WEBVTT - Why Is the North Pole Moving? 0:00:00.200 --> 0:00:02.400 Hey, please take a second and leave us a review 0:00:02.480 --> 0:00:06.279 on Apple Podcasts, Spotify, or wherever you listen to the podcast. 0:00:06.960 --> 0:00:12.720 Thanks a lot. Hey, Welcome to Science Stuff reproduction of iHeartRadio. 0:00:13.039 --> 0:00:15.480 I'm hore, Hey cham and today we're answering the question 0:00:15.880 --> 0:00:20.880 is the North Pole moving? What actually is the true 0:00:20.880 --> 0:00:24.040 North Pole of the Earth? Is it changing? And should 0:00:24.079 --> 0:00:29.200 Santa Claus consider moving somewhere else. We're going to talk 0:00:29.240 --> 0:00:32.440 to a planetary scientists about this, and as you'll see, 0:00:32.640 --> 0:00:35.480 there are a lot of surprising things to learn about 0:00:35.479 --> 0:00:38.800 what we call the North Pole. Now, this is part 0:00:38.840 --> 0:00:41.519 of a two part holiday special, so be sure to 0:00:41.640 --> 0:00:44.480 check out next week's episode about how the New Year 0:00:44.960 --> 0:00:48.880 is changing. But for now, check under the tree because 0:00:49.000 --> 0:00:52.040 we're going to find out if scientists have been naughty 0:00:52.120 --> 0:00:57.760 or nice in tracking scantus address. Enjoy and happy holidays. 0:01:01.720 --> 0:01:04.760 Hey everyone, So the holidays are upon us, and I 0:01:04.760 --> 0:01:07.959 thought I check in with my friend, planetary scientist, doctor 0:01:08.120 --> 0:01:11.800 Matt Siegler, a professor at the University of Hawaii who 0:01:11.800 --> 0:01:16.319 works with NASA and the European Space Agency on several projects. 0:01:16.440 --> 0:01:19.520 The first thing I asked was what exactly is the 0:01:19.680 --> 0:01:24.880 North Pole? So here's my conversation with doctor Siegler. Well, 0:01:24.920 --> 0:01:27.040 welcome back, doctor Siegler. Happy holidays. 0:01:27.200 --> 0:01:28.440 Oh, happy holidays to you. 0:01:28.560 --> 0:01:30.119 Do you have any big plans for the holidays? You're 0:01:30.120 --> 0:01:33.600 in Hawaii? Is it weird to celebrate Christmas in Hawaii? Yeah? 0:01:33.760 --> 0:01:36.000 This is actually going to be our first Christmas staying 0:01:36.040 --> 0:01:38.759 over in Hawaii, So we'll see what Hawaii Christmas has 0:01:38.800 --> 0:01:39.199 the store. 0:01:39.319 --> 0:01:42.400 Did they just play that song male Likelikimaka twenty four 0:01:42.400 --> 0:01:43.000 to seven there? 0:01:44.959 --> 0:01:47.600 Yeah, yeah, until you go and say, at least it's 0:01:47.640 --> 0:01:49.760 a catchy song. It could be worse, and. 0:01:49.720 --> 0:01:51.560 It always puts a smile on your face. Nothing wrong 0:01:51.600 --> 0:01:51.800 with that. 0:01:52.400 --> 0:01:54.200 We'll see after a whole season of it. 0:01:55.240 --> 0:01:57.280 Well, today, I thought it'd be fun to ask some 0:01:57.480 --> 0:02:01.280 holiday and New Year's related questions about science. And you're 0:02:01.280 --> 0:02:03.600 a planetary scientist, so I thought you'd be the perfect 0:02:03.600 --> 0:02:06.400 person to talk to us about this. Okay, great, Okay. 0:02:06.480 --> 0:02:10.000 The first question is what is the North Pole? Yeah? 0:02:10.000 --> 0:02:13.320 So there are two North poles? Wait what this is 0:02:13.320 --> 0:02:15.520 the first thing to think about. There's the North Pole 0:02:15.760 --> 0:02:19.640 that we spin on right the rotational axis of the Earth. 0:02:20.480 --> 0:02:23.919 But on top of that, there's this magnetic North Pole, 0:02:24.320 --> 0:02:27.680 and we'd really love it if the two lined up right, 0:02:27.720 --> 0:02:29.960 that would make the Earth make sense that there's a 0:02:29.960 --> 0:02:32.160 big magnet in the center of the Earth and it's 0:02:32.200 --> 0:02:33.000 spinning right. 