A history is inferred from traces

The question is retained before an explanation is adopted.

Selected milestones in standard cosmology. Their spacing is schematic. [1-3]

Different observations constrain cosmic history: expansion, element abundances and ancient radiation.

Would one model account for all three? Which new result would require its parameters or assumptions to be revised?

The past has left evidence. It has not submitted a memoir.

First minutes Light nuclei

380,000 years Atoms; ancient light released

First stars Hundreds of millions of years

9.2 billion years Solar system forms

13.8 billion years Present epoch