WEBVTT - Can 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>Christian Seger here. Okay, so you have this amazing idea

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<v Speaker 1>to start your own business, a licorice themed food truck.

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<v Speaker 1>You got liquorice Ravioli, licorice gumbo. It's genius, right, But

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<v Speaker 1>the bank turned you down and your Kickstarter campaign failed

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<v Speaker 1>the fund. Fortunately, you know where you might be able

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<v Speaker 1>to find a large stash of gold if you can

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<v Speaker 1>only get to the end of this rainbow you've been

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<v Speaker 1>following for six hours. But wait a minute, is it

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<v Speaker 1>actually possible to get to the end of a rainbow?

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<v Speaker 1>And if so, what will you find when you get there?

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<v Speaker 1>Let's start with the bad news. Sorry, everyone, lepre cons

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<v Speaker 1>are liars. You cannot reach the end of the rainbow.

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

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<v Speaker 1>where the rainbow seems to meet the land, and then

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

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

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

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

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

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<v Speaker 1>refracts through water droplets suspended in the air on the

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<v Speaker 1>opposite side of you from the sun. Those water droplets

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<v Speaker 1>act like both a mirror and a prism. Like 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 the 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 water. This sudden

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<v Speaker 1>change in speed bends the trajectory of the light and

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<v Speaker 1>disperses white light into the whole roy g BIV spectrum.

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<v Speaker 1>The reason you see a nice ordered gradient of colors

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<v Speaker 1>within a rainbow, going from red to violet is because

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

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<v Speaker 1>at a slightly different angles. So, for example, red light

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

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<v Speaker 1>and all the other colors are somewhere in between. So

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<v Speaker 1>all right, let's find a rainbow. To do this, you

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<v Speaker 1>need to locate your anti solar point. That your anti

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<v Speaker 1>solar point is really just the point in space that's

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<v Speaker 1>a d eighty degrees or exactly opposite from the sun.

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<v Speaker 1>A simple way to find this is to go outside

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<v Speaker 1>and look for the shadow of your own head. Now

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<v Speaker 1>imagine drawing a straight line in three dimensions from the

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<v Speaker 1>sun through your head to the shadow of your head.

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<v Speaker 1>Now look up. If there is a rainbow to be seen,

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<v Speaker 1>you will find it by facing away from the sun

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<v Speaker 1>and looking for an arc forty two degrees above that

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<v Speaker 1>line from the sun to your anti solar point. Notice

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<v Speaker 1>that 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.

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

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

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<v Speaker 1>the variable of your own position, and you could be

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<v Speaker 1>walking forever, or at least until your rainbow disappears. Trying

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<v Speaker 1>to find the end of a rainbow is sort of

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

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<v Speaker 1>Somebody else could stand at the apparent end of your rainbow,

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<v Speaker 1>but you will never ever reach this location yourself. But

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<v Speaker 1>here's another thing. A rainbow isn't actually a bow. Rainbows

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<v Speaker 1>are circular. Usually, when you're standing on the ground, most

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<v Speaker 1>of the rainbow is blocked by the horizon. In rare cases,

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<v Speaker 1>like if you're in an airplane or something, you'll actually

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<v Speaker 1>be able to see the entire rainbow as a round,

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<v Speaker 1>spectacular beauty. But there's an obvious takeaway from this. It

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<v Speaker 1>doesn't actually meet the ground anywhere. There's just the altitude

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<v Speaker 1>where you can't see it anymore. Despite all this science

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<v Speaker 1>that is quite well understood, you're going to find plenty

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<v Speaker 1>of people on the Internet swearing up and down that

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<v Speaker 1>they have found the end of a rainbow. And look,

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<v Speaker 1>I don't know what to tell you. I'm not sure

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<v Speaker 1>what's up with that. Check out the brain stuff channel

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<v Speaker 1>on YouTube, and for more on this and thousands of

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<v Speaker 1>other topics, visit how stuff works dot com.