Gravity acceleration
Galileo drew attention to the fact that any falling body flies slowly at first, and then faster and faster - its movement accelerates. The scientist wanted to measure exactly how much the fall accelerates, that is, how much the speed of a falling object increases every second. But how to make such measurements? Throwing balls from a high tower is useless: they fall too quickly, and Galileo had nothing to measure short periods of time - stopwatches did not exist then.
The scientist decided to slow down the fall so that it became accessible to measurement with his meager means. Let, Galileo decided, let the ball roll down an inclined groove. If the slope is small, the ball will roll so slowly that you can watch the change in its speed.
Galileo took a board three fingers thick and twelve cubits long (by our standards this is approximately seven meters), placed it on its edge and cut a groove along the entire board. He covered the groove with the smoothest parchment, and carefully smoothed and polished the parchment so that the small bronze ball would roll along the groove without interference.
However, he still needed a watch for measurements. There was some semblance of a clock then, but with a very imperfect mechanism. A contemporary of Galileo, the astronomer Tycho Brahe, bought a mechanical clock for his observatory, but almost never used it. They were extremely capricious and unreliable.
In short, Galileo did not have a watch. Such an obstacle, of course, could not stop him. Galileo made a homemade water clock.
He took a bucket, drilled a hole in its bottom and placed a glass under it. Galileo poured water into the bucket and plugged the hole.
During the experiments, the scientist launched a ball along the chute with one hand, and with the other he controlled his watch: he would release the ball and open the hole, and as soon as the ball rolled to the intended line, he would plug the hole and remove the glass with the water that had flowed into it.
Galileo weighed the glass and determined the time intervals by the amount of water collected in it. He jokingly said:
My seconds are wet, but at least I can weigh them.
Of course, with this method of measuring time it was very easy to make a mistake. To reduce the magnitude of the possible error, Galileo repeated each experiment several times, trying to train himself to open and close the hole in a bucket of water as quickly as possible. The scientist acquired great skill in this troublesome task.
First, Galileo launched a ball from the upper end of an inclined chute so that it rolled along its entire length. In this case, a full glass was filled with water. Then Galileo marked the groove along its length into four equal parts and began to note the time during which the ball traveled only a quarter of the entire path. In this case, only half a glass of water was collected - exactly half as much as in the first case.
Then the scientist rolled the ball from the middle of the gutter, that is, he let it run half the way, and again weighed the incoming water.
Galileo made several hundred such experiments and became convinced that the fall of a ball along an inclined chute was not just accelerated motion, but uniformly accelerated.
The speed of the ball's fall increases evenly - it arrives every second, so to speak, in equal portions. The free fall of objects occurs according to the same law.
However, Galileo himself was never able to accurately measure how much the speed of falling objects increases - he made a mistake that reduced the acceleration value by exactly half. This error of Galileo was corrected by other scientists. It has now been established that a freely falling body accelerates its movement by 9.81 meters per second in one second.
The value of 9.81 meters per second is called the acceleration of gravity under the influence of gravity.
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But at home in his office, which became the first physical laboratory on our planet, Galileo managed to slow down his fall. It became accessible to both the eye and careful, leisurely study.
For this purpose, Galileo built a long (twelve cubits) inclined trench. The inside was upholstered with smooth leather. And he lowered polished balls of iron, bronze, and bone down it.
For example, I did this.
A thread was attached to the ball, which was in the groove. He threw it over the block, and hung a weight at its other end, which could be lowered or raised vertically. The weight was pulled down by its own weight, and up, through the thread, by a ball from an inclined chute. As a result, the ball and weight moved the way the experimenter wanted - up or down, quickly or slowly, depending on the inclination of the chute, the weight of the ball and the weight of the weight. The ball and weight could thus move under the influence of gravity. And this was the fall. True, not free, artificially slowed down.
First, Galileo found the law for the steady state of this system: the weight of the weight multiplied by the height of the raised end of the inclined chute must be equal to the weight of the ball multiplied by the length of the chute. This is how the condition for equilibrium of the system appeared - the Galilean law of the inclined plane.
Nothing has yet been said about the fall and its secrets.
Immobility is not difficult to study: it is constant over time. Seconds, minutes, hours pass - nothing changes.
Scales and rulers - that's all you need for measurements *.
