Fascinating and unusual desktop science, this is a model of the original pendula used to calculate the size of the earth. Elegant curved stand holds a swinging pendulum , the point of which traces onto a fine sand base. As the arc of the pendulum keeps moving (very slightly) the pendulum traces complicated and beautiful patterns in the sand. Each swing is on a slightly different arc. Constant movement, constantly-changing patterns. Stands an impressive 38 cm high, by 20 wide. Great gift or acquisition for home or office - guaranteed to draw attention.