Henry cavendish is a British chemist and physicist. 173 1 year1October 10 was born in Nice, Sardinia. 1742 ——1748 studied at haikner school. 1749- 1753 s
Henry cavendish is a British chemist and physicist. 173 1 year1October 10 was born in Nice, Sardinia. 1742 ——1748 studied at haikner school. 1749- 1753 studied at Peter College, Cambridge University. After living in London, cavendish worked as an assistant in his father's laboratory and did a lot of electrical and chemical research. His experimental research lasted for 50 years. 1760, cavendish was elected as a member of the Royal Society of London, and 1803 was elected as one of the foreign members of the French Society 18. 18 10 On February 24th, cavendish died in London and remained unmarried for life.
Chinese name: mbth, henry cavendish: henry cavendish Nationality: British birthplace: Nice, Sardinia Date of birth:173 10 June10 Date of death:1865438+24 February 2000 Occupation: chemist, physics.
Measuring gravitational constant
Major achievements include determining that water is a compound instead of simple materials, chemical field, physical field, calculation of earth density, academic contribution, chemical research, discovery of carbon dioxide, discovery of hydrogen, observation of inert gas, physical research, electrical research, weighing the earth, torsion balance experiment, anecdotes, Frankenstein, regarding fame and fortune as clouds, laboratory, sleeping manuscript, concentration and shyness, independent biography, and major achievements in the chemical field. He determined the composition of water and proved that water is not an element but a compound. He also found nitric acid. In the field of physics, cavendish published few papers on physics before his death. It was not until Maxwell reviewed and published his manuscript that people realized that he had made many important discoveries in electricity. He found that the acting force between a pair of charges is inversely proportional to the square of the distance between them, which is part of Coulomb's law later deduced by Coulomb. He proposed that there is "electricity" around every charged body, which is very close to the electric field theory; Cavendish proved that the capacitance of a capacitor is related to the substance inserted into the plate. The concept of electric potential was first put forward by Cavendish and played an important role in the development of electrostatic theory. He also suggested that the potential on a conductor is proportional to the current passing through it. Newton was a scientist who measured the gravitational constant after he discovered the law of universal gravitation. Calculating the density of the earth Cavendish measured the density of the earth by calculating the constants in Newton's law of universal gravitation, and then calculated the density of the earth. His guiding ideology is extremely simple, using two big shot puts to get them close to two small balls. The mutual attraction between the balls is measured from the torsion angle of the line from which the balls are suspended. According to the law of universal gravitation, the constant g can be found. According to cavendish's many experiments, he calculated that the average density of the earth was 5.48 1 times that of water (the value in the 20th century was 5.5 17, with an error of about 0.65253%), and determined the gravitational constant (the gravitational constant G he measured was (6.754 0.041). This value is the same as the modern value (6.6732 0.003/kloc-0 /×10n m2/kg 2; , almost, calculated the mass of the earth. Known as the first person on earth. The historical controversy about cavendish's measurement of G is worth mentioning. The above statement that cavendish calculated the density of the earth from the gravitational constant is completely wrong. Cavendish used the proportional relationship between the sphere and the earth to measure the mass of the earth, thus obtaining the average density of the earth. Without using the value of g, the gravitational constant g does not appear indirectly or directly anywhere. This is also a common fallacy in physics teaching in China. In fact, from the perspective of the history of science, Cavendish can be said to have never had a G. When Cavendish was alive, there was still no G in Newton's gravitational equation. At that time, astronomers were more concerned about the density of each star. As long as we know the density of the earth, the density of other planets can be easily calculated. Therefore, cavendish, as a hipster in physics, naturally wants to lead the fashion without hesitation. His thesis is entitled "Experiment to Determine the Density of the Earth". G first appeared in the paper of 1873, and it was mentioned 75 years later in Cornu, A. and Baille, J.B.' s paper "Mutual Determination of Attribution Constants and Average Density of the Earth". G officially entered people's field of vision until 1894, when a man named C.Vernon Boys put forward