Brownian Motion

#Brownian_motion

Today's topic is very dry, very. Exotic doesn't matter here. This means that in physics, topics like time travel, black hole, wormhole, holographic principal, big bang, string theory, and drive drive type are usually considered a bit exotic. None of that here so enter at your own risk. Let's start.

The question that often arises is why a country spends so much time and money trying to learn something new in science that has little effect on everyday life? This question actually seems a little difficult to answer to me and this is the origin of this post. The work we are trying to write today does not seem to matter in our daily lives, but it is not very true. The effect of today's topic or work falls on everything from meal time to something that we may not know for a long time due to lack of time. One thing to keep in mind is that nothing in the world has yet been discovered that has not had an impact on our daily lives. I mean, the discovery of Facebook has had an impact on the daily life of Gazi Rakayet Bhai. Want more examples?

The topic of today's post is Brownian Motion. Einstein did this in 1905. In that year he submitted 4 research papers. It is said that he should have received four Nobels from those four papers. However, today's topic is relatively less discussed because he is more familiar with the famous Onara relativity theory. Today's topic is very much related to his thesis. The background knowledge of this work is similar to the concept of the thesis you did in PhD. There is less discussion about it because Uni is not basically in this research field but this work is famous because it has dispelled the long-held suspicion of scientists that there is no such thing as an atom. When scientists could not come up with an explanation for a phenomenon after experimenting for centuries, he put it down on paper in just one month. It has completely redefined modern physics.

Today's post is arranged in this way. First of all, what is a thought experiment? An analogy is then presented to give a basic idea of ​​Brownian motion. Then how it was written and who discovered it. The next section describes what Einstein did in his paper and followed it by writing a section on the significance of Einstein's work. And finally, trying to figure out why science is important.

Then the post is over. At this point you will be able to leave Huff thinking that God has saved him. Post finished.

.. Thought experiment.

For today's writing, we need to know a little bit about what is meant by thought experiment. As you can see from the term, it is an experiment that is done only by thinking. This term has been around for a long time, but Einstein has made it popular. He was forced to experiment with this thought because he had no chance to go to the laboratory and experiment, so he experimented thoughtfully. This is exactly how he wrote his famous four papers. Just sat at his own table and did thought experiments. Thought experiments are such that suppose you are thinking of doing an experiment but that experiment can be practically done again or you have no chance to go to the right lab. So you thought about it and tried to understand what would happen if such an experiment was actually done or what the result might be. For example, suppose you sit at a table in the house and think about what might happen if you go somewhere on a plane and start walking inside the plane.

.. The basic idea of ​​Brownian motion.

Suppose the current is gone in a hurry in Dhanmondi. So a boy named Jessia was sitting on the roof of a house in Dhanmondi drinking tea and thinking about Salman Apur. What will you do if you see this, how will you do this type. Suddenly he heard the sound of a rock falling on the gate of his house. He has a bad head. Who slaps so many nights? Luckily he had a torch light but there is a small problem with the torch. When you tip it, the torch lights up for a second and then goes out for another second. This is how the torch works. So seeing that there is no other way and that torch Maral Salman noticed Apur's position. Pressing for the first time, Apu is 10 feet away on the right side of the gate. As soon as he saw it, the torch went out according to the rules. A second later, when the torch was lit, it was seen that Apu had changed her position. Now he is 5 feet to the left. When the torch went out again and lit up, Apu was seen 2 feet in front of the gate. Keep in mind that every time the torch is lit, Apu is seen in different positions or places. It is important to keep this in mind.

Come on now. You take Salman Apur's first position as a point 'A'. Take the second position as ‘B’, the third position as ‘C’. In this way, within 10 minutes, mark each position on paper with A, B, C. Did? Now add two points one by one. That is, draw a line from A to B. Draw a line from B to C. Draw the line in this way until the very last point.

Now you look at your graph. What are you looking at? You see a zigzag situation i.e. once Salman Apu went here and once went there and once he went there and so on and so forth. There is no pattern to move from one position to another. It seems that Salman Apu came to the gate after drinking alcohol today. And you don't need a deadly IQ to understand it. Even if it is Mofiz like me, and if you show it to anyone, they will say that there is really no pattern to change this position. It's a zigzag path and a random thing.

OK.

Now do you want to impress your girlfriend? Here you go. You tell him with this example that this kind of random process is called stochastic process. Probability plays a big role here but it should continue even if we don't know it at the moment.

