Space Physics and Astronomy - SS1 Physics Past Questions and Answers - page 4

The Big Bang theory proposes that the universe originated from a singularity, a point of infinite density and temperature, approximately 13.8 billion years ago. According to this theory, the universe has been expanding ever since, cooling down and allowing matter and energy to form. The Big Bang theory is supported by various lines of evidence, such as the observed redshift of distant galaxies, the abundance of light elements, and cosmic microwave background radiation. It provides a comprehensive framework for understanding the evolution and structure of the universe.

The cosmic microwave background (CMB) radiation is the residual heat radiation left over from the early stages of the universe, about 380,000 years after the Big Bang. It is often referred to as the "afterglow" of the Big Bang. The CMB radiation was discovered accidentally in 1965 by Arno Penzias and Robert Wilson, and its existence provided strong evidence in support of the Big Bang theory.

The CMB radiation is observed as a nearly uniform glow of microwaves coming from all directions in space. Its discovery and subsequent measurements have revealed important information about the early universe. The uniformity and isotropy of the CMB radiation indicate that the universe was once in a hot, dense state. The precise measurements of the CMB radiation have also helped determine the composition and age of the universe, as well as its rate of expansion.