the expression of gravity field number G in the Royal Society. After Cavendish, later generations also sorted out G=3*g/4piRp according to his experimental results, where G is the acceleration of the earth's gravity and R is radius of the earth. There is no doubt that Cavendish's experiment is only a little distance from G, and later generations can sort out G directly from his results. It's a pity that he has nothing to do with G's decision, so physicists agree with Cavendish more emotionally. If something similar happens to one of them in the future, he can hardly be regarded as the first creator, and he will surely die unsatisfied. So they defended Cavendish, saying that in the era of Cavendish, scientists still used the same unit for gravity and mass, while in astronomy, the geometric constant in the formula can be regarded as a defined Gaussian gravitational constant, and radius of the earth also knows it, so it can generally be said that in astronomical units, G is the reciprocal of the density of the earth, and Cavendish measured the density of the earth, so it can be calculated naturally. Academic contribution cavendish published few papers. He has never written a book. In the long 50 years, only 18 papers have been published. Except one paper published in 177 1, the rest are experimental and observational, and most of them are about tank chemistry, published in the journals of the Royal Society from 1766 to 1788. The other part is the research on the freezing point of liquid substances, published in 1783 to 1788. There is also a part about the study of the average density of the earth, published in 1798. After his death, people found that he had a large number of manuscripts, which had been hidden and unpublished. There are quite a few unpublished papers in this part. The electrical part was written by Professor Max willman, a great physicist in19th century, and published in 1879. The chemical and mechanical parts were edited and published by Edward Pusso at 192 1. He studied the composition of the air near 1784, and he also found nitric acid. Henry cavendish and Cavendish have done research on thermal theory, thermometry, meteorology and geomagnetism. When he finished his last experiment, he was nearly 70 years old. In physics, his main achievement is to verify Newton's law of universal gravitation through the torsion balance experiment, and to determine the gravitational constant and the average density of the earth. Cavendish's experiment to verify the law of gravity used his own "torsion balance" as a tool, which was later called the famous "Cavendish Experiment". Someone once said, "No one lives to be 80 years old and still talks as little as cavendish." In a History of Chemistry, an example of Cavendish's fear of communication was cited. One day, an English scientist and an Austrian scientist visited Sir Banks' home, and it happened that cavendish was also present. Banks introduced me. When introducing each other, Banks once praised Cavendish, a distant guest. The guest who met for the first time told Cavendish that he admired him very much, and said that the biggest gain of coming to London this time was to make a special trip to visit the famous scientist. When cavendish heard this, he was very coy at first, and finally he was completely at a loss. He rushed out of the room and got into the carriage and went home. It can be seen from this record that cavendish was withdrawn. After cavendish left Cambridge University, he attended the meeting of the Royal Society with his father and attended the dinner of the Society at noon every Thursday. 1760 was elected as a member of the royal society. Until 2 1 century, in Britain, anyone who holds the title of FRS (member of the Royal Society) is still respected by people. Then in 1783, he studied the composition of air, did many experiments and published a paper entitled "Air Experiment". It was at this time that he discovered that water was composed of two elements: hydrogen and oxygen. Cavendish's last study was about the average density of the earth. The figure he proposed is 5.448 g/cm3, which is recognized as 5.48 g/cm3. This shows that the experiment is quite accurate. He also has a job that was recognized after 100 years, and that is about the existence of rare elements. Chemical Research During Cavendish's long life, he made a series of important discoveries-among them, he was the first person to separate hydrogen, and he was also the first person to combine hydrogen and oxidation into water. The discovery of carbon dioxide cavendish pointed out that mercury must be used instead of water to collect fixed air (carbon dioxide); The density of fixed air (carbon dioxide) is 1.57 times that of physical method air. Experiments show that fixed air (carbon dioxide) can be dissolved in the same volume of water, which is the same as the gas exhaled by animals and the gas produced by charcoal combustion. He also found that in ordinary air, if the content of fixed air (carbon dioxide) accounts for 1/9 of the total volume, the burning candle will be extinguished in it. He measured the weight of fixed air discharged from limestone, marble, pearl ash and other substances by acid, and calculated the content of fixed air in these substances. These experimental studies have made people know more about the properties of carbon dioxide. Cavendish's paper published in 1767 introduced his experiments on water and fixed air. Boiling the well water of a deep well, it is found that fixed air escapes and white precipitate is produced at the same time. He thinks that white sediments and fixed air are originally soluble in water, and they may be calcareous soil soluble in water. To prove this point, he introduced fixed air into clear limewater, which initially produced milky white precipitate. After the fixed air is continuously introduced, the precipitate is dissolved again and the solution is clear and bright again. At this time, he boiled the solution and immediately released fixed air (carbon dioxide) like well water and produced white precipitate. Cavendish's experiment and his explanation made people realize a universal natural phenomenon. In limestone-covered areas, rainwater or spring water containing carbon dioxide flows through limestone strata, slowly dissolving part of limestone to form bicarbonate solution. When these solutions drip slowly in rocks, carbon dioxide may escape accidentally due to temperature changes or evaporation of water vapor, and calcium carbonate will crystallize and accumulate over time, gradually forming strange scenes such as stone bells, stone milk and stalagmites. There is a scientific explanation for karst landforms. Cavendish published his first paper "On Artificial Air" in 1766. The term "artificial air" was first coined by Boyle. Used to refer to a gas that exists in a substance and can be released by chemical reaction, such as carbon dioxide produced by the reaction of carbonate with acid in Priestley. In this article, Cavendish made a rigorous and detailed study on the physical properties of various gases, especially the density, under the premise of strictly maintaining the temperature and pressure conditions. This article won him the Copley medal of the Royal Society. The discovery of hydrogen 178 1 year, Cavendish first produced "combustible air" (i.e. hydrogen) through the reaction of iron with dilute sulfuric acid. He used drainage and gas collection method to dry and purify the generated gas in multiple steps. Then he measured its density and studied its characteristics. He explained by phlogiston theory that in the reaction between acid and iron, phlogiston in acid is released, forming pure phlogiston-"combustible air". Later, when he learned that priestley found that there was "dephosphorization gas" (oxygen) in the air, he mixed the air with hydrogen and started the reaction with electric spark, and concluded that "after continuous experiments, I found that combustible air can consume about15 of the air, and water droplets appeared on the reaction container." Then cavendish continued to study the volume ratio of hydrogen and oxygen, and reached the conclusion of 2.02: 1. At that time, there was a dispute about the right to discover that hydrogen can be burned in oxygen to produce water. Because priestley, Watt and cavendish have all done similar experiments. 1785, Watt was elected as a member of the Royal Society, and the dispute ended in a settlement between the parties. Observation of Inert Gas in cavendish Hydrogen Plant cavendish keenly noticed that the generated water contained a small amount of nitric acid. He thinks this is the reason why reverse oxygen contains new substances (mainly nitrogen). 1785, cavendish introduced an electric spark into the mixture of oxygen and air to combine oxygen and nitrogen in the air, and then absorbed the generated nitrogen oxides with sodium hydroxide solution. It was found that a small amount of air remained, about1120, which could not react with oxygen to generate compounds and was absorbed by sodium hydroxide. After hundreds of experiments and analysis, his conclusion seems very accurate today. In the air, 20.833% is dephosphorized air (the measured value is oxygen accounting for 20.95%), and 79. 