Final answer:
The evidence supporting the Big Bang Theory includes the observed expansion of the universe, the abundance of light elements that matches predictions, and the Cosmic Microwave Background radiation, which is remnant heat from the Big Bang.
Step-by-step explanation:
The three main pieces of evidence supporting the Big Bang Theory are:
- Expansion of the universe: In the year 1929, Edwin Hubble observed that galaxies were generally receding from us, which provided the first clue that the Big Bang theory might be correct.
- Abundance of light elements: The presence of hydrogen (H), helium (He), and lithium (Li) in the universe is almost exactly as what the Big Bang predicts. Elements were first fused within the early universe after the Big Bang.
- Cosmic Microwave Background (CMB) radiation: This is the remnant heat leftover from the Big Bang. The spectrum of cosmic microwave radiation is the most perfect blackbody spectrum ever detected, characteristic of a temperature of 2.725 K, the expansion-cooled temperature of the Big Bang's remnant. This radiation can be measured coming from any direction in space not obscured by some other source and is compelling evidence of the initial explosion.