Words of Water Wisdom: Rainbows

From time to time, we like to collect our favorite quotes, sayings, and statistics about water and share them with readers. Today we’re celebrating a phenomenon that can’t happen unless water is present – the rainbow.

We wondered: What, exactly, are the conditions that need to be present for a rainbow to form? Besides water, of course.

What are the best conditions for rainbows to form?

We usually see rainbows at the tail end of a rain storm, when the clouds are breaking up and the rain is moving away. Here are the ideal conditions for spotting a rainbow:

• Sun: Rainbows are best seen when the sun is behind you and water droplets in the air are in front of you.
• Angle: The lower the angle of the sun on the horizon, the more complete rainbow you’ll see. The angle should be at least 42 degrees relative to your position on the ground.
• Water: Misty conditions are ideal, but even fog can produce one – these are called fogbows. See also moonbows and wet road rainbows.
• Fullness: You’ll see a more complete arc the lower the sun is in the sky. This effect tends to max out when the sun is directly on the horizon – at sunrise or sunset.
• Circular: Rainbows are actually circular. If you were flying up in the clouds, you’d be able to see the entire thing.
• Water composition: Rainbows over saltwater will have a smaller radius beause saltwater has a higher refractive index than freshwater.

Where did the idea of leprechauns hiding pots of gold at the end of a rainbow come from, anyway?

It’s hard to know for sure, but they aren’t here to defend themselves, so let’s blame the Vikings. They were notorious raiders, and they tended to bury their treasure in unknown locations. After some vigorous raiding that began in Ireland in 795 AD, the Vikings eventually sailed away, leaving the locals to wonder just where they had stored all their plundered loot. Some say leprechauns found their treasure and decided to store it in an even safer location – at the ends of rainbows.

But, of course, we all know that the only thing we’ll find at the end of a rainbow is ourself – if we’re lucky enough to ever make it there.

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