English: In the photo above, taken in the 1950s, Simpson is bent over reams of images of clouds that she filmed during long flights between islands in the tropical Pacific. From the photos, she is drawing detailed maps of cloud formations. These observations underpinned her first major contribution to atmospheric science: the boat-rocking hypothesis that tropical clouds weren’t just the passive result of atmospheric circulation, as meteorologists of the day believed, but were in fact the cause of it.