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The zigzag motion of molecules in a liquid

Let me tell you why, something always keeps moving in a liquid. Robert Brown, an English botanist, made a chance discovery in 1827. He was studying pollen grains floating in water under the microscope when he noticed the zigzag motion of particles. At first Brown thought that the particles were moving because the pollen was alive. But further experiments revealed that even 100 years old pollen grains and non-living particles moved around Later in 1905, Albert Einstein, gave a mathematical explanation for this phenomenon. A French physicist, J. B. Perrin succeeded in verifying Einstein’s analysis and for his work he was awarded the Nobel Prize for Physics in 1926. Hence, the erratic and constant movement of tiny particles when they are suspended in a fluid or gas came to be known as Brownian Motion. Studies have shown that Brownian Motion is affected by temperature, viscosity and size. Motion becomes more rapid and the particles moved farther in a given time interval when the temperature was raised, when the viscosity of the fluid was lowered or when the average particle size was reduced.  You can also verify Brownian Motion by observing under a microscope a fine powder of mixed in water.

Web references :

Robert Brown, originator of Brownian movement and the cell nucleus
Robert Brown
Einstein Year - Brownian Motion