Scales (Slide Rule): Difference between revisions

The operations of a slide rule are performed by adding physical lengths together between scales to find results.  This is best illustrated through simple "linear" scales (such as those found on standard rulers, or the "number line" learned from elementary school).  Taking two copies of the number line (of the same size) and laying them next to each other, it is possible to use the physical properties of the scale to add without any extra manipulation.  Labeling the two scales "X" and "Y," we can observe an example:<blockquote>2+3=5</blockquote>On the first scale (X) we find the number 2.  We can align the base of scale Y (called the "index") with it so that the 2 on X is next to 0 on Y.  We then find the number 3 on scale X, and look for what number on scale Y is aligned with it (which is the number 5).  Most operations on slide rules use this method to find various results.