Cosmology: from theory to data, from data to theory

Abstract

Cosmology has come a long way from being based on a small number of observations to being a data-driven precision science. We discuss the questions "What is observable?", "What in the Universe is knowable?" and "What are the fundamental limits to cosmological knowledge?". We then describe the methodology for investigation: theoretical hypotheses are used to model, predict and anticipate results; data is used to infer theory. We illustrate with concrete examples of principled analysis approaches from the study of cosmic microwave background anisotropies and surveys of large-scale structure, culminating in a summary of the highest precision probe to date of the physical origin of cosmic structures: the Planck 2013 constraints on primordial non-Gaussianity.Comment: 49 pages, 22 figures. Lectures given at the International School of Physics Enrico Fermi "New Horizons for Observational Cosmology", June 30-July 6, 2013, Varenna, Italy and at the Paris Ecole Doctorale for Astronomy and Astrophysics. Proceedings of the Enrico Fermi School (eds A. Cooray, A. Melchiorri, E. Komatsu, Italian Physical Society). Updated figures and references wrt published versio