Why hasn't anyone ever touched a rainbow?

When I created The Rainbow, I didn't seriously enough take into account that I don't know for sure exactly what people think a rainbow IS.

One possibility is that some people think a rainbow is like a picture painted on a wall, something you can get closer to by moving toward the wall. You maybe can't 'touch' a painted rainbow, in the sense that it's only paint, but you can touch the paint itself, if you get close enough.

Someone else might think the rainbow is like an image projected on a screen. Again, maybe technically speaking you can't touch this rainbow, but you can get closer and closer to the screen, and even touch it.

But neither of these are the truth. You can't touch a rainbow because it's a phenomenon of light - there is nothing to touch. There is no screen to touch, either. And it's definitely not paint, with some substance of its own.

What sort of phenomena is it, then? Well, before I try to define or describe what sort it is, let me suggest a way for you to see what sort it is:

When seeing a rainbow, or looking at a picture or video of a rainbow, note the location of the sun. It will always be behind the person seeing/photographing/filming the rainbow. Always.

Pay close attention to that one fact, while looking at rainbows, and it will sink in what exactly a rainbow is.

Let me know what you think a rainbow is.