The first of five clues. Each one below gives a little more away.
No two people have ever seen the same one of me.
I am really a full circle. The ground hides the rest.
Newton decided how many colours I have, and added one extra for luck.
You can never reach my end, because I move when you do.
I appear after the rain, in an arc.
Rainbow
It is not an object in the sky at all. It is an angle — 42 degrees from the light behind your head — which is exactly why it moves when you do.
Descartes worked out the geometry in 1637 by tracing light through a glass sphere, and found that rays leaving a raindrop concentrate at about forty-two degrees. Newton added the colours in 1666, splitting sunlight with a prism, and settled on seven mainly because he wanted the count to echo the notes of a musical scale. Look carefully and there is often a second, fainter bow at fifty-one degrees with its colours reversed, from light that bounced twice inside each drop. The band of darker sky between the two even has a name: Alexander's dark band.
Reading five clues at once is not the game. In the real thing they arrive one at a time and every wrong guess costs an hour. Play mystery #11 · today's mystery · the vault
Previous: mystery #10. Next: mystery #12. Or try #25, #26, #27, #28, #29, #30.