* (That is why, from ancient times, statics began to develop, a branch of physics that deals with all kinds of immobility: balanced scales, blocks, levers. All these things are necessary, understanding them is important and useful; it is not for nothing that the famous Greek Archimedes devoted a lot of time to them. Even in immobility, he noticed much that was necessary for the inventors of “possible machines.” However, to be picky, this was not yet real physics. It was only a preparation for it. True physics began with the study of movements.)
Then Galileo began to study the movement of balls. This day was the birthday of physics (alas, its calendar date is unknown). Because it was then that a time-varying process was subjected to the first laboratory study. Not only rulers were used, but also watches. Galileo learned to measure the duration of events, that is, to perform the main operation inherent in any physical experiment.
The legend of Galileo's laboratory clock is instructive. At that time it was impossible to buy a stopwatch in a store. Even walkers haven't been invented yet. Galileo got out of the situation in a very special way. He counted the time with the beats of his pulse, then, as long-time biographers assure, he made a good laboratory clock from unexpected components: a bucket, scales and a crystal glass. He made a hole in the bottom of the bucket through which a steady stream of water flowed. From the sun, he noted how many ounces of water flowed out per hour, and then calculated the weight of the water flowing out per minute and per second.
And here's the experience. The scientist lowers the ball into the gutter and immediately places a glass under the stream. When the ball reaches a predetermined point, he quickly moves the glass away. The longer the ball rolled, the more water flowed in. All that remains is to put it on the scales - and the time is measured. Why not a stopwatch!
“My seconds are wet,” Galileo said, “but they can be weighed.”
Observing elementary rigor, it is worth noting, however, that these watches are not as simple as they might seem. It is unlikely that Galileo took into account the decrease in pressure (and therefore speed) of the water jet with a decrease in the water level in the bucket. This can be neglected only if the bucket is very wide and the stream is narrow. Perhaps it was so.
13/05/2002
The evolution of pendulum clocks lasted more than three hundred years. Thousands of inventions on the way to perfection. But only those who put the first and last point in this great epic will remain in historical memory for a long time.
The evolution of pendulum clocks lasted more than three hundred years. Thousands of inventions on the way to perfection. But only those who marked the first and last point in this great epic will remain in historical memory for a long time.
TV clock
Before any news programs on television, we see a clock, the second hand of which, with great dignity, counts down the last moments before the start of the program. This dial is the visible part of the iceberg called AChF-3, Fedchenko's astronomical clock. Not every device bears the name of its designer, and not all inventions are reported in encyclopedias.
The watch of Feodosius Mikhailovich Fedchenko was awarded this honor. In any other country, every schoolchild would know about an inventor of this level. And here, 11 years ago, an outstanding designer quietly and modestly passed away and no one even remembers him. Why? Probably, at one time he was stubborn, did not know how to flatter and be hypocritical, which science officials did not like so much.
An accident helped Fedchenko invent the famous watch. One of those mysterious accidents that so adorns the history of science.
The first two points in the history of pendulum clocks were set by two great scientists - Galileo Galilei and Christiaan Huygens, who independently created clocks with a pendulum, and the discovery of the laws of pendulum oscillation came to Galileo also by accident. A brick will fall on someone's head and nothing will happen, not even a concussion, while for another a simple apple is enough to awaken a thought dormant in the subconscious to discover the law of universal gravitation. Great accidents happen, as a rule, to great personalities.
In 1583, in the Pisa Cathedral, an inquisitive young man named Galileo Galilei did not so much listen to a sermon as admire the movement of chandeliers. Observations of lamps seemed interesting to him and, returning home, nineteen-year-old Galileo made an experimental installation to study the oscillations of pendulums - lead balls mounted on thin threads. His own pulse served as a good stopwatch for him.
Thus, experimentally, Galileo Galilei discovered the laws of pendulum oscillation, which are studied in every school today. But Galileo was too young at that time to think about putting his invention into practice. There are so many interesting things around, we need to hurry. And only at the end of his life, an old, sick and blind old man, remembered his youthful experiences. And it dawned on him - attach an oscillation counter to the pendulum - and you will get an accurate clock! But Galileo’s strength was no longer the same, the scientist was only able to make a drawing of a clock, but his son Vincenzo completed the work, who soon died and the creation of pendulum clocks by Galileo did not receive wide publicity.
