No, you can't fly over a rainbow

Today, many major news outlets published some genuinely beautiful images taken by Melissa Rensen. She was flying over the Caribbean sea and captured stunning images worthy of any desktop wallpaper, showing colours stretching across the ocean below her. The news outlets have decided that she “flew over a rainbow”. She definitely did not.

Headlines

Various nonsense headlines about flying over a rainbow.

The same news agencies tweeted the picture and many others have jumped on the bandwagon, expressing their delight that someone managed to get a picture at the exact moment they flew over a rainbow. The reactions to these tweets were similar. Alex Smith, Former Ed Miliband aide, tweeted, “So striking it beggars belief. A plane passenger captures a rainbow from above.” It certainly does beggar belief.

She didn’t fly over a rainbow. You can’t fly over a rainbow for the same reason you can’t approach one: a rainbow isn’t a physical object that exists out there at a specific location, like some kind of Epic Pride Bridge or a course from Mario Kart. You can’t actually check the end of a rainbow to see if there’s a pot of gold. The fact that a rainbow appears to exist at a certain distance from you is an optical illusion.

Rainbow

One of Rensen's beautiful images.

You can see a rainbow when light passes through water droplets and is reflected and refracted. It’s all about angles and perspective. I could ask you to stand on a rock, which appears to be under a rainbow. That will be great for Instagram, a picture of you standing directly under a rainbow. But if you were to look up at that time, you wouldn’t see the rainbow. Actually, for you it would be even further away but at the same angle. It’s all relative. The rainbow is an optical phenomenon caused by light refracting in water drops and that’s it. A rainbow doesn’t exist at specific GPS coordinates, and you certainly can't walk towards it. This also means that a plane can’t fly through, over, or under it.

Rainbows are genuinely interesting when they really are photographed from a plane. At the right angle, you’re able to see the full arc of a rainbow, something not usually possible for us on the ground. You can also see a “glory” (technically not a rainbow, I believe) as shown below, with the shadow of the plane in the middle. It’s all about angles.

Glory

A glory. Image credit unknown.

So how did Melissa Rensen take such amazing pictures? The plane’s window can be partially polarised depending on the angle from the sun. What she caught on camera is an optical illusion caused by taking a photograph through a polarised window. That’s it. She didn’t fly over a rainbow because you can’t fly over a rainbow. Half of the tweets about these photos were from people who thought you can fly over a rainbow, which is a bit disappointing. I don't expect everyone to understand the physics but it's a pretty basic fact that the rainbow isn't an actual bridge of colour. When I read the headline I wondered if the next would be “Man finally escapes from his own shadow, leaves it with someone else.”

Science is often accused of ruining the mystery and beauty of things like this. The mystery? Possibly. But the beauty? Not a chance. Understanding something doesn’t make it less beautiful. Indeed, for some people it can become more beautiful, or at least beautiful in an entirely new way. When scientists and philosphers have attempted to argue this point, they have often used the rainbow as an example. Richard Dawkins even titled one of his books Unweaving the Rainbow, inspired by this argument. I’d rather finish this entry with Sagan than Dawkins, so here’s Carl Sagan discussing the very same argument but using the example of a sunset instead (because fuck Dawkins).

"It is sometimes said that scientists are unromantic, that their passion to figure out robs the world of beauty and mystery. But is it not stirring to understand how the world actually works — that white light is made of colors, that color is the way we perceive the wavelengths of light, that transparent air reflects light, that in so doing it discriminates among the waves, and that the sky is blue for the same reason that the sunset is red? It does no harm to the romance of the sunset to know a little bit about it."