0:02:33.200 --> 0:02:33.760 Uh huh. 0:02:33.800 --> 0:02:34.440 But they don't. 0:02:35.480 --> 0:02:39.800 They don't. Okay, here's the first thing to know about 0:02:39.880 --> 0:02:44.120 the North Pole. There are actually two North poles. There's 0:02:44.120 --> 0:02:47.119 the pole around which the Earth spins, and then there's 0:02:47.160 --> 0:02:50.920 the pole of the Earth's magnetic field. And they're both 0:02:51.000 --> 0:02:54.799 different and they're both changing. Okay, we'll tackle them one 0:02:54.840 --> 0:02:58.160 at a time, and we'll start with the earth spin axis. 0:02:59.080 --> 0:03:02.240 The spin act of the Earth that we rotate around 0:03:02.600 --> 0:03:04.960 does points in different directions over time. 0:03:05.040 --> 0:03:08.120 We're spinning in place. We're also spinning around the Sun. 0:03:08.240 --> 0:03:10.560 But you're saying, on top of that, like we're sort 0:03:10.600 --> 0:03:12.760 of like a top that's kind of wobbling. Yeah. 0:03:12.840 --> 0:03:14.440 Then there are a couple of ways you wabble. There's 0:03:14.480 --> 0:03:16.200 the one where the stick on top of the top 0:03:16.280 --> 0:03:17.239 goes in a little circle. 0:03:17.320 --> 0:03:17.840 Uh huh. 0:03:17.880 --> 0:03:20.760 That's called procession of the orbit. And then there's the 0:03:21.080 --> 0:03:23.640 how the top like tips to the side or not, 0:03:23.919 --> 0:03:26.000 and that's called obliquity change. 0:03:26.040 --> 0:03:28.320 Wait wait, wait, so we're wobbling and we're tilting at 0:03:28.320 --> 0:03:29.320 the same time right now. 0:03:29.639 --> 0:03:32.960 Yes, yes, okay, we're always wobbling and tilting. 0:03:33.400 --> 0:03:35.920 So it turns out the spinning of the Earth is 0:03:36.040 --> 0:03:39.840 changing in two ways. Think of the Earth like a top, 0:03:40.240 --> 0:03:42.400 like the toy you spin and throw on the table. 0:03:42.760 --> 0:03:47.400 That top doesn't usually stay perfectly upright. It wobbles, and 0:03:47.560 --> 0:03:52.240 eventually it starts to tilt. The wobbling is called procession, 0:03:52.720 --> 0:03:54.520 and it's sort of like if you stuck your arm 0:03:54.640 --> 0:03:57.600 up above your head and then waved it around in 0:03:57.640 --> 0:04:01.480 a circle. And the tilting is called obliquity, and it's 0:04:01.560 --> 0:04:04.520 kind of how tilted we are relative to the sun. 0:04:04.800 --> 0:04:07.680 And it turns out both of those things are changing 0:04:08.000 --> 0:04:09.440 with different timescales. 0:04:11.160 --> 0:04:15.960 It happens like the procession. That wobble circle is about 0:04:15.960 --> 0:04:17.320 twenty six thousand years. 0:04:17.520 --> 0:04:20.200 Twenty six thousand years to do one wobble. 0:04:20.080 --> 0:04:24.120 Yes, to be one wah. So the north Star will 0:04:24.160 --> 0:04:26.800 be the north Star, but thirteen thousand years from now 0:04:26.880 --> 0:04:29.560 or so, a star called Vega is going to be 0:04:29.600 --> 0:04:30.200 the north Star. 0:04:30.480 --> 0:04:32.719 Really, we're wobbling that much. 0:04:32.680 --> 0:04:35.480 Yeah, And so we move across the sky like that. 0:04:36.920 --> 0:04:40.280 Yes, the north Star won't always be the north Star. 0:04:40.800 --> 0:04:43.320 And this one just effect whether you can navigate in 0:04:43.400 --> 0:04:47.400 the open ocean. It could affect who you are if 0:04:47.440 --> 0:04:49.080 you believe in astrology. 0:04:50.520 --> 0:04:54.320 And one of the big ramifications this change, this procession 0:04:54.640 --> 0:04:58.480 causes those zodiac signs to change by about one sign 0:04:58.520 --> 0:04:59.719 every two thousand years. 0:05:00.160 --> 0:05:02.159 You mean they shift in the sky kind of. Yeah. 0:05:02.200 --> 0:05:05.240 So the zodiac sign is the sign that's behind the 0:05:05.279 --> 0:05:08.359 sun the day you were born, but now, because of 0:05:08.440 --> 0:05:12.599 this procession of the equinoxes and moving about in two 0:05:12.600 --> 0:05:16.279 thousand years, your zodiac sign is actually off by a 0:05:16.360 --> 0:05:19.880 month from what the ancient Greeks use the zodiac signs. 