About 1905 Einstein published a work about diffusion of hard spheres and brownian motion. One effluence of that is the so called "Viscosity Equation" which was/is very important for dertermining moleculat weight of macromolecules by viscosity of solutions.



What I like to know: Was there any relation to the other

topics Einstein worked on? Is something known on Einsteins reason

work on Viscosity?


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    $\begingroup$ Dear Georg, the most important Einstein's papers on intrinsic viscosity were actually published in 1906 and 1911, i.e. after his miraculous year. The relationship with the Brownian motion is self-evident - it's about the motion of spheres in liquids. However, Einstein was always fascinated by - many things including - hydrodynamics. For example, in 1926, he wrote about meandering rivers in "The Cause of the Formation of Meanders in the Courses of Rivers and of the So-Called Baer's Law" $\endgroup$ – Luboš Motl Jan 28 '11 at 18:29
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    $\begingroup$ From what I understand, Einstein wanted to provide a solid foundation for the theory of the atomic structure of matter. Remember, that the atomic hypothesis was not universally accepted before 1905. Einstein's work on viscosity, specific heat of solids, Brownian motion etc. was intended to demonstrate a direct link between the atomic hypothesis and the observed macroscopic properties of matter. $\endgroup$ – user346 Jan 28 '11 at 18:31
  • $\begingroup$ If you want some relationship between the solutions to equations of hydrodynamics and those of general relativity, we have had a map of the kind you need for 2 weeks, see arxiv.org/abs/1101.2451 $\endgroup$ – Luboš Motl Jan 28 '11 at 18:31
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    $\begingroup$ Dear @Georg, it was on this server but I also remember the tea from a book by Einstein that I read about 5 times when I was a high school student haha. It was called "How I see the world" (Czech translation). $\endgroup$ – Luboš Motl Jan 28 '11 at 20:55
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    $\begingroup$ Einstein’s early work and PhD thesis was on issues concerning atomic theory and thermodynamics. In particular he had his thesis published in Annalen der Physik 19 (1906) p.289 with the title "A new estimation of molecular dimensions" or something like that. $\endgroup$ – Vagelford Jan 28 '11 at 21:11

From my studies of Einsteins work I am under the impression that the most important motive for his works stems from his interest in understanding physics from the point of view that matter exists of atoms and molecules that follow paths in a space-time continuum.

In the sense that he was strongly influenced by the idea of a deterministic-materialistic universe - the Kant-Laplace universe. This point of view easily explains why he couldn't accept quantum physics where the concept of probablities - without underlying mechanism - supersedes determinism.

I believe the comment of user346 is important: "[...] the atomic hypothesis was not universally accepted before 1905 [...] a direct link between the atomic hypothesis and the observed macroscopic properties of matter".

In my view his work on the SRT has the same motive: understanding space-time relations from the point of view of light rays imagined as moving more or less like macroscopic objects.


Although the notion of viscosity in gases and liquids was known well before 1906, as well as its derivation from statistical mechanics, the atomistic structure of matter was still under experimentally discovering, so it was a hot topic at that time.


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