Teisserenc de bolt was the first man to discover the earths atmosphere. He lived in France for most of his life and was the first person to figure out that the earths atmosphere had different layers and he also figured out at what heights each layer was at.
On this website they explained how they sent up animals into the atmosphere to see if they would survive. And they later found out the air got thinner as they went farther up. So they altered a suit for a man to go up into the atmosphere in.
This website explained how hard it would’ve been to get to the atmosphere to study it back in the 20th century. It tells a couple stories of people trying to study the atmosphere in different ways.
Earlier philosophers all had different beliefs about the atmosphere. And so they all came together and put all their beliefs and ideas about what was beyond the earths surface and came up with the idea of the atmosphere.