Alexander Dahl (November 29, 1892 in Barmen – December 15, 1978 in Wuppertal) was a German industrialist, author and balloonist. He was the first person to take a photograph of the Earth's curvature from an open hydrogen gas balloon in 1933.
First photograph of Earth's curvature
The first image showing the Earth's curvature was taken at a height of 11300m on 31 August 1933 from the high performance (9.800 cbm) hydrogen gas balloon Bartsch von Sigsfeld. The official purpose of the flight was not to gain maximum height, but rather to measure the effect of sun radiation within the tropopause. However, as part of the flight, the crew also set the first height record for unaided altitude flight in an open air balloon.