Tuesday, January 06, 2004
It might be fair to ask, in light of this empirical revelation, what's actually going on here. Clanet et al. don't have a theoretical argument that explains the 20 degrees but it is clear that this angle allows a stone to hit the water for the least amount of time (they measured this with a high speed video camera). Hitting for the smallest time period allows less of the stones energy to dissipate with each collision, therefore giving it more energy to continue moving parallel to the water and into skipping glory.
UPDATE: Chris Genovese writes about the same paper here with a couple of interesting extra links.