What do you mean there is no scientific proof for rainbows?! Did you sleep through your science class?

Light is comprised of a series of colours. In order: Red, orange, yellow, green, blue, indigo and violet. When the light passes through anything, it will become bent, refracted light.The rain must always be present for a rainbow to appear in the sky, because it needs something to go through in order for the colours to show, and the light to bend. It's why you see rainbows in sprinklers. It why you see them in crystals.