Measurements of an effect named after this phenomenon and of a torsional oscillator were used by Bishop and Reppy to confirm the BKT theory. That effect named after this phenomenon is analogous to gravity waves and is exhibited in Rollin films. Landau predicted very-high-frequency oscillations in the orientation of the Fermi surface named after this phenomenon. The hydrodynamic modes corresponding to this phenomenon in a fluid arise due to coupling between the density and the momentum density. The two-fluid model of superfluids predicts a diverging (*) thermal conductivity due to the existence of a temperature mode named the “second” kind of (10[1])this phenomenon. A quantity associated with this phenomenon is equal to the square root of “adiabatic index times Boltzmann’s constant times temperature over mass.” For 10 points, Isaac Newton calculated the isothermal speed of what phenomenon, which he measured by clapping while walking around Trinity College? ■END■