WEBVTT 00:00:15.000 --> 00:00:17.000 Every second, 00:00:17.000 --> 00:00:20.000 one million tons of matter is blasted from the Sun 00:00:20.000 --> 00:00:24.000 at the velocity of one million miles per hour, 00:00:24.000 --> 00:00:26.000 and it's on a collision course 00:00:26.000 --> 00:00:27.000 with Earth! 00:00:27.000 --> 00:00:29.000 But don't worry, 00:00:29.000 --> 00:00:32.000 this isn't the opening of a new Michael Bay movie. 00:00:32.000 --> 00:00:37.000 This is The Journey of the Polar Lights. 00:00:37.000 --> 00:00:38.000 The Northern and Southern Lights, 00:00:38.000 --> 00:00:40.000 also known as the Aurora Borealis 00:00:40.000 --> 00:00:42.000 and Aurora Australis, respectively, 00:00:42.000 --> 00:00:44.000 occur when high energy particles from the Sun 00:00:44.000 --> 00:00:46.000 collide with neutral atoms in our atmosphere. 00:00:46.000 --> 00:00:48.000 The energy emitted from this crash 00:00:48.000 --> 00:00:50.000 produces a spectacle of light 00:00:50.000 --> 00:00:52.000 that mankind has marveled at for centuries. 00:00:52.000 --> 00:00:54.000 But the particles journey isn't just as simple 00:00:54.000 --> 00:00:56.000 as leaving the Sun and arriving at Earth. 00:00:56.000 --> 00:00:58.000 Like any cross-country road trip, 00:00:58.000 --> 00:00:59.000 there's a big detour 00:00:59.000 --> 00:01:02.000 and nobody asks for directions. 00:01:02.000 --> 00:01:03.000 Let's track this intergalactic voyage 00:01:03.000 --> 00:01:06.000 by focusing on three main points of their journey: 00:01:06.000 --> 00:01:07.000 leaving the sun, 00:01:07.000 --> 00:01:09.000 making a pit stop in the Earth's magnetic fields, 00:01:09.000 --> 00:01:12.000 and arriving at the atmosphere above our heads. 00:01:13.000 --> 00:01:15.000 The protons and electrons creating the Northern Lights 00:01:15.000 --> 00:01:17.000 depart from the Sun's corona. 00:01:17.000 --> 00:01:18.000 The corona is the outermost layer 00:01:18.000 --> 00:01:19.000 of the Sun's atmosphere 00:01:19.000 --> 00:01:21.000 and is one of the hottest regions. 00:01:21.000 --> 00:01:24.000 Its intense heat causes the Sun's hydrogen 00:01:24.000 --> 00:01:25.000 and helium atoms to vibrate 00:01:25.000 --> 00:01:27.000 and shake off protons and electrons 00:01:27.000 --> 00:01:31.000 as if they were stripping off layers on a hot, sunny day. 00:01:31.000 --> 00:01:33.000 Impatient and finally behind the wheel, 00:01:33.000 --> 00:01:36.000 these free protons and electrons move too fast 00:01:36.000 --> 00:01:38.000 to be contained by the sun's gravity 00:01:38.000 --> 00:01:40.000 and group together as plasma, 00:01:40.000 --> 00:01:42.000 an electrically charged gas. 00:01:42.000 --> 00:01:43.000 They travel away from the sun 00:01:43.000 --> 00:01:44.000 as a constant gale of plasma, 00:01:44.000 --> 00:01:47.000 known as the solar wind. 00:01:55.000 --> 00:01:58.000 However, the Earth prevents the solar wind 00:01:58.000 --> 00:01:59.000 from travelling straight into the planet 00:01:59.000 --> 00:02:00.000 by setting up a detour, 00:02:00.000 --> 00:02:02.000 the magnetosphere. 00:02:02.000 --> 00:02:03.000 The magnetosphere is formed 00:02:03.000 --> 00:02:04.000 by the Earth's magnetic currents 00:02:04.000 --> 00:02:06.000 and shields our planet from the solar winds 00:02:06.000 --> 00:02:08.000 by sending out the particles around the Earth. 