The book "Physics, told at night"

Physics has an incredible biography. You can find everything in it: successes and failures, hopes and crumbling dreams, machinations of ill-wishers and envious people, creative impulses and fortitude.

In this book you will not find a single formula, but you will learn about great physical ideas and especially about the people who stand behind them: from Newton and Galileo to Einstein, Feynman, Fermi and Bohr; from Faraday and Maxwell to Schrödinger, Dirac, Heisenberg and Pauli; from the origins of science to the problems of time and space, the nature of light and heat; from the discovery of an atom to the principles of quantum mechanics; from observations of the starry sky to the fundamental ideas of modern astronomy and cosmology.

Excerpt from the book
Amazing substances or is it still just movement?

When Feynman was a freshman, he often heard discussions of his older roommates regarding problems of mathematics and physics. Once, two of them tried unsuccessfully to solve a problem in theoretical physics. Feynman's solution to this problem seemed clear, and he proposed "using the Baronallai equation."

The surname of Baronallai did not say anything to Feynman's roommates. Feynman learned about this equation from the Encyclopedia Britannica, but did not know how to correctly pronounce the last name. After it turned out that the discussion was about the Bernoulli equation, the problem in physics was really quickly solved - and Feynman very soon became famous as the genius of mathematics.

The Bernoulli family in mathematics is like the Bach family in music. Over four generations, she gave eleven outstanding mathematicians: four Nikolauses, three Johannes, two Jacobes, two Daniels. One of Daniel Bernoulli was not only a famous mathematician, but also made a significant contribution to the field of physics.

Once during a trip to Europe, during a conversation with strangers, Daniel Bernoulli introduced himself. “Then I am,” his interlocutor answered, “Isaac Newton.” Daniel Bernoulli was happy to tell this story, as he saw in it a sincere display of respect for him.

In his Hydrodynamics, published in 1738, Daniel Bernoulli successfully applied Newton's laws to liquids and gases. At the same time, Bernoulli, of course, proceeded from the fact that gases consist of atoms - from a myriad of small solid particles that are in constant motion, more or less freely move past each other and at the same time continuously hit the walls of the vessel, giving rise to way gas pressure.

In a glass vessel of a larger volume containing the same number of atoms, the gas pressure is less, since collision with the walls of the vessel occurs less frequently. Bernoulli took up the consideration of the specific question of how the gas pressure would change if the side length of the cubic vessel was doubled, which would accordingly increase the volume of the vessel by eight times. Since then the opposite walls of the vessel will be located farther from each other and, therefore, the particles will have to cover twice as much distance from one wall to another, then, therefore, they will hit the vessel walls two times less often. However, due to the fact that at the same time the surface of the walls of the vessel will become eight times larger, the gas pressure as a whole will decrease by one eighth of the original value. If, on the contrary, reduce the volume of the vessel by half,

About seventy years earlier, Robert Boyle, learning about Otto von Guericke's experiments, also wanted to devote himself to this amazing vacuum. Together with Robert Hooke, he established that this more or less airless space transfers light and electric forces without changes, however, it cannot conduct sound and that combustion cannot occur in it. Until that time, all studies dealt exclusively with vacuum. Then Boyle's acquaintance, the theologian, Jesuit father Linus prompted him to the idea of ​​experimenting not with the vacuum, but with the air itself. The reason for this was Linus's doubts. The Jesuit father considered Gerike's experiments improbable. Linus thought that if air can be rarefied, then it should also be compressed. However, this, in his opinion, was absurd.

Boyle began to consider this idea and conducted his "New physical and mechanical experiments concerning the elasticity of air and its effects." Indeed, in 1660, Boyle presented a table, the data of which showed that when the volume is reduced by half, the gas pressure doubles.

Boyle saw the reason for the increase in gas pressure in small, springy particles located on top of each other: during compression, the gas pressure increased, as if during compression of a box filled with rubber balls. Newton also believed that gas pressure is caused by particles at rest, but repelled by each other. Only Daniel Bernoulli put forward the correct idea - about moving particles. It was Bernoulli who managed to find the right relationship between pressure and volume. However, his idea was not successful.

In his Physics, Aristotle spoke of the following four elements: fire, water, earth and air. However, at the same time, Aristotle did not mean the real substances themselves or the fire itself. Elements - water, earth and air, although they remind of aggregate states - liquid, solid and gaseous, however, have no analogies in the world around us. When, at the beginning of the 18th century, Georg Stahl expressed the idea that when a body is burned, a phlogiston is released - from the Greek "fuel" - and turns into fire, for many this element - fire - took on its concrete form.

The more phlogiston the body contained, the better it burned. In this case, combustion was presented as a separation of two substances. After some time, it turned out that during combustion the body becomes heavier. What at first glance might have looked like a contradiction was resolved by artificial means: a negative mass was attributed to the phlogiston - thus an explanation was given of why the fire rises.

Antoine Lavoisier saw this completely differently - and as a result became one of the founders of modern chemistry. Lavoisier believed that during combustion there was not a separation of the two substances, but, on the contrary, their combination. In combustion, he saw a combination with oxygen and thus managed to explain why the body becomes heavier during combustion. At the same time, he found a compelling tool to answer the ancient question of the difference between an element and a compound. If a substance can be chemically converted into substances that are heavier than itself, then, according to Lavoisier, we are talking about a chemical element.

When in 1789, in the year of the French Revolution, Lavoisier published his new theory of chemical elements, there were already twenty-three of them. 282 Among these twenty-three elements was a substance that is not considered to be an element today - caloric. The calorific, however, was not Aristotle's fire, but a substance of heat, which Lavoisier considered as part of chemical reactions.

For Joseph Black, who lived at the same time as Lavoisier, calorie was an elastic fluid. This idea made, it would seem, some phenomena well understood. From this point of view, the caloric penetrates into the heated body. This is noticeable when stretching the body. When compressed, the gas gives off tangible heat, since the heat is squeezed out of it. During evaporation, the substance absorbs the calorific value, and during condensation, the calorific value is again released as condensation heat. To melt ice, you need heat. When ice freezes, it gives off this heat.

Earl Rumford doubted the existence of a caloric. For a long time, during careful measurements, he tried in vain to determine the weight of heat, the weight of the calorific. Instead of simply assuming that heat, like light and electricity, is weightless, Rumford, in the negative outcome of his experiments, saw an indication that “heat is nothing but the internal, vibrating movement of the particles that make up a heated body ".

Rumford made this assumption, having a good reason for this. In Munich in 1798, at his request, gun trunks were drilled with dull steel drills in artillery workshops at his request. Hot hot drills now and then plunged into the water. Thus, with the same drill, water was brought to a boil for several days and weeks. As a result, it became quite obvious that heat cannot be a substance, since in this case it would one day have to exhaust itself. Obvious for Count Rumford was also what heat actually was: since it was continuously formed due to movement, then, according to Rumford, it itself should have been part of the movement.

Earl Rumford was not able to convince the scientists of his time. Reflecting on heat, physicists of that era considered it not in the form of the smallest particles in constant motion, but as before in the form of an amazing substance.

Daniel Bernoulli saw in the particles in constant motion the cause of gas pressure. For Count Rumford, this movement manifested itself additionally as heat. The kinetic theory of heat, from the Greek word kinema for movement, was created from the ideas of Bernoulli and Rumford. In particular, this way physics came to the discovery of the atom. However, this became possible thanks to another huge breakthrough in physics, namely the discovery of the law of conservation of energy.

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