The ruler is a great educational equalizer—students in San Francisco and Sub-Saharan Africa can both learn the basics of geometry using nothing more than a stick with regularly spaced marks. Their ...

One ruler is cooled to liquid nitrogen temperature and another is left at room temperature. The two rulers are compared to show that the cooled ruler has contracted. This demonstration requires ...

Equipment: Two 12" rulers, a small (~2L) dewar of liquid nitrogen, safety goggles and safety gloves. What it does: One ruler is cooled to liquid nitrogen temperature and one is left at room ...

When I sew my aprons, I like to have a ruler to line up the pockets before I sew them onto the apron front. I now use a wooden ruler that I found at a thrift shop, since the cheap plastic rulers kept ...