Galileo di Vincenzo Bonaulti de Galilei (February 15, 1564 – January 8, 1642), who was 77 years old, was an Italian astronomer, physicist, and engineer, and the founder of modern natural sciences in Europe. Galileo is known as the "father of observational astronomy", "father of modern physics", "father of scientific methods", and "father of modern science".
Galileo studied velocity and acceleration, gravity and free fall, relativity, inertia, and the principles of projectile motion, and engaged in applied science and technology research. He described the properties of pendulums and "still water equilibrium", invented thermometers and various military compasses, and used telescopes for astronomical scientific observations. His contributions to observational astronomy include using telescopes to confirm the phase of Venus, discovering Jupiter's four largest satellites, observing Saturn's rings, and analyzing sunspots.
Galileo's advocacy of heliocentrism and Nicolai Copernicus was controversial throughout his life, as most people supported the geocentric model (such as the Tychonic system), but he faced opposition from astronomers who doubted heliocentrism due to the lack of stellar parallax. This matter was investigated by the Roman Inquisition in 1615 and the conclusion reached was that heliocentrism was "foolish and absurd in philosophy.". Due to obvious contradictions with papal rule in many places, it is formally heretical. Galileo later defended his views in the "Dialogue on Two Major World Systems" (1632), which seemed to have attacked Pope Urban VIII and distanced him from Jesuits, who had always supported Galileo. He was tried by the religious tribunal and found to have strong suspicion of heresy, and was forced to back down.
He spent the rest of his life under house arrest. During his house arrest, he wrote "Two New Sciences," which summarized his work forty years ago on two sciences now known as kinematics and material strength.

Galileo was born on February 15, 1564 in Pisa, Italy (part of the Duchy of Florence). He was the first of six children of Lutens, a Catholic, composer, and music theorist Vincenzo Galilei and Giulia (n é eAmmanati). [2]
Name Source
Galileo tended to address himself only by his own name. At that time, surnames were optional in Italy, and his surname had the same origin as his surname Galilei. His name and surname both come from his ancestor Galileo Bonaiuti, who was an important physician, professor, and politician in 15th century Florence. In the late 14th century, in memory of him, his descendants called themselves Galileo. Galileo Boniuti was buried in the same church as the Holy Cross Church in Florence, and about 200 years later, his more famous descendant Galileo Galilei was also buried. When he mentions his name, he sometimes uses Galileo Galilei Linceo, referring to him being a member of the elite scientific organization Lincei Academy among Italian humans. In the mid-16th century, Tuscan families usually named their eldest son after their parents' surnames. Therefore, Galileo Galileo may not necessarily be named after his ancestor Galileo Boniuti. The Italian male name is "Galileo" (hence the surname "Galileo"), which comes from the Latin word "Galil æ us", meaning "Galilee". This is an important region in the Bible of northern Israel.
The biblical roots of Galileo's name and surname will become the theme of famous puns. In 1614, during the Galileo Incident, one of Galileo's opponents, Dominican priest Tommaso Caccini, delivered a controversial and influential sermon to Galileo. He pointed out in it Acts 1:11: "Galileans, why do you gaze at heaven?".

Childhood period
Similar to the situation of a middle-class child, he received private education. At around the age of 10, his family moved from Pisa to Florence, where Galileo continued his studies and was later sent to the Camaldolese Monastery in Vallambroso. Galileo told his family that he wanted to be trained to become a missionary, but his father wanted Galileo to follow in the footsteps of his fellow celebrities and become a doctor. Vincenzo sent Galileo back to Florence, where he continued to study religion through correspondence.

