# Why don't we feel the difference in Earth's angular velocity

• mowi
In summary: This is a bit of a simplification, but yes, things that are farther away from the center of the Earth move faster than things that are closer to the center.
mowi
why don't we feel the difference in Earth's angular velocity between standing on north or south pole versus standing on the equator?
Thank you

The angular velocity (what angle the Earth turns per time unit) is the same at the poles as on the equator. Are you thinking of acceleration?

The angular velocity is the same in both cases, so there is no difference. Are you asking why we can't feel the difference in the tangential velocity?

That is what i meant Drakkith tangential velocity

You can never feel a difference in velocity. You can only feel acceleration.

things farther away from a center of axis cover larger distances than nearer objects within the same timeframe . farther away objects move faster, right?

mowi said:
things farther away from a center of axis cover larger distances than nearer objects within the same timeframe . farther away objects move faster, right?
So what? You cannot feel velocity. You are currently moving at a velocity of ca 30 km/s relative to the Sun. Do you feel that? What distance is covered depends on which reference frame you consider.

Orodruin said:
So what? You cannot feel velocity. You are currently moving at a velocity of ca 30 km/s relative to the Sun. Do you feel that? What distance is covered depends on which reference frame you consider.
if we are in a car moving in circles. when we increase the velocity of the car, we would then feel that change in velocity as being pushed stronger away from the center of the circle!

mowi said:
things farther away from a center of axis cover larger distances than nearer objects within the same timeframe . farther away objects move faster, right?

How much different do you feel on an aeroplane, moving at 1,000 km/h, compared to a car at 100 km/h, compared to walking at 5 km/h?

mowi said:
if we are in a car moving in circles. when we increase the velocity of the car, we would then feel that change in velocity as being pushed stronger away from the center of the circle!

If you are talking about that, how do you know it doesn't feel different at the poles from the equator? Maybe it does feel different?

mowi
mowi said:
if we are in a car moving in circles. when we increase the velocity of the car, we would then feel that change in velocity as being pushed stronger away from the center of the circle!
My emphasis.

Exactly, but this is not due to the velocity, it is due to the acceleration, i.e., change in velocity.

mowi
so my question is why don't i feel the change in velocity if i go on a direct flight from the pole to the equator.

mowi said:
so my question is why don't i feel the change in velocity if i go on a direct flight from the pole to the equator.
Because it is minuscule compared to the Earth's gravitational acceleration.

mowi
Orodruin said:
Because it is minuscule compared to the Earth's gravitational acceleration.
thank you!

mowi said:
thank you!

There's lots online about variations in the Earth's gravity for various reasons:

https://en.wikipedia.org/wiki/Gravity_of_Earth

Interesting fact of the day: if you tunnel down into the Earth, gravity increases for a bit! See the section on "Depth" on the above page.

mowi
mowi said:
if we are in a car moving in circles. when we increase the velocity of the car, we would then feel that change in velocity as being pushed stronger away from the center of the circle!

Orodruin said:
My emphasis.

Exactly, but this is not due to the velocity, it is due to the acceleration, i.e., change in velocity.

To expand a bit on Orodruin's answer, we need to take into account the fact that in a car the centripetal force on your body is provided by contact with the car itself. However, when dealing with the rotation of the Earth, it's gravity that is providing the centripetal force keeping you moving in a circle.

The difference between the two is that the contact force between the car and your body only acts at the surface of your body on your skin. The force on all of your internal organs is transferred from your skin through the physical bonds making up your tissues and organs. Since your body is not a rigid object, things end up shifting around and compressing or stretching a bit depending on where they're located and what they're made up of. All this compression and shifting and such is what you're actually feeling.

In contrast, gravity is not a contact force and can pull on ALL of your organs and tissues at the same time with approximately the same strength. Since there is almost no difference in the strength of gravity on any part of your body you cannot actually feel gravity by itself. An astronaut in orbit is actually in continuous free fall and cannot feel gravity pulling on them. It is only when gravity is opposed by another force, such as the normal force provided by the surface of the Earth, that you feel anything.

