What do we learn from CMB observations

TL;DR

This paper explains how cosmic microwave background (CMB) observations reveal key information about the early universe, including primordial density fluctuations and gravitational waves, by analyzing temperature anisotropy and polarization.

Contribution

It provides a non-expert, quantitative overview of how CMB data constrains cosmological parameters and enhances understanding of the early universe.

Findings

CMB measurements are crucial for determining cosmological parameters.

CMB data provides insights into primordial density perturbations.

Potential detection of gravitational waves from the early universe.

Abstract

We give an account, at non-expert and quantitative level, of physics behind the CMB temperature anisotropy and polarization and their peculiar features. We discuss, in particular, how cosmological parameters are determined from the CMB measurements and their combinations with other observations. We emphasize that CMB is the major source of information on the primordial density perturbations and, possibly, gravitational waves, and discuss the implication for our understanding of the extremely early Universe.