In the mid-20th century, the Steady State theory and the Big Bang theory competed to describe the origin and evolution of the cosmos. The accidental discovery of Cosmic Microwave Background Radiation (CMBR) in 1965, combined with observations of galactic spectra, provided the critical evidence that resolved this debate.
Explain how scientific observations of:
provide robust evidence to support the Big Bang model over the Steady State model, demonstrating that the Universe is actively expanding and that it must have originated from an extremely hot, dense singularity.