The difference in the normal force at the equator and the normal force at the poles is very, very small. Far too small for you to tell the difference between the two.

mowi
Drakkith said:
To expand a bit on Orodruin's answer, we need to take into account the fact that in a car the centripetal force on your body is provided by contact with the car itself. However, when dealing with the rotation of the Earth, it's gravity that is providing the centripetal force keeping you moving in a circle.

The difference between the two is that the contact force between the car and your body only acts at the surface of your body on your skin. The force on all of your internal organs is transferred from your skin through the physical bonds making up your tissues and organs. Since your body is not a rigid object, things end up shifting around and compressing or stretching a bit depending on where they're located and what they're made up of. All this compression and shifting and such is what you're actually feeling.

In contrast, gravity is not a contact force and can pull on ALL of your organs and tissues at the same time with approximately the same strength. Since there is almost no difference in the strength of gravity on any part of your body you cannot actually feel gravity by itself. An astronaut in orbit is actually in continuous free fall and cannot feel gravity pulling on them. It is only when gravity is opposed by another force, such as the normal force provided by the surface of the Earth, that you feel anything.

The difference in the normal force at the equator and the normal force at the poles is very, very small. Far too small for you to tell the difference between the two.
thank you!

Orodruin said:
Because it is minuscule compared to the Earth's gravitational acceleration.
So, to expand on the answer to the question @mowi really intended to ask; the rotation of the Earth does impact the surface gravity -- or, rather, it causes the surface to not be perfectly spherical, which means that when you are on a pole, you are closer to Earth's center and thus the gravitational acceleration is higher than at the equator. In addition, the centrifugal force itself reduces your apparent weight on the equator. Further description and magnitude of the two effects (from PeroK's link):
The surface of the Earth is rotating, so it is not an inertial frame of reference. At latitudes nearer the Equator, the outward centrifugal force produced by Earth's rotation is larger than at polar latitudes. This counteracts the Earth's gravity to a small degree – up to a maximum of 0.3% at the Equator – and reduces the apparent downward acceleration of falling objects.

The second major reason for the difference in gravity at different latitudes is that the Earth's equatorial bulge (itself also caused by centrifugal force from rotation) causes objects at the Equator to be farther from the planet's centre than objects at the poles. Because the force due to gravitational attraction between two bodies (the Earth and the object being weighed) varies inversely with the square of the distance between them, an object at the Equator experiences a weaker gravitational pull than an object at the poles.

In combination, the equatorial bulge and the effects of the surface centrifugal force due to rotation mean that sea-level effective gravity increases from about 9.780 m/s2 at the Equator to about 9.832 m/s2 at the poles, so an object will weigh about 0.5% more at the poles than at the Equator.
https://en.wikipedia.org/wiki/Gravity_of_Earth

The difference in weight between the equator and the pole of an average adult is approximately the same as before and after emptying your bladder. Do you feel especially lighter after you pee?

BoB

Orodruin
The polar axis of the Earth is smaller than the equatorial radius. This makes people heavier at the poles than at the equator. The difference in radii in the Earth Ellipsoid is an even greater difference that the centrifugal force contribution to gravity.

The acceleration due to gravity swamps the centrifugal force due to Earth's rotation, which only causes you to feel about 0.3% lighter at the equator than the pole - re: http://image.gsfc.nasa.gov/poetry/ask/a11511.html. So weighing out in Brazil is not going to help you much on 'Biggest Loser'.

mowi said:
so my question is why don't i feel the change in velocity if i go on a direct flight from the pole to the equator.

Because Mother Nature did not equip our inner ear with the extreme sensitivity to detect that miniscule acceleration.

Artillerymen are usually credited with figuring out a practical use for your Coriolis effect. Sometimes Napoleon, sometimes the WW1 Germans. Cannonballs were the only thing that moved fast enough you had to worry about it.

http://warfarehistorynetwork.com/daily/military-history/world-war-i-weapons-germanys-big-guns/
With all the scientific calculations and engineering problems engendered by this project, the research of Coriolis was reviewed by Professor von Eberhardt, and an additional adjustment made. Having been advised that the projected firing site was in the forest of Crépy-en-Laonnois, near Laon, and the target Paris, he calculated the distance between the two as 67.6 miles. The firing vector was close enough to a north-south axis, bringing the Coriolis Effect into play. Coriolis and von Eberhardt knew that Laon and Paris were traveling at different speeds. Although each rotated once in 24 hours, Laon was farther from the equator than Paris and thus moving somewhat slower in miles per hour. A point on the equator travels at 1041.66 mph.

