Galileo·Galileo di Vincenzo Bonaulti de Galilei, an Italian astronomer, physicist and engineer, and the founder of modern European natural science, was 77 years old.Galileo is called the "father of observational astronomy", "father of modern physics", "father of scientific methods" and "father of modern science".
Galileo studied velocity andacceleration、gravityandFree fall、relativity、inertia, projectile motion principle, and engaged in applied science and technology research, describedpendulumAnd "hydrostatic balance", inventedthermometerAnd various military compasses, andtelescope。His contributions to observational astronomy include the use of telescopes toVenusPhase confirmation and discoveryJupiterThe four largest satellites of,Saturn RingObservation andsunspotAnalysis of.
GalileopromoteHeliocentric theoryandNicolaus Copernicus Doctrine has always been controversial in his life. At that time, most people were in favor of the geocentric model(e.g. Tychonic system)However, he met the opposition of astronomers, who were short ofStellar parallaxAnd doubt heliocentrism.This matter was investigated by the Roman Inquisition in 1615, and the conclusion was that heliocentrism was "stupid and absurd in philosophy".Due to the obvious contradiction with the papal rule in many places, it is heretical in form.Galileo later wrote a dialogue on the two main world systems”(1632), which seemed to attack the PopeUrban VIII And alienated him fromJesuitThe latter has always supported Galileo.He was tried by the Inquisition, and was found "strongly suspicious of heresy" and forced to retreat.
He spent the rest of his life under house arrest.During the period of house arrest, he wrote "Two New Sciences", which summarized that he was now calledkinematicsandMaterial strengthWork done in two sciences.
Galileo was born in Pisa, Italy, on February 15, 1564(part of the Principality of Florence)Rutens, Catholic, composer and music theorist Vincenzo Galilei and Giulia (n é e Ammannati) are the first of six children.[2]
Name Source
Galileo tended to address himself only by his own name.At that time, the surname wasItalyIt is dispensable. His surname has the same origin as his surname Galilei.His name and surname both come from his ancestor Galileo Bonaiuti, who was an important doctor, professor and politician in Florence in the 15th century.In the late 14th century, in memory of him, his descendants called themselves Galileo.Galileo Bonaiuti was buried in the same church of Saint Cross in Florence. About 200 years later, his more famous descendant Galileo Galilei was also buried.When he mentioned his name, he sometimes used Galileo Galilei Linceo, which means that he is a member of Lincei Acadamy, the elite scientific organization among Italian human beings.In the middle of the 16th century, Tuscan families usually named their eldest son after their parents.Therefore, Galileo Galilei is not necessarily named after his ancestor Galileo Bonaiuti.The Italian male's name is "Galileo"(Hence the surname "Galileo")It comes from the Latin "Galile ∨ us", meaning "Galilee", which is an important biblical region in northern Israel.
The biblical roots of Galileo's name and surname will become the subject 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.In it, he pointed out that Acts 1:11: "Men of Galilee, why do you stare at heaven?".[3]
Galileo
Childhood
Similar to a middle-class child, he received a private education.When he was about 10 years old, his familyPisaMoved toFlorence(Florence) Galileo continued his studies there and was sent toValon BrosaCamaldolese monastery in Vallambroso.Galileo told his family that he hoped to be trained as a missionary, but his father hoped that Galileo would follow in the footsteps of his fellow celebrities and become a doctor.Vincenzo sent Galileo back to Florence, where he passedinstruction by correspondenceContinue to study religion.[4]
Cardinal Bellarmine once wrote in 1615 that the Copernican system could not be defended without "the 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 is so important to him that he initially intended to call his dialogue on the "two main world systems" "maritime ups and downs dialogue".The tide is based onInquisitionRemoved from the title.
For Galileo, the tide is caused by the back and forth movement of water in the ocean, which is due to the acceleration and deceleration of the earth's surface caused by the earth's rotation and revolution around the sun.He distributed his first tidal description to Cardinal Orsini in 1616.His theory makes people understand for the first time the importance of the shape of the sea basin to the size and time of tides;For example, he correctly explained that the tide in the middle of the Adriatic Sea is insignificant compared with the tide at the end.However, as a general explanation of the causes of tides, his theory failed.
