The Cosmic Microwave Background: The history of its experimental investigation and its significance for cosmology

TL;DR

This review traces the discovery and significance of the cosmic microwave background, highlighting its role in confirming the Big Bang, inflation, and enabling precision cosmology through experimental advancements.

Contribution

It provides a comprehensive overview of the experimental history of CMB research and its impact on understanding cosmological models and fundamental physics.

Findings

CMB discovery confirmed the Big Bang model

Precision measurements have refined cosmological parameters

Experiments have tested inflation and General Relativity on cosmic scales

Abstract

This review describes the discovery of the cosmic microwave background radiation in 1965 and its impact on cosmology in the 50 years that followed. This discovery has established the Big Bang model of the Universe and the analysis of its fluctuations has confirmed the idea of inflation and led to the present era of precision cosmology. I discuss the evolution of cosmological perturbations and their imprint on the CMB as temperature fluctuations and polarization. I also show how a phase of inflationary expansion generates fluctuations in the spacetime curvature and primordial gravitational waves. In addition I present findings of CMB experiments, from the earliest to the most recent ones. The accuracy of these experiments has helped us to estimate the parameters of the cosmological model with unprecedented precision so that in the future we shall be able to test not only cosmological models but General Relativity itself on cosmological scales.