Subsequently, Christian Huygens had to prove throughout his life that the honor of creating the first pendulum clock belonged to him. On this occasion in 1673 he wrote:
“Some claim that Galileo tried to make this invention, but did not complete the job; these persons rather diminish the glory of Galileo than mine, since it turns out that I completed the same task with greater success than he.”
It is not so important which of these two great scientists is “first” in creating clocks with a pendulum. Much more significant is that Christiaan Huygens did not just make another type of watch, he created the science of chronometry. Since that time, order has been restored in the construction of watches. The “horse” (practice) no longer ran ahead of the “locomotive” (theory). Huygens' ideas were brought to life by the Parisian watchmaker Isaac Thuret. This is how clocks with various designs of pendulums invented by Huygens saw the light of day.
The beginning of the “career” of a physics teacher
Feodosia Mikhailovich Fedchenko, born in 1911, knew nothing about the passions for the pendulum of three hundred years ago. And he didn’t think about watches at all. His “career” began in a poor rural school. A simple physics teacher was forced to become an involuntary inventor. How else, without the proper equipment, can you explain the fundamental laws of nature to inquisitive children?
A talented teacher constructed complex demonstration installations and, probably, schoolchildren did not miss his lessons. The war changed the fate of the young inventor; Fedchenko became an outstanding mechanic of tank instruments. And here was the first bell of fate - after the end of the war, Feodosius Mikhailovich was offered a job at the Kharkov Institute of Measures and Measuring Instruments, in a laboratory where, among the scientific topics, the following was written down: “Investigating the possibility of increasing the accuracy of a clock with a free pendulum of the “Short” type.”
His reference book was “Treatise on Hours” by Christian Huygens. This is how F. M. Fedchenko met his famous predecessors Christian Huygens and Wilhelm X. Short in absentia.
The penultimate point in the history of pendulum clocks was set by the English scientist Wilhelm H. Short. True, for a long time it was believed that it was impossible to create a clock with a pendulum more accurate than Short's clock. In the 20s of the 20th century, it was decided that the evolution of pendulum time devices was completed. Each observatory was not considered sufficiently equipped if it did not have Short's astronomical clock, but they had to be paid for in gold.
One copy of Short's watch was purchased by the Pulkovo Observatory. The English company that installed the time keeper forbade even touching it, otherwise it abdicated all responsibility for setting up the cunning mechanism. In the 30s, the Main Chamber of Weights and Measures in Leningrad was tasked with unraveling the secret of Short's clock and starting producing similar devices on its own. The talented metrologist I. I. Kvanberg looked at the clock mechanism for a long time through the hermetic glass of the cylinder and tried, without drawings, to make a copy. The copy was good enough, but not perfect. It was impossible to see all the English subtleties through the glass. However, before the war, the Etalon factory produced several copies of Kvanberg watches.
It was this “simple” topic - to make a watch more accurately than Short did - that was entrusted to the newcomer F. M. Fedchenko, who came to the Kharkov after the war institute
Back to the roots
The Kharkov craftsman established that back in 1673, Christiaan Huygens in his “Treatise on Clocks” said almost everything about how to make pendulum clocks. It turns out that in order for the clock to be accurate, it is necessary that the center of gravity of the pendulum in space describes not an arc of a circle, but part of a cycloid: the curve along which a point on the rim of a wheel rolling along the road moves. In this case, the pendulum's oscillations will be isochronous, independent of amplitude. Huygens himself, who theoretically substantiated everything, tried to achieve his goal by making thousands of inventions, but did not come close to the ideal.
Huygens' followers, including Short, achieved accuracy in a different way - they isolated the pendulum as much as possible from external influences, placing the precision clock deep in the basement, in a vacuum, where vibration and temperature changed minimally
Fedchenko, on the other hand, wanted to fulfill Huygens’ dream and create an isochronous pendulum. They say that everything perfect is simple. So Fedchenko hung the pendulum on three springs in total - two long ones on the sides and one short one in the middle. It would seem nothing special, but on the way to the discovery there were thousands of experiments. We tried springs thick and thin, long and short, flat and with a variable cross-section. Five long years of patient and painstaking work, the disbelief of his colleagues, they simply stopped paying attention to him, and suddenly a happy accident, thanks to an elementary mistake in assembling the suspension.