0:05:19.920 --> 0:05:22.120 Wait, wait a minute, are you saying that astrology has not 0:05:22.279 --> 0:05:24.520 kept up with modern physics. Is that what you're saying. 0:05:24.760 --> 0:05:28.560 Yeah, most astrologers have not kept up with modern astronomy 0:05:28.960 --> 0:05:32.160 and the change of the zodiac signs. I hope this 0:05:32.200 --> 0:05:35.600 doesn't like end anyone's marriage or cause anyone trouble that 0:05:35.600 --> 0:05:38.120 you've been reading the wrong zodiac sign your whole life. 0:05:38.200 --> 0:05:39.880 It's like, oh, I thought I loved you because you 0:05:39.920 --> 0:05:42.400 were a Gemini, but it turns out, actually, in two 0:05:42.400 --> 0:05:45.360 thousand years, you're gonna be a pisson. It's over. It's over. 0:05:45.480 --> 0:05:48.280 Yeah, love is not eternal. It's only for roughly a 0:05:48.320 --> 0:05:49.520 two thousand year period. 0:05:51.600 --> 0:05:54.400 Yes, the wabbling of the Earth means you can't really 0:05:54.480 --> 0:05:59.200 trust zodiac signs, which I know is totally a Scorpio 0:05:59.279 --> 0:06:01.600 thing to say. And it turns out we have all 0:06:01.640 --> 0:06:06.080 the other planets to blame for this wobble. Wow, I'd 0:06:06.080 --> 0:06:08.480 never review that. And why are we processing? Is that 0:06:08.480 --> 0:06:10.680 the right word? Why are we wobbling? 0:06:11.200 --> 0:06:14.320 So that has to do a little bit with how 0:06:14.560 --> 0:06:17.440 all the planets yank on each other. Jupiter is the 0:06:17.440 --> 0:06:20.240 big dominant one in the Solar system, so that has 0:06:20.279 --> 0:06:22.960 a big effect on us. Venus is the closest one 0:06:22.960 --> 0:06:25.120 to us, so that has an effect. And the way 0:06:25.320 --> 0:06:28.560 all the gravity of these different planets kind of yank 0:06:28.600 --> 0:06:31.120 on each other a little bit causes these tops to 0:06:31.200 --> 0:06:35.040 wobble in this weird way. Whoah, And so we influence 0:06:35.080 --> 0:06:38.640 how Venus wobbles and Mars wobbles. 0:06:38.880 --> 0:06:42.200 Interesting, So right now we are breaking up marriages in bars, 0:06:42.640 --> 0:06:48.320 I guess. So that's our wobble. But like doctor Seger says, 0:06:48.640 --> 0:06:53.040 our overall tilt relative to the Sun is also changing 0:06:53.560 --> 0:06:56.839 about every forty one thousand years. 0:06:57.720 --> 0:07:00.160 That's our obliquity. So it's the twenty three and a 0:07:00.200 --> 0:07:03.920 half degree tilt that the Earth has that causes seasons 0:07:03.960 --> 0:07:06.440 and all that, and that wobbles a little, but only 0:07:06.520 --> 0:07:09.520 like about a degree or so over time, I see. 0:07:09.560 --> 0:07:12.920 And that's good because that little wobble of the degree 0:07:13.040 --> 0:07:16.440 or so and the power round or oval Earth's orbit 0:07:16.560 --> 0:07:20.400 is all those things mess with our climate. So when 0:07:20.400 --> 0:07:23.760 we go in and out of ice ages, it's because 0:07:23.880 --> 0:07:28.320 of these orbital changes, these things called Malankovitch cycles. 0:07:28.000 --> 0:07:29.280 No kidding, go on. 0:07:29.560 --> 0:07:33.800 But luckily this tilt, the obliquity doesn't change very much 0:07:34.000 --> 0:07:37.360 because the Moon actually is so big and massive compared 0:07:37.400 --> 0:07:39.520 to the Earth, and that's enough that it kind of 0:07:39.560 --> 0:07:41.000 acts as a balance. 0:07:41.880 --> 0:07:43.680 It gives more like inertia kind of. 0:07:43.920 --> 0:07:46.720 Yeah, And so that moment of inertia of the Earth 0:07:46.760 --> 0:07:49.600 Moon system is pretty big, and so we don't wobble 0:07:49.880 --> 0:07:53.160 that much other planets. Wow, And so we don't have 0:07:53.360 --> 0:07:56.640 as extreme ice ages as Mars does for instance. 