Working period
Galileo studied medicine at the University of Pisa in 1580.
Cardinal Bellamy once wrote in 1615 that the Copernican system could not be defended without a true proof that "the sun did not turn around the earth and the earth turned around the sun.". Galileo believed that his tidal theory provided such evidence. This theory was so important to him that he initially intended to refer to his dialogue on the "two major world systems" as the "dialogue on the ups and downs of the sea.". The term "tide" was removed from the title according to the order of the religious tribunal.
For Galileo, tides were caused by the back and forth movement of water in the ocean, which was due to the Earth's rotation and orbit around the sun causing a slight acceleration and deceleration on the Earth's surface. He distributed his first tidal description to Cardinal Orsini in 1616. His theory provided the first understanding of the importance of basin shape in determining the size and timing of tides; For example, he correctly explained the insignificant tides in the central Adriatic Sea compared to the end. However, as a general explanation of the tidal cause, his theory is a failure.
If this theory is correct, then there will only be one climax per day. Galileo and his contemporaries realized this deficiency because Venice had two orgasms every day, rather than one, approximately 12 hours apart. Galileo ruled out that this abnormal phenomenon was caused by some secondary factors, including the shape, depth, and other factors of the sea. Albert Einstein later stated that Galileo developed his "fascinating arguments" and accepted them without criticism out of a desire for physical proof of the motion of the Earth. Galileo also refuted the idea that the moon, as known to ancient and contemporary John Kepler, caused tides. Galileo was also not interested in Kepler's elliptical planetary orbits. In his dialogue (Fourth Giornata), Galileo continued to advocate for his tidal theory.

The Debate between Comets and Meteors
In 1619, Galileo argued endlessly with Jesuit college student Romano and mathematics professor Orazio Grassi. At first, there was a debate about the nature of comets, but by the time Galileo published Il Saggiatore in 1623 (his last salvo in the debate), it had become a widespread controversy over the essence of science itself. The title page of this book describes Galileo as the philosopher and "Matematico Primario" of the Grand Duke of Tuscany. [7]
Due to containing Galileo's rich ideas on how to practice science, the "analyst" is known as his scientific manifesto. In early 1619, Father Gracie anonymously published a booklet titled "Astronomical Controversy of Three Comets in 1618", discussing the properties of a comet that appeared in late November 1618. Gracie's conclusion is that this comet is a hot object that moves along a large arc at a constant distance from Earth, and because it moves slower in the sky than the moon, it must be further away than the moon. [1] [8]
Gracie's arguments and conclusions were criticized in subsequent articles, including the Comet of Discourse, a disciple of Galileo, and one of the lawyers named Florence, published in the name of Mario Giqu é ci, although it was largely written by Galileo himself. Galileo and Guiducci did not provide a definitive theory about the properties of comets, although they did make some temporary speculations, people guessed wrong. (At that time, Tycho Brahe proposed the correct method for studying comets.) At the beginning of Galileo and Gideon's words, he unjustly insulted Jesuits. Christopher Schner, along with various professors, made disparaging comments about the Roman Academy scattered throughout the entire work. The Jesuits were angered and quickly engaged in a debate with Gracie about his own balance of Dao, astronomy, and philosophy. His pen name was Sarsio Sigensano, who appeared to be a student of his own.

The appraiser is Galileo's devastating response to the astronomical balance. It has been widely regarded as a masterpiece of dialectical literature, in which the argument of "Sarsi" has been scorned. It has been widely praised, especially admired by the new Pope Urban VIII. In the first decade of Rome, Barberini, the future city of Urban VIII, fell on the side of Galileo and the Licien Academy.
The dispute between Galileo and Gracie caused many Jesuits who originally sympathized with him to permanently distance themselves, and Galileo and his friends firmly believed that these Jesuits were the cause of his later condemnation. However, the evidence for doing so is at best ambiguous.

