Give the reason why earth does not have a perfect spherical shape
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Why is the planet Earth not a perfect sphere?
Originally Answered: Why is earth not a perfect circle?
Little Miss Half-a-Geometer says “a circle is all points equidistant from a common center in two dimensions, also the limit case of an ellipse (but don’t worry too much about that second one, it’s really more relevant to orbits than the shapes and topology of planets)” You mean to ask why the earth is not a perfect sphere. And now, to the answer:
Because it’s rotating and with the exception of the very thin crust and a relatively small inner core, the earth is fluid or semi-fluid. When you rotate a fluid in hydrostatic equilibrium (floating ball of fluid), it flattens out due to the increased “centrifugal” force[1] at the equator.
Those who are strong with the geometry may be pretty quick to see that there’s something not quite right about that sentence. And you’re so close to being correct. See, a sphere is every single point equidistant in three dimensions from a common origin. So how can there be more force on the equator than on the poles if the moment arm (distance from the common center) is the same in all relevant directions?
Axis of rotation. The moment arm is measured through the spinning body’s axis of rotation. So that at the poles, the moment arm is negligible, but at the equator, there is a marked difference in the centrifugal force acting on the planet. This means that the equator is stretched more at the equator, hence, not a perfect sphere.
1: Centrifugal force doesn’t actually exist as such. It is an inertial force, so it’s kind of the lack of force. More simply, the reaction force to the centripetal, or center-seeking
Gravitational force remains same everywhere. So, it seems that earth must be perfect sphere. But gravity is not only force working on earth. Earth is slightly wider at equator than across the pole. Cause for that difference is the centrifugal force exerted at equator due to the rotation of earth.
There are many more ways to be an imperfect sphere than to be a perfect one, and no special reason to be a perfect sphere.
In fact, if you start with a perfect sphere, it will gradually move to a slightly perfect sphere … this is because the slightest change will move it away from being perfect. The slightest change from imperfection, on the other hand, is more likely to take it to another imperfect sphere (a different one) than it is to take it towards a more perfect spehere.
If you start out far from perfect, accumulated small changes will shift the shape closer to spherical (knocking off corners for example) until the shape is close enough to perfect that small changes are as likely to add as remove from the perfection.
In the specific case of the earth, the flattened ball shape is a sign of it’s molten past. At that time the Earth was more gooey… since it spins as well, there was a tendancy for the goo to bulge at the equator due to centrifugal effects. The Earth cooled in that shape
Originally Answered: Why is earth not a perfect circle?
Little Miss Half-a-Geometer says “a circle is all points equidistant from a common center in two dimensions, also the limit case of an ellipse (but don’t worry too much about that second one, it’s really more relevant to orbits than the shapes and topology of planets)” You mean to ask why the earth is not a perfect sphere. And now, to the answer:
Because it’s rotating and with the exception of the very thin crust and a relatively small inner core, the earth is fluid or semi-fluid. When you rotate a fluid in hydrostatic equilibrium (floating ball of fluid), it flattens out due to the increased “centrifugal” force[1] at the equator.
Those who are strong with the geometry may be pretty quick to see that there’s something not quite right about that sentence. And you’re so close to being correct. See, a sphere is every single point equidistant in three dimensions from a common origin. So how can there be more force on the equator than on the poles if the moment arm (distance from the common center) is the same in all relevant directions?
Axis of rotation. The moment arm is measured through the spinning body’s axis of rotation. So that at the poles, the moment arm is negligible, but at the equator, there is a marked difference in the centrifugal force acting on the planet. This means that the equator is stretched more at the equator, hence, not a perfect sphere.
1: Centrifugal force doesn’t actually exist as such. It is an inertial force, so it’s kind of the lack of force. More simply, the reaction force to the centripetal, or center-seeking
Gravitational force remains same everywhere. So, it seems that earth must be perfect sphere. But gravity is not only force working on earth. Earth is slightly wider at equator than across the pole. Cause for that difference is the centrifugal force exerted at equator due to the rotation of earth.
There are many more ways to be an imperfect sphere than to be a perfect one, and no special reason to be a perfect sphere.
In fact, if you start with a perfect sphere, it will gradually move to a slightly perfect sphere … this is because the slightest change will move it away from being perfect. The slightest change from imperfection, on the other hand, is more likely to take it to another imperfect sphere (a different one) than it is to take it towards a more perfect spehere.
If you start out far from perfect, accumulated small changes will shift the shape closer to spherical (knocking off corners for example) until the shape is close enough to perfect that small changes are as likely to add as remove from the perfection.
In the specific case of the earth, the flattened ball shape is a sign of it’s molten past. At that time the Earth was more gooey… since it spins as well, there was a tendancy for the goo to bulge at the equator due to centrifugal effects. The Earth cooled in that shape
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Hey mate!
here's your answer
centrfugal force doesn't actullaly exist as such . the earth is by mass mainly liquid iron that is spinning every 24 ~ hours in a day . it is fair to say that the mantel is viscous liquid in behaviour.
hope it will help Full for you
thanking you for asking this question
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aryatripathi47:
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