00:02:08.000 --> 00:02:10.000 Their opportunity to continue the journey 00:02:10.000 --> 00:02:11.000 down to the atmosphere 00:02:11.000 --> 00:02:12.000 comes when the magnetosphere is overwhelmed 00:02:12.000 --> 00:02:14.000 by a new wave of travellers. 00:02:14.000 --> 00:02:17.000 This event is coronal mass ejection, 00:02:17.000 --> 00:02:18.000 and it occurs when the Sun shoots out 00:02:18.000 --> 00:02:21.000 a massive ball of plasma into the solar wind. 00:02:22.000 --> 00:02:23.000 When one of these coronal mass ejections 00:02:23.000 --> 00:02:25.000 collides with Earth, 00:02:25.000 --> 00:02:26.000 it overpowers the magnetosphere 00:02:26.000 --> 00:02:28.000 and creates a magnetic storm. 00:02:28.000 --> 00:02:30.000 The heavy storm stresses the magnetosphere 00:02:30.000 --> 00:02:31.000 until it suddenly snaps back, 00:02:31.000 --> 00:02:34.000 like and overstretched elastic band, 00:02:34.000 --> 00:02:37.000 flinging some of the detoured particles towards Earth. 00:02:37.000 --> 00:02:39.000 The retracting band of the magnetic field 00:02:39.000 --> 00:02:41.000 drags them down to the aurora ovals, 00:02:41.000 --> 00:02:42.000 which are the locations 00:02:42.000 --> 00:02:44.000 of the Northern and Southern Lights. 00:02:45.000 --> 00:02:48.000 After travelling 93 million miles across the galaxy, 00:02:48.000 --> 00:02:50.000 the Sun's particles finally produce 00:02:50.000 --> 00:02:52.000 their dazzling light show with the help of some friends. 00:02:52.000 --> 00:02:55.000 Twenty to two hundred miles above the surface, 00:02:55.000 --> 00:02:56.000 the electrons and protons meet up 00:02:56.000 --> 00:02:58.000 with oxygen and nitrogen atoms, 00:02:58.000 --> 00:03:01.000 and they sure are happy to see each other. 00:03:01.000 --> 00:03:03.000 The Sun's particles high five the atoms, 00:03:03.000 --> 00:03:04.000 giving their energy 00:03:04.000 --> 00:03:07.000 to the Earth's neutral oxygen and nitrogen atoms. 00:03:07.000 --> 00:03:08.000 When the atoms in the atmosphere 00:03:08.000 --> 00:03:09.000 are contacted by the particles, 00:03:09.000 --> 00:03:12.000 they get excited and emit photons. 00:03:12.000 --> 00:03:14.000 Photons are small bursts of energy 00:03:14.000 --> 00:03:15.000 in the form of light. 00:03:15.000 --> 00:03:16.000 The colors that appear in the sky 00:03:16.000 --> 00:03:19.000 depend on the wavelength of the atom's photon. 00:03:19.000 --> 00:03:21.000 Excited oxygen atoms are responsible 00:03:21.000 --> 00:03:22.000 for the green and red colors, 00:03:22.000 --> 00:03:24.000 where as excited nitrogen atoms produce 00:03:24.000 --> 00:03:26.000 blue and deep red hues. 00:03:26.000 --> 00:03:28.000 The collection of these interactions 00:03:28.000 --> 00:03:30.000 is what creates the Northern and Southern Lights. 00:03:35.000 --> 00:03:37.000 The polar lights are best seen on clear nights 00:03:37.000 --> 00:03:40.000 in regions close to magnetic north and south poles. 00:03:40.000 --> 00:03:41.000 Nighttime is ideal 00:03:41.000 --> 00:03:43.000 because the Aurora is much dimmer than sunlight 00:03:43.000 --> 00:03:46.000 and cannot be seen in daytime. 00:03:46.000 --> 00:03:47.000 Remember to look up to the sky 00:03:47.000 --> 00:03:49.000 and read up on the Sun's energy patterns, 00:03:49.000 --> 00:03:52.000 specifically sunspots and solar flares, 00:03:52.000 --> 00:03:53.000 as these will be good guides 00:03:53.000 --> 00:03:55.000 for predicting the auroras.