# Daniil Bernulli

Date of Birth: 09/02/1700

Age: 82

Place of birth: Groningen

Citizenship: Switzerland

**Background**

Daniel Bernoulli was born on January 29 1700g. in Groningen (Holland), where his father taught mathematics at university. In 1705g. the family moved to Basel (Switzerland), where Johann Bernoulli "inherited" the position of professor of mathematics after the death of his elder brother Jakob. Daniel studied at the Basel school. After graduating from high school in 1713g. he was sent to France to improve the knowledge of the French language. After returning home in 1716, he received the title of Master of Philosophy. At the insistence of his father, Daniel began to study medicine, as the most practical of the professions. He studied in Heidelberg, Strasbourg and after defending his thesis "On the breath" in 1720 became a licentiate of medicine. But Daniel`s heart did not lie to the medical practice, he was more attracted to the mathematical sciences. In 1724 it is published the first scientific treatise Daniel Bernoulli "mathematical exercise". In the same year he became a member of the Scientific Academy in Bologna and received an offer to head the academy in Genoa. While Daniel was thinking, it`s an invitation from Russia to join the newly created by Peter I St. Petersburg Academy. The offer was tempting, but Daniel did not want to part with his brother Nicholas, with whom he had a touching friendship. The difficulty was resolved very simply. The then president of the St. Petersburg Academy of LL Blumentrost invited both Bernoulli. By sending their sons on a long journey, Johann Bernoulli admonished them with these words: "... It is better to suffer some of the harsh climate of the ice of the country, which welcomes musical, than to die of hunger in a country with a temperate climate, in which the musical offend and despise."

In October 1725 the brothers arrived in St. Petersburg. Daniel received the chair of physiology, Nikolai - mathematics. The brothers immediately involved in the work of the Academy. Unfortunately, Nicholas Bernoulli`s activities did not last long. The climate of the northern capital was too severe for him. Eight months after his arrival in St. Petersburg Nicholas died. Daniel Bernoulli remained in St. Petersburg until the summer of 1733 he led the research, has lectured and participated in the debates. Returning to Basel, Bernoulli received the university department of anatomy and botany, but was more concerned with experimental physics. In 1750 he headed the department of physics, which held until the last days of his life. Science was the only passion of Daniel Bernoulli. Perhaps that is why he was not married. Because science classes he had a strained relationship with his father, with whom they fought all the time priority disputes. Father and son are independently engaged in the same problems and doing well. This is clearly evidenced by the following fact. In 1732, the Paris Academy of Sciences announced a competition on the theme "On the mutual inclination of the planets." Two works from the collection of the contest had been recognized as the best, and it was decided to split the prize between the authors. When opened the envelope with the motto, it turned out that the father and son avtory- Bernoulli. "I am glad that your son is printing Bernoulli and stores hereditary glitter names" -pisal Leibniz, Johann Bernoulli. Daniel Bernoulli was a very kind person. He sacrificed the university, where he taught, large sums of money, built a cheap hotel for traveling students, helping the needy, etc. He was a stranger to envy and happy scientific achievements obtained by other. Daniel Bernoulli scientific authority was very high. Evidence of this was his election as a member of many foreign academies of sciences (besides St. Petersburg) - Berlin (. 1747g), Paris (1748.), The Royal Society (1750.). Until the last days of his life he was engaged in scientific activities. March 17, 1782 the servant found him fallen asleep in a chair forever.

A significant contribution was made by Daniel Bernoulli in mathematics. He dealt with a Riccati equation, which is commonly found in a variety of mechanics problems. Bernoulli calculated the limit of the expression (1 + 1 / n) n. It is now the well-known number of e - base of natural logarithms. Successfully engaged Bernoulli theory of series, a variety of special functions, probability theory. He introduced the concept of moral expectation, which then widely used by Laplace, Poisson. In gambling a moral expectation of the loss exceeds the moral expectation of winning. Subsequently, the concept of moral expectations have not received further development. Bernoulli proposed to solve the problem of probabilistic methods of differential calculus, counting unit "infinitesimal" compared with other "big numbers", appearing in the problem.

Daniel Bernoulli`s contribution to science can not be overestimated. Together with MV Lomonosov he was behind the kinetic theory of gases. His works can be found anticipation of Gay-Lussac`s Law, Clapeyron and Charles. Daniel Bernoulli was the first who expressed the opinion that the gas pressure due to the thermal motion of molecules. In hydrodynamics, Bernoulli equation given the steady motion of an ideal incompressible fluid. It expresses the law of conservation of energy. Bernoulli`s Equation allows us to understand many phenomena of fluid mechanics and aerodynamics. It is used in calculating various conduits, pumps and flowmeters study filtration processes, etc. Together with some other relations Bernoulli equation written for a medium with variable density "RO", constitutes the basis of gas dynamics. Daniel Bernoulli, together with Euler belongs to the main credit for the development of the mechanics of liquid bodies. More than fifty years (from 1727 to 1778 gg.) Daniel Bernoulli studied oscillations. In his first works he studied small oscillations cargo suspended on a flexible string and rope hanging heavy uniform. In later works he studied the vibrations of strings and rods, introduced the concept of a simple harmonic oscillation and substantiated the position that the total oscillation of the system is obtained by adding simple harmonic oscillations. This important principle was later called the principle of superposition (overlay) oscillations. Daniel Bernoulli with D`Alamberom, Euler, and Lagrange can be considered the founder of mathematical physics.