1 00:00:02,040 --> 00:00:07,320 Speaker 1: Welcome to brain Stuff from How Stuff Works. Hey, brain Stuff, 2 00:00:07,400 --> 00:00:11,000 Speaker 1: Christian Seger here. Okay, so you have this amazing idea 3 00:00:11,240 --> 00:00:15,080 Speaker 1: to start your own business, a licorice themed food truck. 4 00:00:15,360 --> 00:00:19,439 Speaker 1: You got liquorice Ravioli, licorice gumbo. It's genius, right, But 5 00:00:19,920 --> 00:00:23,560 Speaker 1: the bank turned you down and your Kickstarter campaign failed 6 00:00:23,560 --> 00:00:27,240 Speaker 1: the fund. Fortunately, you know where you might be able 7 00:00:27,280 --> 00:00:30,800 Speaker 1: to find a large stash of gold if you can 8 00:00:30,880 --> 00:00:33,199 Speaker 1: only get to the end of this rainbow you've been 9 00:00:33,240 --> 00:00:36,120 Speaker 1: following for six hours. But wait a minute, is it 10 00:00:36,120 --> 00:00:38,560 Speaker 1: actually possible to get to the end of a rainbow? 11 00:00:38,600 --> 00:00:41,440 Speaker 1: And if so, what will you find when you get there? 12 00:00:41,960 --> 00:00:45,360 Speaker 1: Let's start with the bad news. Sorry, everyone, lepre cons 13 00:00:45,440 --> 00:00:48,479 Speaker 1: are liars. You cannot reach the end of the rainbow. 14 00:00:48,760 --> 00:00:51,000 Speaker 1: If you were to mark on a map the place 15 00:00:51,040 --> 00:00:53,840 Speaker 1: where the rainbow seems to meet the land, and then 16 00:00:53,880 --> 00:00:57,440 Speaker 1: travel to that location, you would not be standing inside 17 00:00:57,480 --> 00:01:00,640 Speaker 1: a glorious pillar of colors. There would be nothing there 18 00:01:00,760 --> 00:01:05,040 Speaker 1: except probably the fresh smell of a recent rain shower. 19 00:01:05,480 --> 00:01:07,959 Speaker 1: To understand why this is, we need to look at 20 00:01:07,959 --> 00:01:12,480 Speaker 1: how rainbows form. Rainbows are created when sunlight reflects and 21 00:01:12,560 --> 00:01:16,680 Speaker 1: refracts through water droplets suspended in the air on the 22 00:01:16,760 --> 00:01:21,280 Speaker 1: opposite side of you from the sun. Those water droplets 23 00:01:21,319 --> 00:01:24,560 Speaker 1: act like both a mirror and a prism. Like a mirror, 24 00:01:24,720 --> 00:01:28,840 Speaker 1: they reflect the sunlight back towards you, but like a prism, 25 00:01:28,880 --> 00:01:32,480 Speaker 1: they also bend and disperse the light. This is because 26 00:01:32,640 --> 00:01:36,039 Speaker 1: rays of light shining through the air change speed when 27 00:01:36,080 --> 00:01:40,319 Speaker 1: they enter a different medium, for example water. This sudden 28 00:01:40,440 --> 00:01:43,560 Speaker 1: change in speed bends the trajectory of the light and 29 00:01:43,640 --> 00:01:47,880 Speaker 1: disperses white light into the whole roy g BIV spectrum. 30 00:01:48,720 --> 00:01:52,080 Speaker 1: The reason you see a nice ordered gradient of colors 31 00:01:52,120 --> 00:01:55,680 Speaker 1: within a rainbow, going from red to violet is because 32 00:01:56,160 --> 00:01:59,600 Speaker 1: this refraction bends each of the different colors of light 33 00:01:59,720 --> 00:02:03,600 Speaker 1: at a slightly different angles. So, for example, red light 34 00:02:03,640 --> 00:02:07,960 Speaker 1: bends at forty two degrees, violet light bends at forty degrees, 35 00:02:08,000 --> 00:02:11,679 Speaker 1: and all the other colors are somewhere in between. So 36 00:02:11,880 --> 00:02:14,320 Speaker 1: all right, let's find a rainbow. To do this, you 37 00:02:14,360 --> 00:02:18,239 Speaker 1: need to locate your anti