[90-365] 3rd. November 2020- If I believed in pots of gold at the end of the rainbow I would be moved on opening the curtains this morning to see this sight. But I don't think you need to believe in superstition to marvel at a rainbow. The facts behind the rainbow are awe inspiring enough.
The most awe inspiring fact about a rainbow to me is that no two people are looking at the same rainbow. When I first realised that it blew my mind. Even the person standing next to you is seeing a different rainbow to the one you see. The refracted coloured light is from individual drops of water in an incredibly thin arched line one water droplet thick, perfectly aligned at the correct angle between the sun and your eye, so the person next to you is seeing the refracted light from different drops of water.
But even more amazingly those drops of water are constantly falling and being replaced by others which also line up perfectly giving the impression of a stable unmoving image.
Why is it an arc shape? Because all along that arc the water droplets achieve the correct angle to refract the light, outside of that arc shape they don't achieve the correct angle between the sun and your eye. Because we see the rainbow from the ground it appears as an arc. If you ever get to see a rainbow from a plane it is circular. So more of a rainwheel than a rainbow.
The French word for rainbow is "arch in the sky" "arc en ciel". In looking up the word in other languages I liked the Finnish word Sateenkaari literally translated as rain arc. The Italians call it a lightning bow "arcobaleno" associating it with stormy weather.
In Greek mythology Iris is the personification of the rainbow linking humanity to the Gods. It's apt then that we have an iris in our eye which controls the amount of light we see.