Kepler gave three theories about the motion of the planets in the early 18th century. Kepler is an assistant to astronomer Tycho Brahe. Tycho recorded very finely without binoculars, changing the location of Mars over time over many years. Kepler obtained his formulas by analyzing Tyco’s record of Mars. Kepler’s first law states that the orbit of any planet around the Sun is an ellipse and the Sun is in a focus of this ellipse. Kepler, however, could not say why the planet’s orbit would be elliptical. Many years later, in 184, astronomer Edmund Haley came to Cambridge University and asked Isaac Newton the question, “If the force of gravity acts as a disproportionate square of distance, what should the planet’s motion look like?” Newton immediately answered – elliptical. But it took Newton three months to answer Haley’s question in detail,

When a planet orbits the Sun’s central force field, Newton’s second law of mechanics is used to determine the planet’s trajectory (r) with the main axis a elliptical of an ellipse, the eccentricity and the angle (q) of the planet with the main axis. Can be expressed as (Figure 1). But this equation is a general equation. That is, it can be used to describe any conic cross section of a circle, ellipse, parabola or hyperbola (Figure 2). The shape obtained by intersecting a cone with a plane is called conic cross section. In this equation, if the concentricity is zero, then the orbit of the planet will be circular, if the concentricity is between 0 and 1, then it will be elliptical, if it is equal to 1, it will be elliptical and if it is more than 1, it will be elliptical.

That is, in the case of the disproportionate square principle of the Sun’s gravitational ball, a planet can take any orbit (circle, ellipse, ellipse or ellipse). If the planet has a high kinetic energy, it will move in an elliptical or elliptical path and will never return to the Sun. And if the planets are in the orbit of the sun, their concentration is unlikely to be zero. So basically they will take elliptical orbits. In fact, there is almost no possibility of a planet in a circular path. If the speed of the planet is high, then the farther it goes from the sun, the slower the attraction of the sun will return to the sun. As it gets closer to the sun again, its speed will increase and it will continue to turn away from the sun.

Thus the asymmetry of the planet’s motion will give it an elliptical orbit. The circular path is not impossible according to Kepler’s first law, because the circle is a part of the ellipse, but in reality it is almost impossible to have a circular orbit, requiring special primitive conditions. However, many of the planets discovered in the outer solar system, which are very close to their stars, are slowly getting closer to the circle due to the elliptical path of the planets.

**Author:** Astrophysicist and Professor, Riverside College, California, USA