Brownian Motion

Brownian Motion: 

The nature is full of beauty and elegance.

From your daily life experiences, you are perhaps most familiar with 'motion'.

The motion of your bicycle 🚲, the motion of the earth 🌎, the Sun,stars, galaxies, vehicles, aeroplane,etc. is the eternal part of nature that makes the universe exist.

Everything is eternally in motion.

A basic question that may arise in your mind is that what constitutes this eternal movement of these stuff in nature around us? That's what I have been fascinated to write this article!

    Brownian Motion:

In 19th century,there were enough experimental data to validate the kinetic theory of gases but the existence of atoms or molecules were still a mystery for physicists because there were no any direct experimental evidence for them.

Most physicists thought that the molecules are alive and hence they have ability to move and perform various movements.But this idea had no any experimental support.

In 1827,a botanist named Robert Brown discovered that a  "pollen grain" suspended in water performs an eratic and continuous irregular motion.He suggested that this continuous irregular motion (zig zag trajectory) occurs due to the bombardment of surrounding molecules (here water molecules) with the pollen grains.He observed this phenomenon through his high power microscope.This phenomenon was later called"Brownian Motion".

In the above picture,the size of pollen grains is quite big compared to the size of water molecules and so the water molecules are almost invisible when you look at the pollen grains.

   

                  Why Brownian Motion?

The discovery of brownian motion was an overwhelming evidence of the existence of molecules.The crucial thing is that the brownian motion is not due to new kind of force or new kind of unknown motion.

It is actually a random motion of brownian particles (suspended particles like pollen grain) that results from the continuous bombardment of molecules of liquid (water) with the brownian particles.

Here is an analogy to understand it easily:

When you are somehow stuck in the crowd of people as in some ceremonial fair or festival, you can't come out of it in a straight line as you wish to,but rather you will have to follow a random zig zag path because your body will be randomly pushed or pulled here and there by other people.Thus, you can think of your body as a brownian particle and other people's bodies as surrounding molecules.

 Thank you for reading this!

Author: scientificirfan

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