Imagine in your mind a shallow pool where the water lies perfectly still like a pane of glass. There is no wind, rain or anything to disturb the stillness of the pool. For the sake of the experiment, imagine a rock is dropped from some distance above the water, falling with a splash into the direct center of the pool. The splash would cause a rippling effect, concentric circles expanding like waves from the focal point until the entire surface becomes alive with a kinetic frenzy of movement before eventually returning to stillness.
Imagine now that we repeat this experiment under the exact same conditions. We drop the rock from above the exact center of the pool and observe the result.