0:07:57.160 --> 0:07:58.520 Interesting, all thanks of the Moon. 0:07:58.800 --> 0:08:04.560 Yeah, thank you many yes. 0:08:02.720 --> 0:08:06.320 So this holiday season, if you're feeling thankful, be sure 0:08:06.360 --> 0:08:08.760 to thank the Moon for the fact we're not living 0:08:09.040 --> 0:08:11.880 in an ice age. Okay, when we come back, we're 0:08:11.920 --> 0:08:14.640 going to tackle the other North pole of the Earth 0:08:14.920 --> 0:08:17.400 the magnetic north pole, and we're going to talk about 0:08:17.400 --> 0:08:20.480 how it used to be in the south pole. Stay 0:08:20.520 --> 0:08:35.520 merry with us, We'll be right back. Welcome back. We're 0:08:35.559 --> 0:08:38.840 celebrating the holidays by asking if the North pole is moving, 0:08:39.120 --> 0:08:43.640 and the answer is yes. We just talked about how 0:08:43.640 --> 0:08:47.040 the spinning axis of the Earth is changing. It's wobbling 0:08:47.280 --> 0:08:51.080 and it's tilting in cycles that last twenty six and 0:08:51.240 --> 0:08:53.800 forty one thousand years due to the polling of the 0:08:53.880 --> 0:08:57.360 Earth by the other planets in the Solar System. Now, 0:08:57.360 --> 0:08:59.640 as it turns out, there is a third way in 0:08:59.760 --> 0:09:02.559 which the spinning north pole of the Earth is changing, 0:09:02.920 --> 0:09:07.800 and that is because of plate tectonics. Here's planetary scientists, 0:09:07.920 --> 0:09:09.160 doctor Matt Siegler. 0:09:10.559 --> 0:09:14.400 If you slowly move continents around over you know, millions 0:09:14.440 --> 0:09:18.440 of years, that will actually change the axis along which 0:09:18.440 --> 0:09:19.000 we rotate. 0:09:19.160 --> 0:09:23.040 No wait, like the moving continents can cause the Earth 0:09:23.080 --> 0:09:24.800 to wobble too, yeah, or. 0:09:24.920 --> 0:09:28.400 Cause the spin axis to change, because the axis upon 0:09:28.480 --> 0:09:31.559 which we spin is controlled by that moment of inertia 0:09:31.640 --> 0:09:34.599 of the planet and by where you put your mass 0:09:34.679 --> 0:09:35.360 on that ball. 0:09:36.480 --> 0:09:39.400 What doctor Ziegler is saying is that as the continents 0:09:39.480 --> 0:09:43.840 move because of plate tectonics. That changes how the mass 0:09:43.880 --> 0:09:47.200 of the Earth is distributed, which can change which way 0:09:47.280 --> 0:09:50.280 the Earth is spinning, sort of like if you're an 0:09:50.280 --> 0:09:52.840 ice skater and you're spinning on the ice, if you 0:09:52.880 --> 0:09:55.800 suddenly move an arm or one leg out, you're going 0:09:55.840 --> 0:09:57.360 to be thrown out of balance. 0:09:59.559 --> 0:10:03.320 That's a called true polar wander. Whoah, if it's different 0:10:03.360 --> 0:10:06.559 from this apparent polar wander, this motion that I was 0:10:06.559 --> 0:10:09.640 talking about relative to the zodiac signs uh huh. But 0:10:09.880 --> 0:10:13.760 true polar wander is that the spin axis can actually 0:10:13.920 --> 0:10:17.880 change if you move enough mass around woa, like continent 0:10:17.960 --> 0:10:20.080 scale masses, big big masses. 0:10:20.200 --> 0:10:22.480 So then the spin axis has been changing relative to 0:10:22.520 --> 0:10:22.960 the Earth. 0:10:23.400 --> 0:10:26.360 Yes, but that's over a very slow time, right, because 0:10:26.360 --> 0:10:29.440 it takes millions of billions of years for continents to 0:10:29.559 --> 0:10:30.720 really move that much. 0:10:32.280 --> 0:10:34.960 And now we get to the magnetic north pole of 0:10:35.000 --> 0:10:38.240 the Earth. As you probably know, the Earth acts like 0:10:38.280 --> 0:10:42.640 a giant magnet. He creates a big magnetic field and 0:10:42.679 --> 0:10:45.800 the center of that field is a line that runs 0:10:45.880 --> 0:10:48.440 through the Earth. One side of that line is what 