RISE Science - Earth Science Practice Questions - RISE Science - High School Earth Science Exam

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Measurements of primordial gas clouds in the early universe reveal an elemental mass abundance ratio of approximately 75% hydrogen and 25% helium, with only trace amounts of lithium. Why is this ratio considered major evidence for the Big Bang?

Stellar fusion alone would have converted all hydrogen into iron by now. Nuclear synthesis models of the hot, dense early universe accurately predict this exact 3:1 H-to-He ratio. Planetary accretion requires helium to ignite nuclear fission in rocky planet cores. Radioactive decay of heavy uranium naturally yields 75% hydrogen over geologic time.

Correct Answer:

Nuclear synthesis models of the hot, dense early universe accurately predict this exact 3:1 H-to-He ratio.

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