How does Brownian motion prove the existence of atoms?

Brownian motion is observational evidence for the instantaneous imbalance of forces acting on pollen grains in suspension. Einstein produced three papers providing a mathematical explanation for Brownian Motion which could then be used to predict behaviour.

Atomic theory at that time, predicted the behaviour of many physical and chemical processes, but there was no direct experimental proof of the existence of atoms, but Brownian Motion gave another clue.

Finally, the French Physicist Jean Perrin used Einstein's predictions to calculate Avogadro's constant to a hitherto unachieved level of precision. i.e. experimental evidence of Einstein's explanation removed remaining doubts for their existence.

(edited 5 years ago)

Reply 2

Eimmanuel

Study Forum Helper

Original post by uberteknik

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Finally, the French Physicist Jean Perrin used Einstein's predictions to calculate the size of atoms, which removed remaining doubts for their existence.

Do you have a scientific reference that shows Jean Perrin calculated the size of atoms? I thought he was credited for measuring Avogadro’s constant using Einstein's explanation of Brownian motion and the results.

Reply 3

uberteknik

Original post by Eimmanuel

Agreed, my bad. amended accordingly. Here's a translation of Perrin's Nobel lecture given 11 December 1926:

https://www.nobelprize.org/nobel_prizes/physics/laureates/1926/perrin-lecture.html

(edited 5 years ago)

Reply 4

Eimmanuel

Study Forum Helper

Original post by uberteknik

Agreed, my bad. amended accordingly. Here's a translation of Perrin's Nobel lecture given 11 December 1926:

https://www.nobelprize.org/nobel_prizes/physics/laureates/1926/perrin-lecture.html

I knew about this link but I don't know about the reference that Perrin had computed the size of the atoms which was mentioned in post 2 previously.

Thanks for clearing my doubts. :smile: