this question also qualifies as a NA question!

process of elimination is the king here!

yet means and

I love how J.Y. reference back to previous videos. It helps me in so many ways, and bring the course all together to show how it overlaps. Thank you J.Y. 🥲

My understanding is that it's a correlation between dimness and heat.

sun dim→ more heat in the atmosphere (3.8 Billion years ago)

/more heat in the atmosphere →/sun dim (today)