Rutgers University Astrophysics Colloquium

The high and dry desert of the Chilean Andes is a magnificent site from which to observe the universe. The Atacama Cosmology Telescope (ACT) made measurements of the cosmic microwave background (CMB) from there for fifteen years, with a series of three cameras. ACT was designed to complement Planck, the latest and most sensitive CMB satellite. To compete with the powerful data set provided from a major space mission requires years of observations from bespoke arrays of thousands of detectors; for ACT these were cooled to 100 mK and deployed on the eponymous special-purpose 6 m telescope, on a plateau at 5190 m. The resulting maps of the microwave sky provide myriad probes of the universe across many scales of length and time. How the ACT instrument worked and some of the ways its data have and will inform our understanding of cosmology and astrophysics will be discussed, capped off with a quick look toward future developments.