167% is phlogiston air. In phlogiston air, there is1120 of the total air volume, which is not easy to react with other gases. Cavendish's conjecture was not confirmed until 1894 when Rayleigh and Ramsey discovered the rare gas argon. When lavoisier put forward the oxidation theory, cavendish agreed with the simplicity of the oxidation theory, which was beneficial to the development of chemistry, but he was unwilling to give up his phlogiston theory, so he turned his research focus to the field of physics. Physical Research and Electrical Research Cavendish observed the torsion balance with a telescope outdoors, and Cavendish did a lot of important but unknown research on electricity. He submitted a paper to the Royal Society in 1777, arguing that the force between charges may be inversely proportional to the square of the distance, which was later proved by Coulomb through experiments and became Coulomb's law. He and Faraday demonstrated that the capacitance of a capacitor will change with the medium between plates, put forward the concept of dielectric constant, and deduced the formula of a flat capacitor. He was the first to apply the concept of electric potential to explain electrical phenomena. Through a lot of experiments, the relationship between potential and current was put forward, which was rediscovered by ohm in 1827, that is, ohm's law. Cavendish's research on electricity is basically unpublished. James clerk maxwell devoted himself to sorting out Cavendish's personal experimental records in recent five years, and published Maxwell's annotation research on electricity in Cavendish in 1879. Cavendish's achievements in electricity are only known to the world. 1797 Weighing the earth, Cavendish completed the accurate measurement of the density of the earth. The device he used was designed by john mitchell, but Mitchell himself died soon, leaving the device to wollaston and then being transferred to cavendish. The device consists of two 350-pound shot puts and a torsion balance system. In order to eliminate the airflow interference, cavendish installed the device in a closed room and observed the torque change with a telescope outdoors. Later, he submitted a report to the Royal Society, which gave a relatively accurate value of the current earth density. This kind of measurement is called "the new era of weak force measurement". Many articles claim that Cavendish worked out the constant of universal gravitation. In fact, Cavendish only cared about the density of the earth at that time, and nothing else was involved. Cavendish's measurement results can be used to calculate the gravitational constant and the mass of the earth. Torsion Scale Experiment 1789, British physicist cavendish successfully measured the value of the gravitational constant by using the torsion scale, which proved the correctness of the law of gravitation. Cavendish's thinking to solve the problem is to change the small change that is not easy to observe into the obvious change that is easy to observe, and then calculate the schematic diagram of the small change according to the relationship between the obvious change and the small change: Cavendish put an iron ball with a large mass and an iron ball with a small mass at both ends of the torsion balance. A steel wire with good toughness is tied to the bracket in the middle of the torsion scale, and there is a small mirror on the steel wire. When the mirror is illuminated with parallel light, the light spot will be reflected to a far place, and the position of the light spot at this time will be marked. Use two iron balls with the same mass to attract two iron balls on the torsion balance at the same time. Because of gravity. The torsion balance has a slight deviation. However, the apogee reflected by the light source has moved a great distance. He used this to calculate the constant g in the formula of universal gravitation. The ingenuity of this experiment lies in amplifying the effect of weak force. Especially the use of light reflection. Cavendish's gravitational constant g = 6.67 *10-1The interesting anecdote Frankenstein is said that Cavendish is well educated, but not as gentle as Britain. He is untidy, and almost no clothes can't be buttoned; He is unsociable, talkative, never married, and leads a strange reclusive life. In order to engage in scientific research, cavendish turned the living room into a laboratory, and put many observation instruments at the bedside of the bedroom, so as to observe the astronomical phenomena at any time. He inherited a large inheritance from his ancestors and became a millionaire. But he is not stingy at all. Once, one of his servants borrowed money from him because he was ill. Without hesitation, he wrote a check for10,000 and asked if it would be enough. Cavendish likes books very much. He numbered his large collection of books according to different categories and managed them in an orderly way. Whether he borrowed books or even read them himself, he went through the registration formalities without exception. Cavendish can be regarded as a scholar who lived and worked until he was 79 years old and was still doing experiments on the eve of his death. Cavendish won many nicknames in his life, such as Frankenstein, giant of science, the richest scholar and the most learned millionaire. Henry cavendish regarded fame and fortune as a cloud. Once Cavendish attended a banquet, an Austrian scientist flattered Cavendish to his face. He was coy at first, but then he was at a loss. Finally, he stood up and rushed out of the room and went home in a carriage. Cavendish is taciturn. He often sits beside visiting guests without saying a word, thinking about scientific problems