1 00:00:01,920 --> 00:00:06,560 Speaker 1: Welcome to brain Stuff production of I Heart Radio. Hey 2 00:00:06,559 --> 00:00:09,320 Speaker 1: brain Stuff, Lauren Bogelbaum here with a classic episode for 3 00:00:09,360 --> 00:00:12,400 Speaker 1: you from our former host, Christian Sagar, about the stunning 4 00:00:12,440 --> 00:00:15,560 Speaker 1: science behind the Northern Lights. I wanted to run this 5 00:00:15,600 --> 00:00:18,840 Speaker 1: one because well, hey, it's really cool. But b I'm 6 00:00:18,880 --> 00:00:22,239 Speaker 1: loving the series His Dark Materials from the BBC and HBO, 7 00:00:22,640 --> 00:00:25,479 Speaker 1: so they've been on my mind and they're not a sponsor. 8 00:00:25,560 --> 00:00:33,360 Speaker 1: I just dig the show anyway. Here's Christian. Hey brain Stuff, 9 00:00:33,360 --> 00:00:36,960 Speaker 1: this is Christian Sagar. We've all heard of the Northern lights, right, 10 00:00:37,080 --> 00:00:40,960 Speaker 1: those beautiful manifestations of colors that are in the sky. Well, 11 00:00:41,080 --> 00:00:44,760 Speaker 1: they've inspired many myths in Viking legends. They were considered 12 00:00:44,880 --> 00:00:49,120 Speaker 1: the by Frost, the many colored bridge between Earth and Asgard, 13 00:00:49,200 --> 00:00:52,120 Speaker 1: the home of the gods, and in Finland they actually 14 00:00:52,120 --> 00:00:54,880 Speaker 1: believed the lights were a sign of the archangel Michael 15 00:00:55,200 --> 00:00:59,639 Speaker 1: battling the devil bills above. Scandinavians believed that they were 16 00:00:59,680 --> 00:01:02,960 Speaker 1: reflect actions off of the shields of the Valkyries. But 17 00:01:03,120 --> 00:01:06,399 Speaker 1: despite being observed for thousands of years, there are still 18 00:01:06,680 --> 00:01:10,640 Speaker 1: many misconceptions about what the Northern lights are. First of all, 19 00:01:10,720 --> 00:01:14,520 Speaker 1: it's false that their sunlight reflecting off of polar ice caps. 20 00:01:14,640 --> 00:01:17,959 Speaker 1: It's also false that their moonlight reflecting off of ice 21 00:01:18,000 --> 00:01:21,640 Speaker 1: crystals in the air. The Aurora borealis, as it was 22 00:01:21,720 --> 00:01:26,600 Speaker 1: coined by Galileo Galilei and means northern dawn or dawn 23 00:01:26,600 --> 00:01:30,000 Speaker 1: of the North in Latin, is also at the South pole, 24 00:01:30,200 --> 00:01:34,720 Speaker 1: known as the Aurora Australia's. In eighteen nine six, their 25 00:01:34,800 --> 00:01:40,039 Speaker 1: real origin was discovered by Norwegian scientist Christian Burkeland. He 26 00:01:40,280 --> 00:01:44,600 Speaker 1: tested his theory in controlled experiments, and here's the truth 27 00:01:44,640 --> 00:01:48,040 Speaker 1: of the matter. Solar winds stream away from the Sun 28 00:01:48,160 --> 00:01:53,480 Speaker 1: and flow around the Earth's magneto sphere. They're charged electrons 29 00:01:53,600 --> 00:01:57,520 Speaker 1: interact with elements in our atmosphere at points where the 30 00:01:57,560 --> 00:02:02,160 Speaker 1: magneto sphere is weakest, the no in the south poles. 31 00:02:02,160 --> 00:02:06,640 Speaker 1: So these solar winds the Sun's corona continuously amidst them 32 00:02:06,960 --> 00:02:11,600 Speaker 1: a stream of electrically charged particles. They stream away from 33 00:02:11,600 --> 00:02:15,800 Speaker 1: the Sun at speeds of one million miles per hour. 34 00:02:16,320 --> 00:02:19,280 Speaker 1: They reach Earth in forty hours from the Sun. Now, 35 00:02:19,320 --> 00:02:22,520 Speaker 1: this is forty times faster than a spacecraft needs to 36 00:02:22,560 --> 00:02:27,200 Speaker 1: be to escape Earth's gravity. It's pretty fast. Solar activity 37 00:02:27,320 --> 00:02:31,440 Speaker 1: currently follows an eleven years cycle and longer cycles affect 38 00:02:31,520 --> 00:02:34,799 Speaker 1: the aurora, and we've actually seen them increased solar activity 39 00:02:34,800 --> 00:02:37,920 Speaker 1: in the last few centuries. When they get here, though, 40 00:02:38,360 --> 00:02:42,600 Speaker 1: these solar winds strike the magnetic force generated by the 41 00:02:42,600 --> 00:02:46,760 Speaker 1: Earth's core. Then they flow through this magneto sphere, a 42 00:02:46,840 --> 00:02:52,560 Speaker 1: shield area of charged electrical and magnetic fields. This shield 43 00:02:52,760 --> 00:02:56,120 Speaker 1: is then blown into a tear drop shape by the 44 00:02:56,160 --> 00:03:00,160 Speaker 1: solar winds. The magneto sphere