Biography of Galileo Galilei | Physicist and Italian astronomer

The great physicist and Italian astronomer had to face an inquisition for defending the new theories about the universe.
The scientific revolution of the Renaissance had their start in the Copernican heliocentrism and its culmination, a century later, in the mechanics of Newton. His most eminent representative, however, was the Italian scientist Galileo Galilei. In the field of physics, Galileo made the first laws of motion; in astronomy, he confirmed the Copernican theory with his telescopic observations. But none of these valuable contributions would have such far-reaching consequences as the introduction of the experimental methodology, achievement that it has earned the consideration of father of modern science.
On the other hand, the Inquisition that Galileo for defending heliocentrism was subjected would end up raising his figure to the status of symbol: in the serious mistake committed by the ecclesiastical authorities has wanted to see the final rupture between science and religion, and despite the outcome of the process, the triumph of reason over medieval obscurantism. Similarly, famously attached to it after forcible retraction (Eppur if muove, 'and yet the Earth moves') has become the emblem of the unstoppable power of the truth to any form of dogmatism established.

Galileo Galilei
Galileo Galilei was born in Pisa on February 15, 1564. What little that is known of his mother, Giulia Ammannati through letters, di Pescia, not composed her a figure too flattering. His father, Vincenzo Galilei, was Florentine and came from a family that long ago had been distinguished; forced musician of vocation, economic difficulties to engage in trade, profession that led him to settle in Pisa. Man of wide culture humanist, was a consummate performer and a composer and music theorist; his works on music theory enjoyed a certain notoriety at the time.
It had to inherit Galileo not only taste in music (played the lute), but also the independent character and fighting spirit, and may that contempt for trust blind in the authority and taste by combining theory with practice. Galileo was the eldest of seven brothers of which three (Virginia, Michelangelo and Livia) would end up contributing, over time, to increase their economic problems. In 1574, the family moved to Florence, and Galileo was sent a while to the monastery of Santa Maria di Vallombrosa, as a student, or perhaps as a novice.

Academic youth

In 1581 Galileo entered the University of Pisa, where he enrolled as a student of medicine by his father's will. Four years later, however, he left the University without having obtained any title, but with a good knowledge of Aristotle. Meanwhile, there had been a determinant fact in his life: his initiation in mathematics (aside from his university studies) and the consequent loss of interest in his career as a physician.
Back in Florence in 1585, Galileo spent some years devoted to the study of mathematics, but also interested in philosophy and literature, which showed preferences for Ariosto front Tasso; from that time dates his first work on the Centre of gravity of bodies (which then would recover, in 1638, as an appendix which would be his main scientific work) and the invention of a hydrostatic balance for determining specific weights, two contributions in the line of Archimedes, whom Galileo wouldn't hesitate to describe as "superhuman".
After some tutoring in mathematics in Florence and Siena, he tried to get a regular job in the universities of Bologna, Padua and Florence itself. In 1589 he finally got a square in the Pisa study, where their dissatisfaction by the impoverished perceived salary could not less than become manifest in a satirical poem against the academic dress. In Pisa, Galileo wrote a text about the movement that remained unpublished, in which, inside even in the framework of the medieval mechanics, criticized the Aristotelian explanation of falling bodies and the movement of projectiles.

The experimental method

In continuity with this criticism, a certain historiographical tradition has forged the story (today generally considered unlikely) of Galileo materially refuting Aristotle through the procedure of launching different weights from the top of the Campanile of Pisa, before disgruntled looks of the peripatetics. Nearly two thousand years ago, Aristotle had claimed that heavier bodies fall faster; According to this legend, Galileo would have shown the falsity of this concept with the simple procedure to simultaneously drop bodies of different weight from the top of the tower and see that everyone came to the ground at the same time.

Recreation of the plane tilted Galileo (Museo Galileo, Florence)
If true, the birth of modern scientific methodology could dated in the episode of the Tower of Pisa. And it is that, in times of Galileo, science was essentially speculative. The ideas and theories of the great sages of antiquity and of the fathers of the Church, as well as any concept mentioned in the Holy Scriptures, were revered as definite and immutable truths which could add little more than glosses and comments, or abstract speculations that not altering their substance. Aristotle, for example, had distinguished between natural movements (stones fall to the ground because it is its natural place, and smoke, for being hot, ascends to the Sun) and violent (as the of an arrow launched at the sky, which is its natural place); scholars of the time of Galileo were dedicated to reason about as sterile as this, ratings looking for a pointless conceptual refinement.
Instead, Galileo was based on the observation of the facts, subjecting them to measurable and controlled conditions in experiments. It is probably fake it to stop dropping weights from the Tower of Pisa; but it is quite true that it constructed an inclined plane of six meters long (straightening to reduce friction) and a water clock that measured the rate of descent of balls. Observation arose hypothesis that had corroborated in new experiments and mathematically formulated as universally valid laws, because, according to a famous concept of yours, «the book of nature is written in mathematical language». With this mode of proceeding, today natural and at that time new and scandalous (by questioning ideas universally admitted and the authority of the scholars and doctors), Galileo inaugurated the methodological revolution that has earned him the title of "father of modern science".

