The first in a (hopefully) series of posts inspired by topics covered in my upcoming textbook on singular optics.
Crewed balloon rides have a surprisingly large role in the history of science. The first untethered balloon flight was performed in Paris on November 21, 1783, and the achievement of human flight opened up new possibilities for scientific measurement and, indeed, exploration.

The first untethered balloon flight, November 21, 1783.
Primarily, ballooning offered a novel opportunity to study the chemical properties of the upper atmosphere and the wind currents at high altitudes, and it filled this role for over a century. Unfortunately, many early flights were deadly: I’ve blogged before about the fateful 1875 flight of Gaston Tissandier, Joseph Croce-Spinelli and Théodore Sivel, in which 2 of the 3 balloonists succumbed to oxygen deprivation.
Other discoveries awaited the adventurous at high altitudes. Half of the 1936 Nobel Prize in Physics went to Victor Francis Hess for the discovery of extraterrestrial radiation (cosmic rays) from a balloon in 1913 (though hints of cosmic rays appeared even earlier).
In the 21st century, one wouldn’t think that there would be any physics left to be observed by balloon. Recently, however, I came across a 2002 paper¹ by scientists from Hungary and Switzerland, titled “First observation of the fourth neutral polarization point in the atmosphere.” In this paper, the researchers describe how they used measurements from a hot air balloon to verify a prediction of optical science that had remained untested for over 150 years!

A modern hot air balloon, from Wikipedia, because it seems like I should have one in this post. Photo by Kropsoq.
The discovery is not, admittedly, Earth-shattering, so to speak, but it is a fascinating epilogue to an extended period of the history of physics and a testament to the ingenuity of scientists!
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