On a tramp in the Blue Hills I came upon a dry dead tree, all of which was left was the trunk. I pushed on it and it pushed back (for every action, there is a reaction), and I pushed on it again. It pushed back again. I started pushing on it rhythmically, and at some level of vibration I realized I had its resonant frequency, so I only needed to push on it a little bit at that frequency, it was storing the energy as does a plucked string, only with each little tap I was increasing the energy going through the wooden 'string'. At last it was too much energy, and it busted into kindling at the nodal points.

Good, good, good, good vibrations. . .