solar point. That your anti 38 00:02:18,240 --> 00:02:20,639 Speaker 1: solar point is really just the point in space that's 39 00:02:20,639 --> 00:02:24,440 Speaker 1: a d eighty degrees or exactly opposite from the sun. 40 00:02:25,120 --> 00:02:27,320 Speaker 1: A simple way to find this is to go outside 41 00:02:27,480 --> 00:02:30,120 Speaker 1: and look for the shadow of your own head. Now 42 00:02:30,160 --> 00:02:33,520 Speaker 1: imagine drawing a straight line in three dimensions from the 43 00:02:33,560 --> 00:02:36,519 Speaker 1: sun through your head to the shadow of your head. 44 00:02:37,000 --> 00:02:39,799 Speaker 1: Now look up. If there is a rainbow to be seen, 45 00:02:40,240 --> 00:02:43,000 Speaker 1: you will find it by facing away from the sun 46 00:02:43,120 --> 00:02:47,679 Speaker 1: and looking for an arc forty two degrees above that 47 00:02:47,760 --> 00:02:51,880 Speaker 1: line from the sun to your anti solar point. Notice 48 00:02:51,919 --> 00:02:55,440 Speaker 1: that the apparent location of your rainbow depends on three things. 49 00:02:55,680 --> 00:02:58,600 Speaker 1: Where the sun is, where the water droplets are, and 50 00:02:58,639 --> 00:03:02,320 Speaker 1: where your eyes are. Change any one of those variables 51 00:03:02,400 --> 00:03:05,200 Speaker 1: and you'll see a different rainbow or none at all. 52 00:03:05,720 --> 00:03:08,400 Speaker 1: So no matter where you see your rainbow, if you 53 00:03:08,480 --> 00:03:10,960 Speaker 1: try to walk out to meet it, you'll be changing 54 00:03:11,000 --> 00:03:14,120 Speaker 1: the variable of your own position, and you could be 55 00:03:14,120 --> 00:03:18,200 Speaker 1: walking forever, or at least until your rainbow disappears. Trying 56 00:03:18,240 --> 00:03:20,200 Speaker 1: to find the end of a rainbow is sort of 57 00:03:20,240 --> 00:03:22,919 Speaker 1: like trying to walk to the end of your own shadow. 58 00:03:23,400 --> 00:03:27,040 Speaker 1: Somebody else could stand at the apparent end of your rainbow, 59 00:03:27,120 --> 00:03:31,440 Speaker 1: but you will never ever reach this location yourself. But 60 00:03:31,680 --> 00:03:35,640 Speaker 1: here's another thing. A rainbow isn't actually a bow. Rainbows 61 00:03:35,680 --> 00:03:39,240 Speaker 1: are circular. Usually, when you're standing on the ground, most 62 00:03:39,280 --> 00:03:42,680 Speaker 1: of the rainbow is blocked by the horizon. In rare cases, 63 00:03:42,720 --> 00:03:45,440 Speaker 1: like if you're in an airplane or something, you'll actually 64 00:03:45,480 --> 00:03:48,200 Speaker 1: be able to see the entire rainbow as a round, 65 00:03:48,320 --> 00:03:52,720 Speaker 1: spectacular beauty. But there's an obvious takeaway from this. It 66 00:03:52,800 --> 00:03:57,440 Speaker 1: doesn't actually meet the ground anywhere. There's just the altitude 67 00:03:57,440 --> 00:04:01,680 Speaker 1: where you can't see it anymore. Despite all this science 68 00:04:01,880 --> 00:04:04,880 Speaker 1: that is quite well understood, you're going to find plenty 69 00:04:04,880 --> 00:04:07,480 Speaker 1: of people on the Internet swearing up and down that 70 00:04:07,560 --> 00:04:10,240 Speaker 1: they have found the end of a rainbow. And look, 71 00:04:10,240 --> 00:04:12,160 Speaker 1: I don't know what to tell you. I'm not sure 72 00:04:12,200 --> 00:04:19,359 Speaker 1: what's up with that. Check out the brain stuff channel 73 00:04:19,360 --> 00:04:21,520 Speaker 1: on YouTube, and for more on this and thousands of 74 00:04:21,520 --> 00:04:37,680 Speaker 1: other topics, visit how stuff works dot com.