1609, Galileo made an astronomical telescope (later called galileo telescope) and used it to observe celestial bodies. He found the unevenness on the surface of the moon and drew the first map of the moon himself. 161065438+17 October, Galileo discovered four moons of Jupiter, which provided conclusive evidence for Copernicus' theory and marked the beginning of its victory. With the help of a telescope, Galileo also discovered Saturn's rings, sunspots, the rotation of the sun, the profit and loss phenomena of Venus and Mercury, the balance between the moon's Sunday and Zhou Yue, and the fact that the Milky Way is composed of countless stars. These discoveries ushered in a new era of astronomy. Galileo wrote the Star Messenger, letters about sunspots, dialogues between Ptolemy and Copernicus, talks about two new sciences, mathematical proofs and testers.
To commemorate Galileo's achievements, people named Io, Europa, Ganymede and Callisto as Galileo satellites. Galileo aimed his telescope at the Milky Way in the sky. People used to think that the Milky Way was a white fog formed by the condensation of water vapor on the earth, and Aristotle also thought so. Galileo decided to use a telescope to test whether this statement was correct. He was surprised when he pointed his telescope at the blurred band of light in the night sky. It turned out that it was not a cloud at all, but a gathering of thousands of stars in Qian Qian. Galileo also observed the mottled clouds in the sky-the so-called clusters, and found that clusters are also gathered by many stars, such as Orion cluster, Orion cluster and honeycomb cluster.
Galileo's main contributions can be divided into the following five aspects: ① Mechanics Galileo was the first scientist to introduce experiments into mechanics. He combined experiments with mathematics and determined some important laws of mechanics. 1582, after long-term experimental observation and mathematical calculation, he got the isochronous law of pendulum. Later, he dropped out of school on 1585 due to family financial difficulties. When he left the University of Pisa, he deeply studied the works of ancient Greek scholars Euclid and Archimedes. He wrote his first paper entitled "Balance" based on the principle of lever and buoyancy. Soon after, he wrote a paper on gravity, which revealed the essence of gravity and center of gravity for the first time and gave an accurate mathematical expression, so he became famous at one fell swoop. At the same time, he questioned many viewpoints of Aristotle. During the period of 1589 ~ 159 1, Galileo made a detailed observation on the motion of falling objects. Theoretically and experimentally, it is denied that Aristotle, who has ruled for thousands of years, established the correct "law of free fall" on the "law of falling body motion", that is, under the condition of ignoring air resistance, balls with different weights fall to the ground at the same time, and the falling speed has nothing to do with the weight. According to V. viviani, a student in Galileo's later years, the falling experiment was conducted in public on the leaning tower of Pisa: 1589, one day, Galileo dropped an iron ball weighing 10 pounds and landed almost at the same time, and all the competitors present were dumbfounded and shrugged their shoulders in laughter. However, Galileo's works did not clearly indicate that the experiment was carried out on the leaning tower of Pisa. So it has been controversial for several years. Galileo made a detailed study on the basic concepts of motion, including center of gravity, speed and acceleration, and gave a strict mathematical expression. Especially the concept of acceleration is a milestone in the history of mechanics. With the concept of acceleration, the dynamic part of mechanics can have scientific basis, while before Galileo, only the static part was described quantitatively. Galileo informally put forward the law of inertia (see Newton's law of motion) and the law of motion of objects under the action of external forces, which laid the foundation for Newton to formally put forward the first and second laws of motion. Galileo was the pioneer of Newton's creation of classical mechanics. Galileo also put forward the law of resultant force and projectile motion's law, and established Galileo's relativity principle. Galileo's contribution to mechanics is various. This is described in detail in his mechanical book Dialogue between Two New Sciences and Mathematical Proof written in his later years. In this immortal book, besides dynamics, there are many contents about mechanics of materials. For example, he expounded the bending test and theoretical analysis of beams, and correctly summarized the mechanical similarity relationship between the bending capacity and geometric dimensions of beams. He pointed out that for cylindrical beams of similar length, the bending moment is proportional to the cube of radius. He also analyzed the simply supported beam under concentrated load and correctly pointed out that the maximum bending moment is under load and is proportional to the product of its distance to two points. Galileo also analyzed the problems that should be paid attention to when applying the beam bending theory to practice, and pointed out that the size