Galileo Galilei
If this theory is correct, there will only be one climax every day.Galileo and his contemporaries realized this deficiency, because Venice had two climaxes every day instead of one, about 12 hours apart.Galileo ruled out that this anomaly was caused by some secondary reasons, including the shape, depth and other factors of the sea.Albert Einstein later said that Galileo had developed his "fascinating arguments" and accepted them uncritically out of his desire for physical proof of the earth's movement.Galileo also refuted the idea that the moon, as known to ancient and contemporary John Kepler, caused the tides.(Galileo is also not interested in Kepler's elliptical planetary orbits.) Galileo is talking(The fourth giornata)Zhong also continued to advocate his tidal theory.[5-6]
Controversy between comets and determiners
In 1619, Galileo argued with Jesuit College 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 (this was his last rescue in the debate), it had become a widespread dispute about the nature of science itself.The title page of this book describes Galileo as a philosopher of the Grand Duke of Tuscany and "Matematico Primario".[7]
Because the "analyst" contains Galileo's rich ideas on how to practice science, it is called his scientific declaration.At the beginning of 1619, Father Gracie anonymously published a pamphlet, The Astronomical Controversy of Three Comets in 1618, discussing the nature of a comet that appeared in late November 1618.Gracie came to the conclusion that the comet was a hot object, and it kept a constant distance from the earth along a large arc. Since it moved slower in the sky than the moon, it must be farther than the moon.[1][8]
Gracie's arguments and conclusions were criticized in subsequent articles. Mario Guiqucci, the comet of discourse, was published in the name of Galileo's disciple, one of the lawyers named Florence, although it was written by Galileo himself to a large extent.Galileo and Guiducci did not provide a definitive theory about the nature of comets. Although they did put forward some tentative conjectures, people were wrong.(At that time, Tycho Brahe proposed the correct method for studying comets.)In Galileo and Gidditch'sDiscursiveIn the beginning, he insulted the Jesuits without reason.Christophe Schner, as well as the comments of various professors, disparaged the Rome Institute scattered throughout the work.Jesus would be irritated, and Gracie would soon debate his own Taoist astronomy and philosophical balance with an answer. His pseudonym, Sarsio Sigensano, seemed to be a student of his own.[6]
The appraiser was Galileo's devastating reply to the astronomical balance.It has been widely regarded as a masterpiece of dialectical literature, and the argument of "Sarsi" has been scorned.It was widely praised, especially by the new Pope Urban VIII.In Rome in the previous decade, Barberini, the future city VIII, fell on the side of Galileo and the Lincea Academy.
The dispute between Galileo and Gracie alienated many Jesuits who had sympathized with him permanently. Galileo and his friends believed that these Jesuits were the reason for his later condemnation.However, the evidence for doing so is at best ambiguous.[9-10]
In the whole world before Galileo's conflict with the church, most educated people agreedAristotleThe geocentric view of, that is, the earth is the center of the universe, all celestial bodies revolve around the earth, or the strong earthquake system combines geocentrism and heliocentrism.[11]
yesHeliocentric theoryGalileo's works combined scientific and religious objections.The scientific objection came from Tycho Brahe and others, because if the heliocentric theory was true, the annual star parallax should be observed, although it was not yet.(It was only in 1838 that Friedrich Bessel was able to observe it accurately.) Copernicus and Aristarchus correctly assumed that parallax was negligible because the star was so far away.However,Tycho Brahe (Tycho) retorted that since stars seem to have measurable angular size, if stars are so far away and their apparent size is due to their physical size, they will be much larger than the sun.In fact, it is impossible to observe the physical size of distant stars without modern telescopes.In Tycho system, the star is slightly farther than Saturn, and the size of the sun and the star is comparable.[12]
Religion opposes the heliocentric theory. For example, Psalms 93:1, 96:10 and 16:30 of the past dynasties appear in the Bible, including written instructions, "The world is also built and it cannot move." Psalm 104:5 says in the same way: "He (the Lord) laid the foundation of the earth, do not move it forever." Ecclesiastes 1:5 further says: "The sun also rises, and the sun sets, and go to the place where it rises."Joshua 10:14 says, "The sun stands in Gibeon...".[13]
Galileo based on hisAstronomical observation（Sidereus Nuncius1610) defended heliocentrism.In December 1613, Cristina, the Grand Duchess of Florence, and Benedetto Castelli, a friend and follower of Galileo, faced the Bible and opposed the Earth Movement.According to Maurice Finochiaro, out of curiosity, this was done in a friendly and cordial way.Prompted by this event, Galileo wrote a letter to Castelli, in which he argued that heliocentrism was not in fact contradictory to the Bible text. The Bible was the power of belief and morality, not the authority of science.The letter was not published, but it was widely circulated.Two years later, Galileo wrote a letter to Christina herself, expanding the previous argument from eight pages to forty pages.[1]
In 1615, Father Nicola Lorini submitted Galileo's work on heliocentrism to the Roman Inquisition. He claimed that Galileo and his followers were trying to reinterpret《Bible》, which is regarded as a violation of the Trent Parliament and looks like Protestantism.Lorini especially quoted Galileo's letter to Castelli.Galileo went to Rome to defend himself and his ideas of Copernicus and the Bible.At the beginning of 1616, Monscot Francesco Ingoli launched a debate with Galileo and sent him an article aboutCopernicus systemThesis of.Galileo later said that he thought this article was helpful to the subsequent anti Copernican actions.According to Maurice Finochiaro, the religious tribunal may entrust Ingoli to write expert opinions on disputes, and this article provides "the main direct basis" for the actions of the religious tribunal.[12]
This article focuses on eighteen physical and mathematical arguments against heliocentrism.It mainly drew on Tycho Brahe's argument, and highlighted Tycho's argument, that is, heliocentrism requires stars to be much larger than the sun.Ingoli wrote that the distance from stars in the heliocentric theory is very large, "clearly proving that the size of stars is so large, because they may exceed or equal to the size of the Earth's own orbit".This article also includes four theological arguments, but Ingoli suggested that Galileo focus on physical and mathematical arguments, and he did not mention Galileo's biblical ideas.In February 1616, a commission of inquiry announced that heliocentrism was: "Philosophical stupidity and absurdity are official heresies because they are obviously contradictory to the meaning of the Bible in many places".The religious judge found that the idea of the earth movement "has accepted the same judgment in philosophy, and... is wrong in theological truth... at least in faith".[9]
Pope Paul V instructed Cardinal Bellamin to submit this discovery to Galileo and ordered him to give up the heliocentric theory.On February 26, Galileo was summoned to Bellamin's residence and ordered: "Completely give up... the view that the sun is stationary at the center of the world and the earth is moving, so he no longer holds, teaches or defends it, either orally or in writing."[14]
The decree of the Index Society prohibits Copernicus' Revolution and other heliocentric works until they are corrected.Bellamy's instructions did not prevent Galileo from discussing heliocentric theory as a mathematical and philosophical thought, as long as he did not advocate its physical truth.[15]
In the next decade, Galileo was far from controversy.When he was elected Cardinal Maffeo Barberini as Pope Urban VIII in 1623, he resumed his plan to write the book.Barberini was Galileo's friend and admirer, and in 1616 he opposed Galileo's admonition.The Dialogue on the Two Major World Systems was published in 1632, with the official authorization of the Inquisition and the permission of the Pope.
