XVII century - the century of enlightenment. In many branches of knowledge, the forces of advanced minds replaced the religious basis for cognizing the world with a purely scientific one. A unique phenomenon in this process is the Bernoulli family, which gave several world-class scientists at once. One of the most striking names from this galaxy is Daniel Bernoulli. The scale of talent and the diversity of scientific interests, he resembled the great scientists of the Renaissance.
The main merit of him and other family members to future generations is to give mathematics the role of a universal tool for research in various fields of science - in physics, chemistry, biology, and many others.
Mathematics as a Family Affair
The ancestors of the Bernoulli family were originally from Flanders, from the area of the Southern Netherlands, which later became part of Belgium. In Antwerp, where one of the ancestors of the famous family, Jacob, lived, oppression of Protestantism supporters began, which included Bernoulli. They were forced to leave first to Germany, and then to Basel, where they received Swiss citizenship. The son of Jacob, Nikolai, who is designated Elder on the family tree, had 11 children. He became the founder of the famous mathematical dynasty. One of Jacob's children, Johann, taught at the University of Groningen. In this Dutch city, on January 29, 1700, Daniel Bernoulli was born (1700-1782).
When the future great scientist was 5 years old, Johann Bernoulli returned with his family to Basel, where he received the post of professor of mathematics. After he began to educate Daniel, it became clear that he was gifted no less than his brothers - Jacob and Nicholas the Younger. But Johann suggested for Daniel a more profitable - merchant or medical - career, therefore, at his insistence, from the age of 15, Daniel Bernoulli began to study medicine, first at the University of Basel, and then in Heidelberg, Germany.
Medicine and Math
Interest in the study of flows in a liquid and gaseous medium manifested itself in Daniel, when he became a student of the famous English physician William Harvey. He carefully examined his work on the study of blood flow in the human body - Harvey was the pioneer of the large and small circles of blood circulation.
Soon, Daniel Bernoulli defended his thesis and tried to get the post of teacher. At that time, the selection of applicants was often carried out by lot. The young scientist's attempt was unsuccessful, but became the reason for his interest in the mathematical aspects of probability theory.
In 1724, Daniel moved to Venice to continue studying practical medicine with the famous doctor Antonio Michelotti.
Danila Ivanovich
In Italy, he became seriously ill, but continued his research. He conducted many experiments to find patterns in the behavior of water when it flows out of a container and passes through tubes of different sections. This work created him credibility in a new field of physics, which he called hydrodynamics.
In 1725, Daniel Bernoulli received an invitation from the Russian Empress Catherine I to take the post of head of the department of mathematics at the Academy of Sciences of St. Petersburg. She counted on his participation, as a prominent specialist in hydrodynamics, in the creation of a cascade of fountains in Peterhof.
The scientist’s stay in Russia was marked by tragedy - 9 months after arriving in St. Petersburg, his brother Nikolai, who came with him, died of a fever. Despite the difficult moral condition that accompanied him during his entire stay in a foreign country, Daniel accumulated material for his main scientific work, Hydrodynamics, published in 1738. It formulated the main provisions of the laws that determine the nature of flows in liquids and gases, which received the name Bernoulli.
Longing for home forced the scientist to apply for a position in Basel, where Daniel Bernoulli returned in 1733. Since then, his biography was connected only with this city, where he lived without a break until his death in 1782.
Relationship with father
When in 1734, Daniel submitted his "Hydrodynamics" to a competition at the Paris Academy of Sciences, it turned out that his rival was his father. The decision of the Academy was a compromise, but it provoked anger on the part of the parent. Daniel Bernoulli and Johann Bernoulli were declared equal winners, but being on the same level with his son seemed humiliating to the old professor.
Daniel’s relationship with his father was broken, despite the desire of his son to establish them. When publishing Hydrodynamics in Strasbourg in 1738, he defiantly added to his name on the title page "the son of Johann." But the elder Bernoulli was implacable. A year later, his book "Hydraulics" was published. He specifically dated it to 1732 to indicate his priority.
Daniel Bernoulli and his contribution to the development of probability theory
In “Comments of the St. Petersburg Academy” Bernoulli published a work in which he considered the statement, called the St. Petersburg paradox. It concerned the game, first mentioned by Daniel’s nephew, Nikolai: when tossing a coin n times, the “eagle” that came out brought the player a win in the amount of 2 to the power of n coins. The mathematical calculation of the probability of winning leads to an infinite value, but common sense shows that the reward for participating in the game must have a finite value. In resolving the paradox, Daniel uses the replacement of the mathematical expectation of winning with a moral one, as well as the relationship of probability and personal utility.
Another important Bernoulli study in this area was connected with the main profession of Daniel - the medical profession - and with new branches of science, mathematical statistics and the theory of errors. He published a paper on the effectiveness of smallpox vaccinations.
Heritage
The work of Daniel Bernoulli in the theory of differential equations is highly appreciated by “pure” mathematicians. And mathematical physics is a branch of science where the scientist is considered one of the founders.
A true universal physicist, in addition to the fundamental laws of hydrodynamics, Bernoulli enriched the kinetic theory of gases and the theory of elasticity, which is devoted to a whole series of works on string vibrations. Modern aerodynamics is also based on the findings first made by Daniel.
Paris, Berlin, Bologna, St. Petersburg Academy of Sciences, the Royal Society of London - Daniel Bernoulli was a member of these scientific associations. A photo with his portrait adorns the walls of many scientific institutions bearing his name, including a laboratory at the Institute for Mathematical Studies of Complex Systems at Moscow State University.