However, these two people don't get along well. Kepler felt that Tycho was hiding something from his mentor. "Tycho didn't give me a chance to share his practical knowledge, except the conversation at dinner. Today I will talk about apogee, and tomorrow I will talk about the intersection of other planets. " Kepler repeatedly threatened to leave.
Finally, Tycho gave in completely. He said, take the data of Mars and analyze these observations. Kepler boasted that he would get the answer in eight days. He doesn't know that the movement of Mars, which is easy to see in the night sky, has been recorded completely and accurately; He doesn't know that these movements are far from the existing predictions. This project made Kepler do it for eight years instead of eight days. When he finished the work, he found that the mistakes were not only in Copernicus and Ptolemy's system, but also in Tycho's system.
However, Tycho did not live to see the fruits of Kepler's hard work. 160 1 year, Tycho, who was legendary and opinionated all his life, died of bladder rupture (it is said that he drank too much beer at the royal banquet and found it inconvenient to leave, so that he could not stop). Before he died, he begged, "Don't let me die in vain." Kepler succeeded Tycho as an imperial mathematician at his request.
Kepler once talked about his mentor's rich data accumulation: "Tycho is rich in the world, but like most rich people in the world, he doesn't know how to use this wealth properly." Kepler is now in charge of Tycho's database, and he knows how to use it correctly.
Unlike Tycho, Kepler thought Copernicus's thought was correct. Starting with the problems encountered by Mars, he began to look for evidence of the general outline of the solar system in Tycho's rich data. Observations show that planets, especially Mars, run at different speeds, sometimes slow, sometimes fast, and the closer they get to the sun, the faster they get. Kepler spent six years trying to explain this strange phenomenon with various hypotheses. Every hypothetical attempt is accompanied by complicated calculations. Of course, he doesn't have a computer to process data for him, or even a pocket calculator or slide rule. Therefore, dealing with these problems requires a lot of time, concentration and special skills. Finally, he came to the conclusion that the orbit of the planet can't be round.
1609, Kepler published his achievements in a book called Astronomia Nova, and he put forward the first two of the three laws of planetary motion later known as Kepler. For people who care about this kind of problem, the publication of this book is like an earthquake. Kepler's view is completely contrary to his own Platonism and Christian theology. He thinks that the planets do not run along the mysterious and perfect circular orbit in Aristotle and ptolemaic system, but along the elliptical orbit, a kind of imperfect oblate orbit. Unlike a perfect circle, an ellipse has two centers, namely the focus. Kepler said that the sun is located in one of the focal points. This is the gist of Kepler's first law. This idea alone is enough to lead the Presbyterian cardinals to suppress the publication of this book, which is exactly the case.
Kepler put forward a mathematical formula in the second law to describe the speed change of the planet when it orbits the sun. In short, when the planet revolves around the sun, the straight line from the sun to the planet sweeps the same area in the same time interval, no matter where the planet is in orbit. As a result, the closer the planet is to the sun, the shorter the connection line, and the faster the speed of the planet, so that it can sweep the same area.
At the same time, in 1604, that is, in less than 40 years, Kepler saw a second new star, called "Kepler Star". This incident shocked the intellectual circles in Europe, and it merged with the influence brought by the Renaissance and the Religious Reform, which aroused a turbulent wave of new knowledge and questioning atmosphere. A group of philosophers who followed the Epicurus tradition went further, and they even suggested that perhaps a large number of atoms were accidentally aggregated to form a new star. But Platonism, which emphasizes harmony and "nature", still occupies a dominant position in the hearts of humanists. As a devout religious person, Kepler opposed the idea that the universe was dominated by chance. He likes to compare this sentence with the salad his wife prepared for him at dinner:
"It seems," I said loudly, "that if plates, lettuce leaves, salt grains, water droplets, vinegar oil and sliced eggs fly around in the air, they will never stop, and maybe they will eventually get together by chance to form a salad." The wife said, "Yes, but it won't be as exquisite and beautiful as what I made."
Kepler is still influenced by Platonism, and now he has begun to determine the relationship between the distance between the planet and the sun and the time it takes for the planet to make a circle. He is sure that there must be such a relationship. He succeeded. 16 19 years, he published the third law in the book world harmony. He said that the square of the period of any planet's rotation around the sun is directly proportional to the cube of the half-length diameter of its orbit. This formula applies to every observation he recorded. Kepler was very satisfied with this. He regarded this law as strong evidence of the ultimate harmony and perfection of the universe.
Later, it was discovered that Kepler's laws of planetary motion also applied to celestial bodies that Kepler didn't know and never thought of. When Galileo first observed Jupiter's four moons through a telescope, the observation showed that they revolved around the planet according to the same principle. Many years later, when multi-satellite systems were discovered, people found that they also obeyed the same law.
Kepler's three laws also foreshadowed important changes in science. Unlike the Greeks and many others who came later, Kepler did not try to explain why the planets moved, but only how they moved. He used mathematics and observation data to discuss planetary motion, as the scientific writer Bruce Gregory wrote: "Kepler is far more than just describing planetary motion; He invented a method to treat the movement of celestial bodies, which is still valuable today. "
For the mechanism of planetary motion, Kepler not only tried to give a scientific explanation, but also was very interested in the book on magnetism published by william Gilbert (154 1- 1603) in 1600. Kepler's work shows that he suspects that the sun exerts some kind of physical control on the planet in the form of magnetic field, thus making the planet rotate.