in his mind, which makes some idle literati feel embarrassed and disappointed. He devoted his life to scientific research and achieved fruitful results, but only published two unimportant papers. (In fact, it is because he is so withdrawn and shy that even he and the housekeeper need to communicate by letter; Even when I attend the weekly party held by the bank, I ask the participants to pretend that he doesn't exist and ask him for advice like no one else's watching. Maybe you can get a vague answer or an angry scream. ) In memory of this great scientist, the people in the laboratory set up a monument specially for him. Later, his descendants' relative, S.C. cavendish, Duke of Devon VIII, donated a fortune to Cambridge University on 187 1 to build a laboratory. It was originally a teaching laboratory of physics department named after H. Cavendish, and later it was expanded into a research and education center including the whole physics department, and was named after the whole Cavendish family. The center pays attention to independent, systematic and group pioneering experiments and theoretical exploration, in which the key equipment advocates independent control. This laboratory has made great contributions to the development of physical science. In the past century, the number of Nobel Prize winners trained by Cavendish Laboratory has reached 26. Maxwell, Rayleigh, J·J· Thomson, Rutherford, etc. Has presided over the laboratory. Sleeping Manuscript 18 10 After Cavendish's death, his nephew Qizhi left 20 bundles of experimental notes left by Cavendish intact in the bookcase, and no one touched it. Who knows that the manuscript was kept in the bookcase for 70 years until 187 1. When Maxwell, another master of electricity, applied to be a professor at Cambridge University and was in charge of building Cavendish laboratory, these intelligent and painstaking notes were given a chance to return to the world. Maxwell carefully read the work of predecessors 100 years ago and was shocked. He even lamented, "Cavendish is perhaps the greatest experimental physicist of all time. He almost foresaw all the great facts in electricity. These facts later became famous through the works of Coulomb and French philosophers. " From then on, Maxwell decided to put aside some of his own research topics and try to sort out these manuscripts, so that Cavendish's brilliant thoughts could be handed down. It's really a masterpiece, the romance of two generations. Cavendish, who is dedicated and shy, also takes part in some social activities. Joseph banks, a famous naturalist, holds a gathering of scientific celebrities at home once a week, and cavendish will also attend. Banks specifically warned others not to go near the man who stayed in the corner. If he expresses his opinion on a certain issue, people will pretend to be indifferent to him and pretend not to hear him. If the issue under discussion has nothing to do with science, people will hear a sudden exclamation behind them and turn around to see that cavendish is moving towards another quieter corner. Cavendish was the most talented and eccentric British scientist of his time. Several writers have written biographies for him. In the words of one of them, he was very shy, "almost to the point of getting sick." He feels embarrassed when he comes into contact with anyone, and even his housekeeper has to write to him. Once, when he opened the door, he saw an Austrian admirer who had just arrived from Vienna standing on the doorstep. The austrians were very excited and full of praise. For a time, cavendish listened to the praise as if he had received a sap; Then, he couldn't stand it any longer. He ran along the path and left the front door open. It was several hours before he was persuaded to go home. Sometimes, he ventured into the society-he was especially keen on the weekly scientific gathering held by the great naturalist joseph banks-but Banks always made it clear to other guests that everyone should not go near Cavendish or even look at him. People who want to listen to his opinion are advised to wander around him as if they didn't mean to, and then "pretend that no one there talks like that". If they talk about science, they may get a vague answer, but more often, they hear an angry scream (he seems to have been screaming), turn around and find that there is really no one, and suddenly cavendish flies to a quieter corner. Cavendish, an independent biography in Chapter 4 of A Brief History of Everything, was born in England in 173 1. He spent his whole life in laboratories and libraries, and made many experimental explorations in chemistry, heat and electricity. However, due to his contempt for honor, he paid little attention to publishing experimental results and gaining priority in discovery, which led to many of his achievements not being published. It was not until the middle of19th century that people found some extremely precious materials from his manuscripts, which proved that