Radar was the key technology to win the Battle of Britain against the Nazis. To protect their secret weapon, British Intelligence invented a propaganda campaign that claimed their pilots could see in the dark because they ate a lot of carrots.
You've probably heard the myth that eating lots of carrots will magically improve your vision. The bad news is that it's a total lie. The good news? It's one that helped the Allies defeat the Nazis.
Here's the truth: Carrots are rich in beta carotene (Vitamin A), and thus, eating lots of carrots helps promote good eye health. That's a different thing entirely from vision; pumping yourself full of Vitamin A doesn't bring you any closer to 20/20 than doing push-ups all day would.
So why do we think carrots help us see better? Smithsonian Magazine reports the theory of John Stolarczyk, curator of the World Carrot Museum (Yes! It exists). According to Stolarczyk, the myth began during World War II, when the Nazis were bombing the bejeezus out of London at night. Then, seemingly out of no where, the British Royal Air Force started shooting down more Nazi planes. How did they do it? With the help of a new radar that the RAF, of course, did not want anybody to know about. Smithsonian explains:
The Royal Air Force were able to repel the German fighters in part because of the development of a new, secret radar technology. The on-board Airborne Interception Radar (AI), first used by the RAF in 1939, had the ability to pinpoint enemy bombers before they reached the English Channel. But to keep that under wraps, according to Stolarczyk’s research pulled from the files of the Imperial War Museum, the Mass Observation Archive, and the UK National Archives, the Ministry provided another reason for their success: carrots.
When the papers asked how pilots where shooting down planes in the dark, the RAF simply responded that pilots had been hitting their root veggies hard. A bold-faced lie! But one that helped save London—and the world—from Nazi tyranny. [Smithsonian]