A close cousin of desktop zen gardens, a sand pendulum is a decorative piece that relies on momentum to furrow fractalesque patterns into a plot of sand. These contraptions are mesmerizing to watch, make great gifts, and are great additions to any peaceful area of your home.
The tip of the pendulum only just touches the sand, so only a little bit of energy is lost due to friction. This means that the pendulum can be swinging for a few minutes. The gravitational forces and the forces from the earths rotation play a vital role in creating these beautiful and mesmerizing geometric patterns.