The surface of the massive ocean is shimmering in the warm rays of afternoon sunlight. The clear blue sky above is soon to be covered with clouds formed from the evaporation taking place presently.
The water molecules with kinetic energies large enough to overcome the intermolecular forces detach themselves from the ocean and begin their journey upwards. The lighter air above the surface rises gradually, making its way through the atmosphere, taking with it tiny dust particles suspended in the air that would later form the reason for the cloud’s particles.
They finally reach around 20,000 kilometres above earth’s surface where the temperature drops to a chilly -20 degrees. The triangular shape of the water molecules combines to form millions of hexagons. The Cirrus clouds formed at this altitude are cold enough for the ice crystals to form, with the ice nucleus at its centre. Its thin, wispy strands contained numerous such crystals suspended in the air, facing downwards. The dropping temperature forms ice crystals, drastically reducing its ability to hold on to the moisture. The orientation of these crystals forms the basis for reflecting, refracting and dispersing the sunlight.
And when the sunlight hits these frozen supercooled droplets, its medium changes drastically and each wavelength of the light is affected differently. The common light is now dispersed into various wavelengths, each one bending at a different angle, giving birth to a beautiful set of colors in the sky.
Kaushik. Fire Rainbows, A Rare Cloud Phenomenon. 2009. theamusingplanet.com. Web. 30 Jul. 2017.
The arc is seen to be parallel to the horizon, such is its length.