Life: Galileo began to go to school in 1572, and moved to Florence with his family to study in a monastery in 1575. In 1589, he was hired as a professor of mathematics at the University of Pisa. In 1591, he taught at the University of Padua in Venice. In 169, he returned to Florence, and in 1611, he went to Rome and served as an academician of Lin Si Academy of Sciences. In February 1633, 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 scenery was bleak. He died on January 8, 1642. More than 3 years later, on November 1, 1979, the Pope had to declare at a public meeting that Galileo's sentence in 1633 was unfair. In October, 198, the case was re-examined, and a committee of world-renowned scientists including different religious beliefs was formed in Romania to study the whole story of Galileo's case, the relationship between science and religion, and the scientific value of Galileo's theory and its contribution to modern scientific thought.
Main contributions: It can be divided into the following three aspects:
① Mechanics Galileo was the first scientist to introduce experiments into mechanics. He determined some important laws of mechanics by combining experiments with mathematics. Around 1582, after long-term experimental observation and mathematical calculation, he got the isochronous law of pendulum. Then he dropped out of school in 1585 because of family financial difficulties. When he left Pisa University, he deeply studied the works of ancient Greek scholars Euclid and Archimedes. He wrote his first paper entitled "Balance" based on the principle of leverage 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 accurate mathematical expressions, so he became famous. At the same time, he questioned many of Aristotle's views.
from 1589 to 1591, Galileo made a detailed observation of the falling body. It is theoretically and experimentally denied that Aristotle, who 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 Galileo's student V. viviani in his later years, the falling experiment was conducted in public on the Leaning Tower of Pisa, but it is not clearly stated in Galileo's works that the experiment was conducted on the Leaning Tower of Pisa. Therefore, there has been controversy in recent years.
Galileo studied the basic concepts of motion, including center of gravity, velocity and acceleration, and gave strict mathematical expressions. Especially the concept of acceleration is a milestone in the history of mechanics. With the concept of acceleration, the dynamic part of mechanics can be based on science, 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 a pioneer of Newton in the creation of classical mechanics.
Galileo also put forward the law of resultant force and the law of projectile motion, and established Galileo's relativity principle. Galileo's contribution to mechanics is various. This is described in detail in his mechanical work "Conversation and Mathematical Proof of Two New Sciences" 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 concluded 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 radius cube. 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 the 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 will be destroyed under their own weight. According to his experiments, he concluded that when the size of an animal's body decreases, the strength of its body does not decrease proportionally. He said, "A puppy may be able to carry two or three dogs of the same size on its back, but I believe a horse may not even be able to carry a horse of the same size."
② Astronomy He was the first scientist who made great achievements in observing celestial bodies through telescopes. These achievements include: it is found 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 motion" with experiments, and completely denied Aristotle and Ptolemy's "theory of earth motion" which ruled for more than a thousand years.
③ Philosophy Throughout his life, he insisted on fighting against idealism and scholasticism of the church, and advocated using concrete experiments to understand the laws of nature, believing that experience is the source of theoretical knowledge. He denies that there is absolute truth and absolute authority to master the truth in the world, and opposes blind superstition. He acknowledged the objectivity, diversity and infinity of matter, which are of great significance to the development of materialistic philosophy. However, due to historical limitations, he emphasized that only material attributes that can be summarized as quantitative characteristics exist objectively.
Galileo "gave up" Heliocentrism because he supported Heliocentrism after he was imprisoned. He said that "considering all kinds of obstacles, the shortest line between two points is not necessarily a straight line". It is precisely because of this idea that he gave up temporarily for eternal support, instead of being heroic like Bruno, but he can continue to contribute his own strength to science.
Galileo Galilei,1564-1642) was a great astronomer, physicist, mechanic and philosopher in the late Italian Renaissance, and also a pioneer of modern experimental physics. He is an indomitable fighter for the truth. Engels called him "one of the giants who can break the old theory and create a new theory regardless of any obstacles".