Earlier, Pope Urban VIII personally asked Galileo to put forward arguments in support of and against heliocentrism in his book, and be careful not to advocate heliocentrism.He again requested that his views on the matter be included in Galileo's book.Galileo only satisfied the latter of these requests.
Trial of Galileo,1632
Whether unintentionally or intentionally, Simplicio is the defender of Aristotle's geocentric view in Dialogue on Two Main World Systems, and often falls into his own mistakes, sometimes even fooled.In fact, although Galileo published the character in his book (the preface after Aristotle, a famous philosopher, pointed out Simplicius's Italian Latin, "Simplicio"), the Italian name "Simplicio" also has the connotation of "fool".Simplicio portraysDialogue on two major world systemsAppear in the form of propaganda books: attack on Aristotle's geocentrism and defense of Copernicus' theory.Unfortunately, due to Galileo's relationship with the Pope, he put Ullus VIII's words into Simplicio's mouth.[11]
Most historians agree that Galileo did not act out of malice and were blind to the reaction of his book.However, the Pope did not despise suspicious public ridicule, nor was he an advocate of Copernicus.
Galileo alienated one of his biggest and most powerful supporters,the popeHe was summoned to Rome in September 1632 to defend his works.He finally arrived in February 1633 and was brought under the charge of the judge Vincenzo Maculani.Throughout the trial, Galileo firmly believed that since 1616, he had faithfully kept his promise and did not hold any condemned opinions. At first, he even refused to defend these opinions.However, he was finally persuaded to admit that, contrary to his true intention, he was《DialogueIt is likely that the readers of this book will get the impression that it is to defend Copernicus.In view of Galileo's rather implausible denial that he once held Copernican thoughts after 1616 or planned toIn conversationDefending these ideas, he concluded in the final interrogation in July 1633 that if he did not tell the truth, he would be threatened with torture, but despite the threat, he still firmly denied it.[1]
The decision of the Inquisition was delivered on 22 June.It is divided into three basic parts:
Galileo was found to be a "strong skeptic of heresy" (although he was never formally accused of heresy, which saved him from corporal punishment), that is, he held the view that the sun does not move at the center of the universe.The earth is not its center and is moving. It may be considered contrary to the Bible and may defend a view.He was asked to "oppose, curse and hate" these opinions.
The Inquisition was pleased to sentence him to formal imprisonment.The next day, this was reduced to house arrest, and he was under house arrest all his life.
He's disgustingdialogueProhibited;In addition, he is prohibited from publishing any of his works, including any works that he may write in the future, during the action not announced in the trial.[16]
According to popular legend, Galileo reportedly muttered the rebellious phrase "while it is moving" after withdrawing the theory that the earth moves around the sun.The Spanish painter Bartolom é Esteban Murillo or his school painters hid these words in a painting created in the 1640s until the restoration work in 1911.This painting depicts a imprisoned Galileo, apparently gazing at the word "E pur si muove" written on his wall.Dungeons.The earliest written records in the legend can be traced back to a century after his death, but Stillman Drake wrote: "There is no doubt that these famous words were attributed to Galileo long before his death."[17-18]
After spending some time with the friendly Archbishop of Siena, Ascanio Picolomeni, Galileo was allowed to return to his villa in Atheteri near Florence in 1634, where he spent part of his house arrest.For the next three years, Galileo was instructed to read seven meditation hymns once a week.However, his daughter Maria Celeste reduced his burden after obtaining permission from the church.[19-20]
When Galileo was under house arrest, he devoted his time to one of his best works《Two New Sciences。Here, he summarized the work he had done forty years ago, involving two kinds of science now called kinematics and material strength, which were published in the Netherlands to avoid the appearance of censorship procedures.This book was highly praised by Einstein.Because of this work, Galileo is often called "the father of modern physics".In 1638, he was completely blind, suffering from hernia and insomnia, so he was allowed to go to Florence for medical advice.[21]
Dava Sobel argued that before Galileo's trial and judgment of heresy in 1633, Pope Uber VIII became absorbed in the intrigues of the court and national issues, and began to fear persecution or threats to his own life.In this case, Sobel believed that Galileo's problem was raised to the Pope by insiders of the court and Galileo's enemies.Because he was accused of being powerless in defending the church, Urban reacted to Galileo out of anger and fear.[15][22-26]
The character's old age
Galileo continued to receive tourists until 1642. After suffering from fever and heart disease, he died on January 8, 1642 at the age of 77.Ferdinando II, Archduke of Tuscany, wishes to bury his body inSanta Croce Next to him is the tomb of his father and other ancestors, and his honor marble tomb is erected.
