# How can the diameter of a rainbow be measured?

To quote from the great SNL philosopher, Mango, "Can you touch a rainbow ? Can you put the wind in your pocket? No! Such is Mango." I think he has it right. I don't know much about the optics of rainbows, but I'm pretty sure they move relative to the observer, so they do not have an objective diameter. At least that's what I thought until I found this answer on the magical internet here : "It's probably not impossible, but it is difficult. A rainbow looks circular because it's basically the circle where a cloud of rain droplets intersects with your cone of vision, like the circle on the end of an ice-cream cone. Imagine said ice-cream cone with the point in your eye (don't actually try this experiment unless you're looking for a career in piracy). Now make the cone bigger and bigger until the round end hits the cloud of raindrops that are reflecting the sun's light. The big circle on the end of that cone is where the rainbow appears to be -- as someone else pointed...