Primordial Gravitational Waves and Cosmology

Astronomical Inflation In astronomy, according to the theory of inflation, the universe underwent a period of extremely accelerated expansion when it was only a fraction of a second old. This process made the universe flat, isotropic, and homogeneous, and it explains how quantum mechanical seeds developed into the large-scale structure we observe today. The theory also predicts that gravitational waves were produced during the early inflationary phase. Alternative theories either predict no gravitational waves or waves with different properties. Krauss et al. (p. 989 ) review how primordial gravitational waves could provide information on the physics shortly after the Big Bang and how they could be detected indirectly through their imprint on the cosmic microwave background radiation—relic radiation from the Big Bang released when the universe became transparent to electromagnetic radiation.