You don't need to send anything to 35k feet; you only need a camera with a decent telephoto lens and a long lake on clear day with calm winds. From one shore of

You don't need to send anything to 35k feet; you only need a camera with a decent telephoto lens and a long lake on clear day with calm winds. From one shore of the long lake, view objects at the far shore from normal standing height using the camera+lens. If you then carefully lower the camera to the ground, you can watch objects (boats! people! small buildings!) dissapear behind the curvature of the lake's surface. Dan Olson ("Folding Ideas") demonstrates this experiment in the video[1] I recommended in an earlier post[2]. [1] https://www.youtube.com/watch?v=JTfhYyTuT44 https://www.youtube.com/watch?v=JTfhYyTuT44 [2] https://news.ycombinator.com/item?id=24637001 https://news.ycombinator.com/item?id=24637001