protects Earth from danger is 45 00:03:00,280 --> 00:03:04,960 Speaker 1: solar and interstellar particles, and most are directed away from Earth, 46 00:03:05,080 --> 00:03:09,720 Speaker 1: but some are trapped near the magnetic poles. The electrons 47 00:03:09,840 --> 00:03:14,120 Speaker 1: from these solar winds interact with elements in Earth's atmosphere 48 00:03:14,160 --> 00:03:17,440 Speaker 1: somewhere between sixty to two hundred miles up in the air. 49 00:03:18,040 --> 00:03:20,960 Speaker 1: This is ten times higher, by the way than most 50 00:03:21,080 --> 00:03:27,080 Speaker 1: airlines fly. These electrons collide with oxygen and nitrogen, transferring 51 00:03:27,200 --> 00:03:31,440 Speaker 1: energy into these gases and making them excited. When they 52 00:03:31,480 --> 00:03:35,200 Speaker 1: calm down, they emit photons and small little bursts of 53 00:03:35,320 --> 00:03:40,160 Speaker 1: energy form light. The shifts and flow of this energy 54 00:03:40,240 --> 00:03:46,080 Speaker 1: can reach twenty million ampiers at fifty thousand volts. Compare 55 00:03:46,160 --> 00:03:49,640 Speaker 1: that to your circuit breaker at home disengaging over fifteen 56 00:03:49,680 --> 00:03:54,119 Speaker 1: to thirty ampiers at one volts, so it's a lot 57 00:03:54,160 --> 00:03:57,760 Speaker 1: of energy. Now, the color of the aurora depends on 58 00:03:57,800 --> 00:04:01,720 Speaker 1: which element, whether it's oxygen or nitrogen, that is struck 59 00:04:01,880 --> 00:04:06,000 Speaker 1: and at what altitude it's struck at. Since it's dimmer 60 00:04:06,000 --> 00:04:10,240 Speaker 1: than sunlight, the aurora actually can't be seen during the day. 61 00:04:10,280 --> 00:04:15,000 Speaker 1: But oxygen emits either a greenish yellow light somewhere around 62 00:04:15,080 --> 00:04:17,200 Speaker 1: up to a hundred and fifty miles up in the air, 63 00:04:17,760 --> 00:04:20,880 Speaker 1: or a red light over a hundred and fifty miles 64 00:04:20,920 --> 00:04:24,400 Speaker 1: up in the air. Nitrogen, however, emits a blue light 65 00:04:24,760 --> 00:04:27,200 Speaker 1: up to sixty miles up in the air. If you 66 00:04:27,240 --> 00:04:31,200 Speaker 1: blend them all together, however, you can produce purples, pinks, 67 00:04:31,480 --> 00:04:34,880 Speaker 1: and white light. But one note. While some say they 68 00:04:34,960 --> 00:04:38,320 Speaker 1: have quote heard the Northern lights, the air where they're 69 00:04:38,360 --> 00:04:41,600 Speaker 1: formed is actually too thin to conduct sounds, so that's 70 00:04:41,680 --> 00:04:45,200 Speaker 1: not possible. It would be impossible for sound to travel 71 00:04:45,279 --> 00:04:48,640 Speaker 1: from the upper atmosphere to the ground. So you're probably 72 00:04:48,680 --> 00:04:51,120 Speaker 1: asking yourself, these sound pretty cool. Where do I get 73 00:04:51,160 --> 00:04:53,640 Speaker 1: to see the Northern lights? Where do they occur? Well, 74 00:04:53,880 --> 00:04:58,680 Speaker 1: they center around Earth's magnetic poles, not the geographic polls, 75 00:04:59,000 --> 00:05:03,560 Speaker 1: and they're in ring shaped spots called auroral ovals. These 76 00:05:03,600 --> 00:05:07,680 Speaker 1: are between five hundred and fifteen hundred kilometers wide and 77 00:05:07,760 --> 00:05:13,279 Speaker 1: expand during geomagnetic storms. These roughly correspond to the Arctic 78 00:05:13,400 --> 00:05:17,280 Speaker 1: and Antarctic circles and can be seen from space, so 79 00:05:17,320 --> 00:05:22,360 Speaker 1: the best places to see them are Central Canada, Alaska, Greenland, 80 00:05:22,880 --> 00:05:27,240 Speaker 1: Northern Scandinavia, and northern Russia. And yes, if you're asking, 81 00:05:27,600 --> 00:05:32,680 Speaker 1: other planets also have auroras. They've also been observed on Saturn, Jupiter, 82 00:05:33,120 --> 00:05:41,880 Speaker 1: and Urineus. Today's episode was written by Christian and produced 83 00:05:41,920 --> 00:05:44,200 Speaker 1: by Tyler Klang. Brain Stuff is a production of I 84 00:05:44,279 --> 00:05:46,280 Speaker 1: Heart Radio's How Stuff Works. For more in this and 85 00:05:46,360 --> 00:05:48,839 Speaker 1: lots of other colorful topics, visit our home planet, how 86 00:05:48,880 --> 00:05:51,400 Speaker 1: stuff Works dot com. And for more podcasts in my 87 00:05:51,440 --> 00:05:54,400 Speaker 1: heart Radio, visit my heart Radio app, Apple Podcasts, or 88 00:05:54,440 --> 00:05:56,120 Speaker 1: wherever you listen to your favorite shows.