1 00:00:02,290 --> 00:00:11,560 You've seen the sunset, right? 2 00:00:11,560 --> 00:00:14,419 And if you get up early enough, maybe you've seen it rise, too. 3 00:00:14,419 --> 00:00:18,960 But have you ever wondered, if the sun rises every day and sets every night, where does 4 00:00:18,960 --> 00:00:22,699 it go when we can't see it? 5 00:00:22,699 --> 00:00:25,879 Well, nowhere. 6 00:00:25,879 --> 00:00:29,859 It's actually us that goes somewhere, because we're on the Earth and our planet is always 7 00:00:29,859 --> 00:00:32,500 turning or spinning on its axis. 8 00:00:32,500 --> 00:00:36,020 Imagine a line passing through the center of the Earth that goes both through the North 9 00:00:36,020 --> 00:00:40,960 pole and the South Pole. We call that invisible line the axis. Earth spins around on this 10 00:00:40,960 --> 00:00:45,520 axis like a top. This spinning movement is called the Earth's rotation, and the Earth's 11 00:00:45,520 --> 00:00:50,479 rotation is what gives us day and night. Every day, all year. If you're on the side of the 12 00:00:50,479 --> 00:00:54,579 Earth that's facing away from the Sun, as the Earth is spinning, it's night. If you're 13 00:00:54,579 --> 00:00:59,679 on the side facing the Sun, it's, you guessed it, day. Now hold on tight, because the Earth 14 00:00:59,679 --> 00:01:03,979 is actually moving in more ways than one. At the same time that the Earth spins on its 15 00:01:03,979 --> 00:01:09,200 axis it also orbits or revolves around the Sun this movement is called its 16 00:01:09,200 --> 00:01:13,640 revolution one full orbit all the way around the Sun is one revolution and the 17 00:01:13,640 --> 00:01:18,379 earth takes 365 days or one year to complete a revolution so have you got 18 00:01:18,379 --> 00:01:22,579 all of this so far the earth is rotating on its axis creating day and night and 19 00:01:22,579 --> 00:01:26,599 the same time it's revolving all the way around the Sun now here's the thing as 20 00:01:26,599 --> 00:01:31,019 the earth is both rotating and revolving it's not sitting straight up and down 21 00:01:31,019 --> 00:01:34,019 Its axis is actually tilted just a little. 22 00:01:34,019 --> 00:01:38,019 It's not all that much, but this tilt causes one part of the Earth to lean towards the Sun, 23 00:01:38,019 --> 00:01:40,019 while another part of it is leaning away. 24 00:01:40,019 --> 00:01:45,019 This means that different parts of our planet's surface gets different amounts of sunlight and heat. 25 00:01:45,019 --> 00:01:47,019 So, why am I telling you all of this? 26 00:01:47,019 --> 00:01:51,019 Well, as the Earth travels around the Sun, it creates a pattern throughout the year. 27 00:01:51,019 --> 00:01:55,019 This pattern happens over and over again, and I'm sure you've noticed it. 28 00:01:55,019 --> 00:01:58,019 At certain times of the year, you see the Northern Hemisphere leans towards the Sun, 29 00:01:58,019 --> 00:02:00,019 and the Southern Hemisphere leans away. 30 00:02:00,019 --> 00:02:05,319 And at other times, the southern hemisphere leans towards the sun, and the northern hemisphere leans away. 31 00:02:05,319 --> 00:02:08,219 That pattern, my friend, is what makes seasons. 32 00:02:08,219 --> 00:02:13,219 When the part of the world that you're living in is leaning towards the sun, it's warm and the days are long. 33 00:02:13,219 --> 00:02:18,020 Summer. When you're on the part that's leaning away from the sun, it's cold and the days are short. 34 00:02:18,020 --> 00:02:20,419 Winter. In between, it's spring or autumn. 35 00:02:20,419 --> 00:02:25,219 If the Earth weren't tilted, we would have the same season all year long. 36 00:02:25,219 --> 00:02:29,520 So, revolution, rotation, orbit. Is your head spinning? 37 00:02:29,520 --> 00:02:32,860 Let's do a demonstration to shed a little light on these concepts. 38 00:02:36,719 --> 00:02:39,699 Okay, you're going to need a globe and a table lamp without a shade, 39 00:02:40,039 --> 00:02:41,460 plus a table to put them both on. 40 00:02:41,680 --> 00:02:43,939 Put the lamp in the center of the table and turn it on. 41 00:02:44,199 --> 00:02:45,680 Put the globe on one side of the table. 42 00:02:46,039 --> 00:02:46,699 Now hit the lights. 43 00:02:46,819 --> 00:02:47,719 The globe is Earth. 44 00:02:47,879 --> 00:02:48,580 Makes sense, right? 45 00:02:48,699 --> 00:02:52,539 The lamp at the center of the table is the sun at the center of the solar system. 46 00:02:52,659 --> 00:02:54,120 Now slowly spin the globe. 47 00:02:54,280 --> 00:02:57,599 As the Earth rotates, the sun lights up one side of the planet better than the other. 48 00:02:57,919 --> 00:03:01,400 It's day where the light is shining more brightly on the globe and night where it's not. 49 00:03:01,400 --> 00:03:05,000 Now let's see what the Earth's revolution around the Sun looks like. 50 00:03:05,000 --> 00:03:09,020 Give the globe a few spins with one hand while slowly pushing the globe in a circle around 51 00:03:09,020 --> 00:03:11,319 the Sun, or the lamp with your other hand. 52 00:03:11,319 --> 00:03:14,979 So do you notice how the Earth keeps rotating as it revolves around the Sun? 53 00:03:14,979 --> 00:03:18,780 If this were the real Sun and Earth, by the time you get back to where you started, the 54 00:03:18,780 --> 00:03:22,360 globe would have completed 365 rotations, or days. 55 00:03:22,360 --> 00:03:24,199 And that's another year gone by. 56 00:03:24,199 --> 00:03:30,120 So what does all this show us? 57 00:03:30,120 --> 00:03:34,800 It shows that what looks to us to be the motion of the Sun in the sky is really caused by 58 00:03:34,800 --> 00:03:36,300 the motion of the Earth. 59 00:03:36,300 --> 00:03:37,300 So now you know. 60 00:03:37,300 --> 00:03:41,340 When you look up and see the Sun setting or rising, it's not going around us. 61 00:03:41,340 --> 00:03:45,199 It's sitting pretty much at the center of the solar system while we and the seven other 62 00:03:45,199 --> 00:03:47,240 planets go around it. 63 00:03:47,240 --> 00:03:51,639 That Sun always got to be the center of attention.