Explanation: In WW2, Britain spread word that carrots improved night-time vision, and that its pilots were eating lots of carrots, in order to ‘explain’ why they were intercepting Nazi planes over Britain so reliably at night.

In reality, they’d figured out how to fit radar on their fighter planes, and wanted to keep that a secret for as long as they could. The hope was that Nazis keeping tabs on civilian British news would fall for the ruse, and buy UK plane radar a little more time undetected.

Carrots may prevent nutritional deficiencies that lead to poor night-time vision, but they aren’t going to make your MK1 eyeballs into NODs.

One of my favorite historical “old wives tales” readily disproven, like cracking your knuckles causing arthritis or sitting too close to the TV (which definitely used to be a problem).
Wait, cracking knuckles is unproblematic?
The myth was that it caused arthritis. A chap called Donald Unger decided to test it by only cracking the knuckles in one hand and never the other, for decades. There was no difference between the two hands.