If tiny particles like pollen are added to clear water and observed through a micrscope they will be seen to move about randomly. This was an early clue to the fact that matter is made of individual...
The brownian motion is the random movemement of microscopic particles suspended in a liquid or gas, caused by collisions with molecules of the surrounding medium.
Molecules in a fluid move constantly, freely, randomly, in all directions and with all possible velocities. This erratic motion of the molecules causes them to collide with anything in their path....