First of all, Kepler's law shows an extremely brave creative spirit in scientific thinking. Long before Copernicus founded the heliocentric universe system, many scholars had put forward different opinions on the concept of heavenly movement and quietness. But no one has ever dared to doubt the idea that celestial bodies follow a perfect uniform circular motion. Kepler resolutely denied it. This is a very bold idea. Copernicus knew that the combination of several circles could produce an ellipse, but he had never used an ellipse to describe the orbit of a celestial body. As Kepler said, "Copernicus was not aware of the wealth he had at his fingertips."
Secondly, Kepler's law completely destroyed Ptolemy's current wheel system, liberated the Copernican system from the shackles of this wheel, and brought it full integrity and rigor. Copernicus abandoned a preconception of the ancient Greeks, namely the essential difference between heaven and earth, and obtained a much simpler system. But it still needs thirty or so circles to explain the apparent motion of celestial bodies. Kepler found the simplest world system and solved it all with only seven ellipses. From then on, it is possible to simply and accurately calculate the motion of the planet without the help of any current wheel and eccentric circle.
Third, Kepler's law makes people's understanding of planetary motion clear concepts. It proves that the planetary world is a symmetrical (that is, what Kepler calls "harmony") system. The central celestial body of this system is the sun, dominated by a certain unified force from the sun. The sun is located at one of the focal points of each planet's orbit. The planetary revolution period is determined by the distance between each planet and the sun, and has nothing to do with mass. In the Copernican system, although the sun is at the "center" of the universe, it does not play this role, because no planet's orbital center coincides with the sun.
There are many scientific discoveries in the history of science due to scientific experiments and recorded data made by predecessors. But like the discovery of the laws of planetary motion, from Tycho’s 20-plus years of diligent observations to Kepler’s long-term and meticulous calculations, scientific cooperation with such a difficult road and such brilliant results is rare. All this is obtained without a telescope!