0:10:48.480 --> 0:10:50.959 we call the North pole and the other side is 0:10:51.000 --> 0:10:54.480 what we call the South cole. That magnetic North Pole 0:10:54.800 --> 0:10:58.760 is where all compasses point to, and according to doctor Siegler, 0:10:58.920 --> 0:11:02.880 where that North pole is has been changing a lot. 0:11:03.520 --> 0:11:05.960 I mean, Santa, you better pack your bags. 0:11:08.679 --> 0:11:13.079 So the magnetic pole of the Earth has actually moved 0:11:13.200 --> 0:11:16.720 quite a bit. So right now it's kind of in 0:11:16.840 --> 0:11:20.840 northern Canada somewhere, but a couple hundred years ago it 0:11:20.920 --> 0:11:24.120 was in Siberia, and a couple hundred years before that 0:11:24.200 --> 0:11:26.800 it had moved around Greenland, and then now it's like 0:11:27.280 --> 0:11:29.040 kind of moving back towards Siberia. 0:11:29.760 --> 0:11:33.240 That's right. The magnetic north pole changes on the scale 0:11:33.320 --> 0:11:37.160 of a hundred years. In fact, it's changing right now. 0:11:37.880 --> 0:11:40.640 Scientists estimate that the North pole is moving on the 0:11:40.679 --> 0:11:44.320 surface of the Earth about a kilometer a week, which 0:11:44.360 --> 0:11:47.680 is about one hundred and forty meters a day. This 0:11:47.840 --> 0:11:51.440 means where your compass points to today is different from 0:11:51.440 --> 0:11:54.520 where your compass will point to tomorrow. And where is 0:11:54.520 --> 0:11:59.560 it going to point next. Scientists don't really know. 0:12:00.520 --> 0:12:03.840 So the magnetic north pole has been doing its own 0:12:03.920 --> 0:12:08.439 like chaotic journey around roughly the physical spinning north Pole. 0:12:08.520 --> 0:12:11.559 Uh huh, but it's chaotic, I mean it's unpredictable. 0:12:11.840 --> 0:12:15.920 Yeah, it kind of changes its direction sometimes and it's 0:12:16.040 --> 0:12:19.880 going on its weird separate wobble, but it's a little 0:12:19.880 --> 0:12:21.080 more bizarre how it does. 0:12:22.120 --> 0:12:24.920 So we can't tell where the magnetic north pole is 0:12:24.960 --> 0:12:28.800 going to move to. It's unpredictable. And that is because 0:12:28.800 --> 0:12:32.800 of what actually makes the Earth's magnetic field, which is 0:12:33.000 --> 0:12:34.160 the Earth's core. 0:12:35.800 --> 0:12:40.040 So Earth has a big iron core, iron, nickel, sulfur 0:12:40.120 --> 0:12:42.640 or a few other molecules in there or whatever, and 0:12:43.200 --> 0:12:45.760 that core is about as big as Mars, right, So 0:12:45.800 --> 0:12:47.160 it's a big why core? 0:12:47.360 --> 0:12:48.160 Right? Yeah? 0:12:48.240 --> 0:12:51.120 Yeah, So Mars is about half the diameter of Earth, 0:12:51.200 --> 0:12:53.840 and so we have this huge chunk of iron in 0:12:53.880 --> 0:12:55.560 the center of the Earth as big as Mars. 0:12:55.880 --> 0:12:57.839 That's incredible. I didn't know if that big. 0:12:58.080 --> 0:13:02.880 Yeah, it's really high pressure. It's really hot down there, 0:13:03.120 --> 0:13:06.120 and it's hot enough that at least for the outer 0:13:06.240 --> 0:13:10.319 part of that core, it becomes liquid. And then roughly 0:13:10.440 --> 0:13:13.520 the inner third of that liquid core is under so 0:13:13.720 --> 0:13:18.320 much pressure that it's a solid again, right, like solid 0:13:18.360 --> 0:13:19.480 hunk of iron. 0:13:19.320 --> 0:13:22.559 At the very very center. Yeah. Okay, okay, So we've. 0:13:22.400 --> 0:13:25.800 Got a little ball of iron swimming in a Mars 0:13:25.880 --> 0:13:30.960 size ball of liquid iron, and those two things spin 0:13:31.600 --> 0:13:35.160 kind of differently from each other really, yeah, such that 0:13:35.240 --> 0:13:37.440 the solid one is kind of like the spinning blade 0:13:37.480 --> 0:13:40.800 of the blender, and then you have the liquid around 0:13:40.840 --> 0:13:43.120 that's kind of getting churned up and mixed up. 0:13:43.920 --> 0:13:45.920 So at the center of the Earth, we have a 0:13:46.000 --> 0:13:49.960 solid ball of iron that's about two thousand kilometers wide, 0:13:50.280 --> 0:13:53.880 and that's spinning inside of a swirling ocean of liquid 0:13:53.920 --> 0:13:58.720 iron that's about two thousand kilometers And all that moving 0:13:58.800 --> 0:14:02.920 and spinning iron is what causes the earth magnetic field. 