We love physics because physics helps us to understand the world around us and this universe and satisfy our curiosity. Studying physics develops our critical thinking and problem solve skills. Here we will learn how physicists thought about ATOMS in accordance with their hypothesis.
1. What Thought About Atoms in Ancient time?
Idea of atoms goes back to the ancient Greeks, a time of birth of science Democritus who died sometimes close to 370 B.C., did propose that the complex nature of the world could be explained if all things were composed of different kinds of unchangeable atoms, each type with its own shape and size, in constant motion. " The only existing things are atoms and empty space; all else is mere opinion," he wrote. Aristotle's suggestion that everything in the universe is made up from the four "elements" fire, earth, air, water proved much more popular and enduring. Aristotle's four elements were accepted for two thousand years.
Although the Englishman Robert Boyle used the concept of atoms in his work on chemistry. And atoms became a part of scientific thought. Lavoisier identified many real elements, pure chemical substances, and he realized that burning is simply the process by which oxygen from the air combines with other elements.
In the early years of the nineteenth century, John Dalton put the role of atoms in chemistry on a secure footing. He stated that matter is made up of atoms, which are themselves indivisible; that all the atoms of one element are identical, but that different elements have different kinds of atoms; that Atoms cannot be created or destroyed, but are rearranged by chemical reactions; and that a chemical compound, made from two or more elements, is composed of molecules, each of which has a small, fixed number of atoms from each of the elements in the compound.
2. What Thought About Atoms in Nineteenth Century?
Joseph Gay-Lussac established by experiment that if the compound produced is a gas, the volume of that third gas is also in a simple proportion to the other two.
Italian Amadeo Avogadro used this evidence, in 1811, to derive his famous hypothesis, which says that for any fixed temperature and pressure equal volumes of gas contain the same number of molecules, whatever the chemical nature of the gas. It can be proved that each liter of gas at a pressure of one atmosphere and zero temperature contains 27x1021 molecules. Characteristics of gases had been explained in detail, using the concept of atoms, by the James Clerk Maxwell and Austrian Boltzmann.
During the 1860s and 1870s, these pioneers developed the idea that a gas is made up of very many atoms or molecules, which can be thought of as tiny, hard spheres that bounce around, colliding with one another and with the walls of the container that holds the gas. This related directly to the idea that heat is a form of motion-when a gas is heated, the molecules move faster, which increases the pressure on the walls, and if the walls are not fixed in place, the gas will expand.
Any one molecule might be moving in any direction in the gas at any time, but the combined effect of many molecules colliding with the walls and produces a steady pressure. This led to the development of a mathematical description of gas processes called statistical mechanics. But still there was no direct proof that atoms existed.
In 1898, Boltzmann published his detailed calculations in the hope" that, when the theory of gases is again revived, not too much will have to be rediscovered", in 1906 ill and depressed, unhappy about the continuing operations of many leading scientists to this Kinetic theory of gases, he killed himself, unaware that a few months before an obscure theorist called Albert Einstein had published a paper that established the reality of atoms beyond reasonable doubt.
3. What is Einstein's Atoms?
Einstein introduced relativity theory. Another concerned the interaction of light with electrons and was later recognized as the first scientific work dealing with what we now call quantum mechanics-it was for this work that Einstein received the Nobel Prize in 1921. Another paper was a deceptively simple explanation of a puzzle that had baffled scientists since 1827 - an explanation that established, as far as any paper ever could, the reality of atoms.
Einstein later said that his major aim at that time was to find facts which would guarantee as much as possible the existence of atoms of finite size.
British botanist Thomas Brown noticed that when a pollen grain floating in a drop, it is seen to bounce around in an irregular fashion that is now called Brownian motion. Einstein showed that this motion, although random, obeys a definite statistical law, and that the pattern of behavior is exactly what should be expected if the pollen grain is being repeatedly "kicked" by unseen, submicroscopic particles that move in accordance with the statistics used by Boltzmann and Maxwell to describe the way atoms move in a gas or liquid.
You or I, used to the idea of atoms, can see at once that if pollen grains are being jostled by unseen collisions then it must be moving atoms that push them around. After Einstein's paper appeared, there was no longer room to doubt.
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