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The story of wave-particle duality in quantum mechanics has been told a thousand times. This modest contribution is to get back to a few points, including memories of a discussion we had on a possible experimental evidence of quantum effects at macroscopic scale, but in a way totally unrelated to the experiments he and his group made quite later to exhibit a model of wave-particle duality. The more general question of interpreting/understanding quantum mechanics will be also scrutinized oncemore. [ABSTRACT FROM AUTHOR]

As pointed out long ago by Laplace, viscosity may become a large perturbation to capillary phenomena, especially close to solid surfaces where molecules may stick. A spectacular consequence of this is the impossibility for a triple line to move on a solid if the liquid/vapor interface is considered as a material surface and if the usual no slip boundary condition is enforced. As shown recently this specific phenomenon of contact line motion can be described by coupled van der Waals and fluid equations, yielding a rational theory that is divergence free and consistent with the equilibrium results. Far from the triple line, the equations of fluid mechanics are recovered in their usual form. In this approach, the contact line move close to the solid by evaporation or condensation, which requires (for evaporation) the molecules to jump above a high potential barrier on their way from the liquid to the vapor. An Arrhenius factor makes this process intrinsically slow, compared to molecular speeds. For (realistic) very small Arrhenius factors, the motion of the triple line induces a dynamical change of the functions in the van der Waals equations. This may lead to dynamical wetting and dewetting transitions, that is, to a change of the contact angle from a finite to a zero value or conversely. The dynamical wetting transition has been observed in liquids flowing down a plate (see Blake and Ruschak, Nature 282 (1979) 489–491) cusps on the contact line appear when it recedes faster than the speed of transition. Similar ideas account well also for the known sensitivity of contact line mobility to vapor pressure. To cite this article: Y. Pomeau, C. R. Mecanique 330 (2002) 207–222. [Copyright &y& Elsevier]