Science Questions

Wed, 19th Mar 2003

Part of the show Cambridge Science Festival - Is there Life in Outer Space

Question

Billy asked:

Where does the rainbow end?

Answer

Disappointing news for Billy - the rainbow doesn't touch the ground and there is no end to it. Light from the sun looks white, but it is actually made of lots of different colours. Normally they are all mixed together. A rainbow in droplets

A rainbow is formed when light from the sun meets raindrops in the air and the raindrops separate out all these different colours. Because rainbows are made in the sky they don't touch the ground.

So if you're on the ground, however far you walk, the end of the rainbow will always look as if it were on the edge of the horizon.

But what people don't realise is that rainbows are actually complete circles, and obviously a circle has no end. You never see the whole circle because the earth's horizon gets in the way.

Apparently, if you see a rainbow from a plane it should be almost a complete circle. Another interesting fact about rainbows - have you ever noticed that you'll only ever see a rainbow if the sun is behind you? You can also sometimes see miniature rainbows in your garden if you're watering your plants with the sun behind you...

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