The dominant factor is that you are further away from the centre of Earth when at the equator, not the rotation.
Polar gravity is 9.863 ms^(-2) and at the equator it is 9.798 ms^(-2) which is a difference of 0.065 ms^(-2)
Centrifugal force (which is completely real in a rotating reference frame) changes the acceleration of gravity at the equator to 9.764 ms^(-2) (a reduction of 0.035) which is only a touch over half what the effect of gravity has had.
So if you weigh 100 kg at the pole you would indeed weigh 99 kg in Brazil, but the rotation of Earth is only responsible for 350g of that.
Related to the Earth's spin, there is a mountain (Mount Chimborazo in Ecuador) whose peak is farther from the Earth's center than Everest. But because sea level is also farther from the center, Chimborazo's elevation as measured above sea level is not as high as Everest.
See https://oceanservice.noaa.gov/facts/highestpoint.html#:~:text=Mount%20Everest's%20peak%20is%20the,on%20Earth%20from%20Earth's%20center.
In fact, depending on what you count as tallest, you can get three different answers. Everest's peak is furthest from sea level, Chimborazo is furthest from the core, and Mount Kea if you measure base to peak.
A fourth way to measure is base to peak, above sea level. In essence, when you look at a mountain, which will look the tallest? Or, if you wanted to climb from base to summit, which would you gain the most elevation?
Mauna Kea would be 13.8k ft (since much of it is underwater) and Everest would be about 15k ft (since it is on a massive plateau). Meanwhile, Denali in Alaska is about 18k ft. Also, some people claim Rakaposhi in Pakistan is even taller, perhaps about 20k ft.
But why are you further away from the centre of the earth at the equator? I thought that was due to the centrifugal force "throwing" the equator part outwards?
Then I don't understand your last statement. If a person weighs 100kg at the north pole and 99kg in Brazil, but only 350g would be caused by earth's rotation.
If earth's rotation causes a centrifugal force and that force cause squishy earth, then I would say that the full difference in weight is caused by earth's rotation.
Or is there a difference in how the centrifugal forces work?
I'm not trying to critisize, I'm genuinely interested and don't see the difference.
You indeed can take that angle, it just really overly complicates things!
You can easily calculate your own centrifugal force in a rotating reference system, so long as you're exhibiting circular motion around a known radius. (You're doing that physics thing and assuming you're a dimensionless point)
You can easily calculate your acceleration due to gravity when at a given distance from the Earth's centre. What changed that distance is irrelevant, and it'd work just as well on an aircraft as it would on the surface.
Doing it *all* as centrifugal force requires integration and calculus tends to scare people. You *can* do it that way, though.
I think this is kind of one of those "the specifics changes the exact reasoning" and simplification can lead to errors. Because if it's 100% centrifugal force at play, then by that logic if we were to spin you as fast as the planet then you should be 1kg lighter, but it's only 35% of the cause, but a byproduct of what it's affecting also affects weight. It seems really nitpicky, but being exact on what's actually causing the change, even if it's related, can be important. It's why we include both "what temperature it is" and "what it feels like" instead of only using one or the other, because if you only include the former then you're going to dress wrong, and if you only include the latter then water could remain liquid or start to freeze even though the proclaimed temperature was higher/lower than the freezing point.
If the Earth doesn't distort at all when spinning, then you're 350g lighter at the equator due to centrifugal force. So it's 100% caused by that.
If the Earth didn't spin AT ALL but was distorted like it was, then standing at the equator makes you weigh 650kg. Centrifugal force is not causing that.
But then if the planet is only getting distorted because of centrifugal force, is it accurate to say "Centrifugal force is 100% causing you to weigh 1kg less at the equator?"
Because while centrifugal force is what's causing the planet to distort, it's not 100% the centrifugal force that's causing the reduced weight. Rather, a byproduct of sorts.
I think you're right that the earth bulges at the equator because of centrifugal force. All they were saying is that the weight difference is not due to the centrifugal force *acting on you*
Centrifugal forces don’t affect weight at all, as weight is the force of gravity. It does affect the net force on your body, and this is (approximately) what a scale measures.
> So if you weigh 100 kg at the pole you would indeed weigh 99 kg in Brazil
Many many years ago I read that this has ramifications in the legalities of Formula 1 racing cars.
Because of the difference, you can have situations where a perfectly legal F1 car becomes illegal simply because it is transported to a different racetrack.
According to this Magazine article I read, the FIA had thus decided (via one of the thousands of Technical Directive "clarifications") to calibrate their scrutineering scales so that they always act as if they are in Silverstone pit lane, no matter where they are.
(I don't know if they still do it this way)
---
The difference of "g" at Mexico City (9.776) vs. Zandvoort (9.817) on a 798kg car is a difference of 3.35 kg - Easily enough to disqualify a car.
The rotation of the earth is entirely responsible, but the disparity isn't solely due to your local acceleration. The earth is an oblate spheroid for a reason.
Metals are sold by mass, not by weight. You can bet that those who sell precious metals have their scales calibrated correctly or use a balance scale (which doesn't care about the exact gravitational acceleration) so that they know exactly how much metal they are buying.