The years fruitful in Padova (1592-1610)

The death of his father in 1591 meant for Galileo the obligation to take responsibility for his family and care for the dowry of his sister Virginia. They began a series of economic difficulties that would not make more aggravated in the following years; in 1601 had to provide the dowry for his sister Livia without the collaboration of his brother Michelangelo, who had gone to Poland with money that Galileo had lent him and that he never gave (later, Michelangelo was established in Germany thank you again to the aid of his brother, and then sent to live with him in his family).
The need for money in that time was increased by the birth of three sons of the own Galileo: Virginia (1600), Livia (1601) and Vincenzo (1606), incurred from its marriage with Marina Gamba, which lasted from 1599-1610 and with whom he did not marry. All this made insufficient small improvement achieved by Galileo in his remuneration to the elected, in 1592, to the Chair of mathematics at the University of Padua by the Venetian authorities who ran it. There was recourse to tutorials, advances and even loans. Despite everything, the stay of Galileo in Padua, which lasted until 1610, constituted the most creative, intense and so happy your life period.

Galileo Galilei (detail of a portrait by Domenico Tintoretto, c. 1606)
In Padua he had occasion Galileo deal with technical issues such as military architecture, the castrametacion, the topography and related topics who tried in their particular classes. Then date also various inventions, as a machine for raising water, a thermoscope and a mechanical calculation procedure that exposed in his first printed work: operations of the geometric and military compass (1606). Designed initially to solve a practical problem of artillery, the instrument did not hesitate to be perfected by Galileo, which expanded its use in the solution of many other problems. The usefulness of the device, at a time that is had not entered still the logarithms, allowed him to earn some income through its manufacturing and marketing.
In 1602 Galileo resumed his studies on movement, focusing on the isochronism of the pendulum and the displacement along a slope, with the object of establishing what was the law of fall of the bass. It was then, and until 1609, when he developed the ideas that thirty years later they would constitute the core of their speeches and demonstrations mathematics around two new sciences (1638), work which summarizes his splendid contribution to physics.

The astronomical discoveries

In July 1609, visiting Venice (to ask for a pay rise), Galileo had news of a new optical instrument that a Dutch had presented to the Prince Mauricio de Nassau; It was the telescope, whose practical importance caught Galileo immediately, devoting their efforts to improve it to make it a real telescope. But he said having succeeded in perfecting the device thanks to theoretical considerations on the optical principles that were based, is likely to make it through successive attempts practices that, at most, be supported in some very summary reasoning.

Galileo demonstrates the telescope to the Doge of Venice (fresco by Giuseppe Bertini)
Either way, its undeniable merit resided in that it was the first that was right in instrument take a decisive scientific advantage. Between December 1609 and January 1610, Galileo made with his telescope the first observations of the Moon, playing what he saw as proof of the existence in our mountains and satellite craters showing their community of nature with the Earth. the traditional Aristotelian thesis about the perfection of the celestial world, requiring complete sphericity of the stars, were put into question.
The discovery of four satellites of Jupiter contradicted, moreover, the principle that the land had to be the center of all the movements that occur in the sky. At the end of 1610, Galileo observed that Venus had phases like the moles, made that interpreted as a confirmation of empirical to the heliocentric system of Copernicus, since this, and not the geocentric of Ptolemy, was able to provide an explanation for the phenomenon.
Eager to publicize his discoveries, Galileo wrote hastily a short text which was published in March 1610 and which did not hesitate to make you famous throughout Europe: the sidereal Messenger. Its original title, Sidereus Nuncius, means 'sidereal nuncio' or 'the Messenger of the stars', although it also supports translation 'sidereal message'. The latter is the sense that Galileo, years later, he said have had in mind when criticized you the arrogance of attributing the heavenly Ambassador status. Praise in Italian and Venetian dialect held the work. Tommaso Campanella wrote from his prison of Naples: «After your Nuncio, oh Galileo, must be renewed all of science». Kepler, distrustful at first, then understood all the benefits that they derived from using a good telescope, and also got it hooked to the wonderful news.
The book was dedicated to the Grand Duke of Tuscany Cosimo II de Medici, and in his honor, the satellites of Jupiter were there «planets Mediceos» name. This Galileo ensured his appointment as mathematician and philosopher of the Tuscan Court and the possibility of returning to Florence, which had been struggling since several years ago. The job included an Honorary Chair in Pisa, without teaching obligations, so long sheltered hope was fulfilled and he did prefer an absolute to a Republic as Venetian monarch, since, as he wrote, "it is impossible to get any payment of a Republic, by splendid and generous can be, which does not perform any obligation; Since, to get some of the public, we must satisfy the public".