0:14:03.840 --> 0:14:06.920 And so that ore is mostly made of iron, which 0:14:07.320 --> 0:14:11.719 you know conducts electricity. And when you take a conductor 0:14:11.840 --> 0:14:14.600 and you spin it, you cause a magnetic field. 0:14:15.559 --> 0:14:18.040 Just see any metal, if you spin any metal. Yeah, 0:14:18.200 --> 0:14:20.600 Like if I take a bar of iron and I 0:14:20.640 --> 0:14:22.560 spin it, it's going to create a magnetic. 0:14:22.200 --> 0:14:25.600 Field, yes, And then that causes a magnetic field in 0:14:25.640 --> 0:14:29.320 the core. And then there's this feedback where the magnetic 0:14:29.360 --> 0:14:32.320 field gets stronger and stronger, and that's what we call 0:14:32.400 --> 0:14:33.560 a magnetic dynamo. 0:14:34.640 --> 0:14:37.560 So the spinning iron core of the Earth is what 0:14:37.680 --> 0:14:40.960 makes the earth magnetic field. But here's the thing. The 0:14:41.000 --> 0:14:45.760 part of the core that's liquid doesn't spin and flow smoothly. Yes, 0:14:45.880 --> 0:14:49.920 turbulence and swirls and eddies, and all that turbulence makes 0:14:49.960 --> 0:14:53.160 the overall magnetic field on predictable. 0:14:55.120 --> 0:14:59.040 The solid core is spinning. In the liquid core, it 0:14:59.120 --> 0:15:03.360 causes little turbulence and eddies and such in the liquid core. 0:15:03.680 --> 0:15:04.400 Uh huh. 0:15:04.440 --> 0:15:08.720 Those are motion of electrical conducting material, and so those 0:15:08.720 --> 0:15:11.960 all cause a little magnetic field, uh uh huh. And 0:15:12.080 --> 0:15:15.040 they all kind of build together and give you north 0:15:15.080 --> 0:15:17.320 pole on a south pole for the whole Earth. 0:15:17.440 --> 0:15:20.560 Oh, it's like there's a massive magnetic fields down there 0:15:20.560 --> 0:15:23.200 in the Earth's core, but overall you can they just 0:15:23.240 --> 0:15:25.080 add up together. By the time you pull out to 0:15:25.200 --> 0:15:27.520 like the Earth's surface, it just feels like one big 0:15:27.600 --> 0:15:29.320 giant magnetic field exactly. 0:15:30.280 --> 0:15:33.760 And so because you have all this weird turbulence going on, 0:15:34.160 --> 0:15:36.880 it doesn't actually always line up in the right direction 0:15:37.000 --> 0:15:38.520 to be pointing due. 0:15:38.320 --> 0:15:39.640 North right, uh huh. 0:15:39.720 --> 0:15:42.280 It kind of wobbles around a lot, right, as all 0:15:42.280 --> 0:15:46.640 these little eddies and currents going on inside interact. Sometimes 0:15:46.640 --> 0:15:48.960 they'll line up with the spin axis of the Earth, 0:15:49.000 --> 0:15:52.440 and sometimes they don't. And that's happening on the scale 0:15:52.480 --> 0:15:54.760 of hundreds of years. It's like a tug of war 0:15:54.840 --> 0:15:58.040 where the pole of the magnetic field of the Earth 0:15:58.120 --> 0:15:59.400 is just migrating around. 0:16:01.080 --> 0:16:03.520 Yes, if you look up pictures of where the magnetic 0:16:03.600 --> 0:16:07.080 north pole has been where scientists think it may go next, 0:16:07.520 --> 0:16:10.240 it's not a smooth path. It looks like the path 0:16:10.400 --> 0:16:13.640 a drunk elf would take if they had too much echnogy. 0:16:15.400 --> 0:16:19.440 And it gets even wilder. Scientists believe that in the past, 0:16:19.720 --> 0:16:24.160 the magnetic field of the Earth has even flipped, it 0:16:24.200 --> 0:16:27.560 has turned completely around to the point where the north 0:16:27.640 --> 0:16:30.920 pole was actually in the south pole of the Earth. 