Second prediction from Big Bang Model:
Abundance of the light elements
Big Bang Nucleosynthesis
T, both high enough at start to fuse protons into heavier
elements
T,   both dropping quickly so only have time enough to
fuse a certain amount.
Simple models of expansion predict 25% abundance He
25% is the amount of He observed
Abundance of 2H, 3He, 7Li depends on normal matter
Suggests normal matter is only 5% of critical
But we need to also consider “dark matter” and its gravity