WEBVTT - Why Can't You Reach the End of a Rainbow?

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<v Speaker 1>Welcome to brain Stuff from how Stuff Works, Hey, brain Stuff,

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<v Speaker 1>Lauren Vogel bomb here as far as get rich quick

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<v Speaker 1>schemes go, Stumbling upon gold the end of a rainbow

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<v Speaker 1>sounds pretty delightful, But is it actually possible to get

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<v Speaker 1>to the end of a rainbow? And if so, what

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<v Speaker 1>would you find when you got there. Let's start with

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<v Speaker 1>the bad news. Leprechns are liars. You cannot reach the

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<v Speaker 1>end of a rainbow that appears in the sky. If

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<v Speaker 1>you were to mark on a map the place where

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<v Speaker 1>the rainbow seems to be the land, and then travel

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<v Speaker 1>to that location, you would not be standing inside a

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<v Speaker 1>glorious pillar of colors. There would be nothing there except

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<v Speaker 1>probably the fresh smell of a recent rain shower. To

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<v Speaker 1>understand why this is, we need to look at how

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<v Speaker 1>rainbows form. Rainbows are created when sunlight reflects and refracts

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<v Speaker 1>through water droplets suspended in the air in front of

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<v Speaker 1>you while the sun is behind you. Those water droplets

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<v Speaker 1>act like both a mirror and a prism. A mirror,

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<v Speaker 1>they reflect the sunlight back towards you, but like a prism,

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<v Speaker 1>they also bend and disperse that light. This is because

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<v Speaker 1>rays of light shining through the air change speed when

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<v Speaker 1>they enter a different medium, for example droplets of water.

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<v Speaker 1>This sudden change in speed bends the trajectory of the

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<v Speaker 1>light and disperses white light into the whole roy g

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<v Speaker 1>BIV spectrum. The reason you see a nice ordered gradient

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<v Speaker 1>of colors within a rainbow going from red to violet

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<v Speaker 1>is because this refraction bends each of the different colors

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<v Speaker 1>of light at a slightly different angle. So, for example,

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<v Speaker 1>red light bends at forty two degrees, violet light bends

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<v Speaker 1>at forty degrees, and all the other colors are somewhere

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<v Speaker 1>in between. So, okay, let's find a rainbow. To do this,

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<v Speaker 1>you need to locate your antisolar point. Your anti solar

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<v Speaker 1>point is the point in space that's a hundred and

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<v Speaker 1>eighty degrees or exactly opposite from the sun. A simple

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<v Speaker 1>way to find this is to go outside and look

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<v Speaker 1>for the shadow of your own head. That's your antisolar point.

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<v Speaker 1>Now imagine drawing a line straight from the sun through

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<v Speaker 1>your head to the shadow of your head. Now look up.

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<v Speaker 1>If there is a rainbow to be seen, you will

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<v Speaker 1>find it by facing away from the sun and looking

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<v Speaker 1>forty two degrees above your anti solar point. Notice that

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<v Speaker 1>the apparent location of your rainbow depends on three things.

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<v Speaker 1>Where the sun is, where the water droplets are, and

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<v Speaker 1>where your eyes are. Change any one of those variables

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<v Speaker 1>and you'll see a different rainbow or none at all. So,

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<v Speaker 1>no matter where you see your rainbow, if you try

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<v Speaker 1>to walk out to meet it, you'll be changing the

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<v Speaker 1>variable of your own position, and you couldn't be walking forever,

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<v Speaker 1>or at least until your rainbow disappears. Trying to find

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<v Speaker 1>the end of a rainbow is sort of like trying

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<v Speaker 1>to walk to the end of your own shadow. Somebody

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<v Speaker 1>else could stand at the apparent end of your shadow

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<v Speaker 1>or rainbow, but you will never ever reach this location yourself.

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<v Speaker 1>You can, of course, find earthly rainbows and a waterfall

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<v Speaker 1>or the spray of a sprinkler or hose. You might

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<v Speaker 1>even perceive yourself to be standing right next to one,

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<v Speaker 1>depending on the angle of light coming into the water.

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<v Speaker 1>But here's one more thing. Those rainbows you see in

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<v Speaker 1>the sky aren't actually bows. Rainbows are circular. Usually, when

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<v Speaker 1>you're standing on the ground, most of the rainbow is

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<v Speaker 1>blocked by the horizon. In rare cases, like if you're

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<v Speaker 1>in an airplane, you'll be able to see the entire rainbow,

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<v Speaker 1>rain hoop, rain loop, rain Hole. It's around spectacular beauty,

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<v Speaker 1>but there's an obvious takeaway from this. It doesn't ever

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<v Speaker 1>actually meet the ground anywhere. Today's episode was written by

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<v Speaker 1>Joe McCormick and produced by Tyler Clang. For more on

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<v Speaker 1>this and lots of other light topics, visit our home planet,

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<v Speaker 1>how Stuff Works dot com