Wherever a moving ship may be heading, at its bow will always be seen the swirl of the wave it cuts through. For people on the ship, the movement of that swirl will be the only noticeable movement. Only by following closely, moment by moment, the movement of that swirl and comparing that movement with the movement of the ship, will we realize that at every moment the movement of the swirl is determined by the movement of the ship, and that we were misled by the fact that we ourselves were imperceptibly moving.