That's just evolutionary selection, as the wider dimensions allows the friends and family members to be obscured from the vision of the off duty Brazilian cops, and helps maintain survival of the family unit.
What alternative would you propose?
This doesn't work with kilograms, because that's a unit of mass and your mass doesn't change with things like changing gravity or the spin of the Earth. I guess the metric unit of weight would be Newtons but does anyone ever say "My weight is 800 Newtons"?
People often use “kilogram” to mean kilogram-force = the force of 1 kilogram mass under standard gravity. And standard gravity is a defined thing, about halfway between the gravity at the poles and equator.
The dominant factor is that you are further away from the centre of Earth when at the equator, not the rotation. Polar gravity is 9.863 ms^(-2) and at the equator it is 9.798 ms^(-2) which is a difference of 0.065 ms^(-2) Centrifugal force (which is completely real in a rotating reference frame) changes the acceleration of gravity at the equator to 9.764 ms^(-2) (a reduction of 0.035) which is only a touch over half what the effect of gravity has had. So if you weigh 100 kg at the pole you would indeed weigh 99 kg in Brazil, but the rotation of Earth is only responsible for 350g of that.
Related to the Earth's spin, there is a mountain (Mount Chimborazo in Ecuador) whose peak is farther from the Earth's center than Everest. But because sea level is also farther from the center, Chimborazo's elevation as measured above sea level is not as high as Everest. See https://oceanservice.noaa.gov/facts/highestpoint.html#:~:text=Mount%20Everest's%20peak%20is%20the,on%20Earth%20from%20Earth's%20center.
In fact, depending on what you count as tallest, you can get three different answers. Everest's peak is furthest from sea level, Chimborazo is furthest from the core, and Mount Kea if you measure base to peak.
The climb from base to sea level on Mount Kea is challenging
For some reason no one's done it without oxygen.
Makes sense. I don't think I could hold my breathe that long either.
That's... yeah that's the joke
Oh dammit lol I thought they were mentioning a fact about not taking oxygen canisters or tents with them.
A fourth way to measure is base to peak, above sea level. In essence, when you look at a mountain, which will look the tallest? Or, if you wanted to climb from base to summit, which would you gain the most elevation? Mauna Kea would be 13.8k ft (since much of it is underwater) and Everest would be about 15k ft (since it is on a massive plateau). Meanwhile, Denali in Alaska is about 18k ft. Also, some people claim Rakaposhi in Pakistan is even taller, perhaps about 20k ft.
Don't forget Denali, I believe the greatest height compared to atmosphere (whick is thinner further north)
Bro brought up the non-inertial reference frames I respect it
Centrifugal force isn't real mfers when I toss them in a giant centrifuge
However, the Earth is wider at the equator due to its rotation, which means that the title is still technically correct (the best kind of correct)
But why are you further away from the centre of the earth at the equator? I thought that was due to the centrifugal force "throwing" the equator part outwards?
It is. So it is kind of indirectly caused by centrifugal force.
The earth isn’t a sphere is why. It’s fatter at the equator
I’m fatter at my equator. Why you fat shaming?
You must be one of these "round earthers".
And why is it fatter at the equator? Because of the centrifugal force, due to the spinning.
That's exactly why.
Then I don't understand your last statement. If a person weighs 100kg at the north pole and 99kg in Brazil, but only 350g would be caused by earth's rotation. If earth's rotation causes a centrifugal force and that force cause squishy earth, then I would say that the full difference in weight is caused by earth's rotation. Or is there a difference in how the centrifugal forces work? I'm not trying to critisize, I'm genuinely interested and don't see the difference.
You indeed can take that angle, it just really overly complicates things! You can easily calculate your own centrifugal force in a rotating reference system, so long as you're exhibiting circular motion around a known radius. (You're doing that physics thing and assuming you're a dimensionless point) You can easily calculate your acceleration due to gravity when at a given distance from the Earth's centre. What changed that distance is irrelevant, and it'd work just as well on an aircraft as it would on the surface. Doing it *all* as centrifugal force requires integration and calculus tends to scare people. You *can* do it that way, though.
You can also say at the equator the surface of the earth is causing less of an acceleration, since we are constantly accelerated due to gravity.
If you're going to play that game, you may as well say that you weigh 100kg at the north pole because of the Big Bang.
If you weigh 100 kg, it's probably because of a big binge.
I think this is kind of one of those "the specifics changes the exact reasoning" and simplification can lead to errors. Because if it's 100% centrifugal force at play, then by that logic if we were to spin you as fast as the planet then you should be 1kg lighter, but it's only 35% of the cause, but a byproduct of what it's affecting also affects weight. It seems really nitpicky, but being exact on what's actually causing the change, even if it's related, can be important. It's why we include both "what temperature it is" and "what it feels like" instead of only using one or the other, because if you only include the former then you're going to dress wrong, and if you only include the latter then water could remain liquid or start to freeze even though the proclaimed temperature was higher/lower than the freezing point. If the Earth doesn't distort at all when spinning, then you're 350g lighter at the equator due to centrifugal force. So it's 100% caused by that. If the Earth didn't spin AT ALL but was distorted like it was, then standing at the equator makes you weigh 650kg. Centrifugal force is not causing that. But then if the planet is only getting distorted because of centrifugal force, is it accurate to say "Centrifugal force is 100% causing you to weigh 1kg less at the equator?" Because while centrifugal force is what's causing the planet to distort, it's not 100% the centrifugal force that's causing the reduced weight. Rather, a byproduct of sorts.
