Recent observations of the cosmic microwave background are allowing us to scrutinize the ‘Lambda - Cold Dark Matter' cosmological model, and to weigh in on possible cracks in this model that may be appearing from different astronomical observations. I will describe recent results from the Atacama Cosmology Telescope, and show how the relic CMB light can be used as a backlight to weigh cosmic structures, and to map out the dark matter and cosmic gas over half the sky. I will also describe prospects for an improved view of the physics of the early universe from these data, and from the upcoming Simons Observatory.
