Neil deGrasse Tyson Explains Earth’s Magnetic Field and Magnetic Poles

hey chuck hey hey what's happening neil i'm back in your face that's right which means that we're gonna we're gonna find out about something um hopefully that is delightfully obscure obscure but yes but the whole part is it will be obscure the hope is that it's nonetheless interesting yeah well that's yeah so far so far it's going good all right so i want to talk about earth's magnetic field all right already you got me if i yeah this is good stuff already okay so um it's we all know it has a magnetic field and you learn that as a child when you have a compass right particularly if you were like you know in one of the scouts programs you have a compass and the needle points north and so that's north okay so um so the north side of the needle points north and that's how you know it's north so let me start out by saying we all know that in magnetic fields opposites attract right you knew this yes well you you take the north and the north you put them together and they it's very cool because they they repel yeah and you and then you have magnet races push them across the table yes you push them across the table and that's how you have a magnet okay so if you flip it around then the north sticks to the side okay right so what that means is if the needle on your compass is magnetized north then it's actually pointing to the earth's south magnetic pole right that makes sense because that means what you're calling the north pole is actually the south pole right i just want to start there wow okay okay thanks for ruining everything and now i don't know what to believe okay period right earth's south magnetic pole is in the north because all north magnetic poles point to it right okay interesting i just didn't know if you knew that uh you know what don't shoot the messenger i know it now and i i gotta tell you i wish i didn't okay so now that that's actually very cool but wait there's more uh so earth's magnetic field um is not aligned with earth's rotation axis okay so santa claus is up there on the north pole all right and your compass doesn't actually point to him okay well it does point to him if you're exactly on the longitude where the north magnetic pole is found if you are anywhere else you are not pointing to the top of earth's rotation axis you are pointing to some place in northwest canada because our magnetic pole is tipped relative to our what we call the geographic pole okay so the geographic poles so the earth sits if you ran the pole an actual pole through it if you did it's on this tilted axis it's tilted that's correct it's tilting it's tilted by a lot so it's so a compass sort of points north sort of and by the way i i in the scout manuals this is the device we use to find our way when we're lost well it's like getting directions in the hood you know now see what you want to do here man what you want to do you want to go straight down right go straight right now now that's my cousin that's my cousin boo right when you get to cousin boo's house you won't make a left that's exactly what it says on the compass right so so you uh so what they the the manuals for using a compass know about this and it's it's called an offset so depending on where you are on earth's surface when you whip whip out the the compass you would put an angle offset to find out what true north is but that changes depending on where you are on earth's surface so it's what i always had an issue with is if you knew where you were on earth service you wouldn't need the company in the first place absolutely that's like people say i lost my keys well where'd you leave them last what what what well what was the last place you left i left them on the counter except like that is a stupid question right that is crazy right you know another stupid one is uh someone gets injured skiing and they got to be like hauled off to the hospital and someone asked him did that did that happen on your last run exactly yes of course it did now you know uh the thing is i love excruciating pain and skiing the pain enhances the skiing experience so when when my tibula is sticking out of my leg that's when i want to get back on the chairlift [Laughter] all right so anyway so so that's what that's where that is all right so in the era of gps which knows exactly where the poles are and what the grid system is like compasses are basically completely obsolete plus if you know any astronomy you'll know which way north is and which way the sun is pointing i mean so so the compass i think is overrated in this regard um compared with other ways you can also find out where where you are but anyway so that's earth's magnetic field it's relatively weak okay it's weak so if you take a bar magnet i don't know if anyone still has them you can do this tie a string in the middle where it's balanced and just sort of suspend it there it will slowly line up with earth's magnetic field okay provided the string is is is twisty enough so that it can aim where it wants it'll slowly line up and the north is going to point north to earth south magnetic field right it turns out as weak ass as this field is it's not always at the same strength nor is it always oriented the same way the magnetic pole of the earth flips and it has flipped many times wow i don't know if anybody knew that that's i don't know okay this is good stuff and now i'm really intrigued at 100 of the times people of the occasions where people say i hear the world is going to end and earth's axis is going to flip because they heard something about earth's axis flipping right and they think somehow santa claus is going to be south instead of north when what they read about earth's axis flipping has been entirely related to the magnetic field flipping gotcha and on earth so the earth is not actually tumbling over so that top is bottom and bottom is top that has never happened that's never happened correct what's happening is the actual magnetic field which is the thing surrounding the earth that orientation changes right and it's not just the part of it we measure and see is outside of the earth right but it's generated from d from the inside of the but i haven't gotten there yet but i'm just saying that this can reduce in strength come back in a reversed polarity reduce the strength and come back again and that flips and this this goes on every million years so now i got to know this in that process is it a is it an equal diminishing so that it actually goes down to not being there at all and then oh we think so yes so what you have you have volcanic deposits that had uh metallic ingredients in it and when the iron when the the the lava freezes basically hits room temperature and freezes um it's uh it locks in the magnetic orientation of where that lava was at that time and so people who study this can track the orientation of these magnetic um rocks as as they get yeah brilliant it's complete that is insane yes yes oh my god that's crazy yes yes okay so i love it so people wondered by the way we are shielded from harmful particles from the sun by this magnetic field it gets channeled towards the magnetic poles and it it collides with the atmosphere and renders it aglow and it creates the northern and southern lights the aurora borealis and the aurora australis okay earth's force field that is or facts that is earth's magnetic force field directing deflecting particles and that's why they don't all go to santa claus they go to that the best shows are in this ring it's called a ring it's a highly luminous ring where you have the best action of this uh excited air molecules and it's over canada