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 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."

Second: 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.

Third: philosophy

Throughout his life, he insisted on fighting idealism and scholasticism, 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.

Fourth: heat

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.

Fifth: the 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 Copernicus' geocentric criticism. 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.

Sixth: Invent the telescope.

During the 18 years when Galileo worked in the University of Padua, he initially focused on the mechanical research that he had always been interested in, and he discovered an important phenomenon in physics-the inertia of the motion of objects; I did a famous slope exercise and summarized the quantitative relationship between the falling distance of an object and the elapsed time. He also studied the movement of shells and laid the foundation of parabola theory.

The concept of acceleration was first put forward by him: even in order to measure the temperature rise of patients with fever, the famous physicist invented the first air thermometer in 1593 ... However, an accidental event made Galileo change his research direction. He turned from the study of mechanics and physics to the boundless space.

It was1June 609. Galileo heard a news that Lipski, a Dutch optician, saw something invisible to the naked eye in the distance with a kind of lens in an accidental discovery. "Isn't this just what I need?" Galileo was very happy. Soon, one of Galileo's students wrote from Paris, further confirming the accuracy of the news. The letter said that although I don't know how Lipski made it, the optician must have made a lens barrel, which can magnify the object many times.

"lens barrel!" Galileo read the letter several times, and then hurried into his laboratory. He found paper and a gooseneck pen and began to draw a schematic diagram of lens imaging one by one. Galileo was inspired by the hint of the lens barrel. It seems that the secret of lens barrel magnifying objects lies in the choice of lenses, especially how to match convex lenses and concave lenses. He found the information about the lens and kept calculating, forgetting that he climbed the window at dusk and how dawn entered the room.

After a whole night, Galileo finally understood that if the convex lens and concave lens are placed at a proper distance, as the Dutch saw, distant objects invisible to the naked eye can be seen clearly after magnification.

Galileo was very happy. He forgot to rest and immediately began to grind his glasses, which was a time-consuming and meticulous job. He worked for several days, grinding out a pair of convex lenses and concave lenses, and then made an exquisite sliding double-layer metal tube. Now, it is time to test his invention.

Galileo carefully placed a large convex lens at one end of the tube and a smaller concave lens at the other end, and then pointed the tube out of the window. When he looked at one end of the concave lens, a miracle appeared. The church in the distance seems to be close at hand. He can clearly see the cross on the bell tower, and even a pigeon resting on the cross is very realistic.

The news that Galileo had built a telescope spread at once. "The news that I made a telescope spread to Venice." In a letter to my brother-in-law, Galileo wrote: "A week later, I was asked to show this telescope to the Speaker and Members of Parliament. They were very surprised. Gentlemen, members of parliament.

Although they are very old, they all climbed the tallest bell tower in Venice in order, and looked at the ships in the distance of the port and saw them clearly. Without my telescope, I can't see for two hours. The utility of this instrument can make objects 50 miles away look as if they are within 5 miles. "

The telescope invented by Galileo, after continuous improvement, has a magnification of more than 30 times, which can enlarge the object by 1000 times. Now, he seems to have clairvoyance, and can spy on the secrets of the universe.

This is an epoch-making revolution in astronomical research. For thousands of years, the era when astronomers only observed the sun, moon and stars with naked eyes has ended, and optical telescopes have been replaced. With this powerful weapon, the door of modern astronomy was opened.

Now, whenever the stars shine or the bright moon is in the sky, Galileo will aim his telescope at the deep and distant sky and observe it day and night, regardless of fatigue and cold.

In the past, people always thought that the moon was a smooth celestial body, which shone by itself like the sun. But Galileo discovered through a telescope that the moon, like the earth where we live, has high mountains and low depressions (Galileo called it "ocean" at that time). He also found from the movement of the bright and dark parts of the moon that the moon itself cannot shine, and the light of the moon comes from the sun.

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 telescope revealed the secrets of one universe after another. He discovered the satellites orbiting Jupiter and calculated their operating periods. Now we know that Jupiter has 16 moons, and Galileo discovered the largest four of them. In addition, Galileo also observed sunspots through a telescope. He inferred from the movement of sunspots that the sun was also spinning.

One exciting discovery after another prompted Galileo to write a book about the latest astronomical discoveries, and he wanted to announce his observations to the world. 16 10 In March, Galileo's Star Messenger was published in Venice, which immediately caused a sensation in Europe.

However, he didn't expect that the secret of the universe uncovered by the telescope greatly angered many people, and a terrible doom was about to befall this outstanding scientist.

Extended data

1February 564 15, Galileo galilei was born into a humble aristocratic family in Pisa, Italy. It is said that his ancestors were famous doctors in Florence, but by his father Galileo Van Sandu's generation, his family had fallen.

Van San is a talented musician. He published several pastoral poems and instrumental works before his death. He is also good at mathematics and proficient in Greek, Latin and English. But wonderful music can't fill a family's stomach, and his mathematical talent can't get him a good position.

Shortly after Galileo was born, Van Sandu opened a small shop selling woolen goods in Florence, not far from Pisa, which was a last resort. But in order to support his family, Fan Sandu had to go into business against his will.

References:

Galileo's Baidu Encyclopedia