Question

18 based on your research throughout the unit, what are two lines of evidence that support the big bang theory as an explanation of the origin of the universe?

Explanation:

• Cosmic Microwave Background (CMB) radiation: This is a faint glow of light that fills the universe. It is considered the afterglow of the Big Bang. The CMB has a nearly uniform temperature across the sky (about \(2.725\) K), which is consistent with the idea that the universe was once in a hot, dense state (as predicted by the Big Bang theory) and has been expanding and cooling ever since.
• The abundance of light elements: The Big Bang theory predicts the relative amounts of light elements (like hydrogen, helium, and trace amounts of lithium) that should have been formed in the early universe. Observations of the abundances of these elements in stars and gas clouds in the universe match very closely with the predictions of the Big Bang theory. For example, about \(75\%\) of the ordinary matter in the universe is hydrogen and about \(25\%\) is helium (by mass), which aligns with Big - Bang nucleosynthesis predictions.

Answer:

1. Cosmic Microwave Background (CMB) radiation.
2. The abundance of light elements (such as hydrogen and helium).