Archive for Thursday, March 20, 2008

Remembering the slide-rule

March 20, 2008

A while back, the subject of slide-rules came up in a discussion with one of our grandsons, and he asked, "What is that?" The kids nowadays have all these wonderful computers with answers to scientific and math problems at their fingertips. Those of us born before 1940 did not have these advantages.

I was first aware of a slide-rule when my brother Tom bought his in the early 1940s. He tried to explain to me how it worked but at that time my only interest was basketball.

At the end of the 16th century, Galileo's design of a sector as a mathematical tool can be seen as the moment when calculation aids ceased to be based upon counting and instead exploit the deeper relationships among numbers. His invention is still in use as a navigational aid in the 20th century three hundred years later. John Napier advanced the understanding of number relationships in 1614 with his invention of logarithms, since logarithms are the foundation on which the slide-rule is built.

William Oughtred in 1620, an Anglican minister, is today recognized as the inventor of the slide-rule. Here is his definition of the slide-rule: He places two scales side by side and slides them to read distance relationships, thus multiplying and dividing directly. He also developed a circular slide-rule. Sir Isaac Newton solved the cubic equations using three parallel logarithmic scales and makes the first suggestion toward the use of a cursor. The word "cursor" is used the same way as is used in our computers today.

Scientists/inventors/chemists/mathematicians, including Gauss, Watt, Priestley, Fulton, Fuller, Einstein, Fermi and Von Braun all added features to the slide-rules to help them in their own inventions or scientific fields.

Hewlett Packard's and Texas Instruments' production of the pocket calculator in the early 1970s ended the manufacturing of slide-rules almost overnight. Now all computers have built in slide-rules.

To prove it, I asked my computer what is the square root of 2,000 and it told me immediately that it is 44.7213595. I use Google Advance and ask it questions like it is a person sitting next to me, and it always gives me an answer. Amazing!

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