The Big Bang and the Early Universe

Running our expanding cosmos backward in time from now to its first few seconds yields a scorching, jammed multitude of particles at its birth. As the universe expanded, nearly all these particles ended up as a cosmic background of light, still visible as static on an old TV, and as invisible dark matter; the rest clumped into galaxies of stars or collapsed to form giant black holes that lurk in the galaxies’ centers. We will discuss how this happened and how we know what we know, including recent results from the James Webb Telescope and the Nanograv gravitational-wave observatory.