mechanics
Galileo was the first scientist to introduce experiments into mechanics, and he used a combination of experiments and mathematics to determine some important laws of mechanics. Around 1582, after a long period of experimental observation and mathematical calculation, he obtained the isochronicity law of the pendulum, and then dropped out of school in 1585 due to financial difficulties in his family. During his absence from the University of Pisa, he delved into the works of ancient Greek scholars such as Euclid and Archimedes. He wrote his first paper titled "Balance" based on the principles of leverage and buoyancy. Not long after, he wrote a paper titled "On Gravity", which for the first time revealed the essence of gravity and center of gravity and provided accurate mathematical expressions, thus gaining great fame. At the same time, he questioned many of Aristotle's views.
Galileo was the earliest person in history to conduct quantitative research on dynamics. From 1589 to 1591, he made detailed observations on the free falling motion of objects, refuting Aristotle's theory of falling motion (heavy objects fall faster than light objects) that ruled for two thousand years, both experimentally and theoretically. He pointed out that if air resistance is ignored, objects of different weights fall to the ground simultaneously, and the speed at which the object falls is independent of its weight. According to the records of Galileo's later student V. Viviani, the falling experiment was conducted on the Leaning Tower of Pisa, but this event is not recorded in Galileo's writings, so it is generally considered unreliable. The first person in history to complete such an experiment was Stefan. In the History of Natural Science, it is recorded that the Dutchman Stefan completed this experiment in 1586 using two lead balls of different weights and proved that Aristotle's theory was incorrect. Centuries after the Stefan experiment, Apollo 15 astronaut David Scott repeated the experiment on August 2, 1971, using a hammer and a feather on the airless surface of the moon, proving and allowing television viewers on Earth to witness two objects falling simultaneously on the surface of the moon.

Galileo conducted detailed research on the basic concepts of motion, including center of gravity, velocity, acceleration, etc., and provided strict mathematical expressions. Especially the introduction of the concept of acceleration is a milestone in the history of mechanics. With the concept of acceleration, the dynamic part of mechanics can only be established on a scientific basis, while before Galileo, only the static part had quantitative descriptions. Galileo also conducted experiments and observations on the motion of objects on inclined planes and projectiles. On the basis of these studies, he proposed the concept of acceleration and its mathematical expression. He informally proposed the law of inertia and the laws of motion of objects under external forces, and proposed the principle of relativity of motion (now known as Galilean relativity). The principle of relativity was proposed in response to criticism of the Copernican system, but its significance goes far beyond this. It was the first to introduce the concept of an inertial reference frame (inertial frame), which Einstein referred to as the Galilean principle of relativity and was the precursor to special relativity. These laid the foundation for Newton's formal proposal of Newton's first law and Newton's second law. Galileo also proposed the theorem of moments and the laws of motion of projectiles. Galileo can be said to be a pioneer of Newton in the establishment of classical mechanics.
Galileo made long-term observations and studies on the motion of pendulums. In later research, it was pointed out that the period of a simple pendulum is directly proportional to the square root of its length. This rule provided a basis for the design of timing mechanisms (pendulum clocks) later on. In 1641, he, who had become blind, had his son draw a design for a pendulum clock for him.

Galileo's contributions in mechanics are multifaceted. This is described in detail in his later work on mechanics, "Dialogue between Two New Sciences of Mechanics and Positional Motion.". In this immortal work, besides dynamics, there is also a lot of content about material mechanics. For example, he elaborated on the bending tests and theoretical analysis of beams, correctly determining 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 cubic radius. He also analyzed simply supported beams under concentrated loads and correctly pointed out that the maximum bending moment is under load, and is proportional to the product of its distance to the two support points. Galileo also analyzed the issues that should be paid attention to when using beam bending theory in practice, pointing out that the dimensions of engineering structures should not be too large, as they will fail under their own weight. He concluded from the experiment that when the size of an animal's body decreases, the strength of its body does not decrease proportionally. He also used this relationship to explain why larger animals are not as capable of carrying their own weight as smaller animals, writing, "A little dog may be able to carry two or three little dogs on its back, but I believe a horse may not be able to carry a horse of the same size as it."
During his imprisonment, Galileo wrote his achievements in mechanics in the form of a three person conversation in his book "Dialogue on Two New Sciences of Mechanics and Positional Motion" (published in 1638).

