Linked Questions
64 questions linked to/from Why is the Earth so fat?
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Why is the Earth not an exact sphere and what makes it bulge at the equator? [duplicate]
In chapter 7 of the Feynman Lectures Volume 1, Feynman explains that the Earth is round due to gravitation as everything attracts everything else. He also says that it is not an exact sphere since it ...
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1
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If Earth is oblate why don't oceans flow to the Poles? [duplicate]
The Poles are ~21 km downhill from the equator in a spherical coordinate system.
So why doesn't water pool there?
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4
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155
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What is the real shape of Earth? [duplicate]
As it now widely dicussed and accepted that Earth is not a 'perfectly round sphere/ball but more a 'oblate spheroid' why then do NASA have 'photographs' of a ROUND Earth?
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The Earth's Equatorial Bulge [duplicate]
It is stated that the Earth is a 'squashed sphere' due to the very slight bulge at the equator. (Thought in reality it's such a small difference, it's essentially spherical)
Typical values:
...
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Correcting for oblateness of the Earth [duplicate]
I'm trying to model numerically the effects of the Earth's oblateness on satellite orbits. I'm seeing precession of the orbit, but not in the plane that I'm expecting. Here's my corrected grav. ...
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How can we explain Saturn's non-spherical shape in terms of forces? [duplicate]
As we know the Saturn's shape is not spherical. In fact, its polar radius is almost 10% smaller than equatorial radius. This flattening is caused by the rapid rotation of this planet.
Image credit: ...
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Equation to predict the shape of a planet [duplicate]
I need help calculating gravity and shape of a planet based on a few factors.
If a mass rotates quickly enough, the inertia (or "imaginary centrifugal force") will pull the mass outward "...
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Estimation of Equatorial Bulge of the Earth [duplicate]
My dynamics lecture notes repeat the Earth's equatorial bulge can be approximated as:
$$ \approx \frac{\Omega^2R}{g} \approx \frac{1}{300} $$
(Do they mean R/300?)
They also include statements like:
...
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Why spinning creates bulges? [duplicate]
Earth isnt a perfect but has bulges because of its spinning. What actually creates the bulges? Is the same reason that makes a liquid have v shape in a rotational tube?
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27
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Simple check for the global shape of the Earth
I have been on a date recently, and everything went fine until the moment the girl has told me that the Earth is flat. After realizing she was not trolling me, and trying to provide her with a couple ...
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Proof that the Earth rotates?
What is the proof, without leaving the Earth, and involving only basic physics, that the earth rotates around its axis?
By basic physics I mean the physics that the early physicists must've used to ...
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7
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If the ground's normal force cancels gravity, how does a person keep rotating with the Earth?
When I am on earth, the weight of my body is countered by the reaction of the ground. So, there is no net force acting on me.
But I am spinning with earth. But if there is no centripetal force then ...
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3
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Why is the Sun almost perfectly spherical?
Relatively recent measurements indicate that the Sun is nearly the roundest object ever measured. If scaled to the size of a beach ball, it would be so round that the difference between the widest ...
user81619
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9
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Is Earth really flattened at the poles because of centrifugal force?
My question is pretty much all in the title. I was always told that our planet is flattened at its poles due to the centrifugal force generated by its own rotation. However I don’t see how centrifugal ...
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Would a giant ball on earth roll towards the poles?
The radius of the earth is higher at the equator than at the pole. Would it mean then, that if I put a giant ball at the equator, it would roll up towards the pole? Why, why not?
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Why is Earth's gravity stronger at the poles?
Many sources state that the Earth's gravity is stronger at the poles than the equator for two reasons:
The centrifugal "force" cancels out the gravitational force minimally, more so at the equator ...
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Distribution of gravitational force on a non-rotating oblate spheroid
Suppose a person is standing on a non-rotating$^1$ oblate spheroid of uniform density. He first stands on one of the poles, then on the equator. In which case is the gravitational force greater?
In ...
user49111
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How can the Moon have such a strong effect on the ocean?
The gravitational acceleration on Earth is approximately $ 10 \mathrm{m}/\mathrm{s}^2 $. Compared to this, the tidal effect of the Moon's gravity gives a local variation in the acceleration of ...
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4
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How do we know that Earth is not perfect sphere?
I've just read here that:
Equatorial radius = 6378.16 kilometers. Polar radius = 6356.78
kilometers, so the difference in circumference is 71.1 kilometers. It
is not a perfect sphere, but kind ...
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Earth as a perfect sphere and an object trying to stand still
I have imagined the Earth as a perfect sphere with uniform mass density and I put an object somewhere between the equator and the north pole at rest with respect to earth. And also in my imaginary ...
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Why don't we consider centrifugal force on a mass placed on earth?
Let us say a block of mass is placed on the surface of earth. Then while drawing the forces on that body, we say:
Force $F = mg$ acting towards the center of Earth.
Normal reaction $N$ offered by the ...
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3
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Does Earth's Rotation Affect Its Shape?
The question I am working on is, "Consider the following.
(a) Find the angular speed of Earth's rotation about its axis. rad/s
(b) How does this rotation affect the shape of Earth?"
I am ...
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Toroidal Planets
I have read online in numerous places about the possible existence of toroidal planets, and I most people seem to believe that they could exist, but they also have no evidence to support this claim. I ...
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How the apparent weight varies due to the rotational motion of Earth?
I learned that as the earth rotates about its axis, the bodies on the earth also follow a circular path. In most books I read, they give the example of a person standing on a weight balance at the ...
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What is an intuitive explanation using forces for the equatorial bulge?
The earth is not a sphere, because it bulges at the equator.
I tried fiddling with centripetal force equations and gravity, but I couldn't derive why this bulge occurs.
