PRIDE CHEKERAT =^2 휋푎
(^32)
푅√푔^ ...................(1.2)^
R is the radius of the central attracting body and g is the
acceleration due to gravity at the surface of the focus. This
clearly shows that the square of the period, T, of motion is
proportional to the cube of the semi-major axis of the orbit.
Planets whose semi-major axis’ magnitude is greater took much
time to orbit the sun. Thus Mercury has a small period of only
88 Earth days at 36 million miles from the sun than Earth with
an orbital period of 365.26 days at a distance of 93 million miles
from the sun and Neptune has a far much greater period of 164.8
Earth years whose average distance from the sun is 2.8 billion
miles.
This is a magnificent planetary model which put astronomy to
another level. With use of Newton’s Universal Gravitational law
and Kepler’s laws, orbits of exoplanets had been calculated,
discovering some with very short periods of even earth hours. It
was discovered that those eight planets in our solar system don’t
orbit the sun in exactly the same orbital plane but they are
oriented at various angles to this plane. Mercury is inclined at 7
degrees to the plane of Earth’s orbit, and Earth’s spin axis is
tilted at 23.5 degree to the elliptical plane. The wobbling of
Mercury’s perihelion fascinated Einstein a lot and it led to his
discovery of General Theory of Relativity.