The first statement can be completed with "the Big Bang theory" or "cosmic inflation" depending on the context of the cooling temperature changes being compared.
The second statement can be completed with "produced in the first moments after the Big Bang" or "formed during nucleosynthesis in the early universe," as this relates to the formation of hydrogen and helium during the early stages of the universe.
So, the completed statements could be:
- Comparing cooling temperature changes at different stages of the universe's life provides evidence of the Big Bang theory.
- Measuring the universe's ratio of hydrogen and helium provides evidence that these elements were produced in the first moments after the Big Bang.