However, after Pope Urban VIII and his nephew Cardinal Francesco Barberini protested, these plans were withdrawn because Galileo was condemned by the Catholic Church for "strongly suspecting heresy".Instead, he was buried in a small room next to the novice church at the end of the corridor from the south end of the cathedral to the Holy Hall.After a monument was erected on his tomb, he was buried in the main body of the cathedral in 1737;In this lift, three fingers and a tooth were taken from his body.One of them is the middle finger of Galileo's right hand, which is currently in Florence, ItalyMuseo Galileo show.[27]
Main contributions
Announce
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Dynamics
Galileo demonstrated the free fall experiment in the Leaning Tower of Pisa
Galileo was the first scientist to introduce experiments into mechanics. He determined some important mechanical laws by combining experiments with mathematics.Around 1582, after a long period of experimental observation and mathematical calculation, he obtained the pendulumIsochronityLaw, and then dropped out of school in 1585 due to family financial difficulties.When he left the University of Pisa, he deeply studied the works of the ancient Greek scholars Euclid, Archimedes and others.He basedLever principleAnd the principle of buoyancy.Soon he wrote the paper "On Gravity", which for the first time revealed the essence of gravity and center of gravity and gave accurate mathematical expressions, so he became famous.At the same time, he questioned many of Aristotle's views.
Galileo was the first person who made quantitative research on dynamics in history.From 1589 to 1591, he made a careful observation of the free falling movement of objects, and experimentally and theoretically rejected Aristotle's view of falling movement, which had ruled for two thousand years(Heavy objects fall faster than light objects)It is pointed out that if the air resistance is ignored, objects with different weights fall at the same time, and the falling speed of the object is independent of its weight.According to the records of V. Viviani, a student in Galileo's later years, the falling body experiment was carried out on the Leaning Tower of Pisa, but this matter was not recorded in Galileo's works, so it is generally considered unreliable.The first person who completed this kind of experiment in historical records is Steven《History of Natural Science》The DutchStevin In 1586, he completed the experiment with two shot put with different weights, and proved that Aristotle's theory was wrong.Centuries after the Stevens experiment, the Apollo 15 astronautsDavid Scott On August 2, 1971, the experiment was repeated on the airless moon surface with a hammer and a feather, which proved and let the television viewers on Earth see two objects falling on the moon surface at the same time.
Galileo studied the motion of objects on an inclined plane[28]
Galileo's basic concepts of motion includefocus、speed、accelerationThey all made a detailed study and gave a strict mathematical expression.In particular, 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. Before Galileo, onlystaticsSome have quantitative descriptions.Galileo also took the objectInclined planeExperiments and observations have been made on the movement of the projectile and the movement of the projectile.On the basis of these studies, he proposed the concept of acceleration and its mathematical expression.He once informally proposedLaw of inertiaAnd the law of motion of objects under the action of external forcesPrinciple of relativity(Now called "Galilean relativity").The principle of relativity was put forward in response to the criticism of Copernicus system, but the significance of the principle is far more than that. It was first proposedInertial reference frame(Inertial system)The concept ofSpecial relativityThe leader of.These were officially proposed by NewtonNewton's first law、Newton's second lawLaid the foundation.Galileo also proposedResultant moment theorem，Projectile motionlaw.stayclassical mechanicsGalileo can be said to be the pioneer of Newton.
Galileo rightpendulumI have made long-term observation and research on the movement of.In later research, it was pointed out that the period of a simple pendulum is proportional to the square root of its length.This rule is the later timing mechanism（Pendulum clock）The design of provides the basis.In 1641, he was blind and asked his son to draw a design for a pendulum clock for him.