Is there
(a) a ...
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Saturn's polar versus equatorial gravity
Wikipedia's reference for Saturn's gravity gives $10.44 m/s^2$ at the equator, but this conflicts with Britannica, which gives $8.96 m/s^2$ at the equator and $12.14 m/s^2$ at the poles. All values ...
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Dark matter and tides
As I understand, "dark matter" is what they call a theoretical substance which is only known by it's influence upon velocity curve of the galaxy.
If indeed the gravity of "dark matter&...
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Centripetal force at the pole is different from the equator
why is the centripetal acceleration in the poles and equator if different? I know that it's related to Equatorial budge. But what I don't get it is that the centripetal force is zero at the poles. ...
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Rotational oblateness
I am trying to compute the amount of oblateness that is caused by planetary rotation. I picture the force of gravity added to the centrifugal force caused by the rotation of the planet as follows:
$\...
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Is effective gravity constant over the surface of the ocean?
According to Wikipedia:
The Earth is not spherically symmetric, but is slightly flatter at the poles while bulging at the Equator: an oblate spheroid. There are consequently slight deviations in ...
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How to theoretically calculate the value of gravitational acceleration of my town?
We normally consider the value of gravitational acceleration $g = 9.8 m/s^2$ while solving the problem. But that is the value of $g$ at poles (if I am not wrong).
My teacher have given as homework ...
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Does General Relativity correctly explain the ellipsoidal shape of the earth?
Does General Relativity theory correctly explain the ellipsoidal shape of the earth?
It seems it does not because the Thirring expression¹ for the force of a spherical shell—of mass $M$, radius $R$, ...
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Intuition $\neq$ Diagram: Weight on North Pole vs Equator
This is a common physics exercise:
Suppose the earth is a sphere of radius $6370$ km. If a person stood on a scale at the north pole and observed the scale reading (his weight) to be $mg$, what ...
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The shape of the earth$\ldots$
....is an oblate spheroid because centrifugal force stretches the tropical regions to a point farther from the center than they would be if the planet did not rotate. So we all learned in childhood, ...
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Air pressure at ground level at the equator and the poles
At the equator at sea level you are about 17 miles higher up than at the poles ie 17 miles further from the center of the earth. Yet the air is not the same as it would be 17 miles up at a higher ...
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Will the Earth flatten out?
Since the rotation of the earth makes it more flat,due to the centrifugal forces, is it not possible for the force to completely flatten out earth into a plane ?
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How does the inner core relieve stress as the Earth's rotation slows?
One of the surprises for me in working out the answer to this question: Why is the Earth so fat? , is that the core is more elliptical than the surface, the extra ellipticity builds up gradually to ...
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How to explain the Earth's Equatorial bulge without centrifugal force?
There are many answers to the question why is the Earth bulged at the equator, see e.g. here, but almost all of them involve centrifugal force. Since it's a fictitious force, how to we explain this ...
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If the Earth rotated slower about its axis, would your apparent weight increase or decrease?
The title above was a question on an exam that was marked wrong for me. I answered that if the Earth rotated slower (i.e. longer days), my apparent weight would increase. I based this on the ...
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2
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What effect does gravity have on a spinning object? [closed]
If gravity was the only force present would gravity, beside pulling, also stop the rotation / spin of a small object its pulling towards it over time?
What would be the effect on an uneven object and ...
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1
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New theory on gravitational force calculation [closed]
Calculation of gravitational force:-
Suddenly it came to my mind on 19th November night that the current calculation of gravitational force is not correct and calculation should be divided into two ...
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Is it mathematically accurate to simply objects to point masses when calculating gravitational forces between them? or is it just an approximation?
I tried searching for the exact mathematical proof that validates this assumption, but I couldn't find any.
Also, is this assumption still accurate if the density of the object resembles a planet (...
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What is happening with the horizontal component of the Earth's centrifugal acceleration?
We know that the equator has the highest centrifugal acceleration caused by the rotation of the earth (a = 0.034m / s2) but it is negligible because the vector of the acceleration of gravity is much ...
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1
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Why doesn't water accumulate at the Equator under the influence of the centrifugal force of the Earth's rotation?
During the rotation of the Earth, a centrifugal force is formed, according to the actions of which ocean water should be collected at the Equator, forming a "hump" hundreds of meters high.
...
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Reaction force of the ground beyond the equator
Let's imagine a person standing somewhere on Earth, but not on the equator, i.e. somewhere with a positive net value of latitude.
Since the Earth spins around its axis and the person spins along, the ...
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2
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Does gravity play a role in the Earth's equatorial bulge? [duplicate]
I'm trying to understand why the Earth bulges at the equator. But before looking at the Earth, which introduces gravity, I wanted to make sure I understood the shape of some rotating objects and if/...
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3
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Does gravity cause the Earth's equatorial bulge?
The way I understand centrifugal force, I don't see how Earth's daily rotation alone would cause equatorial bulges to form. The usual explanation is that the centrifugal force increases with distance ...
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Deformation of Earth caused by centrifugal force
The centrifugal force causes a distension at the equator. With a simple model we can estimate the dimension of this deformation ellipsoid. We start with a mass $m$ at the point $P$ on the surface of ...
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Earth's rotation isn't that orbit?
If the earth is rotating at some $465~\text{m}/\text{s}$ at the equator and that's really fast.
Shouldn't we in that case be in orbit with the earth just not fast enough?
How fast do we need to move?...
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Analytical expressions for acceleration due to zonal harmonics of a gravitational field?
Wikipedia's Geopotential_model; The deviations of Earth's gravitational field from that of a homogeneous sphere discusses the expansion of the potential in spherical harmonics. The first few zonal ...
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