astronomy
Galileo was the first scientist to achieve significant results in observing celestial bodies through a telescope. In 1609, after learning that the Dutch had telescopes, Galileo created the astronomical telescope (later known as the Galileo Telescope) and used it to observe celestial bodies, discovering many previously unknown astronomical phenomena. He found that the number of visible stars increased with the increase of telescope magnification; The Milky Way is composed of countless individual stars; The surface of the moon is rough and uneven (I personally drew the first lunar map), and the phenomenon of Venus's profit and loss; Jupiter has four moons (actually the largest of many Callisto moons, now known as Galilean moons). He also discovered sunspots and believed that sunspots were phenomena on the surface of the sun. Based on the rotation period of sunspots on the solar surface, he determined that the rotation period of the sun is 28 days (actually 27.35 days). In 1637, despite poor eyesight, he also discovered the Sunday and Sunday translations of the moon. These discoveries opened up a new era in astronomy.
Galileo was the first to observe the rings of Saturn, sunspots, lunar mountains, the ups and downs of Venus and Mercury, as well as the equal circumferences of Jupiter's satellites and Venus, using a telescope. He summarized the laws of free fall, inertia, and Galileo's principle of relativity from his experiments. Thus, it overturned many speculations in Aristotle's physics, laid the foundation of classical mechanics, refuted Ptolemy's geocentric system, and strongly supported Copernicus's heliocentric theory.
This series of astronomical discoveries caused a sensation in Europe at that time, and Galileo advocated Copernicus's heliocentric theory in his two newly discovered books, "The Interstellar Messenger" (1610) and "Letters about Sunspots" (1613). Galileo promoted the spread of Copernican theory through his observed facts. At that time, Italy was still under the strict rule of the church, and many people refused to acknowledge new ideas and things that contradicted the Bible and Aristotle's works. In 1613, Copernicus's "On the Motion of the Celestial Body" was banned by the religious court, and Galileo was also warned to abandon Copernican theory. Galileo did not receive a warning and continued to write. In 1632, his "Dialogue between the Two World Systems" was published, which angered the church. The religious court brought Galileo to court, convicted him, and ordered him to repent, abandon the doctrine he had proven, and banned the spread of Dialogue. In 1633, he was sentenced to life imprisonment and designated to reside in the suburbs of Florence. He continued to study hard in the last few years of his life. In 1634, he wrote a book on mechanics called "A Conversation and Mathematical Proof of Two New Sciences".

science
Galileo placed great emphasis on the role of observation and experimentation in the study of dynamics, beam bending, or astronomy. He is also skilled at proposing hypotheses based on observation results, using mathematical tools for deductive reasoning, and seeing if they match experimental or observational results. In the experiment of free fall, he made water droplets fall from the same place one after another, with the same time interval between every two drops. He observed that the distance between two consecutive drops at any given moment was in an equal difference series. He applied the parabolic properties in mathematics to derive a square relationship between the falling distance and time. It is worth noting that he is also very rigorous in theoretical derivation. Although the properties of parabolas were already known in ancient Greece, existing Galileo manuscripts indicate that he recalculated the formula for parabolas from scratch.
Accurate experiments and observations cannot be achieved without measuring instruments. Galileo often personally designed and manufactured instruments. In addition to the aforementioned telescopes, he designed and manufactured instruments such as hydrostatic scales, proportional gauges, thermometers, pendulum pulse meters, etc.
In the scientific research that began with Galileo, scientific experiments were first placed in an important position in the study of mechanics. The experimental science that began with Galileo was the beginning of modern natural science. Galileo's main works include "Dialogue on Two World Systems" (1632) and "Dialogue on Two New Sciences" (1638).

philosophy
Galileo persisted in fighting against the scholastic philosophy of the church throughout his life, advocating the use of concrete experiments to understand natural laws and believing that experiments are the source of theoretical knowledge. He does not acknowledge the existence of absolute truth and absolute authority in the world, and opposes superstition and blind obedience. He acknowledges the objectivity, diversity, and infinite nature of matter, which holds significant importance for modern philosophy. However, due to historical limitations, he emphasized that only material attributes that can be summarized as quantitative characteristics are objectively present. Galileo abandoned the heliocentric theory after being imprisoned for supporting it. He said, "Considering various obstacles, the shortest line between two points is not necessarily a straight line," which is a very modern viewpoint. It is precisely because of such thoughts that giving up temporarily for eternal support did not meet the fate of Giordano Bruno, but could continue to contribute to science.