Neil deGrasse Tyson Explains the Earth's Rotation

[Music] chuck we're back all right i couldn't stay away well yes i got some more explaining to do you got some explanatory oh my god i sound like my mother-in-law that's crazy or ricky ricardo one of the other well my mother-in-law is ricky ricardo so i just i thought i had some more things to say about the rotation of the earth really yeah well we did we did something about what would happen if it stopped we did something about what how many people superman would kill right if you move backwards and stop the earth if he flew backwards slowed down the earth stopped it reversed it stopped it again and sent it back yeah nobody left on earth as if that would actually reverse time though right as if right right as if so even if it did and could he still killed seven billion people okay or however many people were on earth the year of that movie which i think was 1970 in the seven late seventies yeah no then i was old so here you go you've heard of this thing called centrifugal force right the thing that makes you sort of fly off because somebody spun something around and things fly off it's what keeps bucket in the water when you do the whole windmill it sounds like you've done some experiments good if you want to take water in a bucket a bucket of water you can even with a cup of water if you take it and if you if you spin it sort of fast enough like like a windmill style then the water will not come out right even though you it was upside down and if you ever played matchbox cars where the car goes upside down and then comes out the other side you need sufficient centrifugal force to keep the thing up against the track i don't okay i was a hot wheels guy by the way you were okay oh yeah i'm a hot wheels guy i know you said matchbox i get it sorry it was hot wheels that had the loop to loose excuse me forgive my my okay then the track was yellow and it pieced together i remember the whole thing yes and it made for a great way to like slap the bottom of a friend it's like you take that hot wheels track and you just whack somebody oh oh oh oh okay so you had issues as a child okay that's another show we'll have you get them out okay never occurred to me multiple years kicked out of elementary school all right so this it turns out there's no such thing as centrifugal force it's the word we give to this thing that feels like a force operating on you if you are the water in that bucket or if you're in that amusement park where i think they call it the cyclone where you're sort of pinned against the wall of it and it rotates and you feel this pressure increase on you so what's happening is because you're getting spun you have an urge to fly off at a tangent of that circle okay that urge to fly off that is prevented you will feel as a centrifugal force okay okay so if in any moment the walls just disappeared on the cyclone at is it called the cyclone whatever that was called out of the fly i forget the name of it but i do remember i think i'm missing remember because cyclone is the roller coaster at right at coney island at coney island so whatever that thing is we've all done it right and if at any instant while that's spinning the walls just disappeared you would just fly off at a tangent everybody would just fly off going in exactly the tangential direction they were going right at the moment the walls disappeared okay lawsuit lawsuit damn truck you're so cynical chuck so what the wall does is prevent that from happening and then you it feels as though there's a force acting on you and by the way that is the worst ride to take if you get nausea if you feel nausea on on amusement park rides because if you try to throw up the throw up will get pinned to the back of your throat you'd have to like turn your head sideways and then the throw up goes sideways onto the next person so so it's i don't think we have a problem here neil i always notice that that ride always had an extra smell to it compared to other to other rides so anyhow so this centrifugal force you will feel it as though it's a real force and so that's why we gave it a name all right and by the way coriolis force is another fictitious force it feels like it's a real force operating but it's the product of other things going on the coriolis force turns storms into clockwise counterclockwise clockwise direction in the north and clockwise in the south in fact we'll we'll land there at the end of this explainer so what that means is if you're on earth and earth is spinning you ought to feel some centrifugal force yay you ought to now who would feel the most centrifugal force on earth where would you be uh at this at the center like at the equator at the equator okay now of course we all finish one rotation in 24 hours however they're traveling a much bigger distance to do so okay they move the entire circumference of the earth about 25 000 miles in one day whereas as you approach santa claus on the north pole your circle becomes shorter and shorter so you are moving slower and slower okay okay and centrifugal so the people at the people in ecuador should all have their hands up just going okay just like any good amusement park ride all the