This is an interesting question, as it speaks to a larger phenomena within the realm of science: how quickly does expert knowledge filter down into popular knowledge? The detailed answer to that question is beyond the scope of this answer, but let's examine some specifics:

The idea that atmosphere thins as you ascend is a fairly old concept. It was empirically proven in the 17th Century by a group of French Mathematicians. As time went on, various aspects of what 'outer space' and 'atmosphere' were theoretically explored. However: these discoveries were not widely distributed beyond the purely expert circle of amateur scientists/mathematicians and others who made up the intellectual cliques of their era.

In truth, it wasn't widely and publicly known that 'outer-space' existed until wide-spread state sponsored education introduced basic astronomy to the populace. This transition occurred in fits and starts through the latter 19th century and into the 20th. In fact, it continues to this day all around the world. I don't think it would be an outrageous guesstimate to say that with 17% of the World's Population being illiterate, that something greater than 1 in 10 humans doesn't know that the Earth has an atmosphere and outside of it you can't breath.

So, in essence, along with many other 'expert' tiers of knowledge, prior to the widespread popularization of education, it was unlikely that most people knew or cared about things like calculus or optics or any of the other relatively modern mathematical formulations (like the exact nature of an atmospheric envelope).