Question

According to the Big Bang theory of the origin of the universe, the universe has expanded from a hot dense state into a vast, cooler state. What would be considered scientific evidence supporting this theory?
Responses
A Galaxies are moving toward each other.Galaxies are moving toward each other.
B Galaxies are moving away from each other.Galaxies are moving away from each other.
C Cosmic background X-ray radiation was detected in space.Cosmic background X-ray radiation was detected in space.
D The existence of common elements throughout the universe.The existence of common elements throughout the universe.

Answer 1

Best answer: B — Galaxies are moving away from each other.

Explanation:
- Edwin Hubble's observation of galaxy redshifts (recession velocities) is direct evidence the universe is expanding, as predicted by the Big Bang.
- D (common light elements) is also supporting evidence: Big Bang nucleosynthesis predicts the observed primordial abundances of hydrogen, helium, and lithium.
- C is incorrect as written: the observed relic radiation is the cosmic microwave background (CMB), not X‑ray radiation.
- A contradicts the expansion (it would imply contraction).