| Abstract: The Simons Observatory (SO) is a new CMB experiment being built in the Atacama Desert in Chile, due to begin observations in the early 2020s. SO will measure the temperature and polarization anisotropy of the CMB using 60,000 detectors measuring the sky in six frequency bands, and will see both primary and secondary signals. The observatory will have three 0.5-m telescopes and one 6-m telescope. I will describe SO's goals: to characterize the primordial perturbations and look for primordial gravitational waves, to measure the mass of neutrino particles and the number of relativistic species, to test for deviations from a cosmological constant, to improve our understanding of galaxy evolution, and to constrain the duration of cosmic reionization. Much of this science will benefit from combining secondary CMB effects with data from optical surveys, in particular with LSST and DESI. |