Galileo's contribution to mechanics is multifaceted.This is a book on mechanics written in his later years《A Dialogue on Two New Sciences of Mechanics and Position Motion》A detailed description is provided in.In this immortal book, besides dynamics, there are manyMechanics of MaterialsContent of.For example, he explained aboutbeamBased on the bending test and theoretical analysis, the mechanical similarity between the bending capacity and the geometric dimensions of the beam is correctly determined.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 subjected to concentrated load and correctly pointed out that the maximum bending moment is under load and proportional to the product of its distance from two supporting points.Galileo also analyzed the problems that should be paid attention to when the beam bending theory is used in practice, and pointed out that the size of engineering structures should not be too large, because they will be damaged under their own weight.According to his experiments, when the size of an animal is reduced, the strength of its body does not decrease proportionally.He also used this relationship to explain why larger animals are less able to bear their own weight than smaller animals. He wrote: "A puppy may be able to carry two or three puppies on its back, but I believe that a horse may not be able to carry a horse of the same size."
During his imprisonment, Galileo wrote his achievements in mechanics in the form of a conversation between three people in the book "Dialogue on Two New Sciences of Mechanics and Position Motion"(Published in 1638)。
astronomy
Galileo was the first scientist who made great achievements in observing celestial bodies through telescopes.In 1609, Galileo created the astronomical telescope after he learned that the Dutch had a telescope(later referred to asGalileo telescope）And used to observe celestial bodies and discover many previously unknown astronomical phenomena.He found that the number of stars seen increased with the increase of telescope power;The Milky Way is composed of numerous single stars;The surface of the moon is rugged(The first lunar surface was drawn by hand), the profit and loss of Venus;Jupiter has four moons (in fact, it is the largest four of many Ganymedes, now called Galileo satellites).He also found sunspots and believed that sunspots were phenomena on the surface of the sun.From the sunspot's rotation period on the solar surface, he concluded that the sun's rotation period is 28 days(actually 27.35 days)。In 1637, when his eyesight was very poor, he also found that the Sun and the Sun of the moon moved in parallel.These discoveries ushered in 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, and the equal cycles of Jupiter's satellites and Venus with telescopes, and summarized the law of free fall, the law of inertia and Galileo's principle of relativity from experiments.Thus, it overturned many assumptions of 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 shocked Europe at that time. Galileo was introducing his two newly discovered books《Starry Messenger 》(1610) and Letters on Sunspots (1613) both advocated Copernican'sHeliocentric theory。Galileo promoted the spread of Copernicus theory with the observed facts.At that time, Italy was still under the harsh rule of the church, and many people refused to admit that they were not in line with the Bible andAristotleNew ideas and new things that contradict the works.In 1613, Copernicus' "On the Movement of Celestial Bodies" was listed as a forbidden book by the religious court, and Galileo was also warned to give up Copernicus' theory.Galileo did not accept the warning and continued to write. In 1632, his Dialogue between Two World Systems was published, which angered the church.The religious court sent Galileo to the court and sentenced him to be guilty, ordered him to repent, give up the theory he had proved, and prohibited the circulation of Dialogue.In 1633, he was sentenced to life imprisonment and was assigned to live in the suburb of Florence.He still studied hard in the last few years of his life.In 1634, he wrote a book on mechanics - "Talk about Two New Sciences and Mathematical Proof".
science
Galileo telescope[30]
Galileo attached great importance to the role of observation and experiment in the research of dynamics, beam bending and astronomy.He is also good at putting forward hypotheses based on the observation results, and using mathematical tools for deductive reasoning to see whether it is consistent with the experiment or observation results.For example, in the free fall experiment, he let the water drops fall from the same place one after another, with the same time interval between each two drops.He observed that the distance between two successive drops at any time was in the order of equal difference.He used the parabolic property in mathematics to get the square relationship between the falling distance and time.It is worth noting that he is also rigorous in theoretical derivation.Although the nature of the parabola has been known as early as in ancient Greece, the existing manuscript of Galileo shows that he calculated the formula of the parabola again from scratch.
Galileo designed instrument[29]
Accurate experiment and observation cannot be achieved without measuring instruments.Galileo often designed and made instruments himself.In addition to the above telescopes, the instruments he designed and manufactured include hydrostatic balance, scale gauge, thermometer, pendulum pulse meter, etc.
In the scientific research started from Galileo, first of all, scientific experiments were placed in an important position in the research of mechanics.Experimental science from Galileo is the beginning of modern natural science.Galileo's main works are: Dialogue on Two World Systems (1632) and《Dialogue on Two New Sciences》(1638).
Philosophy
Galileo insisted onScholastic philosophyThey argue that concrete experiments should be used to understand the laws of nature and that experiments are the source of theoretical knowledge.He did not recognize the absolute truth and the absolute authority to master the truth in the world, and opposed superstition and blind obedience.He acknowledged the objectivity, diversity of matter and the infinity of the universe, which are of great significance to modern philosophy.However, due to historical limitations, he stressed that only the material attributes that can be summarized as quantitative characteristics are objective.Galileo "gave up" the heliocentric theory after being imprisoned for supporting it.He said, "Considering all kinds of obstacles, the shortest line between two points is not necessarily a straight line." This view is very modern.It is precisely because of such thinking that temporary giving up in exchange for permanent support has not beenGiordano BrunoBut can continue to contribute to science.
