Analysis:

? Galileo (1564 ~ 1642)

Italian astronomer, mechanic and philosopher. /kloc-0 was born in Pisa on February 5th, 564, and 1642/kloc-0 died in Pisa on October 8th. Galileo's surname is Galileo, and his full name is galileo galilei, but now people usually call him Galileo by his first name instead of his last name.

Galileo started school in 1572, and moved to Florence with his family in 1575 to study in a monastery. 1589 was hired as a professor of mathematics at the University of Pisa. 159 1 year, teaching at the University of Padua in Venice. /kloc-returned to Florence in 0/609, 16 1 1 went to Rome and served as an academician of the Academy of Forestry. 1633 In February, he was sentenced to life imprisonment by the Roman Inquisition for "opposing the Pope and promoting evil learning". After 1638, my eyes gradually became blind, and the evening scene was bleak. 1642 65438+ died on1October 8th. More than 300 years later,1979165438+1October 10, the Pope had to publicly announce 1633 that Galileo's judgment was unfair. 1980, 10 In June, the case was retried, and a committee composed of world-renowned scientists with different religious beliefs was formed in Romania to study the whole story of Galileo's case, the relationship between science and religion, the scientific value of Galileo's theory and its contribution to modern scientific thought.

The main contributions can be divided into the following three aspects:

(1) mechanics Galileo was the first scientist to introduce experiments into mechanics. He determined some important mechanical laws through the combination of experiment and mathematics. 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 the records of V. viviani, a student in Galileo's later years, the falling experiment was conducted in public on the leaning tower of Pisa, but Galileo's works did not clearly indicate that the experiment was conducted 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 against idealism and scholasticism of the church, advocated using concrete experiments to understand the laws of nature, and believed that experience was 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.