WEBVTT 00:00:15.801 --> 00:00:17.410 Every second, 00:00:17.410 --> 00:00:20.524 one million tons of matter is blasted from the Sun 00:00:20.524 --> 00:00:24.172 at the velocity of one million miles per hour, 00:00:24.172 --> 00:00:26.119 and it's on a collision course 00:00:26.119 --> 00:00:27.992 with Earth! 00:00:27.992 --> 00:00:29.540 But don't worry, 00:00:29.540 --> 00:00:32.961 this isn't the opening of a new Michael Bay movie. 00:00:32.961 --> 00:00:37.249 This is The Journey of the Polar Lights. 00:00:37.249 --> 00:00:38.760 The Northern and Southern Lights, 00:00:38.760 --> 00:00:40.400 also known as the Aurora Borealis 00:00:40.400 --> 00:00:42.488 and Aurora Australis, respectively, 00:00:42.488 --> 00:00:44.479 occur when high energy particles from the Sun 00:00:44.479 --> 00:00:46.857 collide with neutral atoms in our atmosphere. 00:00:46.857 --> 00:00:48.417 The energy emitted from this crash 00:00:48.417 --> 00:00:50.075 produces a spectacle of light 00:00:50.075 --> 00:00:52.869 that mankind has marveled at for centuries. 00:00:52.869 --> 00:00:54.665 But the particles journey isn't just as simple 00:00:54.665 --> 00:00:56.846 as leaving the Sun and arriving at Earth. 00:00:56.846 --> 00:00:58.320 Like any cross-country road trip, 00:00:58.320 --> 00:00:59.326 there's a big detour 00:00:59.326 --> 00:01:02.122 and nobody asks for directions. 00:01:02.122 --> 00:01:03.463 Let's track this intergalactic voyage 00:01:03.463 --> 00:01:06.244 by focusing on three main points of their journey: 00:01:06.244 --> 00:01:07.317 leaving the sun, 00:01:07.317 --> 00:01:09.530 making a pit stop in the Earth's magnetic fields, 00:01:09.530 --> 00:01:12.092 and arriving at the atmosphere above our heads. 00:01:13.353 --> 00:01:15.635 The protons and electrons creating the Northern Lights 00:01:15.635 --> 00:01:17.428 depart from the Sun's corona. 00:01:17.428 --> 00:01:18.980 The corona is the outermost layer 00:01:18.980 --> 00:01:19.948 of the Sun's atmosphere 00:01:19.948 --> 00:01:21.964 and is one of the hottest regions. 00:01:21.964 --> 00:01:24.251 Its intense heat causes the Sun's hydrogen 00:01:24.251 --> 00:01:25.886 and helium atoms to vibrate 00:01:25.886 --> 00:01:27.954 and shake off protons and electrons 00:01:27.954 --> 00:01:31.087 as if they were stripping off layers on a hot, sunny day. 00:01:31.087 --> 00:01:33.531 Impatient and finally behind the wheel, 00:01:33.531 --> 00:01:36.154 these free protons and electrons move too fast 00:01:36.154 --> 00:01:38.085 to be contained by the sun's gravity 00:01:38.085 --> 00:01:40.230 and group together as plasma, 00:01:40.230 --> 00:01:42.416 an electrically charged gas. 00:01:42.416 --> 00:01:43.446 They travel away from the sun 00:01:43.446 --> 00:01:44.970 as a constant gale of plasma, 00:01:44.970 --> 00:01:47.112 known as the solar wind. 00:01:55.787 --> 00:01:58.058 However, the Earth prevents the solar wind 00:01:58.058 --> 00:01:59.388 from travelling straight into the planet 00:01:59.388 --> 00:02:00.799 by setting up a detour, 00:02:00.799 --> 00:02:02.050 the magnetosphere. 00:02:02.050 --> 00:02:03.269 The magnetosphere is formed 00:02:03.269 --> 00:02:04.475 by the Earth's magnetic currents 00:02:04.475 --> 00:02:06.269 and shields our planet from the solar winds 00:02:06.269 --> 00:02:08.395 by sending out the particles around the Earth. 