Mathematical Experiment Methods
There were two schools of physics in ancient Greece, one represented by the philosopher Aristotle, the other by natural scientistsArchimedesIs representative.Both of them are famous scholars in ancient Greece. Due to their different views and methods, their scientific conclusions are different, forming a sharp opposition.The Aristotelian school's view is to draw conclusions by means of subjective reasoning, which is full of fallacies.The Archimedes' viewpoint relies entirely on the scientific practice method to draw conclusions.
Since the 11th centuryChristian ChurchWith the support of, Aristotle's works were valued by scholastic philosophers who rejected Archimedes' physics and regarded Aristotle's physics as a classic. Any scholar who violated Aristotle's physics was regarded as "heresy".Galileo was skeptical of Aristotle's physics. On the contrary, he paid special attention to Archimedes' research on physics and the combination of mathematics and experiment.
Galileo's experiment on the Leaning Tower of Pisa and his conclusion
Before Galileo's research achievements were recognized, physics and even the entire natural science were just a branch of philosophy, and did not gain its own independent status.At that time, philosophers were bound by theology and Aristotle's dogma, and they struggled to come up with objective laws that conformed to reality.Galileo dared to challenge the traditional authoritative thought. Instead of guessing the cause of things, he first observed natural phenomena and found natural laws.Based on this new scientific thought, Galileo advocated the research method of combining mathematics with experiment.This research method is the source of his great achievements in science, and also his most important contribution to modern science.
Galileo abandoned the theological view of the universe and believed that the world was an orderly whole subject to simple laws. To understand nature, we must carry out systematic experimental quantitative observation and find out its precise quantitative relationship.
Based on new ideas, Galileo advocated new methods(Math Experimental Method)。Using mathematical methods to study physical problems, which was not originally advocated by Galileo, can be traced back to Archimedes in the 3rd century BC, the Oxford School and the Paris School in the 14th century, and the Italian academia in the 15th and 16th centuries. They have made some achievements in this regard, but they did not put experimental methods in the first place, so they failed to make breakthroughs in thought.Galileo's idea of attaching importance to experiments can be seen in the words in a letter he wrote to the Duchess of Christina in 1615: "I would like to ask these clever and careful priests to seriously consider the difference between the speculative principle and the principle confirmed by experiments. You should know that the opinions of the professors doing experimental work are not determined only by their subjective wishes."
Generally speaking, Galileo's research method of combining mathematics with experiment is divided into three steps: ① first, the main part of intuitive knowledge obtained from phenomena is proposed and expressed in the simplest mathematical form to establish the concept of quantity; ②From this formula, another quantitative relationship that is easy to be verified by experiments is derived mathematically; ③Then the quantitative relationship is verified through experiments.His research on the law of uniform acceleration motion of falling bodies is the best illustration.
The simplest assumption that can be made from the acceleration of a falling body may be its instantaneous speedvAnd distancesIs proportional to thisvIt may also be related to the falling timetIs proportional.This is the step ① of the research method.Through mathematical demonstration, it is not difficult to find that the first hypothesis is not tenable for uniformly accelerated motion.So we tookv∝torv=atAssumption ofaIs the acceleration.becausevThe value cannot be measured directly, so this equation is converted into the form of measurable distance.
The final step is to verify by experiment: due to the acceleration of the free falling bodyaIf the value is large, the falling distance will be large even in a short time, which is difficult to measure.In order to "dilute" the acceleration and reduce it, Galileo designed an inclined rolling ball experiment to measure the relationship between the travel and time of the bronze ball rolling down from the smooth small groove on the inclined plane.He repeated the experiment 100 times with a precise leaky kettle.The results obtained are compared with those envisaged in step ②s－tThe quantitative relationship is consistent, and the repeatability is good, which confirms the correctness of the assumption that the falling body will make a uniform acceleration movement.
It can be seen that Galileo's purpose in conducting scientific experiments is mainly to test whether a scientific hypothesis is correct, rather than blindly collecting data and summarizing facts.
Concept and principle innovation
Inertia Principle and New Concepts of Force and Acceleration。It is people's intuitive experience that pushing heavy objects requires more force while pushing light objects requires less force.Aristotle thus reached a universal conclusion: all objects have the nature of keeping still or looking for their "natural place". He believed that "everything in motion must have a promoter", and used the law of proportion to link power and speed.Galileo came up with a new concept. He observed that an object sliding upward along a smooth slope would be decelerated to varying degrees due to different slope angles. The smaller the slope angle, the smaller the deceleration.If sliding on a level surface without resistance, the original speed shall be maintained for permanent sliding.Therefore, we can draw the following conclusion: "If a moving object has a certain speed, it will always maintain this speed as long as there is no external reason to increase or decrease the speed - this condition is only possible on a horizontal plane, because in the case of a slope, the downward slope provides the cause of acceleration, while the upward slope provides the cause of deceleration;";It can be seen that only the movement on the horizontal plane is constant "(Dialogue between Two New Sciences, the third day, question 9, hypothesis 23).In this way, Galileo put forward the concept of inertia for the first time, and for the first time linked the external force with the "external cause of acceleration or deceleration", that is, the change of motion.Combined with the aforementioned experiment of uniformly accelerated motion, Galileo proposed the new concepts of inertia and acceleration, as well as the new laws of motion of objects in uniformly accelerated motion under the action of gravity, which laid the foundation for the establishment of the theoretical system of Newtonian mechanics.This new concept of inertia has overturned the Aristotelian school's view that the movement of objects is driven by spirits or the surrounding air for more than 1000 years, and also clarified the vague "impulse" theory in the Middle Ages.This is the theoretical result of human's long-term research on mechanical movement, and it was supported by the supporters of the theory of ground motion at that time.Although Galileo did not explicitly write down the principle of inertia, he showed that it was an objective law belonging to the nature of objects, and he skillfully used it when studying other physical problems.However, he failed to get rid of Plato's view that planets move in a circle and believed in the existence of "circular inertia", so he failed to extend the concept of inertial motion to all body movements.The complete principle of inertia was formulated by R. Descartes two years after Galileo's death.
