How can physicists be so audacious as to declare all we see, hear and feel is from gravitational instability of quantum fluctuations in ultra-early universe fields encoded in energy-density phonons? Answer: the data reveals it, most precisely by our Planck cosmic microwave background (CMB) team. Over the 25 years from the Planck satellite go-ahead to our 2018 Legacy release, we have established the SMc, the standard model of cosmology, full of dark energy and matter amid the subdominant ordinary baryons and leptons. So far our maps of the early Universe phonons reveal a two-parameter simplicity, an overall amplitude and a nearly scale invariant spectral slope, plus a few slight anomalies. In the next round of cosmic background and galaxy clustering experiments we are in quest of "Beyond the SMc" physics, through the emergence of more parameters to characterize the many quantum fields present, including the fundamental gravitons and the collective phonon, aka the inflation.
This lecture is part of the program Cosmology - The Next Decade.