Several screws were not tightened properly, and the suspension behaved in such a way that the pendulum began to perform isochronous oscillations. The experiments were checked and rechecked, everything remained the same. A three-spring pendulum suspension solved Huygens' problem - when the amplitude of oscillation changed, the period remained unchanged.
The capital, of course, lured away the talented inventor. In 1953 F.M. Fedchenko was transferred to Moscow, to the laboratory of pendulum time instruments of the All-Union Scientific Research Institute of Physical, Technical and Radio Engineering Measurements that was being created.
Of course, Kharkov didn’t like it. Fedchenko was dealt a blow below the belt - they did not give him a high-precision imported machine tool that cost a lot of money. The inventor brought only three copies of the first experimental watch AChF-1 to Moscow. To continue working, the machine was necessary; such equipment was not sold in stores across the country. It was difficult, but it was possible to find the required machine from private owners, and Fedchenko found it. But how to pay? The state institution did not issue cash, especially such an amount - eleven thousand rubles.
Desperate Fedchenko, realizing that without precision equipment he was like without hands, went on a real adventure. He directly turned to the manager of the State Bank and found such convincing words about the significance of his invention that an intelligent and courageous man, a professional in his field, trusted the master, gave him the required amount in cash, requiring simply a receipt as a document. This is one of the examples of "obvious but incredible."
For several more decades, the mechanism of Fedchenko’s astronomical clock was improved, until the famous model “ACHF-3” appeared, which brought fame to both the author and the country. High-precision watches were demonstrated at the World Exhibition in Montreal and were awarded VDNKh medals; descriptions of watches are included in encyclopedias and in various serious publications on chronometry.
The brilliance and tragedy of Fedchenko’s invention
F. M. Fedchenko - created high-precision electronic-mechanical pendulum clocks at a time when quartz, molecular and atomic time devices had already begun to appear. These systems cannot be compared. Each performs its own specific tasks and is irreplaceable in its field. But, unfortunately, not everyone understands this. Feodosia Mikhailovich Fedchenko was never deprived of the attention of scientists and his colleagues. But officials, on whom both the fate of the inventor himself and his invention often depend, do not always know what they are doing.
The USSR State Standards Committee treated the famous designer coolly. In 1973, VNIIFTRI offered to pay the inventor a decent remuneration for more than twenty-five years of work on creating domestic astronomical clocks, which brought the country a huge economic effect and independence from the import of precision watch movements. Gosstandart considered it possible to cut the proposed remuneration by 9 times, citing the fact that “the accuracy of the AChF-3 clock is lower than the current atomic clocks.” Of course, lower. But there are only atomic clocks in the whole country, they are serviced by a whole team of employees, this is the State standard of time and frequency, and Fedchenko’s clocks have a completely different purpose - they are time keepers. Until now, many television centers, airports, cosmodromes, and observatories are equipped with Fedchenko watches.
Would anyone even think of comparing the speed of a bicycle and a space rocket? And Gosstandart compared Fedchenko’s pendulum clocks, which give an error of one second in 15 years, with atomic clocks, which err by the same second in three hundred thousand years. You can only evaluate a system of a similar class. For example, Fedchenko’s watches, compared to Short’s watches, are much cheaper, more economical, more reliable, more convenient to use and much more accurate. Let's not pay attention to short-sighted and unscrupulous officials of all ranks. The main thing is that we will remember and be proud that our compatriot Feodosia Mikhailovich Fedchenko put the last point in the development of pendulum clocks. Listen to how proudly it sounds - from Galileo and Huygens to Fedchenko!
The master, of course, knew his worth and knew that there would be spiteful critics who would try to belittle the significance of his invention. So that they would not forget about his life’s work, Fedchenko himself came to the Polytechnic Museum in 1970 with an offer to accept a gift and exhibit a clock of his design. Today in the small hall of the Moscow museum you can see many masterpieces of watchmaking art, including watches - the inventor with a capital “I” - Feodosius Mikhailovich Fedchenko
New physical device - the heart
Everyone is familiar with the slender tower located in the Italian city of Pisa from numerous paintings and photographs. Familiar not only for its proportions and grace, but also for the disaster hanging over it. The tower slowly but noticeably deviates from the vertical, as if bowing.
The “leaning” Leaning Tower of Pisa is located in the city where the contemporary great Italian scientist was born and carried out many scientific studies Galileo Galilei. In his hometown, Galileo became a university professor. A professor of mathematics, although he studied not only mathematics, but also optics, astronomy, and mechanics.
