Zoom info: https://stanford.zoom.us/j/550904854

The cosmic microwave background provides a unique backlight for illuminating the growth of structures in our universe. Measuring the arcminute-scale lensing deflections experienced by the CMB photons as they travel to our telescopes enables the mapping of the matter distribution to very high redshifts. This lensing signal provides a clean window for constraining fundamental physics, such as the sum of neutrino masses, and enables powerful tests of the standard cosmological model via comparison of high-precision measurements of structure growth at late times with early-time predictions.In this talk, I will present new CMB lensing measurements derived from data release 6 of the Atacama Cosmology Telescope. Our work provides a state-of-the-art lensing power spectrum measurement and an associated signal-dominated lensing mass map that enable a host of cosmological and astrophysical science goals. I will first discuss the novel methods used to tackle key systematics affecting precision CMB lensing. I will then explore the implications of our measurements for tests of cosmic structure growth and the S8 tension.