Keeping with the spirit of Pride Month, I bring you the science behind rainbows, the symbol chosen for the LGBTQ+ community for its happy, positive image. This is meant to represent the vitality of the queer community. It was created to replace the darkness of the pink triangle, which was previously the most prominent gay symbol, functioning as a Nazi tool of oppression. Rainbows are also important symbols for many other cultures, religions and communities. A rainbow is the mythical representation of the unattainable. In some mythologies, it is a bridge between heaven and Earth that only gods can take. For Buddhists and Christians, rainbows symbolize peace and forgiveness. Aside from this pertinent symbolism, from a scientific perspective, rainbows are very simple, naturally occurring phenomena.
Although many people have tried to chase rainbows, they aren’t actually tangible, free-standing objects. You cannot go over it, like Dorothy dreams about doing in The Wizard of Oz or even get to the end of it to find Sir Charms with a pot of gold (or a bowl of Lucky Charms). A rainbow is the product of light, water, and a little bit of physics. White light may seem like the absence of color, but as we know from the research of Isaac Newton, it is actually the sum of all visible wavelengths, from short to long and all those in between.
On a rainy day, the air gets filled with tiny suspended water droplets. Each one has the ability to catch sunlight and become its own part of the rainbow factory. When sunlight enters a droplet, the light is travelling from one medium, air, to another, water. This causes the light to bend slightly in a process called refraction. Different wavelengths of the visible light spectrum will refract at different angles. Shorter wavelengths (blue and violet) bend more than longer ones (red), so when white light refracts, it will also separate by wavelength (colour). As the light exits the water droplet, it refracts again, and is bent downward towards the observer on Earth’s surface. At these angles, dispersed light becomes bright enough to result in a rainbow display in the sky.
A rainbow is most often viewed as a circular arc in the sky, but it can take other forms depending on where it is being viewed from. The arc is the result of the slight differentiation in the angles of light dispersion among the thousands of suspended droplets in the air. This also means that no two observers will experience the same rainbow. Colors in the rainbow may be in slightly different orders depending on where you are standing, and the pattern of droplets in the air relative to where you are observing the rainbow.
So, next time you see a rainbow, remember that you are the only one that can see it the way you see it — and that is a special experience.