30 April 1905

Albert Einstein completes his doctoral thesis at the University of Zurich.

Albert Einstein’s doctoral thesis, which he completed in 1905 at the age of 26, was titled “A New Determination of Molecular Dimensions.” The thesis was submitted to the University of Zurich and was later published as a paper in the Annalen der Physik (Annals of Physics) journal.

In his thesis, Einstein developed a new method for calculating the size of molecules in a liquid by analyzing how they scatter light. This method, known as “Einstein’s theory of Brownian motion,” provided a way to experimentally verify the existence of atoms and molecules, which had previously been debated among scientists.

The theory of Brownian motion played a crucial role in the development of modern physics and chemistry, and it remains an important topic of study to this day. Einstein’s thesis marked the beginning of his scientific career and laid the groundwork for his future groundbreaking work, including the development of the theory of relativity.