The canonical images of Benjamin Franklin’s lightning experiment are wrong. In this respect informs Sao Paulo State Research Foundation.
Long before Benjamin Franklin entered politics and became one of the “Founding Fathers” of the United States, he became famous as a physicist and discoverer of the electrical nature of lightning. For this, among other things, he became an honorary member of the Russian Imperial Academy of Sciences and Arts. In many drawings, Franklin is depicted with a kite that he launches into thunderclouds and a grounded string is stretched.
Breno Arcioli Moura did historical research and found that this depiction was wrong. According to him, the kite experiment was conceived as a simpler version of another experiment invented by Franklin in 1750 – the “watchbox” experiment. As part of this experiment, a steel pole mounted on an insulated stand would be pointed into the sky from the cabin. This pole was supposed to “pull fire from the clouds” and hold it, then, again, a person standing on a tripod could bring their fingers to the pole and light sparks. It is important to note that “fire” (in modern language – charge) will not accumulate on a grounded pole, moreover, do not plan to get lightning inside the tester.
Like other naturalists of the eighteenth century, Franklin envisioned electricity as a fluid that accumulates and then discharges, flowing from one place to another. The general idea behind the watch box and kite experiments was to show that this liquid could also be drawn from clouds.
The kite experiment was an improved version of the same experiment. While the kite had to be held with a string, a steel wire instead of a steel pole had to be fixed to the kite. “A silk ribbon should be tied at the end of the rope near the hand, and you can tie it where the silk and twine meet. [металлический] key. […] As soon as any of the thunderclouds cover the kite, the pointed wire draws electric fire from them and the whole string and the kite become electrified, and the loose wires of the string come out in all directions. And when the rain wets the kite and the string so that it can freely transmit electric fire, you will see that when your finger approaches, it flows abundantly from the key, ”the scientist wrote. Moura analyzed many descriptions of this experiment and concluded that the drawings of a grounded kite or where the experimenter was holding it by the string were incorrect. According to the historian’s reconstruction, the kite using a conductive wire was supposed to draw “electricity” from the cloud and transmit it along a moderately conductive string to a switch attached to it where the “fire” would be stored. At the same time, the twine was held in the hands by means of a silk cord insulator. To start removing the “electricity” from the switch, it was necessary to bring your fingers to it, in case of grounding the “fire” would go into the ground.
The author of the work emphasizes how important it is to use correct illustrations in history and physics lessons so that students do not misunderstand the idea of experiment. The vast majority of 19th and 20th century illustrators had no experience in drawing scientific experiments, and therefore the canonical image of Franklin with a snake must be reconstructed according to historical sources and physics knowledge of that time.