Galileo Galilei (Justus Sustermans portrait, 1636)
However, accept these perks was not a risk-free decision, because Galileo knew well that the power of the Inquisition, in the Republic of Venice, was notoriously higher in his Tuscan country. In various letters had left unmistakable evidence that its review of the overall structure of the firmament had taken him to the same conclusions as Copernicus and frontally rejecting the Ptolemy system, or to advocate heliocentrism opposite the existing exclusivists. Unfortunately, by those same dates such ideas concern also to the inquisitors, but they advocated the opposite solution and began to find Copernicus suspected of heresy.

The battle of copernicanism

In September 1610, Galileo was established in Florence, where, except for brief stays in other Italian cities, had to spend the last stage of his life. In 1611 a German Jesuit, Christof Scheiner, published under the pseudonym a book about sunspots had discovered in his remarks. About the same time Galileo, which had already seen them previously, made them see various characters during his stay in Rome, on the occasion of a trip that was described as triumphant, that served, among other things, as Federico Cesi made him member of the Accademia dei Lincei, own Cesi founded in 1603 and was the first scientific society of lasting importance.
Under its auspices the history and demos on sunspots and their accidents, where Galileo went out to the passage of the interpretation of Scheiner, who intended that the spots were an extrasolar phenomenon («Star» close to the Sun that stood between it and the Earth) was published in 1613. The text triggered a controversy regarding the priority in the discovery that lasted for years and made the Jesuit one of the most ferocious enemies of Galileo, which would not have consequences on the process that was to follow him to the Inquisition. Moreover, it was there where, for the first and only time, Galileo gave the press an unequivocal proof of their adherence to Copernican astronomy, which had already communicated in a letter to Kepler in 1597.
Against academic opponents attacks and the first signs that their opinions could have conflicting consequences with the ecclesiastical authority, the position taken by Galileo was the Defender (in various writings, notably the letter to Mrs Cristina de Lorena, Grand Duchess of Tuscany, 1615) that, even admitting that there could be no contradiction between science and Scripture It was necessary to establish the absolute independence between the Catholic faith and scientific facts. Now however, as he noted the cardinal Belarmino, it could not be said that availability of a conclusive scientific evidence in favour of the motion of the Earth, which, moreover, was in contradiction with biblical teachings; as a result, it could not be but understand the Copernican system as hypothetical.

Galileo before the Inquisition

In 1616 Galileo was claimed for the first time in Rome to respond to accusations against him, battle that was without any fear, presuming a favorable resolution of the Church given. The astronomer was initially received with large samples of respect in the city; but as the debate unfolded, it was clear leaving the inquisitors would not give your arm a twist or would willingly follow brilliant arguments of the pisano. On the contrary, this episode seemed to definitely convince them of the urgency to include the work of Copernicus in the index of banned works: on February 23, 1616 the Holy Office condemned the Copernican system as «false and opposed to the Scriptures», and Galileo received the admonition not to publicly teach the theories of Copernicus.
Aware of that did not have proof that Belarmino claimed, even though his astronomical discoveries will not leave you doubt about the truth of copernicanism, Galileo took refuge for a few years in Florence in the calculation of tables of the movements of the satellites of Jupiter, aimed at establishing a new method for the calculation of the lengths on the high seas , method that tried in vain to sell the Spanish Government and the Dutch.
In 1618 he was embroiled in a new controversy with another Jesuit, Orazio Grassi, with regard to the nature of comets and the inalterability of the sky. That dispute resulted in a text, the assayer (1623), rich in reflections about the nature of science and the scientific method, which contains his famous idea that «the book of nature is written in mathematical language». The book, published by the Accademia dei Lincei, had been dedicated by the new Pope Urban VIII, i.e., to Cardinal Maffeo Barberini, whose election as pontiff filled with joy to the cult world in general, and in particular Galileo, whom the Cardinal had already shown his affection.