00:02:08.395 --> 00:02:10.334 Their opportunity to continue the journey 00:02:10.334 --> 00:02:11.277 down to the atmosphere 00:02:11.277 --> 00:02:12.862 comes when the magnetosphere is overwhelmed 00:02:12.862 --> 00:02:14.829 by a new wave of travellers. 00:02:14.829 --> 00:02:17.111 This event is coronal mass ejection, 00:02:17.111 --> 00:02:18.701 and it occurs when the Sun shoots out 00:02:18.701 --> 00:02:21.154 a massive ball of plasma into the solar wind. 00:02:22.338 --> 00:02:23.932 When one of these coronal mass ejections 00:02:23.932 --> 00:02:25.109 collides with Earth, 00:02:25.109 --> 00:02:26.431 it overpowers the magnetosphere 00:02:26.431 --> 00:02:28.497 and creates a magnetic storm. 00:02:28.497 --> 00:02:30.545 The heavy storm stresses the magnetosphere 00:02:30.545 --> 00:02:31.966 until it suddenly snaps back, 00:02:31.966 --> 00:02:34.416 like and overstretched elastic band, 00:02:34.416 --> 00:02:37.813 flinging some of the detoured particles towards Earth. 00:02:37.813 --> 00:02:39.729 The retracting band of the magnetic field 00:02:39.729 --> 00:02:41.584 drags them down to the aurora ovals, 00:02:41.584 --> 00:02:42.483 which are the locations 00:02:42.483 --> 00:02:44.725 of the Northern and Southern Lights. 00:02:45.709 --> 00:02:48.640 After travelling 93 million miles across the galaxy, 00:02:48.640 --> 00:02:50.130 the Sun's particles finally produce 00:02:50.130 --> 00:02:52.969 their dazzling light show with the help of some friends. 00:02:52.969 --> 00:02:55.195 Twenty to two hundred miles above the surface, 00:02:55.195 --> 00:02:56.849 the electrons and protons meet up 00:02:56.849 --> 00:02:58.870 with oxygen and nitrogen atoms, 00:02:58.870 --> 00:03:01.284 and they sure are happy to see each other. 00:03:01.284 --> 00:03:03.586 The Sun's particles high five the atoms, 00:03:03.586 --> 00:03:04.281 giving their energy 00:03:04.281 --> 00:03:07.087 to the Earth's neutral oxygen and nitrogen atoms. 00:03:07.087 --> 00:03:08.586 When the atoms in the atmosphere 00:03:08.586 --> 00:03:09.823 are contacted by the particles, 00:03:09.823 --> 00:03:12.239 they get excited and emit photons. 00:03:12.239 --> 00:03:14.156 Photons are small bursts of energy 00:03:14.156 --> 00:03:15.489 in the form of light. 00:03:15.489 --> 00:03:16.982 The colors that appear in the sky 00:03:16.982 --> 00:03:19.731 depend on the wavelength of the atom's photon. 00:03:19.731 --> 00:03:21.980 Excited oxygen atoms are responsible 00:03:21.980 --> 00:03:22.806 for the green and red colors, 00:03:22.806 --> 00:03:24.557 where as excited nitrogen atoms produce 00:03:24.557 --> 00:03:26.901 blue and deep red hues. 00:03:26.901 --> 00:03:28.529 The collection of these interactions 00:03:28.529 --> 00:03:30.799 is what creates the Northern and Southern Lights. 00:03:35.382 --> 00:03:37.322 The polar lights are best seen on clear nights 00:03:37.322 --> 00:03:40.252 in regions close to magnetic north and south poles. 00:03:40.252 --> 00:03:41.360 Nighttime is ideal 00:03:41.360 --> 00:03:43.495 because the Aurora is much dimmer than sunlight 00:03:43.495 --> 00:03:46.188 and cannot be seen in daytime. 00:03:46.188 --> 00:03:47.915 Remember to look up to the sky 00:03:47.915 --> 00:03:49.918 and read up on the Sun's energy patterns, 00:03:49.918 --> 00:03:52.550 specifically sunspots and solar flares, 00:03:52.550 --> 00:03:53.097 as these will be good guides 00:03:53.097 --> 00:03:55.098 for predicting the auroras.