of engineering structures should not be too large, because they would be destroyed under their own weight. According to his experiments, he came to the conclusion that when the body size of animals decreases, the strength of their bodies does not decrease proportionally. He said, "A puppy may be able to carry two or three dogs of the same size, but I believe a horse may not be able to carry a horse of the same size." Astronomy He was the first scientist who made great achievements in observing celestial bodies with a telescope. These achievements include: the discovery that the surface of the moon is uneven, Jupiter has four satellites (now called Galileo satellites), the rotation of sunspots and the sun, the profit and loss of Venus and Jupiter, and the Milky Way is composed of countless stars. He confirmed Copernicus's "theory of earth movement" with experiments, and completely denied Aristotle and Ptolemy's "theory of earth movement" which ruled for more than 1000 years. (3) Philosophy Throughout his life, he insisted on fighting idealism and scholasticism of the church, and advocated using concrete experiments to understand the laws of nature, believing that experiments were the source of theoretical knowledge. He denied the existence of absolute truth and absolute authority to master the truth in the world, and opposed blind superstition. He acknowledged the objectivity, diversity and infinity of matter, which is of great significance to the development of materialist philosophy. However, due to historical limitations, he emphasized that only material attributes that can be summarized as quantitative characteristics exist objectively. Galileo "abandoned" Heliocentrism because he supported Heliocentrism's imprisonment. He said, "Considering various obstacles, the shortest line between two points is not necessarily a straight line." It is precisely because of this idea that he temporarily gave up for eternal support, instead of sacrificing for the truth of science like Bruno, but he can continue to contribute his own strength to science. ④ The earliest thermometer was invented by Italian scientist Galileo (1564 ~ 1642) in 1593. His first thermometer was a glass tube with an opening at one end and a glass bulb the size of a walnut at the other. When in use, the glass bulb is heated first, and then the glass tube is inserted into water. With the change of temperature, the water surface in the glass tube will move up and down, and the temperature change and temperature level can be judged according to the movement amount. Thermometers expand with heat and contract with cold, so this kind of thermometer is greatly influenced by environmental factors such as external atmospheric pressure, so the measurement error is large. Later, Galileo's students and other scientists repeatedly improved on this basis, such as turning the glass tube upside down, putting the liquid in the tube and sealing the glass tube. ⑤ Principle of Relativity On the basis of discovering the law of inertia, Galileo put forward the principle of relativity: the laws of mechanics are equivalent in all inertial coordinate systems. For the static inertial system and the moving inertial system, the mechanical process is exactly the same. In other words, the mechanical experiment of any system can't determine whether an inertial system is stationary or moving in a straight line at a constant speed. Galileo wrote in Dialogue: When you observe the mechanical process in a closed moving cabin, "as long as the motion is uniform and never swings from side to side, you will find that all the above phenomena have not changed at all, and you can't determine whether the ship is moving or stationary from any of them. Even if the ship moves quite fast, you will jump the same distance on the bottom plate of the ship as before, and you will not jump further than the bow, although when you jump into the air, the bottom plate under your feet moves in the opposite direction. When you throw anything at your partner, whether he is at the bow or at the stern, as long as you stand on the opposite side, you don't need to use more force. As before, water drops will fall vertically into the water tank below, and not a drop will fall to the stern, although the ship has performed "water drops" in the air many times. The force used by the fish to swim in front of the water bowl is no greater than that used to swim behind the water bowl; They swim leisurely to the bait placed anywhere on the edge of the water bowl. Finally, butterflies and flies will continue to fly around casually, never concentrate on the stern, and will not miss the boat movement because they may stay in the air for a long time and look tired. If you light incense and smoke, you will see the smoke rising upward like a cloud without moving to either side. The reason for all these consistent phenomena is that the motion of the ship is owned by everything on board and the air. " The principle of relativity was put forward by Galileo in response to the geocentric criticism of Copernicus system. The significance of this principle goes far beyond this. The concept of inertial reference system was put forward for the first time. Einstein called it Galileo relativity principle, which was the predecessor of special relativity.