Why is the earth not exactly spherical?

Answer 1

The correct term is oblate spheroid. Oblique means at an angle other than 90 degrees and not parallel. Oblate means disk shaped. When talking about the Earth oblate refers to the circumference around the equator being larger than the circumference around the north and south poles.

The spin of the earth creates a centrifugal force, which flattens out the earth at the poles. It's something like when you take Pizza dough and spin it in the air - it gets flatter and wider as you spin it around.

Answer 2

In physics, an orbit is the gravitationally curved path of one object around a point or another body, for example the gravitational orbit of a planet around a star.

The reason is: Because that's the way gravity works.

Take Newton's simple equation for the gravitational force and direction, and if you

have enough algebra, geometry, and calculus to be able to massage the equation

for a while, you can show that every closed gravitational orbit is an ellipse. In fact,

you can derive all three of Kepler's 'laws' mathematically ... the first of which is that

the orbits of the planets are ellipses with the sun at one focus.

Answer 3

A couple of reasons:

- the Sun is a changing growing/dying object - it's surface (and gravitational field) are constantly changing both due to internal forces and external objects

- other objects in our solar system, galaxy and universe exert force on the Earth

- Earth is not perfectly round or perfectly dense, it has differing density around the globe

The most likely cause of it following an elliptical path is the effect of other solar bodies.

Answer 4

Well, a very specific speed is required for a circular orbit, for the centrifugal force and gravitation to be in equilibrium. (Note: The centrifugal force is a ficticious force, but it still helps to clarify some concepts.)

Let's assume that a planet goes a little slower than what is required for a circular orbit. Then it will not have enough momentum to maintain the circular orbit, and it will get closer and closer to the Sun. But while it does so, it will also get faster. After half an orbit, it will be fast enough to move away from the Sun again - because of its momentum. Then it will return to the place where it was before.

For me, the question is rather, "why are planet's orbits so close to being circular".

Well, a very specific speed is required for a circular orbit, for the centrifugal force and gravitation to be in equilibrium. (Note: The centrifugal force is a ficticious force, but it still helps to clarify some concepts.)

Let's assume that a planet goes a little slower than what is required for a circular orbit. Then it will not have enough momentum to maintain the circular orbit, and it will get closer and closer to the Sun. But while it does so, it will also get faster. After half an orbit, it will be fast enough to move away from the Sun again - because of its momentum. Then it will return to the place where it was before.

For me, the question is rather, "why are planet's orbits so close to being circular".

Well, a very specific speed is required for a circular orbit, for the centrifugal force and gravitation to be in equilibrium. (Note: The centrifugal force is a ficticious force, but it still helps to clarify some concepts.)

Let's assume that a planet goes a little slower than what is required for a circular orbit. Then it will not have enough momentum to maintain the circular orbit, and it will get closer and closer to the Sun. But while it does so, it will also get faster. After half an orbit, it will be fast enough to move away from the Sun again - because of its momentum. Then it will return to the place where it was before.

For me, the question is rather, "why are planet's orbits so close to being circular".

Well, a very specific speed is required for a circular orbit, for the centrifugal force and gravitation to be in equilibrium. (Note: The centrifugal force is a ficticious force, but it still helps to clarify some concepts.)

Let's assume that a planet goes a little slower than what is required for a circular orbit. Then it will not have enough momentum to maintain the circular orbit, and it will get closer and closer to the Sun. But while it does so, it will also get faster. After half an orbit, it will be fast enough to move away from the Sun again - because of its momentum. Then it will return to the place where it was before.

For me, the question is rather, "why are planet's orbits so close to being circular".

Answer 5

A large Mars sized body impacted the early molten Earth at an oblique angle resulting in a chunk of Earth being torn off of the planet which later formed the moon (which is why the chemical composition of the moon is the same as the Earth). The original inertia of the impacting body led to the ejected mass following the same trajectory as the impactor, but that trajectory was effected when the gravity of the planet captured the new moon, leading to an elliptical orbit. After the moon formed it was much closer to the Earth, but it has slowly been getting farther from the Earth. The gravity of the moon causes the tides and also slows the rotation of the Earth, so a day has gone from about 23 hours to a little over 24 hours. The gravity of the Earth has caused the rotation of the moon to slow to the point where the same side always faces the Earth.

Answer 6

If the Earth was not rotating, it would be. However, it IS rotating and this makes the equator "bulge" out due to centrifugal forces.

The Earth is known as an oblate spheroid because of this.

See related link for more information.

Answer 7

Only at a very specific speed would the orbit be circular. If (for example) the speed is slightly less than that required for a circular orbit, Earth gets closer and closer to the Sun - for a while. While this happens, it also gets faster, and eventually gathers enough momentum to move away from the Sun again - the result is the elliptical orbit.

Answer 8

Because that's the way gravity works. Take Newton's formula for gravitational force,

and if you know enough calculus and geometry to play around with the equation for

a while, you discover that all closed orbits are elliptical, and all open ones are hyperbolic.

Answer 9

Well, a very specific speed is required for a circular orbit, for the centrifugal force and gravitation to be in equilibrium. (Note: The centrifugal force is a ficticious force, but it still helps to clarify some concepts.)

Let's assume that a planet goes a little slower than what is required for a circular orbit. Then it will not have enough momentum to maintain the circular orbit, and it will get closer and closer to the Sun. But while it does so, it will also get faster. After half an orbit, it will be fast enough to move away from the Sun again - because of its momentum. Then it will return to the place where it was before.

For me, the question is rather, "why are planet's orbits so close to being circular".

Answer 10

The laws of motion turn out that this is the way the universe functions with gravity pulling planets in to the Sun and inertia keeping them in orbit.