In the last few decades of the nineteenth century, a group of scientists were chasing after a mysterious ray of light. Scientists named it the cathode ray. That group of scientists had the names of many chariot-masters - Julius Placker, Eugene Goldstein, Johann Wilhelm Hitterf, William Crooks, Heinrich Rudolf Herz, J. J. Thomson. In fact, this ray of light can be seen when an electrical connection is made between two electric gates of an airless cathode tube. Scientists are divided on what the ray is. One group's idea is that it is actually an electromagnetic wave. That is, it is merely a ray of light. The biggest supporter of this group is the British scientist Heinrich Herz. German and French scientists, on the other hand, thought it was actually a kind of negative particle current. Scientists on both sides are arguing and trying to prove themselves. This history would require a whole chapter. That's not very important for this book. Interested readers can read my book Quantum Physics published from Anbesha. There is a detailed story of these two groups of scientists.
British scientist Sir JJ Thomson showed evidence in hand. In 1896, he proved by experiment that a cathode ray is actually a stream of tiny particles with a negative charge. In 1891, the British scientist George Johnstone Stony named the particle Electron. Though not official, Thomson's journey began with the discovery of particle physics. But even then scientists could not prove the existence of atoms.
Evidence of the existence of atoms is found years after the discovery of electrons. Through the famous scientist Albert Einstein's explanation of that famous Brownian motion. That was in 1905.
The British scientist Robert Brown conducted an experiment in 1828. He released the pollen of a plant called Clarika pulchella into the water. Then look through the microscope, the particles are scattering. That is, there is no regulation of the motion of the molecules. But why? If for some reason the water is moving, then it may be. Maybe a gentle current of water has been created by pushing something on the pot. Or it may be due to evaporation of water. Brown checked again to ensure the stability of the pot and water. The same result again. So Brown was convinced that the water was not moving for any external reason. There is another reason for the pollination of pollen.
Brown replaced the pollen. He tested a few different species of pollen in water. He then repeated the experiment with dry grass powder, coal or various metals instead of brown pollen. The same result every time. The scattering of particles or particles of various substances in the water is called 'Brownian motion'. For a long time that problem remained unresolved in the world of science. Six years later, Albert Einstein explained Brownian motion. That explanation put an end to the two-thousand-year-old Cold War.
The first proponent of the concept of 'atom' was (arguably) the Indian scientist Kanad. He spoke of the smallest unit of matter 500 years before the birth of Christ. However, Greek scientists began to really think about the atom. The golden age of Greece then. There was a philosopher in Greece then. Lucippus. He realizes very well that no object can be broken one by one. It will reach a state of breaking, then it is not possible to break the object even after hundreds of attempts. The object will reach the smallest size. But Lucippus did not say what the name of the smallest name would be.
Democritus is the most talked about proponent of atomic theory. Student of Lucippus. Democritus named the smallest state of matter, the atom. The meaning of the word atom is indivisible. In Bengali we call it 'atom'. The atom of Demetrius, like that of Kanad or Lucippus, cannot be compared with the modern atom.
Aristotle, one of the greatest philosophers of all time, was born during the lifetime of Democritus. In everything he has shown a wealth of erudition. He had a huge impact on the society. His words were considered immortal by the Greeks.
Aristotle could not accept the atomic theory of Democritus. He thought that the objects could be broken one by one at will. He also preaches like that in public.
But not everyone blew up Democritus. Epicurus was a third century BC philosopher. He is a teacher by profession. He added atomism to the subjects taught. He also wrote several textbooks on atomism. Christianity also saw the emergence of another poet and philosopher named Lucretius in the first century. He was Roman. He was inspired by the philosophy of Epicurus. He highlighted Epicurus' atomism in a long poem.
