The German army was very surprised how quickly the RAF knew there were planes arriving from across the Channel during World War II . And that even when there was poor visibility. They knew nothing of the RADAR stations that were built along the coast of Dover, and the British would certainly not reveal this new invention. Hence, the secret service came up with a hoax we still know today as an explanation. The hoax was that the British were eating a lot of carots containing beta-carotene and that led to an excellent eyesight. Recently it was discovered that the eye contained beta-carotene, so this story did not seem illogical. Still today, this "hoax" is believed as a scientific fact. The relationship between eating carots and having a good vision has never been demonstrated. But we all know the story ...