he had made great contributions to the development of science. Cavendish cavendish's most acclaimed scientific contribution is that he first studied the charge distribution on the conductor and explained the law of electric power interaction with similar experiments in 177 1. In his report to the Royal Society in 1777, he said: "The attraction and repulsion of electricity are probably inversely proportional to the square of the distance between charges. If so, almost all the excess electricity in the object is concentrated near the surface of the object. The electricity is tightly pressed together and the rest of the object is in a neutral state. " At the same time, he also studied the capacity of the capacitor; A group of capacitors with known capacity are manufactured and the capacitance of various instrument samples is measured. The dielectric constants of different substances are predicted, the dielectric constants of several substances are measured, and the concept of "potential" is put forward preliminarily. Cavendish devoted his whole life to scientific research and engaged in experimental research for 50 years. He was withdrawn and rarely contacted with the outside world. Cavendish's main contributions are as follows: 178 1 year produces hydrogen for the first time, and its properties are studied. Experiments show that it produces water after burning. However, it is a great pity that he once mistook the discovered hydrogen for phlogiston. 1785, cavendish discovered the existence of inert gas by introducing electric sparks into the air. He has made many successful experimental studies in chemistry, heat, electricity and gravity, but few of them have been published. A century later, Maxwell sorted out his experimental papers and published a book entitled "Dear Henry cavendish's Electrical Research" in 1879. Only then did people know that Cavendish had done many electrical experiments. Maxwell said: "These papers prove that Cavendish foresaw almost all the great facts in electricity, which became famous in the scientific community through Coulomb and the works of French philosophers." Long before Coulomb, Cavendish had studied the charge distribution on the conductor. 1777, he reported to the Royal Society: "The attraction and repulsion of electricity are probably inversely proportional to the square of the distance between charges. If so, almost all the excess electricity in the object is accumulated near the surface of the object, and the electricity is tightly pressed together, and the rest of the object is in a neutral state. " He also proved the force between charges through experiments. He proved through experiments that before Faraday, the capacitance of a capacitor depended on the substance between two plates. He first established the concept of potential, pointing out that the potential at both ends of a conductor is directly proportional to the current passing through it (Ohm's law is established in 1827). It was impossible to measure the current intensity at that time. It is said that he bravely used his body as a measuring instrument to estimate the current intensity by feeling the electric vibration from his fingers to his arms. One of Cavendish's great contributions is that he completed the torsion balance experiment for measuring gravity in 1789, which was later called the Cavendish experiment. He improved the torsion balance designed by the British mechanic Michel (John Lin Kewei, 1724 ~ 1793), added a small plane mirror to its suspension system, and used a telescope for remote operation and measurement outdoors, thus preventing air disturbance (there was no vacuum equipment at that time). He hung a 6-foot-long wooden pole with 39-inch silver-plated copper wire, fixed a small shot with a diameter of 2 inches at each end of the wooden pole, attracted them with two large fixed shot with a diameter of 12 inch, measured the swing period caused by gravity between the shots, and calculated the gravity of the two shots, and then calculated the mass and density of the earth from the calculated gravity. He calculated that the density of the earth is 5.48 1 times that of water (the modern value of the density of the earth is 5.5 17g/cm3), from which the value of the gravitational constant g can be calculated as 6.754×10n m&; sup2/kg & amp； Sup2 (the first four digits of the modern value are 6.672). The conception, design and operation of this experiment are exquisite. British physicist J.H. Poynting once commented on this experiment: "It initiated a new era of weak force measurement". Cavendish published a paper on artificial air in 1766, and won the Copley Medal of the Royal Society. He made pure oxygen and determined the contents of oxygen and nitrogen in the air, which proved that water is not an element but a compound. He is called "Newton in chemistry". Cavendish worked in his own laboratory all his life and was called "the richest scholar and the most learned millionaire". Cavendish died in March 18 10.