongly supports the so-called concordance model with cold dark matter and dark energy. However, with the increase in precision also came some tension in the data. Direct measurements of the expansion rate of the universe today, H_0, and measurements of the matter power spectrum, sigma_8, each disagree with predictions of the concordance model at 2-3 standard deviations. In this talk, the speaker will review the experimental situation and propose and describe a model in which dark matter interacts with dark radiation which can resolve both discrepancies.