0:16:31.640 --> 0:16:36.400 That would be a huge move for Santa Claus. So 0:16:36.440 --> 0:16:39.160 when we come back, we'll talk about why this happened, 0:16:39.400 --> 0:16:41.680 how we know it happened, and whether we can tell 0:16:41.720 --> 0:16:45.360 if it's going to happen again. So ho ho, hold on, 0:16:45.840 --> 0:17:01.800 don't go anywhere, We'll be right back. Hey, welcome back. 0:17:02.960 --> 0:17:05.840 We're talking about whether the North pole is changing, and 0:17:06.000 --> 0:17:09.879 so far we've learned that it's totally changing. The spin 0:17:10.000 --> 0:17:13.240 ax of the Earth is changing in like three different ways, 0:17:13.480 --> 0:17:17.120 and the magnetic north pole of to Earth is also changing. 0:17:17.440 --> 0:17:21.959 It's meandering around worse than a drunk elf today after Christmas. 0:17:22.240 --> 0:17:25.159 In fact, scientists believe that the magnetic north pole of 0:17:25.160 --> 0:17:29.359 the Earth can even switch and flip upside down, and 0:17:29.400 --> 0:17:32.359 that this has happened several times in the history of 0:17:32.400 --> 0:17:32.800 the Earth. 0:17:34.800 --> 0:17:37.520 Yeah, So that's where it gets even crazier. Right, So 0:17:37.560 --> 0:17:42.000 we have all of these spinning, rotating fluids and the 0:17:42.119 --> 0:17:44.800 solid core of the Earth. So you have all these 0:17:45.080 --> 0:17:48.080 eddies all interacting with each other and right now all 0:17:48.160 --> 0:17:51.439 kind of lining up where the net magnetic field points 0:17:51.480 --> 0:17:54.399 to the north pole. But because they're all fluid and 0:17:54.440 --> 0:17:57.440 can interact in these weird ways, they can all kind 0:17:57.440 --> 0:18:02.200 of work together and flip, and so sometimes the north 0:18:02.280 --> 0:18:06.879 pole magnetically becomes the South pole. Why and vice versa. 0:18:08.200 --> 0:18:10.600 Yes, the magnetic north pole of the Earth can change 0:18:10.680 --> 0:18:13.639 so much it can even end up in the South pole. 0:18:15.000 --> 0:18:19.000 So your compass would point to Antarctica as being due north. 0:18:19.480 --> 0:18:22.679 And this has not just happened once before. It's happened 0:18:22.720 --> 0:18:26.159 maybe thousands of times in the history of the Earth. 0:18:27.080 --> 0:18:30.600 And that switch between the north pole pointing north and 0:18:30.720 --> 0:18:35.439 the north pole pointing south magnetically has happened roughly every 0:18:35.800 --> 0:18:39.480 five hundred thousand years or so. Sometimes it's longer, sometimes 0:18:39.520 --> 0:18:40.040 it's shorter. 0:18:40.960 --> 0:18:43.359 Okay, you might be wondering how we know this and 0:18:43.440 --> 0:18:46.080 the answer is that there's a record of the Earth's 0:18:46.119 --> 0:18:49.639 magnetic field at the bottom of the ocean. At the 0:18:49.680 --> 0:18:52.840 middle of the oceans, there are enormous seams where the 0:18:52.920 --> 0:18:57.719 Earth's tectonic plates are separating, and as they separate, lava 0:18:57.800 --> 0:19:03.440 comes up, creezes and forms thew c floor. Now, when 0:19:03.480 --> 0:19:06.399 the lava freezes and becomes rock, the metal in the 0:19:06.520 --> 0:19:10.960 rock records the magnetic field at the time the lava froze. 0:19:12.320 --> 0:19:15.040 So if you measure the magnetism of the rocks the 0:19:15.080 --> 0:19:18.639 bottom of the ocean, you'll see bands parallel to the 0:19:18.680 --> 0:19:22.920 seam or ocean ridge where the rocks magnetism points one 0:19:22.960 --> 0:19:26.359 way and then another way, and then another way. And 0:19:26.440 --> 0:19:29.600 from the age of the rocks, scientists can tell that 0:19:29.720 --> 0:19:34.159 this flipping of Earth's magnetic field happens on average about 0:19:34.280 --> 0:19:37.720 every five hundred thousand years or so. Sometimes it happens 0:19:37.760 --> 0:19:41.840 more frequently and sometimes less frequently. The last time it 0:19:41.960 --> 0:19:46.040 happened was almost eight hundred thousand years ago. But here's 0:19:46.080 --> 0:19:49.800 the big mystery. Scientists don't know if the magnetic north 0:19:49.840 --> 0:19:54.360 pole switches to the south pole really quickly or really slowly, 0:19:55.040 --> 0:19:56.479 and what happens in between. 