In a sheaf of sunlight which comes through a curtain into a darkened room we notice a tiny twinkling of dust particles on which light is scattered. If air is still, the twinkling is entirely unregulated. The motion is even easier to observe under the microscope. For this purpose it is more appropriate to close some fumes into a transparent vessel intended for observation.
Robert Brown was the first who noticed the motion, therefore it was named after him. We interpret it as a result of knocks between a particle and molecules in gas or fluid. Molecules which hit the particle disorderly, push it now in this now in other way.
The Brown's motion confirms that molecules and atoms in gases and liquids move in a constant disorder. This motion is called the thermic motion.
Vivacity of this thermic motion depends upon the temperature of a substance.
