*In January 8, 2017 were 375 years since the death of the genius Italian scientist Galileo Galilei (15.02. 1564 - 08/01/1642), one of the founders of classical physics and natural science research in general.*

*Everyone knows his discovery in astronomy (satellites of Jupiter, the phases of Venus, etc.), Mechanics (Galilean relativity principle, the law of falling bodies, etc.), His struggle for the approval of world system of Copernicus. However, few people know that Galileo was an engineer and a teacher of engineering disciplines, and imagine very little value to the circumstances of his scientific discoveries.*

**Education and the beginning of Galileo’s scientific researches**

Galileo Galilei was one of the founders of classical physics mostly because he got a university education (incomplete) and engineering.

He was the eldest son of the Florentine Vincenzo Galilei - musician (lutanist), music teacher, author of several works of musicology. Galileo has grown in an atmosphere of art, classical poetry, learned to play the lute perfectly and draw. Some time he even wanted to become a painter. Primary education (reading, writing, Latin, arithmetic) he got at home and in convent school.

In 1581-1585 Galileo studied in Pisa University at the medical faculty, where, along with medical treatises studied philosophy of Aristotle, elementary mathematics, Ptolemy system of the world. Also he studied to compose horoscopes – with the help of them doctors predicted the diseases at that times.

In 1585, Galileo left the university and returned to Florence. Here he took private lessons in Ostilio Ricci - Advisor for Mathematics in the court of the Duke of Florence and Florence lecturer Academy of Arts (Academia del Disegno). Here trained specialists in construction and cars, demand for which in the sixteenth century. constantly growing with the development of artillery and fortification. In this academy, unlike universities, taught mechanics (the science of machines and mechanical arts (crafts)).

Under the guidance of Ricci Galileo studied "The Beginning" of Euclid, Archimedes works and engineering sciences that time, the idea of which give abstracts of lectures Ricci stored in museums today. Ricci taught how to measure the height and depth (including towers and wells) how to determine the proportion of solids, acquainted the audience with the design winders, construction of forts, building canals and regulation of water flows. In this case, he taught mathematics not as a speculative "pure" science, but as a basis for practical calculations.

Even while studying Galileo performed his first independent research topics directly related to the fact that he studied.

We "hydrostatic balance" (1585) gave a description of Galileo invented his scales, which are based on Archimedes' principle. The weights allowed to accurately determine the proportion of solids and subsequently used for centuries. Practical value of work enhanced contained in it the Table of density metals and gems.

In his work "Theorems on centers of gravity of solids" (1586), Galileo considered problems while engineers debated widely and proved some theorems using geometric approach the works of Archimedes. The work made a very good impression on renowned military engineer, author of "The Book of mechanics" Hvidobaldo Marquis del Monte, expert works of Archimedes. He wrote a favorable review of this work and was a patron of Galileo.

You can see one common feature in the first Galileo’s researches: using knowledge of mathematics and physics to solve the problems of engineering practice.

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**Galilei – a teacher, engineer and researcher**

Due to the petition of Hvidobaldo del Monte, Galileo in 1589 received a professorship of mathematics University of Pisa. According to the curriculum he taught geometry and astronomy (by Ptolemy). At the same time doing research in the field of mechanics. In 1590 wrote paperm but rather, outline work "About movement", which drew attention to the existence of discrepancies between the facts and the provisions of the physics of Aristotle.

In 1592, again on the recommendation of Hvidobaldo del Monte, Galileo became a professor at Padua University (Republic of Venice). He lectured that based on the "The Beginning" of Euclid (III-IV century BC.) "Almagest" Ptolemy (second century.) Astronomical "Treatise on the field" Statobosko (XIII.) And at work "Mechanical problems", which was attributed to Aristotle. The latest is the oldest work in theoretical mechanics; It explains the various mechanisms (scales, rotation, wedge, propeller and steering oars, etc.) based on the principle of the lever.

In Padua, Galileo gave private lessons to the military. He taught them geometry, the theory of perspective, fortification, ballistics and other items. Since then we got his manuscript "Machines", "Short instruction of military architecture" and "Treatise on Fortification" (1592-1593). In the last two works Galileo initially draws attention to the fact that the emergence of modern art artillery fortresses construction is significantly different from the ancient, and the ancient treatises on fortification unsuitable for practice.

Galileo taught not only theory but also taught his students to use mathematical tools, including his own invented geometrical and military compass. This tool could measure the distance, height and depth, to determine the angles and so on. He also organized at his home studio, where he hired craftsmen produced these compasses and proportional compasses and some metal parts tools. Incidentally, Galileo's first published work was a practical manual "Operation geometrical and military compass" ( "Le operazioni del compasso geometrico e militare", 1606).

There is written by Galileo an outline of the curriculum for the new academy, which is going to open in Padua, where they prepared military. Galileo wrote that the military needed "knowledge of arithmetic, geometry, mechanical sciences in a variety of applications, artillery science with knowledge of the causes and explanations of many individual cases, that may occur in this area, knowledge of compass and other tools for drawing plans, measuring distances, depths and heights, then - the rules of perspective to properly depict any real or imaginary object, such as a building and part of them or any kind of military vehicles, and, finally, knowledge of military architecture".

Naval Committee of Venetian Arsenal attracted Galileo as expert of Mathematics and Mechanics expertise into new projects warships. Galileo, in particular, performed the calculation of new heavy oars galley.

As an engineer, Galileo developed a design of water-lifting pump that used draft power animals, and received a patent on this design from the Venetian Republic.