This is better news. You just got to know the ABCs of physics. In the language of physics, the branch in which such study is done is called statistical mechanics. Now give me at least two bucks to develop. I gave free knowledge which is against my policy. Some exists in the world called free have never done it before, don't do it yet and won't do it in the future.

.. How and who discovered.

Now let's go to history. Robert Brown was a British scientist whose research area was botany. Unni noticed an interesting thing in the early 1800s. Some flower pollen was taken under a little water and placed under a microscope. Surprised, he noticed that the particles (which are a particle) were moving from one place to another. It looks like a sack that encloses with a drawstring. Moreover, not all the particles are together. One goes this way and another goes that way and one goes a little faster and another goes a little slower. What was going at speed then goes to one side slowly after a while and what was going slow goes to this side at speed again. Robert Brown was very impressed and Unni thought that these particles might have something called life and that is why they are moving. Unni also thought that maybe it is a property of the pollen that if a pollen is collected from a flower that is not yet dead, then this kind of property will show.

So then he collected pollen from a dead flower tree and did the same experiment and got the same result. Eventually he came to the conclusion that this random motion did not mean moving from one position to another.

He thought of this type but could not satisfy himself. So he did the experiment again. This time he did it with particles of dust. Leaving it in the water in the same way, he noticed that the dust was moving back and forth just like the pollen of a flower. They have no definite direction but are moving randomly. So this is the pollen of this flower in the water, the dust which are actually particles and their random way of moving in a zigzag way, this was called Brownian motion. You can do this experiment yourself at home. Just leave some flower pollen in a glass filled with water and you will see that it is behaving in the same way i.e. randomly moving around.

Scientists in the early 1900's could not explain it in any way. No one could understand why they were moving from one side to the other. And the technology of that time was not in a position to understand it. Scientists have tried many things to explain this, but all have failed.

However, the researchers then knew Newton's theory and realized that the flower particles must not move by themselves because no object would move in this way. It was a matter of applying a force to move him but what exactly was happening was implied.

Later, some scientists said that what was happening here was that water atoms were pushing those particles from one side to the other. This is why the particles gain a speed and move from one place to another. At the same time, many famous scientists took the opposite position. They said it was not possible. The argument was that even if water had atoms, it would be much smaller than these particles (flower particles or dust particles) so there was no chance of them being pushed. And even if the water atom pushes, it is not possible to understand it with our eyes because the distance that will be covered in one push will be in a very short time and it is not supposed to be caught in our eyes. Moreover, where is the evidence that there is something that Atom says?

From the above text it is clear that a vague full qualitative (qualitative) explanation was found where there was a situation where this explanation could be either true or false. So whether it happened or not is only quantitative (quantitative, quantitative means God knows, but quantitative means to get a number from a result) can be believed. That is, we need to find out the equations of this process that can describe this process mathematically and then experiment and measure whether the result from this equation supports the observation. The world moves with equations. With the value obtained from the equation. You have to be quantitative. You have to know the numerical aspect of expressing everything because in the end it is more important. It helps scientists in the laboratory. Suppose an experiment is run but it is not known what could happen. Then you can do an analytical simulation first to see what could be the most extreme situation in that experiment or what could be the worst case scenario and prepare yourself accordingly. Consider the example above. You may want to know - - -

- What will be the position of the particle that has been thrown into the water after 10 minutes? Or will not actually change the place?

- What will be the particle speed if it is?

- If the water is heated from not cold, will there be any change in its position or speed?

- What happens if you experiment with oil instead of water?

- What happens if the particle size is enlarged? What happens when you are small?

Thousands of such questions can be asked and you will never know them unless the processor is making a mathematical equation.

.. What did Einstein do?

What did Einstein do? Hey hey hey. He has published the answers to these thousands of questions in the paper. How he proved it mathematically is not important to us because it contains equations but it is important for us to know what he proved.

If a flower pollen type particle is released into water, how exactly will it move from one position to another, where will it go from, where will it go, what kind of liquid will it use, what will be its average speed, whether it actually has atoms, and if so, its size How much? Etc., etc. He has come up with mathematical equations that can tell these things correctly. His equation is a general equation that works for all types of liquids.

The equation in his paper confirms that - - -

- This brownian motion is more in cold water than in hot water;

- This Brownian motion will gradually decrease if a liquid with a higher concentration than water is used;

- The larger the particle, the less this Brownian motion. When the fish swims in the water, the fish goes wherever it goes, does not move back and forth;