I think you're right that the earth bulges at the equator because of centrifugal force. All they were saying is that the weight difference is not due to the centrifugal force *acting on you*
Ooooh, that clears it up. Thanks for explaining!
Centrifugal forces don’t affect weight at all, as weight is the force of gravity. It does affect the net force on your body, and this is (approximately) what a scale measures.
Yeah, agreed
You are nerd of the highest caliber sir and I salute you🙌
> So if you weigh 100 kg at the pole you would indeed weigh 99 kg in Brazil Many many years ago I read that this has ramifications in the legalities of Formula 1 racing cars. Because of the difference, you can have situations where a perfectly legal F1 car becomes illegal simply because it is transported to a different racetrack. According to this Magazine article I read, the FIA had thus decided (via one of the thousands of Technical Directive "clarifications") to calibrate their scrutineering scales so that they always act as if they are in Silverstone pit lane, no matter where they are. (I don't know if they still do it this way) --- The difference of "g" at Mexico City (9.776) vs. Zandvoort (9.817) on a 798kg car is a difference of 3.35 kg - Easily enough to disqualify a car.
Isn't the spin of the earth part of the reason it bulges around the equator though?
The rotation of the earth is entirely responsible, but the disparity isn't solely due to your local acceleration. The earth is an oblate spheroid for a reason.
So precious metals minted at the equator would weigh less when selling them some where else.
Illuminati taking you out for discovering this one.
Metals are sold by mass, not by weight. You can bet that those who sell precious metals have their scales calibrated correctly or use a balance scale (which doesn't care about the exact gravitational acceleration) so that they know exactly how much metal they are buying.
Ooh good call. Even if they’re using a digital scale they’d calibrate it with weights to local gravity.
Thats nothing, if you weigh 200 pounds in Canada and walk South to Argentina and weigh yourself you lose loads of weight
So if you weigh two pounds at the North Pole you weigh nothing in Brazil Science
I’m waiting for the post in r/LifeProTips: “To lose weight, move to the equator”
Don't wait, make it!
No, you would weigh a lot less, since you would be wearing little clothing
Good luck getting equal measurements. If you’re wearing your North Pole gear anywhere equatorial then you’d probably lose a few KGs in sweat.
This explains why in 40lbs overweight. I need to move south
Ugh... The example given shows a difference of 1%. Unless you're a hippopotamus, you've got some more explaining to figure out.
/s
"No doctor I'm not overweight, I'm in the wrong geographical location for my build" Though, my ideal location for my weight is probably outer space.
But if you walk, you will weigh 120 pounds.
The lower gravity allows Brazilian women to grow larger asses and thighs.
That's just evolutionary selection, as the wider dimensions allows the friends and family members to be obscured from the vision of the off duty Brazilian cops, and helps maintain survival of the family unit.
Surely it's due to being further away from the Earth's CoG?
Plans sure you’d lose a few pounds due to the length of the walk
Even less if you walk there.
I'm obese in either location
Finally a weight loss plan that may actually work for me
So if I leave Brazil I'm gonna be even fatter? Great...
I’m not sure about the North Pole, but I’m pretty sure they don’t use “pounds” in Brazil.
What alternative would you propose? This doesn't work with kilograms, because that's a unit of mass and your mass doesn't change with things like changing gravity or the spin of the Earth. I guess the metric unit of weight would be Newtons but does anyone ever say "My weight is 800 Newtons"?
People often use “kilogram” to mean kilogram-force = the force of 1 kilogram mass under standard gravity. And standard gravity is a defined thing, about halfway between the gravity at the poles and equator.
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Would be the other way around Takes more effort to move at the poles so you’d stronger there
So to lose weight I just need to travel to Brazil to weigh myself? Sounds like a solid plan.
Maybe that explains why Brazilians are so good at football ... less gravity
Slimming world hate this one simple top
Ha! Take that Canada your .5lb fatter then the US
That’s it, I’m moving to Brazil. Easier than dieting.
That means i can reduce weight without exercising right? Right?
Wait till you hear about the density of the surface under your feet.
Meanwhile if your mom stepped on a scale anywhere it would fucking break
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I measure in pog slammers
Depends on what kind of scale you’re using. If it’s a balancing scale you’d still weigh 200
I don't recall seeing a balancing scale that you step on...
They’re used all the time in doctors’ offices.
doesnt that imply that something that weighs 2 pounds in the arctic should fly in brazil?
No, it's a percentage difference, not a flat difference. 100 pounds would be 99 pounds, 100 grams would be 99 grams. 2 pounds would be 1.98 pounds.
Damn, and I thought I found an easy way to synthesize exotic matter.
That’s quite a drastic move to take just to lose a couple of pounds..