First edition of dialogue on maximum two world systems (1632)
The new situation encouraged Galileo to write the great work of exposure's Copernican Cosmology that had already announced many years before: dialogue on maximum two world systems (1632); in it, the Aristotelian views espoused by Simplicio is confronted with the new astronomy by Salviati, in form of dialogue moderated by the bona mens Sagredo, who wished to form an accurate judgment of the precise terms on which the controversy unfolded.
The work failed to be at the height of the demands expressed by Bellarmine, since brought, as proof of the movement of the Earth, a false explanation of tides, and although he pretended by resorting to dialogue take a seemingly neutral point of view, the inferiority of Simplicio to Salviati (and therefore of the Ptolemaic system against the Copernican) was so manifest that the Holy Office did not hesitate to open a process to Galileo Despite the fact that this had gotten an imprimatur to publish the book in 1632.

The final sentence

Interpreting the publication of dialogue as an act of disrespect to the prohibition of disclosing copernicanism, longstanding opponents claimed it again in Rome, now in less diplomatic terms, so respond of his ideas before the Holy Office in a process that began April 12, 1633. Old and wise Galileo, to their nearly seventy years of age, was subjected to a humiliating and laborious cross-examination that lasted twenty days, uselessly faced some inquisitors who qualified his book "abominable and most pernicious to the Church than the writings of Luther and Calvin" close-minded, merciless and without possible appeal.

Galileo before the Holy Office (Oil on canvas from Robert-Fleury)
Found guilty despite the resignation of Galileo to defend themselves and their formal withdrawal, it was forced to pronounce the abjuration of his doctrine of knees and sentenced to life in prison. Dialogue concerning the maximum two systems of the world entered in the index of forbidden books and not left it up to 1728. According to a pious tradition, as well known as dubious, pride and stubbornness of the astronomer took him, after his vexatious resignation to believe in what he believed, beating vigorously with the foot on the ground and in front of his pursuers to utter: "And yet moves!" (Eppur if muove, referring to the Earth). However, many of his co-religionists not forgave him the cowardice of his abjuration, attitude that embittered the last years of his life, along with the ostracism he was doomed unfairly.
The penalty was softened to allow you to adhere to it at its fifth of Arcetri, near the convent where in 1616 and with the name of sister Maria Celeste had entered his most beloved daughter, Virginia, who died in 1634. In his retirement, where moral affliction joined the arthritic and blindness, Galileo managed to complete the last and most important of his works: speeches and demonstrations mathematics around two new sciences, published in Leiden by Luis Elzevir in 1638.
In it, on the basis of the discussion on the structure and the strength of materials, Galileo sat physical and mathematical bases for an analysis of the movement that enabled him to demonstrate the laws of the severe drop in vacuum and develop a complete theory of the firing of projectiles. The work was destined to become the cornerstone of the science of mechanics built by scientists of the next generation, with Isaac Newton to the head. At dawn on 8-9 January 1642, Galileo died in Arcetri comforted by two of his disciples, Vincenzo Viviani and Evangelista Torricelli, which was allowed live with him the past few years.
Almost three hundred years later, in 1939, the German playwright Bertold Brecht wrote a play based on the life of pisano astronomer in which it runs on the interplay of science, politics and the social revolution. Although it Galileo ends by saying «I traicioné my profession», the famous playwright believes, charged with melancholy reason, that "miserable is the land that needs heroes". In 1992, exactly three and a half centuries after the death of Galileo, the papal Commission that Juan Pablo II was responsible for the revision of the inquisitorial process recognized the mistake made by the Catholic Church.

Chronology of Galileo Galilei

1564It was born in Pisa.
1574The family moved to Florence.
1581He interrupted his medical studies to study mathematics with O. Ricci. Discover the isochronism of the pendulum oscillations.
1586Constructs the hydrostatic balance to determine specific weights.
1589Professor of mathematics at Pisa.
1592It occupies a Chair in mathematics at the University of Padua. He invented the gas thermometer.
1609Build the telescope in imitation of the invented in the Netherlands toward 1600.
1610He published Sidereus Nuncius (the Messenger of the stars). Discover the phases of Venus.
1611Enters the Accademia dei Lincei, first scientific society of the time.
1615He is denounced to the Inquisition by the Dominican father Lorini.
1616Condemnation of the Copernican system by the Holy Office.
1623He published Il Saggiatore (the assayer).
1624Pope Urban VIII welcomes you in Rome.
1630It presents to censorship his dialogue on the two systems of the world.
1633Condemned by the Holy Office following the publication of its dialogue.
1637The prison is switched's arrest at his home. Discover the libration of the moon.
1638His Discorsi are published in Leiden.
1642Died in Arcetri.

Galileo Galilei and his discoveries

Italian physicist Galileo Galilei and astronomer played a key role in the intellectual movement which transformed the medieval image of the universe and laid the foundations of the conception of the nature of modern science. His theories (whose controversial nature provoked the condemnation of the Catholic Church) have disputed the inherited notions of Aristotelianism and Christian Scholasticism.


Galileo made significant scientific contributions in the field of physics, which put into question theories considered true for centuries. Thus, for example, demonstrated the falsification of the Aristotelian premise that stated that the acceleration of falling bodies - in free fall - was proportional to its weight, and conjectured that, in a vacuum, all bodies fall with equal speed.

Galileo Galilei (portrait of Domenico Crespi)
To this end he designed and measured the results of various experiments, as slide areas slope down along the surface smooth plane inclined with different angle of inclination; It is unlikely however that one of such experiments would consist in drop bodies of different weight from the leaning tower of Pisa, as I had thought for a long time. Other notable findings include the laws of the pendular movement (which began to think, according to the well known story, while observing a lamp that ranged in the Cathedral of Pisa) and the laws of the accelerated movement.
The work which earned him the title of father of modern physics was speeches and demonstrations mathematics around two new sciences (1638), written with the help of his disciple Torricelli, where the results of their research on mechanics systematized. The first two sections are dedicated to the study of the balance of forces and the resistance of the materials, and the last two the motion of falling bodies and the trajectory of the projectile; This division corresponds to two "new sciences" to which the title alludes and which today are called static and dynamic. This work laid the foundations of physics and mathematics for the analysis of the movement and became the starting point of the science of mechanics, which would be continued by later scientists and would culminate in the principles of mathematical natural philosophy (1687) of Isaac Newton.


His contributions in the field of astronomy and the study of the universe were not less important and were collected in works such as the sidereal Messenger (1610), history and demos on sunspots and their accidents (1613) and the famous dialogue on maximum two world systems (1632), where he left patent through a discussion among the characters the superiority of the heliocentric Copernican opposite the medieval exclusivists system. Despite its title, this last work also runs on many other scientific topics, and was the cause of the second Inquisition in which the elderly and Galileo was sentenced to life in prison.

Dialogue on the two maximum systems of the world
From 1609, Galileo improved the telescope, an optical instrument of recent invention, to get a telescope of sixty increases. The instrument, which until then had only been used for practical, such as navigation and war purposes, was transformed into their hands in a powerful environment for the study of the sky: Galileo explored the sky and reached conclusions which deeply revolutionized the way of understanding the order of the universe.
Contrary to general belief, he showed that the surface of the Moon was not crystal clear, but it was covered by craters and mountains, with the remainder refuted the Aristotelian idea of the absolute perfection of the stars. The same result was the discovery of sunspots; their carefully observation also allowed him to determine the period of rotation of the Sun and the direction of its axis.
Galileo discovered, also the four satellites of Jupiter, whose existence showed that not all the stars revolved around the Earth, being possible the rotating subsystems; and rightly established from its observation that the milky way, which had always been a source of confusion and speculation among astronomers, was nothing more than a set of innumerable stars.
His remarks also denied the existence of the eighth celestial sphere where, according to the model of Ptolemy, the stars were: through the telescope could see invisible star to the naked eye, which indicated that they were more distant; on the other hand, while the planets were enlarged in the telescope, the magnitude of the stars, because of its remarkable remoteness, did not suffer an appreciable alteration. Both facts drove you to the accurate assumption of a universe much more extensive of the conceived until then.
The phenomenon of the phases of Venus, which had discussed with his disciple, father Benedetto Castelli, completed his astronomical discoveries, and he provided an important test, although not decisive, on the movement of Venus around the Sun. The defense of the heliocentric Copernican model contrary to the geocentric cosmology of Ptolemy until then, might as well you the condemnation of the ecclesiastical authorities; but such sentence could not wrest the role it had played in the building of the modern vision of the universe. His discoveries, indeed, would be a crucial scientific and even philosophical significance since, upon showed that the universe was more complex and more extensive than had been imagined until then, existing since the time of Aristotle cosmological theories and sistematizas by Ptolemy crumbled.

Scientific methodology

Insofar as introducer of the experimental method in scientific research, should be considered Galileo as the founder of modern science. Although not a specific Treaty devoted to its methodological thinking, to be found in scattered passages of his works, his studies and research followed a precise methodology based on the observation of the facts, experiments and the formulation of theories explanatory. In addition to its outstanding results as a physicist and astronomer, the importance of Galileo is precisely in having created a new scientific mentality, whose bases are still ours. In the history of culture, on the other hand, Galileo has become the symbol of freedom in the investigation against the dogmatism of the established powers.
Extracted from the website: Biografías y Vidas
Biographies of historical figures and personalities

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