Everyone has seen a rainbow, but few know its true shape. Truth be told, a rainbow is not actually a bow. It is a complete circle centred around a very particular point. The reason you only see half of it, it is because the earth is getting in the way around the horizon line.
However, there is a way to see the whole phenomenon: gain height. On board their aircraft, pilots have the opportunity to observe a 360° rainbow from time to time. But drones can do it too. As a proof, see the splendid video below, recently unveiled by an Internet user.
360 degrees, going full-circle
On March 7, 2016, the man saw a rainbow in the sky over Cookstown in northern Ireland. He then had the idea of strapping his smart-phone to his drone, and sending it to observe the phenomenon from a higher vantage point. The result is very successful. You can see on the footage a full multi-coloured circle hanging in the air. It is even accompanied by a second, paler and inverted bow.
'It was just amazing'
The sky was completely grey and the rain was torrential, totally gloomy. [But] the clouds parted, the sun came out and that rainbow formed over the trees.
As many know, the optical phenomenon is due to the reflection, refraction and scattering of the coloured radiations making up the light of the Sun through the raindrops.
As [the quadcopter] rose, the rainbow turned into a full circle. It's impossible to see from the ground. It was just incredible. I'm still very excited.
The second arc that can be observed is, for his part, linked to a double reflection of light in the water droplets. This is why it usually appears inverted (red on the outside and purple on the inside), less sharp, and paler.