Then again the dark age of nuclearism began. Although more philosophers and scientists have worked on atomism. Due to the influence of Christianity, they did not get water. The influence of Aristotle's philosophy on Christianity is widespread. So the atom that Aristotle opposed survived until the Middle Ages. The Pope and the clergy were in great power then. The clergy of the church could not accept Epicurus' atomic concept. So the book written by Lucretius was banned. All copies of his book were destroyed. Only one copy survived. It was rescued in 1418. A copy of it is also made.
Then came Isaac Newton's reign in science. He was a man of deep faith. That is why he did not mention 'atom' in his writings in that way. Because, it can become directly anti-Christian. However, Newton was not an atheist. He was a pioneer of experimental science. Like Aristotle, Newton was not a man who could just run his own ideas as a law of nature. So he accepted the idea of atom. His confidence in the concept of particles was strong. He also saw light as a particle. But he just thought that particles have an attractive and repulsive force.
Medieval scientists did not have such a clear idea about atoms. There was no conclusive evidence for nuclearism. Scientists have not spoken so loudly about the atom. Even then, atomism was not spared from the punishment of the Church-Pope. Was a French philosopher of Newton's time. Pierre Gasendi. Reading Lucretius's book made Gasendi interested in atomism. He wrote a lot about atomism. For this he has to be tortured.
The British scientist Robert Boyle was inspired by the book written by Gasendi. He experimented by inserting gas and mercury into a ‘U’ shaped glass. Show that the volume of gas at the normal pressure of the atmosphere is the same. If the pressure of mercury increases, the pressure of gas is different. As the pressure of mercury gradually increases, the volume of gas also decreases. The same amount of gas, just because the pressure is less, the volume is increasing-decreasing, why? So are gaseous substances made up of tiny particles? There must be space between those tiny particles. As the pressure increases, so do the gaps. This causes the particles to move closer to each other.
Boyle was convinced that the indivisible particle that Democritus spoke of was the aggregate of gaseous matter. Solid objects can be easily converted into liquid and gaseous objects by applying heat and pressure. Solids and liquids are definitely made of atoms. After Robert Boyle's experiment, scientists confirmed another thing. Not all objects are basic substances. The same object may contain a mixture of different substances. Of course, these mixtures are not like water and sugar mixtures. Absolutely chemical process mixing.
In the nineteenth century, there was a real wind of nuclearism. British mathematician John Dalton appeared on the stage of the atom. Dalton is said to be the father of modern atomism. In 1803 he built the first atomic model. The model is known in science as the ‘Dalton Atomic Model’.
Dalton reached a number of conclusions about the atom. He said that every element is made up of tiny particles called atoms. The mass and religion of each atom of a given element are equal. The properties of the element in the atom remain intact. He named the smallest particle of compound matter the compound atom. Atoms of compounds are made up of atoms of more than one element.
Dalton's atomism is completely different and quite tidy than Greek atomism. But Dalton's atomism is not entirely reliable. There is no denying, however, that Dalton's atomism laid the foundation for modern atomism. Dalton's theory of atomism was flawed. However, there was no way to cancel. Apart from that, it is very convenient to get the results of chemical reactions by taking atoms and calculating them. But science always wants proof. The results of chemical reactions match the indirect evidence of atoms. But I want real proof! No one has seen the atom anymore. There was no way to see then. So even accepting the atomic theory was an uncomfortable thing in the minds of scientists.
The article is part of the book Nuclear Physics to be published at the 2021 Book Fair
Then came the Brownian motion problem. In 180, the Scottish scientist James Clark Maxwell tried to explain the motion of atoms mathematically. Be fairly successful. When a gaseous substance is placed in a container, the gas molecules collide with the vessel wall. Again they are in conflict with each other. Maxwell's mathematical equations can explain this conflict. Maxwell's mathematical theory can also explain Robert Boyle's formula.