Galileo attributed the change of the speed and direction of an object or the generation of acceleration to the action of force, which is an objective understanding of the nature of force and the embryonic form of Newton's second law.The discovery of inertial principle breaks the old concept that force is the cause of motion, and believes that force is the cause of changing the state of motion.In his book Mathematical Principles of Natural Philosophy, Newton spoke highly of Galileo's pioneering work on the first and second laws of motion (see Newton's laws of motion).
The principle of motion independence and the law of composition and decomposition of motion.In the study of trajectory, Galileo found that the horizontal and vertical movements are independent and non-interference with each other, but the actual movement track can be synthesized through the parallelogram rule.He completely explained the parabola nature of the trajectory from the uniform acceleration motion perpendicular to the ground and the uniform motion in the horizontal direction, which is a great achievement in the research of motion synthesis and has practical significance.
Concept of inertial frame。When Galileo defended Copernicus' theory of ground motion with the principles of physics, he used the principle of motion independence to explain the reason why stones fell from the top of the mast to the bottom of the mast without shifting to the stern.He further advanced the concept of inertial reference system for the first time with his famous statement that the motion law of objects in the cabin in uniform linear motion is unchanged.This principle was called Galileo's principle of relativity by Einstein, and is the precursor of the special theory of relativity.
Discovery of periodic properties of simple pendulum。Galileo made an experimental study of the pendulum by observing the swing of the church hanging lamp, and found that the period of the simple pendulum is proportional to the square root of the pendulum length, but independent of the amplitude and the weight of the pendulum.The discovery of this rule has established the foundation for the vibration theory and the design scheme of mechanical timing devices.
Limited speed of light and its measurement。The predecessors have never had a clear understanding of whether the speed of light is limited.Galileo observed the lightning phenomenon, thought that the speed of light is limited, and designed a mask scheme to measure the speed of light.However, limited to the experimental conditions at that time, the actual measured time with this measurement method is mainly the reaction time of the experimenter and the movement time of the human hand, rather than the travel time of light.However, if there is a light source with regular light and shade changes or a high-speed mechanical control device instead of manual action, the real speed of light can be measured. Later, the light speed measurement methods such as the wooden satellite eating method, the rotating gear method, the rotating mirror method, the Kerr box method, and the frequency conversion flash method were all used for reference in the light masking scheme.
Development of Several Basic Physics Experimental Instruments。Galileo not only designed and demonstrated many experiments, but also developed many experimental instruments.His craft knowledge is rich and his production skills are superb. Many experimental instruments created by him were influential at that time and later generations. Here are some examples:
Buoyancy balance。This is a direct reading instrument that uses the principle of buoyancy to quickly determine the proportion of gold and silver in gold and silver jewelry.This instrument was already used in the trade of gold and silver jewelry.
thermometer。Galileo's first thermometer is an open liquid thermometer. The glass tube contains colored water and alcohol, and the liquid level is connected with the atmosphere.This is actually a mixture of thermometer and atmospheric pressure gauge, because he did not have a clear understanding of the changes in atmospheric pressure at that time.Nevertheless, its academic value is still great, and temperature has since become an objective physical quantity, no longer a subjective sense of uncertainty.
telescope。The telescope made by Galileo can observe the positive image of objects.After improvement, its magnification gradually increased from 3 to 33;It not only points to the starry sky, but also can be applied to the ship fortress, which has achieved unprecedented fruitful discoveries (see the right picture).This telescope has a simple structure, but its power and resolution are greatly limited by spherical aberration and chromatic aberration.