okay and it's not that's why we get better aurora borealis than they do over in russia because we have the pole over on our side our north american side finally something good about canada and their health insurance okay canada you know we love you you know we love so um so it shield us from that so now here's here's what's going on inside the core you get a magnetic field when you have a fluid in this case it would be sort of molten uh magnetic materials iron and nickel in our core all right and if it's molten it means you can move you convect there's movement within this material we know from basic electromagnetism 101 if you move a charge okay you create a current if you create a current you create a magnetic field right it's called a dynamo theory of magnetic uh fields and this is where we do it in class you take the copper wire the copper wire you pass it through exactly and you see the meter checked and the electricity and the magnetism go together that's why it became one word exactly right early 1800s i got electricity and i got magnetism then you find out one is a manifestation of the other we glued the words together and we made the word electromagnetism sweet so um because of this when you have a molten core of conductive materials in our case it's metal you can generate what's called a dynamo and sustain magnetic fields for millions of years wow okay or magnetic field phenomenon so and as the magnetic field lines get twisted what happens is they can break and reconnect and often when they reconnect they have the opposite polarity than they had before and that's what's been going on on earth that's so cool forever that's so cool and by the way the sun's magnetic field goes through this the sunspot cycle goes through an 11-year uh from peak to low and sunspots always come in pairs there's a positive and a negative because they're magnetic i don't know if you knew they're magnetic they're magnetic i did not know that okay so now watch so watch every 11 years the sun's magnetic field flips and when the sunspots show up again they're now oppositely configured so earth is not the only thing whose magnetic field flips it happens to the sun every 11 years so this is not a new phenomenon the understanding of it is relatively modern you know late 20th century mid to late 20th century but there it is that's our magnetic field there's worries that when we um when the field went to zero and switched maybe all the bad particles would come and kill all life on earth and maybe the the migration that's when a portal to another dimension opens and we are taken over by that'd be a good story right right the magnetic field drops to zero what happens now yeah so so what you do is you can look at what effect that would have there also many animals that it is asserted that they use the magnetic field uh particles in their brain to know which way north and south is there's navigation to migrate uh i've not been as convinced as others have been of that explanation but let's even give it to them fine you would wonder will they not know how to how to how to fly how to swim how to migrate from one place to another to get out of the cold climates in the in the winter and return in the summer you look at the fossil record over those periods and there's no meaningful extinction episodes happening over any of these right so whatever our worries are earth seems life on earth seems to survive them just fine right and everybody knows that birds don't really use the uh magnetic field they use uh google bird maps google bird maps is you know pretty dope man plus they can track you and that's how they know how to [ __ ] on your head google targeting that's funny so there you so there you have it and my my only issue with whether animals use magnetic fields is they don't if the animal knows where the sun rises and sets and there are other ways to know like i said if you didn't have a compass you still can figure it out and so animals are always smarter than i think we give them absolutely and the truth of the matter is um even we as explorers and being out in the sea we didn't use magnetic fields we use the stars we use the stars that's correct right on a cloudy night it's a little harder you could uh crash into the rocks on a cloudy night but on a clear night you couldn't right exactly so yeah all right cool man yeah so there you have it this is magnetic field that's fun stuff i love it and by the way magnetism in general you didn't ask this but i'm putting it out there is to understand it we've known about magnets ever since lodestone was discovered this rock that contained the iron that was magnetized before we isolated the iron from it's called lodestone it's still called lodestone um there's no understanding of magnetic fields without quantum physics okay well then we don't understand magnetism so sorry guys speak your own damn self don't understand right no you got to get down in there and the electrons in in orbit in their their orbital clouds around their the nuclei there's a point where they align with adjacent atoms and once that's aligned and coherent you have a stable magnetic field and if you could create you could create a magnet we used to do this you take a pin right a little steel pin and you take a magnet and it doesn't even have to be a strong magnet and you just stroke it you keep stroking right so there you go and you're aligning all of those magnetic domains to create a coherent magnet now there are other magnets where they only where they'll only stay magnetized in the presence of an electric field and and you remove the electrical then they demagnetize immediately this is how you get electromagnets that's how the trains run uh maybe i don't know enough about trains but i do know that thing that picks up cars in the trash yard not nice it grabs them by their thing i'm not talking about the clamps i'm talking about that no the big the big disc flat thing the distance yeah that comes down and it just shows up so flip the switch magnet on boom there it is and put it bring it to the side magnet off and you can drop it so that's an electromagnet highly uh functional and exploitive of quantum physics nice there you go chuck we ran out of time wow well that was a good one man i uh you know i think this uh this talk will stick with me for a while yeah yeah and santa claus that was a bad magnet joke i'm sorry okay oh oh sorry i missed it sorry yeah i'm sorry man i shouldn't have done that i'm i'm really embarrassed that i actually did that i'm sorry i'm embarrassed i didn't catch it don't you say uh this this this explainer will stick to me for a long time i would have gotten it right oh by the way just one other thing if you're between the north pole geographic pole and the north uh geomagnetic pole if you're between those two your compass will always point due south oh wow right because the this damn thing is broken yep yep that's that's all i'm saying awesome there you go chuck all right we got to call it quits there this has been another star talk explainer venue chuck always good to have you always a pleasure neil degrasse tyson here keep looking you

Channel: StarTalk

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Keywords: startalk, star talk, startalk radio, neil degrasse tyson, neil tyson, science, space, astrophysics, astronomy, podcast, space podcast, science podcast, astronomy podcast, niel degrasse tyson, physics, Chuck Nice, Earth’s magnetic field, magnetic poles, magnetic field, North, compass, geographic poles, dynamo theory, Sun, quantum physics, startalk explainer

Id: E3J8esf3aQQ

Length: 17min 25sec (1045 seconds)

Published: Tue Sep 15 2020