Famous Scientist Kepler stated three laws of planetary motion those laws are known by Kepler’s Law of Planetary Motion. Before Kepler many scientist stated different formulas. One by many scientist explained planetary motion theory but all were not correct. It took time to get the right theory of planetary motion although their hard work took us in the perfect conception. First Plato stated laws of planetary motion, according to Plato’s theory stars moves around the earth in a circular path and other planets move irregular figure. Then Ptolemy explained his theory, according to Ptolemy earth is the center of the universe stars, sun and other planet moving around the earth. Next theory was Heliocentric theory by Nicolas Copernicus, he stated that sun is the center of the universe all the planet moves around the sun in irregular figure. Tycho Brahe could not accept the observation of Copernicus, Tycho Brahe observations were far more accurate than Copernicus.
Johannes Kepler (Photo Credit Wikipedia)
Tycho Brahe’s observation was modified by Kepler which is known Kepler’s law of planetary motion.
Those three laws are
i) Law of orbit
ii) Law of area
iii) Law of time
Before go with Kepler’s Law of planetary motion you need clear concept about conics which are classified into three categories viz Parabola, hyperbola and ellipse.
We only need to get clear concept about ellipse here for Kepler’s law.
Ellipse is a conics which shape is far most like circle has two points name focus F, F’ shown in figure. Those two focus plural name is foci.
Kepler’s First Law – The Law of Orbit:
According to Kepler’s law of orbit any planet moves around the sun in an elliptical area putting sun on a focus of ellipse.
Suppose the earth is moving around the sun it can place the sun any of the two focus point of the ellipse and moves around the sun creating an elliptical path.
There are two figure shows the elliptical paths of any planet according to Kepler Law.
Kepler’s Second law – The Law of Area:
Kepler stated that if a planet moves one point to another point with a certain time and if the planet takes the same time moving another two points then the area of the two different separate points is equal.
Suppose a plate moves A to B point as shown in figure taking time t1 and area is OAB.
Again the planet goes from C point to D point taking t2 time and the area OCD.
If the two times are equal t1 = t2 then the area of two different fields are same according to Kepler’s law of planetary motion.
Hence area OAB = OCD
Kepler’s Third Law – The Law of Time:
The square of the period of revolution of any planet around the sun is proportional to the cube of the semi major axis of its orbit.
Suppose two planets are moving around the sun they are creating separating elliptical path and they have different semi major axis.
Semi major axis of first planet = r1
Semi major axis of second plant = r2
Time period of first planet = T1
Time period of second planet = T2
According to Kepler mathematically,
You can check it out Kirchhoff’s law