equator people all the acquainted people [Laughter] so uh you get a photographer to take your picture and sell it back to you at the end of that exactly so so the equator is about 25 000 miles around and it takes 24 hours for one full rotation okay so if you divide those two numbers you get approximately they're going approximately a thousand miles an hour right okay and that's fast i mean that's faster than you would ever be going in anything in your life that's right okay now you don't feel that because first earth connects you to its surface but also you're moving very uniformly through space to do so and the air around you is moving with you so it's not like air is coming past you with the thousand mile that you feel oh my gosh i'm in motion and i feel the jiggle in the shake by the way pre-galileo people's arguments against earth's motion was if earth were turning and moving we'd feel it right okay why wouldn't you if you're on a horse and buggy you feel that all right you feel the bumps and the wiggles and the jiggles and even if the ride is smooth you feel it so clearly earth can't be moving we of course we're not rotating either everything is moving around us so it wasn't just our ego that supported the idea that we are in the center of all things at the center of wealth it's not just what's happening with our ego it kind of made sense when you thought about it okay right what they didn't realize is that if you made things smoother and smoother and smoother you will feel the motion less and less and less right so ask anybody on an ocean liner when the ocean liner first pulls out from the port you don't really notice that and you look around you say wait a minute why is the dock going by me and you look at it and you realize you're the one in motion not the dock okay and so the bigger the vessel sort of the more stately is its movement through space and time and the less you notice its motion so you know i i was once on a bus on the tunnel going from paris to london okay and this is a long tunnel that not only goes under land but goes under the english channel okay and so um that is very well designed it's very smooth so i'm in a bus and that they drive the bus onto a car and the car has no windows onto a railroad car a car has no window so i'm in there and i feel it kind of move a little bit but it's a slow acceleration and i think it has very high top speeds but i have no concept of this okay now inflate this scenario to the entire earth okay you are moving a thousand miles an hour as earth rotates you are moving 18 what's the 18 miles per second in orbit around the sun and you don't feel any of that okay okay you don't feel anything so here's my point all right so the faster you rotate okay the greater is the centrifugal force you will that will operate on you okay so let's go back to all the residents of ecuador which is not the only country that straddles the equator okay in fact the equator goes entirely through the middle of africa for example all right so so here we go you can ask if it's trying to fling you off the earth okay but the force of gravity is resisting back by what force is it trying to fling you off that upward centrifugal force subtracts from the gravitational force that the earth is trying to put on you it subtracts okay so chuck what do you weigh here here and now uh 192 pounds yeah you used to be like 170 so 178 yeah and now i have a corona baby that i'm pregnant with corona i'm pregnant with a corona baby all right i'll give you 190 pounds okay okay so if you do the math you run to ecuador because we're in the western hemisphere so let's stay there you run to ecuador you will not be 190 pounds you'll be like 185 pounds what that's how significant it is that's if i if i had my math correct and i think i did there are pounds less that you weigh for living on the equator than for living anywhere else simply because the spinning earth is trying to fling you off nice yes yes it's it's significant so this concept how much do you weigh in i just need a plane ticket it changes your weight it won't change your mass oh let's make that clear okay sucks if you chubby on the equator you're chubby everywhere damn it now here's someone who does not benefit from this and that's of course santa claus because as you go from the equator and you go to farther and farther north or south of course this works the other way uh and you go farther and farther away from the equator the circle that you travel is smaller each day your speed is lower we're here in sort of 40 degrees between 30 and 40 degrees latitude most of the population of the world lives at that latitude and north and south and uh at this latitude we're going about 800 miles an hour due east so that's slower than the equator guess who's not moving sideways at all has no sideways velocity it's santa claus on the north pole all he's doing is sort of rotating like this but he's not getting flung so if you weigh santa claus on the north pole that is his authentic earth weight oh sweet okay which is only 322 pounds it's all them cookies and milk actually he's skinny as a rail during the summer yes as as my seven-year-old told me this year santa claus can't exist i went really