During World War II, Dr. Irving Langmuir, a scientist, was hired by the General Electric Company to study how and why ice forms on the wings of airplanes. He and a young assistant named Schaefer went to a mountain in the state of New Hampshire, where snowstorms are common and cold winds blow.
While in New Hampshire, Langmuir and Schaefer were surprised to learn that often the temperature of the clouds surrounding them was far below the freezing point, and yet ice did not form in the clouds. After the War, Schaefer experimented with a machine that created cold, moist air similar to the air found in clouds. To imitate the moist air of a cloud, Schaefer would breathe into the machine. Then he would drop into the freezer a bit of powder, sugar, or some other substance. For weeks and months he tried everything he could imagine. Nothing happened. No crystals of ice were formed. None of the substances would serve as the center of a snow crystal or raindrop.
One July morning, Schaefer was dropping in bits of various substances and watching the unsuccessful results. Finally, a friend suggested that they go to eat lunch, and Schaefer gladly went with him. As usual, he left the cover of the freezer up, since cold air sinks and would not escape from the box.
Returning from lunch, Schaefer was beginning to perform his experiments again when he happened to look at the temperature of the freezer. It had risen to a point higher than that required for ice crystals to remain solid. The warm summer weather had arrived without his noticing it. He would have to be more careful in the future.
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