Räknesticka

Räknesticka, also known as a slide rule, is a mechanical analog calculating device. It was primarily used for multiplication and division, but could also be used for more complex operations like roots, powers, logarithms, and trigonometric functions. The device consists of a sliding part (the slide) that moves within a fixed part (the body). Both parts have logarithmic scales printed on them. By aligning certain marks on the scales, users could perform calculations based on the properties of logarithms.

The principle behind the räknesticka is that the sum of two logarithms corresponds to the logarithm of the product of the numbers they represent (log(a) + log(b) = log(ab)). Similarly, the difference of two logarithms corresponds to the logarithm of the quotient (log(a) - log(b) = log(a/b)). The scales on the räknesticka are arranged such that sliding the scales allows for the addition or subtraction of these logarithmic values, thereby performing multiplication or division visually.

Räknestickor were invented in the early 17th century and were widely used by engineers, scientists, and students for centuries. They were particularly important before the advent of electronic calculators and computers. While the accuracy of a räknesticka is limited by the precision of the scales and the user's ability to read them, they offered a quick and portable way to perform calculations. The widespread use of räknestickor declined significantly in the 1970s with the introduction of affordable electronic pocket calculators. Today, they are mostly considered historical artifacts, though some enthusiasts still use them for their unique mechanical nature.