Carrots contain high amounts of vitamin A and are good for general eye health. However, carrots will not improve night vision. That myth goes back to British propaganda during World War II. In 1940, the German Luftwaffe, or air force, began bombing Britain at night. In response, the British government ordered people to turn off their lights; the government wanted to make it difficult for German pilots to hit their targets. A new technology, radar, allowed the British air force to track and shoot down the German planes without light. To keep the technology secret, the government told the media that their pilots could see the German planes because they consumed so many carrots. Consequently, people began to believe that eating carrots would help them see better in the dark. What is the main idea of the passage?