Daily Archives: May 18, 2011
Swimming Upstream
Contaminants Can Flow Up Waterfalls, Say Physicists
They found that the leaves (and also chalk powder) were able to navigate upstream if the waterfall was less than about a centimetre in height. “For distances of the order of 1 cm or less, some of the floating particles eventually start to “climb up the stream”,” they say.
This apparently refers to particulates; solutes could presumably do this via diffusion to some extent without setting up a counterflow.
The Last Waterbender
Previously, researchers thought that only lasers with a power of 10 watts or greater–the kind of lasers used in micro-machining or surgery–had enough oomph to make water budge. But Olivier and Janine Emile of the University of Rennes in France realized that no one had tried a weak laser in the configuration known as total internal reflection, where the force details come out differently.