why not she said nobody could eat all those cookies without becoming a diabetic oh there we don't know whether he's a diabetic plus it'll be a fun sort of sci-fi film if he gets thin over the summer gets on the sleigh and he's skinny on the sleigh but every stop he makes it gets a little fatter and then the reindeer say we can't do it we can we gotta land this trip i'm done that's pretty good or or he or he gets stuck in the chimney right at some point you're not fitting down the chimney that's all i'm saying that's true so you can ask the question at what speed must earth rotate so that the centrifugal force exactly balances the gravitational weight that you'd otherwise have you might ask that question i just did through you right now so if you spin earth faster and faster and faster right you weigh less and less and less and less so this chuck 190 pounds 185 180 170 150 100 50. there's a point where you will weigh zero and you'll just hover over the equator standing there do you know what speed that is i'll tell you okay if earth rotates once every hour and a half damn okay now that's fast but think about it think about it okay if we rotate once every hour and a half and you're just floating there above the earth you are actually in orbit around the earth that's right okay do you know how long it takes the space station to make one orbit around the earth let me guess 90 minutes ah i you didn't let me guess oh sorry sorry there we go wait wait wait watch this 90 minutes so of course it's a couple hundred miles up so it's a little longer but basically it's in the 90 minute zone okay earth surface up to low what we call low earth orbit leo low earth orbit it all happens in about 90 minutes so you can recover what happens in orbit by spinning the earth so fast that everyone on the equator weighs zero and that happens right when we complete one rotation in basically an hour but i think if you do the math it's 88 minutes but wow good good for these purposes so that's just kind of a fun fact about the rotation of the earth i think that is really cool i mean so you could actually that's like super low earth orbit yes and you don't have to worry about ducking the trees because everybody with you is also orbiting exploding is also floating that's right i left out something earth is slightly flattened at the poles and slightly wider at the equator we might have said this on another explainer so we're oblate we're sort of hamburger shaped rather than prolate which would be hot dog shaped stretched pole to pull where we're flattened at the equator so everyone on the equator is farther away from the center of the earth than people living on the poles people and penguins living near the poles if you're farther away from earth's center the force of gravity on you is less so already their weight is less just because earth is bulbous at the equator relative to the poles then you throw in the rotation on top of it folks on the equator got it made in the shade well watch out atkins diet coming it's a new keto diet it's a new keto diet this super low earth orbit diet earth orbit does super low again diets are so that you lose mass not that you lose weight oh yeah that's just to make that clear forget that and chuck one last thing i said coriolis force was another sort of fictitious force so air pockets going north from the equator overtake the land that they find themselves over because it was going sideways faster than the new place it finds itself okay so it overtakes it air pockets moving due south find themselves on land that's moving faster than they are than they used to be so what happens is if you have a low pressure system air from above it ends up coming in behind it and that creates a general circulation that is counterclockwise for all storms and nearly all tornadoes okay there's some exceptions but it requires extraordinary circumstances to counter balance that so all storms in the northern hemisphere rotate counterclockwise if you sped up earth you increase the coriolis forces and then you have ferocious storms such as what's happening on jupiter ah okay jupiter is way bigger than earth yeah but it's you know 10 times across okay you can fit like 10 earths across the width of jupiter something like that maybe eight earths and jupiter rotates twice as fast as earth does oh there it is so jupiter had the great red spot oh the beautiful red spot it is a storm and it's been raging for more than at least 300 years okay so so these are the consequences of it's a weather man's uh happy place yes i was gonna say yes the weathermen will always have a job on jupiter that is a weather man's dream just like that a 300-year storm yeah i'm never i'll never be fired i've got a lifetime job i shall chuck we got to call it quits there all right all right always good to have you man always good to be here we're done here i've been your host neil degrasse tyson your personal astrophysicist and as always keep looking up

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, earths rotation, earths rotation explained, centrifugal force, super-low earth orbit, low earth orbit, equator

Id: p9MAtyWEjZY

Length: 18min 55sec (1135 seconds)

Published: Tue Feb 02 2021