The speed of sound in a liquid is given by:
$$ v = \sqrt{\frac{K}{\rho}} $$
where $K$ is the bulk modulus and $\rho$ is the density. The bulk modulus of mercury is $2.85 \times 10^{10}$ Pa and the density is $13534$ kg/m$^3$, so the equation gives $v = 1451$ m/sec.
The speed of sound in solids...
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I've just found the intertwiner for the fundamental and $P_1(\mathbb{C}^2)$ representations of $\mathfrak{su}(2)$, but I did it by inspection. For notation info about the $(\pi_\ell,P_\ell(\mathbb{C}^2))$ representations of $\mathfrak{su}(2)$, see my post here. Finding the intertwiner $\phi:P_1(\...
The Course of Theoretical Physics is a ten-volume series of books covering theoretical physics that was initiated by Lev Landau and written in collaboration with his student Evgeny Lifshitz starting in the late 1930s.
It is said that Landau composed much of the series in his head while in an NKVD prison in 1938-1939. However, almost all of the actual writing of the early volumes was done by Lifshitz, giving rise to the witticism, "not a word of Landau and not a thought of Lifshitz". The first eight volumes were finished in the 1950s, written in Russian and translated into English in the late 1950s...
