I would love to get my students using slide rules, but it's difficult to find physical ones for a reasonable price. Virtual slide rules, like those at http://www.antiquark.com/sliderule/sim/, are just not quite the same as a physical thing, which requires force to slide, and good light to see the details.

I miss the days when you could go into any university bookstore and find sliderules in a wide range of prices. Another fond memory is watching my high-school teacher using a broomstick to move the slider on a giant sliderule he had above his blackboard.

What do students miss, using calculators? 1. Concrete notions of the difficulty of measurement, each digit being much harder to obtain than its predecessor. 2. A intuitive feeling for the propagation of uncertainty. 3. The ability to carry the exponents of 10 in their head.

Lacking this sort foundation seems to make it hard for people to connect their calculations, or numbers they read, with reality. This makes it hard to spot errors. It also makes it hard to remember things effectively. For example, I've found that students remember the mantissa of Avogadro's number correctly to 3 digits, but they have no idea on the exponent. The same goes for the speed of light in a vacuum. These errors were rare in the sliderule age, because it was imperative to keep the exponent in your head, as you worked through a calculation.