Completely overthrow Aristotle's material view.The view of nature that dominated Europe in the Middle Ages was Aristotle's view of nature modified by theology, and it became a tool for the feudal theocratic rulers to rule people's thoughts.Aristotle believed that the earth and all things on the earth are composed of four elements, namely, air, fire, water and earth, which are ugly, unclean, imperfect, changeable, born and dead.Fire and air form upward flowing light objects, while water and soil form downward falling heavy objects.The celestial body is a pure, perfect and eternal object composed of the "ether".And because "God hates vacuum", vacuum cannot exist.However, Galileo found from his telescope that there were mountains and depressions on the surface of the moon, which were uneven and not perfect. Venus also had profit and loss changes;There are still active sunspots on the surface of the sun;The explosion of supernovae and its gradual fading and disappearance can be seen directly with the naked eye, which breaks Aristotle's idea that heaven is superior to earth, and the nature of celestial bodies and substances on earth is very different.Galileo learned that all objects are heavy, and there is no absolute light, through the study of floating bodies in hydrostatics.Celestial bodies, the earth and all things on the earth are unified in material structure.Vacuum may also exist and arise, and only in vacuum can we study the real nature of the movement of objects, which completely overthrows Aristotle's material view based on subjective conjecture, thus fundamentally shaking the ideological rule of feudal theocracy.
A pioneer of the scientific revolution.Galileo made epoch-making contributions in the process of human emancipation and civilization development.Under the social conditions at that time, in order to strive for academic freedom free from the oppression of power and old traditions, and for the growth of modern science, he carried out an unremitting struggle, and made a deafening sound to the world.Therefore, he is the pioneer of the scientific revolution, and can also be said to be the "father of modern science".Although he was finally deprived of personal freedom in his later years, his will to create new science has not wavered.His spirit and achievements in pursuing scientific truth will always be admired by future generations.
In 1979, Vatican Pope J. Paul II, on behalf of the Holy See, publicly vindicated Galileo, believing that it was a serious mistake for the Holy See to persecute him more than 300 years ago, which showed that the Holy See finally recognized Galileo's claim that religion should not interfere in science.
Dialogue on Two New Sciences, written by Galileo, was published by Peking University Press in June 2006.The book summarizes Galileo's research achievements in material strength and dynamics, as well as his thoughts on mechanical principles, in the form of dialogue.In April 2020, it was listed in the junior high section of the Reading Guidance Catalog for Primary and Secondary School Students of the Ministry of Education's Basic Education Curriculum and Textbook Development Center (2020 Edition).
Scientific status
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Galileo believed that experiment was the only source of knowledge. He was convinced that the book of nature was written in mathematical language. Only the shape, size and speed that can be attributed to quantitative characteristics are the objective properties of objects.Galileo played an important role in the development of natural science in the 17th century, changing human understanding of material movement and the universe.Galileo devoted his whole life to proving and spreading Copernicus' heliocentric theory.He was persecuted by the church and imprisoned for life.He created modern science based on experimental facts and with a strict logical system.Galileo's scientific discoveries play an extremely important role not only in the history of physics but also in the history of science as a whole.He not only corrected the wrong view of Aristotle, who ruled Europe for nearly 2000 years, but also created a new method to study natural science.When Galileo summarized his scientific research methods, he said, "This is the first time to open the door to a new method. This new method will bring a lot of wonderful results, and in the coming years, it will attract many people's attention." Later, Huygens continued Galileo's research work, and he derived the periodic formula of the simple pendulum and the mathematical expression of the centripetal acceleration.After systematically summarizing the work of Galileo and Huygens, Newton obtained the law of universal gravitation and Newton's three laws of motion.The spiritual wealth left by Galileo to future generations is precious.Einstein once said: "Galileo's discovery and the scientific reasoning method he used are one of the greatest achievements in the history of human thought, and mark the real beginning of physics!" Galileo's main works include "Star Messenger", "Letter on Sunspot", "Dialogue on the Two World Systems of Ptolemy and Copernicus"Talk about Two New Sciences and Mathematical Proof and Experimenter.
Character controversy
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Galileo, Kepler and Tide Theory。CardinalBellamin issued a statement in 1615, saying that the Copernican theory was not tenable unless "there is physical evidence that the sun does not revolve around the earth, but the earth revolves around the sun".Galileo thought that his tidal theory could prove the movement of the earth.This theory is so important that he first named his work "Dialogue on the Two World Systems of Ocean Tide and Flow".The word "tide" was eventually deleted by the order of the Inquisition.Galileo believed that because the earth rotates around the axis and revolves around the sun, the acceleration and deceleration of the movement of the earth's surface caused the tidal surge of seawater.In 1616, he sorted out the first literature on tides and gave it to Cardinal Osney.For the first time, his theory involves the shape and scale of the submarine continental shelf, as well as the time of tide.For example, he correctly calculated that the waves in the middle of the Adriatic Sea were negligible relative to the last wave reaching the coast.However, from the overall perspective of tide formation, Galileo's theory is not tenable.If the theory holds, the tide will rise only once a day.Galileo and his colleagues noticed the shortcomings of this theory, because the tide rises twice a day in Venice, with an interval of 12 hours.Galileo thought that this abnormal phenomenon was only caused by the shape, depth and other problems of the ocean, which was not worth mentioning.Einstein said that Galileo was only eager to give the physical proof of the earth's movement, constructed this "fascinating view" and accepted it completely.Galileo rejected Kepler's view at that time that the moon caused tidal movement, and the latter's view inherited the astrological tradition in Ptolemy's book.He also rejected Kepler's view that planets move in elliptical orbits, believing that circular orbits are "perfect".
