Spinning Blackboard

Sand on the Spinning Blackboard

LOCATION: STATIONED IN BETWEEN ENERGY FACTORY AND WATER WORKS

Draw a straight line from the center of the disk to the outer edge. If you draw the line at a constant speed, you’ll get a spiral with equal spaces between the lines, an Archimedes spiral.  You can find spirals like this in many spider webs.  If you draw the line with increasing speed, you’ll get an equiangular spiral with increasing space between the lines, like the shell of a snail.

Draw circles on the spinning disk. A small circle moving around a larger circle is called an epicycle.  Early astronomers thought the planets moved in epicycles around the earth.  Try drawing circles clockwise and counterclockwise.  Do they look the same?

Challenge: Can you draw a square on the spinning disk? It’s not easy!  When you draw any shape on the spinning disk, the pattern you get isn’t the shape you drew, but a record of how your finger moved relative to the spinning disk.

Spinning Blackboard in between Energy Factory and Water Works