Tis the season for rainbows, when rain - falling between the observer and the sun - allows the sunlight to spread out its spectrum of colours.

It’s always brighter inside the arc of the rainbow. And we’re not just saying that to be poetic. Many light rays refract off water droplets at angles smaller than the rainbow ray, but not greater, so there is a lot more light within the bow.

And because rainbows are a special distribution of colours produced in a particular way with reference to the definite point of the observer, no two observers can see the same rainbow. Even each eye sees its own rainbow. And, yes, there is more than just tourists at the end of the rainbow, so get chasing.