I. Galileo's life
Galileo was born in Pisa on the western coast of Italy on February 15th, 1564. He was originally from Florence and came from a noble family. Galileo's father was a frustrated musician, proficient in Greek and Latin, and quite accomplished in mathematics. Therefore, Galileo received a good family education from an early age.
At the age of 12, Galileo entered the Boullosa Monastery near Florence and received a classical education. At the age of seventeen, he entered the University of Pisa to study medicine, and at the same time devoted himself to studying physics and mathematics. Due to the financial difficulties of his family, Galileo left the University of Pisa without a diploma. In a difficult environment, he still insisted on scientific research, studied many works of Euclid and Archimedes, made many experiments and published many influential papers, which attracted great attention from the academic circles at that time and was called "the contemporary Archimedes".
Galileo was taught mathematics by the University of Pisa at the age of 25. Two years later, Galileo angered the church and lost his job because of the famous experiment on the leaning tower of Pisa. After leaving the University of Pisa, Galileo went to teach at the University of Padua in Venice in 1592 until 161. This period was the golden age for Galileo to engage in scientific research. Here, he has achieved fruitful results in mechanics, astronomy and other aspects.
in p>161, Galileo published his book in the form of popular reading, and named it "Star Messenger". This book was published in Venice, which caused a sensation in Europe at that time and won a high honor for Galileo. Galileo was hired as "court philosopher" and "court chief mathematician", and he returned to his hometown of Florence.
Galileo continued his scientific research in the court of Florence, but his astronomical discoveries and his astronomical works clearly reflected Copernicus and Heliocentrism's views. Therefore, Galileo began to attract the attention of the church. Beginning in 1616, Galileo was brutally persecuted by the Roman Inquisition for more than 2 years.
Galileo's later life was so miserable that Celeste, who took care of his daughter, died before him. The grief of losing his beloved daughter made Galileo blind. Even under such conditions, he still did not give up his scientific research work.
On January 8, 1642, at 4 am, the great Galileo, a fighter who struggled for science and truth all his life, and a giant of science passed away at the age of 78. On the eve of his death, he repeated this sentence: "It takes special courage to pursue science."
ii. Galileo and his scientific discoveries
There are two schools of physics in ancient Greece, one is represented by the philosopher Aristotle, and the other is represented by the natural scientist Archimedes. Both of them were famous scholars in ancient Greece, but because of their different viewpoints and methods, their scientific conclusions were different and formed sharp opposition. Aristotle's view is basically idealistic, and he draws conclusions by subjective thinking and pure reasoning, so it is full of fallacies. The Archimedes school's viewpoint is basically materialistic, and he relies entirely on scientific practice to draw conclusions.
However, since the 11th century, with the support of the Christian church, Aristotle's works have attracted the attention of scholastic philosophers, who rejected Archimedes' physics and regarded Aristotle's physics as a classic, and all scholars who violated Aristotle's physics were regarded as "heresy". But Galileo was skeptical about Aristotle's physics. On the contrary, he paid special attention to the study of Archimedes' physics. He attached importance to integrating theory with practice, observing various natural phenomena and thinking about various problems. When Galileo was eighteen years old, he went to church in Pisa once. He noticed that the ever-burning lamps hanging in the church were regularly swung from left to right by the wind. He timed them according to the beat of his pulse and found that the reciprocating time was always equal. In this way, he discovered the isochronism of pendulum. Later, the Dutch physicist Huygens made a hanging pendulum clock according to this principle, and people called it "Galileo clock".
according to Archimedes' theory, Galileo studied the hydrostatic balance for rapidly determining alloy composition, invented a "small balance" for measuring the density of substances, and wrote a paper called "small balance". Later, he devoted himself to studying the geometry of the center of gravity of objects, and in 1588 published the paper "Center of Gravity of Solids", which attracted the attention of academic circles. The following year, on the recommendation of a friend, he was appointed as a professor of mathematics by the University of Pisa.
