Final answer:
The Steady State Theory and the Big Bang Theory both propose models for the origin of the universe and its expansion. The Big Bang Theory is now the dominant model, supported by evidence such as the redshift of galaxies and the cosmic microwave background radiation.
Step-by-step explanation:
The Steady State Theory and the Big Bang Theory both aim to explain the origin of the universe and the fact that it is expanding. The Steady State Theory, once popular in the 1950s and 1960s, posited that the universe was homogeneous and isotropic, meaning it was the same in every place and all directions, and that it did not change over time. This theory suggested that new matter was constantly being created to maintain the universe's density as it expanded. On the other hand, the Big Bang Theory, which is the prevailing cosmological model today, suggests that the universe began approximately 13.7 billion years ago with an intense expansion from an extremely dense and hot state. This model is strongly supported by observational evidence, such as the cosmic microwave background (CMB), the abundance of light elements, and the expansion of the universe evidenced by the redshift of distant galaxies.
While both theories address the expansion of the universe, it is the Big Bang Theory that has gained widespread acceptance due to an abundance of supportive empirical evidence. Observations such as the redshift of galaxies, which shows that the universe is expanding, and the existence of the CMB radiation have provided strong evidence against the Steady State Theory.