why does the shape of the orbit of the earth is oval instead of circle although equal force acts on it by sun?

Question

earth experiences equal force by the sun at each place in the space but the shape of the orbit of the earth is elliptical.Why????????

Answer 1

I apologize but, the earth's rotation has nothing to do with it.

To answer your question, we need to think more generally about orbiting bodies.

How does an object enter an orbit?
At some point the object gets close enough to a relatively massive object and it's gravity starts to pull the object inward. Once this happens there are four possibilities:

1) The energy of the object is so strong that it slingshots around the massive object. (hyperbolic)

2) The energy of the object is so weak, that it spirals inward towards the object and collides (spiral)

3) The energy of the object is exactly right so that the object enters a circular orbit. (circular)

4) The energy of the object is between that of a hyperbolic behavior (1) and a circular behavior (3).

Now back to the earth:
The earth is an example of the 4th orbit. It would only have a circular orbit if it happened, which is a very low probability, to have exactly the right amount of energy to orbit the sun in a circle.

In a nutshell, the orbit of the earth is elliptical because when it first started orbiting the sun, it's initial energy was not equal to that required for a circular orbit. Which had a extremely low probability of happening in the first case.

Answer 2

Great question! I had to do some research here.

My suspicion was that an ellptical orbit is more stable than a circular orbit, and something like that appears to be the case.

Check out the link below for a better explanation than I can give, but as I understand it, we can (for instance) launch a satellite into Earth orbit that has a perfectly circular orbit. This is tough to do, though.

There are two forces acting upon the satellite: gravity, and its own inertia. Its inertia naturally proceeds along a straight line, but gravity pulls it towards Earth; the resultant of these two forces pulls it back towards Earth, so you have an orbit.

A perfectly circular orbit implies that the ground speed of the satellite (velocity of satellite with respect to the nearest point to it on the Earth's surface) is constant.

But the two forces on the satellite, inertia and gravity, must perfectly cancel in this case! As I said, this is hard to do. It makes sense then that the Earth has an elliptical orbit, because the system is not perfect.

If it were perfectly circular, wow. That would be very odd. Does this help?

Answer 3

The time evolution of a mechanical system is determined by 2nd orther differential equations. In orther to know the position at any instant you should know not only the forces acting on it (which are the second derivatives with respect to time of the position vector) but also initial conditions i.e. position and momentum at the initial time t=0. The system then evolves differently according to the initial condition. Just for a given choice of the initial conditions will the orbit be a perfect circle.

The Spherical Symmetry of the gravitational field which you invoke is NOT responsible for the circular shape of the orbit , but for the conservation of Angular Momentum during the time evolution (and for the orbit to be planar which is a consequence of that)

Answer 4

Each planet in the solar system exerts some gravitational force on the Earth and each of the other planets. Calculating the exact effect on one planet is an extremely complex problem so, although the Sun has the largest effect, the total effect leaves Earth with an elliptical orbit.

Answer 5

Depending upon the location of the object and the speed the orbit can be one of the following. Ellipse, circle, parabola, hyperbola.

The circular orbit is unique and a special case of elliptical orbit . So it is difficult to achieve where as elliptical orbit is very easy. Throw anything if doesn't crash it will be in elliptic orbit.

Answer 6

Compared to the mass of Sun, the mass of a planet is small.

Hence we assume that the Sun is fixed and apply law of gravitation. In that case we get circular orbit. This is only approximation and not correct.

If we consider the center of mass of the Sun and planet, and if we find the motion of one planet relative to another, we will get what is called reduced mass.

Using this reduced mass it is proved that the planets move around a plane curve and then that it is an ellipse.

The only law that is used is the law of gravitation and nothing else.

Answer 7

No, no, no!!! The Earth does **not** experience equal force from the sun at all points of it's orbit. The force is given by F = mMG/r² where F is force (in Newtons) m is the mass of the Earth, M is the mass of the Sun, r is the distance from the center of mass of the Sun to the center of mass of the Earth, and G=6.67*10-11 N× m² / kg²

Now go back and actually **read** and **learn** something about orbital mechanics.


Doug

Answer 8

It is not at all about the force acts in equillibrium.
but we have to consider the phenomenon occured duting coolilg of earth. DFue to surface tension phenomenon earth's shae tend to be circular but the gravitational forces of sun, moon, and jupieter tend to allot the shape "oboloid " shape to earth

Answer 9

The earth is moving in its orbit around the sun and also spins itself. Two forces added together make the orbit elliptical.

Answer 10

It is due to the centrifugal force experienced by the earth as a result of rotation about its own axis.