Aristotle thinks that two objects fall at the same height, and the heavier one hits the ground first than the lighter one. But after repeated research and experiments, Galileo came to the opposite conclusion: the speed of falling objects has nothing to do with weight. In 159, Galileo made a public falling experiment in the leaning tower of Pisa, which proved that Aristotle's statement was wrong, and made Aristotle's theory, which ruled people's minds for more than 2, years, shake for the first time. However, some famous scholars who were invited to watch it denied what they had seen with their own eyes, and they attacked Galileo. Galileo was dismissed from Pisa in 1591.
In the history of science, Galileo was not the initiator of the falling object experiment, but Stevin. But Galileo's experiment on the leaning tower of Pisa had a far-reaching impact.
In p>1592, Galileo came to teach at the University of Padua in Venice and began the golden age of his scientific activities. During this period, he studied a lot of physical problems, such as slope motion, force synthesis, projectile motion and so on. He also studied liquid and heat and invented the thermometer. In 169, Galileo made an astronomical telescope and used it to explore the mysteries of the universe. He found that the surface of the moon was uneven and there were mountains and deep valleys. Jupiter has four satellites revolving around it, and Venus, like the moon, has both gains and losses. Saturn has a halo; The sun has sunspots and can rotate. The Milky Way is made up of thousands of dim stars in Qian Qian. These findings provide strong evidence for the views of Copernicus and Bruno. It dealt a severe blow to the creed of the church.
The following year, he published Star Messenger, which popularly introduced the sky phenomenon he observed to readers and publicized his views. This book caused a great sensation in Europe, so Galileo was called "Columbus in the sky". In 1613, he published On Sunspots in Rome. The book clearly points out in the form of letters that Copernicus' theory is correct and Ptolemy's theory is wrong. Galileo angered the church and began to be tried by the inquisition.
Under the pressure of the Holy See, Galileo continued his scientific research, and in the long-term practice of observing and studying the movement of celestial bodies, he was more convinced of the correctness of Copernicus' theory. In January 1632, Galileo published "Dialogue on Ptolemy and Copernicus' Two World Systems" in Florence. In the book, he talked for four days in the form of a dialogue between three scholars. Three problems are discussed: 1. Prove that the earth is moving; 2. Enrich Copernicus' theory; 3. The tides of the earth. Dialogue summarizes all kinds of scientific discoveries in Galileo's long-term scientific research practice, declares the bankruptcy of Ptolemy's geocentric theory, fundamentally shakes the supreme authority of the church, and thus promotes the development of materialism. Once published, this book was welcomed by readers. But it was opposed by the Roman church. Galileo was imprisoned for a long time.
In p>1636, Galileo secretly completed another great book of his life, Dialogue on Two New Sciences, while in prison. The book was published in Holland in 1638. This great book was also written in the form of a three-person dialogue. "The first day" is about the strength of solid materials, which refutes Aristotle's view that the speed of falling objects depends on their weight. "The next day" is about the reason of cohesion, and discusses the proof of lever principle and the strength of beam. On the third day, uniform motion and natural acceleration motion were discussed. The fourth day is a discussion about the movement of projectiles. This masterpiece fundamentally negates Aristotle's theory of motion.
iii. Galileo's scientific research method
Galileo's demonstration of physical laws is very strict. He established a scientific research method of experimental research on physical phenomena and combining experimental methods with mathematical methods and logical argumentation. For example, in order to illustrate inertia, he designed an ideal experiment without friction: hang a simple pendulum at a certain point O, pull the pendulum ball to the left point A at a certain distance from the vertical position, release the ball, and the ball will swing to the right point B of the vertical position, at which point A and point B are at the same height. If you change the movement route of the simple pendulum with a nail directly below O, the ball will be placed at D with the same height as A and B. Galileo pointed out that the same conclusion would be reached for inclined planes. He butted two inclined planes together, let the ball roll down from rest along one inclined plane, and the ball will roll up the other inclined plane. If there is no friction, the ball will rise to its original height. He reasoned that,