"God has absolute authority in all spheres of the West. ”
In his Principia Mathematica of Natural Philosophy, published in 1687, Newton proposed that although his fundamental laws of mechanics and the laws of universal gravitation could partially explain the motion of the planets in the solar system, there was still an "unsolvable" set of complex equations. He reasoned that "God's intervention" was necessary to keep the solar system stable.
It wasn't until Laplace, in his book The Mechanics of Celestial Mechanics, that he proposed his framework for calculating the motion of the planets and their moons, effectively revealing the stability of the solar system without divine intervention.
When Napoleon asked him why God was not mentioned in his discovery, Laplace replied, "I don't need that assumption." "He has ousted God from the altar of science, and let's approach Laplace, the master of celestial mechanics.
Profile
Laplace (1749-1827) was a French astronomer, analyst, probability theorist and physicist, and a member of the French Academy of Sciences. He was born on March 23, 1749 in Beaumont-Nogge, Calvados, in northwestern France, and died in Paris on March 5, 1827. He is the main founder of celestial mechanics and one of the founders of astroevolution.
Laplace has long been engaged in the study of the theory of the motion of the great planets and the theory of the motion of the moon, and has made a large number of important achievements on the basis of summarizing the research of his predecessors, which are concentrated in the 5 volumes and 16 volumes of his magnum opus "Celestial Mechanics", published in 1799 and 1825. In this work, the term celestial mechanics was first proposed, and it is a representative work of classical celestial mechanics. Laplace is known as the father of the French Newton and celestial mechanics.
Major achievements:
Jupiter-Saturn orbit problem.
Laplace applied Newton's law of gravitation to the entire solar system, and in 1773 solved a famous puzzle of the time: explaining why Jupiter's orbit was shrinking while Saturn's orbit was expanding. That is, it proves that the orbits of Jupiter and Saturn will oscillate around an average value with a period of thousands of years.
This is due to the fact that Jupiter's five orbits around the Sun coincide with the time it takes to orbit Saturn twice, a "resonance" that allows the perturbations they exert on each other to be superimposed for hundreds of years in a row, a series of seemingly negligible effects that can have very real long-term effects when properly timed. As a result, Jupiter is moving slowly inward in a spiral and Saturn is gradually moving outward.
Laplace mathematically proved the invariance of the average motion of the planets, i.e., the orbital magnitude of the planets only changes periodically, and proved it to be eccentricity and inclination to the power of 3. This is known as Laplace's theorem.
Solar system stability issues.
In the solar system, why the eight major planets can maintain long-term stability under mutual interference during the orbit of the sun is a puzzling problem involving complex and difficult calculations of multi-body motion, which has not been solved for a long time.
In 1786, Laplace completed the calculation of the motion of many bodies, and came up with the precession of the planets caused by the interaction of many bodies, but he mathematically proved that the order of magnitude of these precessions was not only very small compared to its orbital motion, but also "self-repairing", so that the entire solar system was stable.
The question of the origin of the nebula.
Laplace elaborated on the nebula origin of stars in 1796. According to Laplace, the solar system was formed by a rotating nebula of hot gas. The nebula gas shrinks due to cooling, so the rotation accelerates, the centrifugal action increases, and the shape gradually tends to be flat disk. When the centrifugal action of the rotating outer gas is so large that it detaches from the interior of the nebula, which continues to shrink, it forms a ring. The nebula continues to shrink, and the separation process repeats itself again and again. The matter in each ring is attracted to each other, and finally it condenses into a planet, and the central part of the nebula condenses into the sun.
Laplace's theory unifies the isotropy, coplanarity and near-circularity of the motion of the planets of the solar system, which is more reasonable than the nebula theory proposed by the German philosopher Immanuel Kant 40 years ago.
At the end of The Celestial Mechanics, Laplace utters a very instructive passage in which he says: "If a man is confined to collecting phenomena, such a scientist is only a 'flower in a greenhouse', and he cannot recognize the great laws of nature." Only by comparing various phenomena with each other and digging out the deep-seated relationships can we find out the laws in them. ”