Eberhardt estimated a rotational speed of 567.126 mph at Paris on the 49th parallel, and 555.55 mph at Laon on the 48th parallel. An adjustment of 11.576 mph, or .003215 miles per second, had to be provided for in the laying of the gun.

The final calculations were assembled. To achieve the required muzzle velocity, a chamber pressure of 59,000 pounds per square inch had to be reached. Flight time was predicted at 176 seconds. This called for an easterly correction of 0.5659 miles or roughly 995.984 yards to compensate for the differing rotational speeds of gun and target. On March 23, 1918 everything was ready to go.

old jim

The Coriolis effect comes into play in long range rifle shooting. It is usually under 6" at 1000 yards, but of course one needs to take care not to adjust the sights shooting N to S and then engage the target shooting S to N, because then your error relative to the target is twice the Coriolis effect.

Dr. Courtney said:
one needs to take care not to adjust the sights shooting N to S and then engage the target shooting S to N, because then your error relative to the target is twice the Coriolis effect.

Sounds not right to me but i think it's just imprecision of English language...

Standing on the equator shooting at something farther north,
one has to aim left(west) because round's velocity has an easterly component greater than that of target. Gun is moving east faster than target. Aiming directly at target would land projectile ahead of target, to its east.

Swapping places now, shooting south back toward the equator,
one must again aim left, this time east, because round's velocity has an easterly component smaller than that of target. Target is moving east faster than gun. Aiming directly at target would land projectile behind target, to its west.

Did you mean
Dr. Courtney said:
one needs to take care not to re-adjust the sights between shooting N to S and then engaging the target shooting S to N, because then your error relative to the target would be twice the Coriolis effect.

i think you did . All i did is try to address a possible mis-interpretation.

Last edited:
Bystander
jim hardy said:
Sounds not right to me but i think it's just imprecision of English language...

Standing on the equator shooting at something farther north,
one has to aim left(west) because round's velocity has an easterly component greater than that of target. Gun is moving east faster than target. Aiming directly at target would land projectile ahead of target, to its east.

Swapping places now, shooting south back toward the equator,
one must again aim left, this time east, because round's velocity has an easterly component smaller than that of target. Target is moving east faster than gun. Aiming directly at target would land projectile behind target, to its west.

Did you meani think you did . All i did is try to address a possible mis-interpretation.

Yes. Thanks for help clarifying.

jim hardy

## 1. Why don't we feel the difference in Earth's angular velocity?

The Earth's angular velocity, or its rate of rotation, is relatively slow compared to other objects in the universe, such as planets and stars. This slow rotation is what allows us to experience a stable and constant sense of gravity, making it difficult for us to feel the Earth's angular velocity.

## 2. Is it possible to feel the Earth's angular velocity?

Technically, yes, it is possible to feel the Earth's angular velocity. However, the sensation would be extremely subtle and difficult to detect. Additionally, our bodies have adapted to the Earth's rotation, so we do not typically perceive any significant motion or changes in our surroundings.

## 3. How does the Earth's angular velocity affect our daily lives?

The Earth's angular velocity is responsible for the length of our days and nights, as well as the changing of the seasons. Additionally, it plays a role in ocean tides and the Earth's magnetic field. However, these effects are not directly felt by humans in our daily lives.

## 4. Does the Earth's angular velocity change over time?

Yes, the Earth's angular velocity is constantly changing, but these changes are very small and occur over long periods of time. This is due to various factors such as the Earth's orbit around the Sun, the Moon's gravitational pull, and the Earth's own internal dynamics.

## 5. How is the Earth's angular velocity measured?

The Earth's angular velocity is measured using a unit called degrees per hour (°/hr). This unit represents the amount of rotation the Earth undergoes in one hour. It can also be measured in radians per second (rad/s), which is a more precise unit commonly used in scientific calculations and experiments.

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