0:19:58.560 --> 0:20:01.879 It's unclear how long it takes the switch from pointing 0:20:01.920 --> 0:20:04.600 north to pointing south. Does it happen in one day 0:20:04.800 --> 0:20:07.000 or does it happen in a couple thousand years? 0:20:07.080 --> 0:20:07.600 We don't know. 0:20:07.880 --> 0:20:10.560 Most estimates are its probably takes a few thousand years, 0:20:10.720 --> 0:20:14.240 But that is a timescale that's difficult to measure on 0:20:14.280 --> 0:20:17.680 the geologic record, right, we can measure hundreds of thousands 0:20:17.720 --> 0:20:20.800 of years. Yeah, that we can measure pretty precisely. When 0:20:20.800 --> 0:20:23.880 you were talking about is it six days or two 0:20:23.920 --> 0:20:27.840 thousand years, like, we can't tell. It's a little tricky 0:20:27.960 --> 0:20:31.639 to tell that precision. That's wild and it's probably a 0:20:31.680 --> 0:20:34.439 little different every time, right, because it's driven by this 0:20:34.560 --> 0:20:38.159 chaotic stirring of the core of the Earth, right, and 0:20:38.240 --> 0:20:41.600 so that's when the Earth's magnetic field will flip, uh huh. 0:20:41.680 --> 0:20:45.639 You'll kind of get this weird period in between where 0:20:45.880 --> 0:20:49.160 the compass would point to all sorts of random directions, right. 0:20:49.440 --> 0:20:52.280 Like there might be a six day or one thousand 0:20:52.359 --> 0:20:55.480 year period where your compass will point to like Panama 0:20:55.640 --> 0:20:57.040 true north of the Earth. 0:20:57.200 --> 0:21:00.719 Yes, because that's where the magnetic field happens to be 0:21:00.720 --> 0:21:05.639 popping out that day. And then from tradition or whatever, 0:21:05.680 --> 0:21:08.000 from the record that we see, it will eventually end 0:21:08.119 --> 0:21:11.080 up where the north pole of your compass would point south, 0:21:11.480 --> 0:21:13.720 and then we'll stay that way, probably for five hundred 0:21:13.720 --> 0:21:15.840 thousand years, and then flip back the other way. 0:21:15.880 --> 0:21:18.639 So the fact that my compass points north now it 0:21:18.760 --> 0:21:20.680 just happens to be like that. Now, at some point 0:21:20.720 --> 0:21:22.439 it's going to change, and it has changed before. 0:21:22.640 --> 0:21:25.760 Yeah, there's a whole history of how this affected early 0:21:26.160 --> 0:21:30.159 navigation when the fourteen hundreds plus, right, especially when you 0:21:30.480 --> 0:21:34.240 live in Europe and you're at pretty high latitudes, that 0:21:34.320 --> 0:21:37.879 little difference matters whether the magnetic north is right on 0:21:37.920 --> 0:21:41.399 the north pole, uh huh. And so this inability to 0:21:41.480 --> 0:21:44.760 actually tell where doe north was really one of the 0:21:44.800 --> 0:21:48.000 things that led the history of exploration of the world 0:21:48.280 --> 0:21:51.320 by the Europeans to be so so kind of random 0:21:51.359 --> 0:21:53.480 in a way where oh, yeah, sometimes we ended up 0:21:53.520 --> 0:21:55.879 in the wrong place and we thought it was somewhere else. 0:21:56.960 --> 0:21:59.639 It's because the magnetic hole moved. 0:22:00.119 --> 0:22:03.240 Yeah, the compass was just not a reliable way to 0:22:03.359 --> 0:22:04.400 navigate perfectly. 0:22:05.680 --> 0:22:09.480 Okay, So that's the Earth's magnetic north pole and it's 0:22:09.560 --> 0:22:12.280