Reminder #232792 that you shouldn’t believe everything you read on the internet.
This photo showing the "moment a plane flies directly over a rainbow" is all over the internet at the moment.
Caters News
Rainbows happen when sunlight is bent by water droplets in the atmosphere and split into individual colours. They're not actually physical objects that sit in one place in the sky (which is why you can never get to the end of a rainbow). For example, ever noticed that the sun's always behind you when you're looking at a rainbow?
The photo actually shows polarised light, and it's not the first time a photo like this has been taken.
It's possible to take a photo like the one above from an aeroplane if you use a polarisation filter on a camera, thanks to a unique set of circumstances. In this blog post from 2008, Claudia Hinz describes the three requirements to get a similar photo for yourself:
1. There is polarised light behind the window
2. The window is made of a double refracting matter
3. A polarisation filter is used in front of the window
As sunlight passes through the atmosphere on a clear, cloudless day it gets scattered by molecules in the air. When the sunlight comes into the atmosphere at 90 degrees it polarises the light, which means the individual waves that make up light move in the same direction, instead of going all over the place.
The windows on an aeroplane are made of thick plastic and tend to be "anisotropic", which means their properties vary across the window. All windows refract, or bend, light. But because of their anisotropy, aeroplane windows give rise to double refraction, splitting a ray of light into two as it is bent. The two rays then are bent differently and have their colours dispersed.
When you look at these rays of light through a polarising filter (or take a picture using a polarising filter on a camera) you see the different bands of colour the light has been split up into, giving a rainbow effect.
Flickr: somethingness / Creative Commons
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