Using a spiral arm to tell the time is a novel and mathematically satisfying experience. This clock comes with a ten year guarantee and a leaflet with some mathematical ideas to explore - in a classroom or at home. A perfect gift for th
The 45 degree sloping bottom divides the glass in two triangular sections. When the glass cup is filled with water, the top section becomes a water prism that allows passing sunlight to project a rainbow on whatever surface it rests on.