Why you can never get to the end of the rainbow, on today's Moment of Science®.
It seems that anything as wonderful as a rainbow must lead to a wonderful place where it touches the ground.
But if you've ever tried to approach a rainbow, you know that the rainbow recedes as you approach. The rainbow appears beyond that stand of trees, or over that next hill. When you move, the rainbow moves with you.
Sooner or later you realize that the end of the rainbow is not in any definite place you can mark on the map. No part of a rainbow is in any definite place, except in relation to your eye.
A rainbow is just a total of all the light coming to your eye from certain directions. The light from a rainbow is sunlight, reflected and broken into colors by water drops.
A rainbow always forms part of a circle, and the center of that circle is the point opposite the sun—from your point of view. The rule is that any water drops forty-two degrees of angle away from that point opposite the sun contribute to the rainbow you see.
Whether the water drops are ten feet away or ten miles away, they reflect light at that same angle and contribute to the same rainbow—for you.
If you walk toward the end of the rainbow, then it stays ahead of you as long as there are water drops in the air ahead of you.
This moment of science comes from Indiana University with production support from the Office of the Provost.
I'm Yaël Ksander.
