Einstein’s PhD thesis, submitted in 1905 was not on either light or relativity, which he is more famous for. It was titled “EINE NEUE BESTIMMUNG DER MOLEKULDIMENSIONEN”, which translates to “A New Determination of Molecular Dimensions”. Thread. https://twitter.com/WhinerVikram/status/1294150234881351681

First, a word on length. There are numerous questions on Quora regarding the length of the thesis. Its easy to check since its available online here. And ….drumroll….., its 21 PAGES LONG.

https://www.research-collection.ethz.ch/bitstream/handle/20.500.11850/139872/eth-30378-01.pdf

In 1905, Einstein published 4 papers, on Brownian Motion, on Photoelectric Effect, on Special Relativity, on Mass-Energy Equivalence, and his PhD thesis. No wonder its not remembered very well. But imagine publishing all those in a single year!!

In his PhD thesis, he came up with a way to calculate the Avogadro number. His calculation was off by a factor of 3 but we will come back to this. In other surprising news, this is the most cited of his papers.

https://arxiv.org/pdf/physics/0504201.pdf

In fact he relied on fluid mechanics. Using change in viscosity of an incompressible fluid due to a solute dissolved in it (in this case sugar in water) he determined the Avogadro number. Later, Jean Perrin won a Nobel Prize following this approach.

https://en.wikipedia.org/wiki/Jean_Baptiste_Perrin

We remember Einstein as a brilliant physicist. Hopefully this thread makes you believe he was even more brilliant!

End of thread.