In the period of Padua, Galileo conducted experiments to study accelerated motion and gradually formulated almost all the main concepts of his dynamics. Then he became a supporter of the world system of Copernicus, although my lectures were to teach the system of Ptolemy.

In the end-1590, Galileo wrote the work «Mechanics», in which for the first time in the world to formulate a number of General provisions regarding vehicles. He notes that the study of machines should take into account the four «objects»: «first – is the cargo that is to be moved from place to place; the second is the force that carries the load; the third is the distance between the start and end point of the movement; the fourth is the time during which must occur move». He also opposed the ideas that the machine can outwit nature (this statement is in the «Mechanical problems»).

The story of the astronomical discoveries of Galileo is widely known, and I talk about it I will not. I note only that, in the summer of 1609, after learning about the existence of the telescope, Galileo invented the design, he manufactured the lenses and tubes, they are constantly improving. That is operated as an engineer-optician. For a time, his telescope was the best in the world. In January 1610 Galileo using his telescope began to examine the nocturnal luminary, and in March he published the book «the Starry messenger» in which he described his astronomical discoveries. This helped him to obtain the rank of chief philosopher and mathematician of the Grand Duke of Tuscany, and in July 1610, he moved from Padua to Florence.

In Florence, Galileo was engaged primarily in astronomy, a criticism of Aristotle's physics and protection system of Copernicus. He continued his experiments with optics, invented the binocular microscope. Performed technical examination of projects of machines and ships, the inventors proposed for the implementation of the government of the Tuscan Duchy.

In 1634 saw the light of Galileo's book «Dialogue on the two chief world systems: Ptolomeo and Kopernikova». It not only disguised as a discussion defended the system of Copernicus the world, but focused on mechanics. For the promotion of kopernicanism Galileo was subjected to trial by the Inquisition, who forbade him to write about astronomy until the end of his days. After this 70-year-old Galileo focused on the problems of mechanics.

In 1638 in Leiden and publisher of Elzeviro he published his book «Conversations and mathematical proofs of the two branches of science pertaining to mechanics and local motion». Two new branches of science, which are referred to in the title of the book is mechanics of materials and teaching run priority movement. This is the first book in the history of science considered the question of the strength of rods and beams under bending, strength of geometrically similar bodies with their own weight, etc. the Book Galileo was also the basis for further research in the field of dynamics H. Huygens and I. Newton.

**As the nature of the formation and activities of Galileo contributed to his scientific discovery.**

As mentioned above, Galileo received a University education (unfinished), and engineering. In university he studied philosophy of Aristotle and Plato, respectively, had an idea about what a scientific theory true, a rigorous proof, able to lead a theoretical discussion. While the engineer Galileo was not interested in the «eternal» problems of «pure» science, and those that pertain to the operation of machines.

This he directly wrote in the beginning of his book «Conversations and mathematical proofs...»: «a Vast field for reflection, I think, gives an inquisitive people the constant activity of your famous Arsenal, Signore, the Venetians, especially in the field of mechanics, because all kinds of tools and machines are constantly used here a large number of artists, many of whom by the observation of the creatures of their predecessors and reflections in the manufacture of its products has gained a lot of knowledge and keenness of thought."

At the same time, Galileo was not an engineer-practitioner and as a scientific consultant engineers. Accordingly, to consider problems arising in practical activities of engineers detached. Thanks was looking for General approaches to solving these problems, and thus laid the foundations of theoretical mechanics. By the way, continued correspondence with Galileo engineering practices. In these letters we discuss many issues about which he later wrote in his «Dialogues on two world systems» and «Conversations about a new branch of science».

In my opinion, if Galileo was the only Professor at the University, he would not have become the founder of classical physics as an exact science. The philosophy of Aristotle and Plato, who taught in universities, argued that accurate calculations can be applied only to ideal mathematical objects, and that the real objects of mathematics can not be applied. At the same time as Galileo engineer be aware of the needs of ballistics, engineering and construction in the execution of accurate calculations, respectively, tried to develop that, again, contributed his research in the field of mechanics.

The fact that Galileo dealt with the problems of motion of bodies is directly related to the fact that he taught ballistics. In this teaching he could rely on the works of Aristotle, and a treatise by Nicolo tartally the «New science». But Aristotle gave a completely incorrect description of the motion of a body thrown at an angle to the horizon, and Tartaglia inaccurate. Aristotle wrote that the body first flies in a straight line below the angle of his left (this movement is violent), and then vertically down (natural movement). Tartaglia – the body first flies in a straight line, then along the arc of a circle, and then straight vertically downward. Being critical-minded person, Galileo could not just tell his disciples to other people's thoughts, and tried to convince himself of the truth of what he taught. It also forced him to constantly reflect on the problems of mechanical motion of bodies, to experiment and to make discoveries in the field of mechanics.** **

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For a long time, the work of Galileo as an engineer and teacher of engineering disciplines and the impact of those activities on his scientific research, has escaped the attention of historians. The first connection of scientific research with Galileo engineering practices analyzed in the 1920s, the famous historian of science Leonardo Olsc in the 3rd volume of his work «the History of scientific literature in the new languages» (this volume in the reading room №2 of the TSA KPI them. Igor Sikorsky). Information on the activities of Galileo as an engineer and scientific consultant engineers prominent in the book of the Italian historian of science Matteo the Valerian «Galileo engineer» (M. Valleriani, Galileo Engineer. Springer, 2010), where the published part of the correspondence of Galileo with the engineers. These two books became the main source materials for this article.