Let us imagine that on one of the beautiful summer days in those distant years we are standing near the Leaning Tower of Pisa, raising our heads and seeing in the upper gallery... Galileo. A scientist admiring a beautiful view of the city? No, he, like a playful schoolboy, throws various objects down!
The openwork Leaning Tower of Pisa was an involuntary witness to the experiments of Galileo Galilei.
Probably our surprise will increase even more if someone at this time says that we are present at one of the most important physical experiments in the history of science.
Aristotle, a broad-minded thinker who lived in the 4th century BC, argued that a light body falls from a height more slowly than a heavy one. The authority of the scientist was so great that this statement was considered absolutely true for thousands of years. Our everyday observations, moreover, often seem to confirm Aristotle’s thought - light leaves slowly and smoothly fly off trees in the autumn forest, large hail knocks heavily and quickly on the roof...
But it was not for nothing that Galileo once said: “... in the sciences, thousands of authorities are not worth one modest and true statement.” He doubted Aristotle's correctness.
Careful observation of the swinging lamps in the cathedral helped Galileo establish the patterns of movement of pendulums.
How will both bodies - light and heavy - behave if they are fastened together? Having asked himself this question, Galileo reasoned further: a light body should slow down the movement of a heavy one, but together they constitute an even heavier body and, therefore, are obliged (according to Aristotle) to fall even faster.
Where is the way out of this logical dead end? We can only assume that both bodies must fall at the same speed.
The experiments are noticeably influenced by the air - a dry leaf of a tree slowly falls to the ground thanks to the gentle blows of the wind.
The experiment must be carried out with bodies of different weights, but approximately the same streamlined shape, so that the air does not make its “corrections” to the phenomenon being studied.
And Galileo drops from the Leaning Tower of Pisa at the same moment a cannonball weighing 80 kilograms and a much lighter musket bullet weighing only 200 grams. Both bodies reach the ground at the same time!
Galileo Galilei. He harmoniously combined the talents of a theoretical physicist and an experimentalist.
Galileo wanted to study the behavior of bodies when they were not moving so fast. He made a rectangular trough with well-polished walls from long wooden blocks, placed it at an angle and let heavy balls down it (carefully, without pushing).
Good clocks did not yet exist, and Galileo judged the time it took for each experiment by weighing the amount of water flowing through a thin tube from a large barrel.
With the help of such “scientific” instruments, Galileo established an important pattern: the distance traveled by the ball is proportional to the square of time, which confirmed his idea about the possibility of a body moving with constant acceleration.
Once in the cathedral, observing how lamps of different sizes and lengths swayed, Galileo came to the conclusion that for all lamps suspended on threads of the same length, the swing period from one top point to another and the height of the rises are the same and constant - regardless of weight! How to confirm an unusual and, as it turned out, completely correct conclusion? What can we compare the oscillations of pendulums with, where can we get a time standard? And Galileo came to a solution that for many generations of scientists will serve as an example of the brilliance and wit of physical thought: he compared the oscillations of a pendulum with the frequency of his own heartbeat!
Appearance and structure of the first pendulum clock invented by Christiaan Huygens.
Only more than three hundred years later, in the middle of the 20th century, another great Italian, Enrico Fermi, would stage an experiment reminiscent of Galileo’s achievements in simplicity and accuracy. Fermi will determine the force of the explosion of the first experimental atomic bomb by the distance to which the blast wave will carry the paper petals from his palm...
The constancy of oscillations of lamps and pendulums of the same length was proven by Galileo, and on the basis of this remarkable property of oscillating bodies, Christian Huygens created the first pendulum clock with a regular course in 1657.
We are all well aware of the cozy clock with a “talking” cuckoo living in it, which arose thanks to Galileo’s powers of observation, which did not leave him even during services in the cathedral.
Do people often think about the question of when and who invented the pendulum watching the pendulum swing in a clock? This inventor was Galileo. After conversations with his father, (more details:) Galileo returned to the university, but not to the Faculty of Medicine, but to the Faculty of Philosophy, where they taught mathematics and physics. At that time, these sciences were not yet separated from philosophy. At the Faculty of Philosophy, Galileo decided to patiently study, whose teaching was based on contemplation and was not confirmed by experiments.