But then a group of scientists declared war on the atom. British physician and scientist Benjamin Collins Brody took the first pen against the atom. He wanted to destroy the idea of atom by writing one article after another. Brody died in 1980. But left a worthy successor. Nobel laureate German chemist Wilhelm Oswald has been opposed to atomic theory since the 18th century. In 1890 he published a book. In his book Outline of General Chemistry, he tried to disprove the atomic concept in various ways. Another stick in this regard was the Austrian physicist Ernest Mack. He attacked the atom in his book The Analysis of Sensations in 1898. Thus, in physics and chemistry, the concept of the atom is artificial and imaginary, much like the symbolism used in algebra. He was deeply rooted in misconceptions until he witnessed Rutherford's particle test in 1911.
In 1902, the Swedish scientist Theodore Siedberg worked on Brownian motion. He tried to come up with an idea of Maxwell's theory of gas motion. Like him, water molecules are also moving all the time. As a result, they are colliding with each other. This push is not supposed to be on either side. Water molecules can move freely. As a result of the collision of one molecule with another, the direction of motion of the molecule changes. Water contains billions upon billions of molecules. They are all running endlessly. And they are pushing each other. Millions of molecules collide in a water container. The direction of the molecules is changing after the collision. The molecule is running and colliding with another molecule. Thus, due to the constant collision, scattered motion is born in the molecules.
Now you can see if you put something relatively big in the water. It will float steadily in the water. That means no movement of it can be seen. Why is this happening? In fact, water molecules are colliding one by one. One molecule may have run north after the collision. At the same time another molecule collided with one of the molecules in the north and returned to the south. Calculating their average value, it can be seen that the number of molecules scattering around from a certain direction is close to the number of molecules scattering from different directions. In other words, if the average value is calculated, it can be seen that the scattering rate of millions of molecules is equal in all directions. So there is a balance of motion anywhere in the pot. So overall the water seems to be stable throughout the pot.
Now let's leave a very small object in the water and see. Then it will be seen that it is no longer stable. The pollen is running. In fact, water seems to be stable because the average velocity of the molecules as a whole is equal. The average velocity is equal, it does not mean that the velocity of all the molecules separately is equal. In fact, if you calculate separately, the average speed will not be calculated.
Suppose 10,000 molecules are running northward from the center of a vessel at the same time. At that time, the number of molecules rushing from the north to the center was 9994. Very close numbers. But not equal. More than six molecules are moving north. Any one of those six molecules is able to push a flower pollen from the center and send it north. Then the pollen reached a place to the north and lost its lure. This is because there are some extra molecules running eastward that have upset the balance of average velocity. Pushing those molecules, the pollen will run east. Going in that direction, it will take a turn by pushing some extra molecules somewhere else. In this way, the direction of the molecule will change again and again. Will not run at a certain speed in any particular direction. Will continue sporadically. This interpretation of Siedberg is quite startling and reasonable. However, it will not work if you are just stuck in the argument. I want mathematical proof.
Albert Einstein appeared on the scene. In 1905 he published an article in the German journal Analine der F্যre Physics. That was the mathematical explanation of Brownian motion. Einstein reached out to Maxwell's formula for this explanation. And to get an explanation of Brownian motion means to have a clear idea about molecules. But Einstein was liberated by mathematical theory. The mathematical explanation must be tested in the laboratory. Einstein will get applause only if it matches.
Now the question is, is Einstein's explanation the last word? Yes, that's right, Jean-Baptiste Peran, a scientist, took on the task. The results were exactly the same as Einstein's calculations. The size of the water molecule can also be deduced from that calculation. For so long the atom has been in the imagination, in reason, in theory of scientists; Einstein brought him out to the real world, to the laboratory. Later it was possible to identify the atom using Einstein's mathematical equations. The concept of the atom, which was born in the hands of Democritus, came to fruition two and a half thousand years later in the hands of Albert Einstein.
Let's go ...
Sources: Inside the Atom / Isaac Asimov, Mass / Jim Baggett, From Zero to the Universe / Mizaran Rahman and Abhijit Roy
i never loved physics and chemistry.