The atmosphere is best pictured as an ocean of air that covers the whole planet. Its waves wash over mountains and valleys, and we live at the bottom of it with it passing right through us. We are not standing beneath the sky; we are living inside it.
Before people could go up into the sky, it was a blank space onto which they projected fantasies and fears. Some even saw it as a 'factory of death' where vapors that carried disease hung in the air. Once balloons let people actually travel there, the sky turned from an imagined idea into a physical thing that could be studied.
While scientists could only argue from the ground, rival theories about how rain forms competed without resolution. Carrying instruments up into the air turned the sky into a laboratory. That produced direct evidence about how temperature changes with height, how rain, hail and snow form, and what causes thunder.
Hanging inside a cloud, an observer is wrapped in white mist that the eye cannot see through. Sound carries strangely there: music from far below can seem to come from the cloud itself, only a few yards away. With sight blocked, your sense of where things are can be badly wrong.
Measurements of temperature and air pressure at different heights were drawn on top of attractive views of the scenery. Pairing hard numbers with images people enjoyed looking at, and with popular talks, made the findings vivid to a general audience. This is how the science of the air reached the public.