## 17 September 2011

### biggest convention of the Slide Rule Cult on Earth coming up in late September 2011!!! Don't miss it! See the magic ANALOG gizmos that computed the Industrial Revolution!!!

Click image to enlarge.

It is very possible that you may never have touched a slide rule. I bought my first hand-held digital scientific calculator around 1973 -- Hewlett-Packard was first, but Texas Instruments hit the market just a few months later -- and this was the death knell of the wonderful analog slide rule, which did its magic by making distance the visual analogue of quantity

The slide rule essentially was adding and subtracting -- you can see how that works by sliding two ordinary rulers back and forth -- but the scales were not linear, but were laid out in logarithms

When you add logarithms, you multiply quantities, and when you subtract one log from another, you are dividing. Slide rules also merrily extracted roots -- square roots, cube roots, 4th and 5th roots, etc. -- and manipulated trigonometric functions (sines, cosines, tangents).

Notice that the slide rule does not use batteries or electricity. It's the perfect computational machine for being stranded for years on a desert island, or after a thermonuclear war wipes out all electrical devices with Big Pulse.

Was the slide rule primitive? You can argue that it's primitive compared to digital calculators and computers. But the Age of the Slide Rule was the tool that computed the Brooklyn Bridge, the Empire State Building, the world's railroads and their steam locomotives and the great industrial steam engines, fixed-wing and rotary aircraft, and finally sent human beings into orbital space and to the Moon. (By the Moon landings, digital computers were available, but every NASA nerd was firmly clutching his/her slide rule.) Einstein computed Relativity on a beautiful German Nestler Mannheim slide rule (the same model Werner von Braun used, I regret to say).

Although a digital calculator/computer can spew out answers like

23.9042281678821308

every numerical constant known in the physical universe only has practical meaning accurate to a maximum of 4 or 5 or 6 decimal places -- all the digits to the right of that are meaningless gibberish -- and a slide rule could give you that realistic and practical kind of accuracy. Sufficient to send a rocket to Venus or build the Brooklyn and Menai Straits Bridges, or the Titanic. (It didn't sink because of its designer's slide rule.)

The Edinburgh eccentric John Napier (Laird Merchiston) published the rules of logarithms in 1614. William Oughtred constructed the first slide rule in 1622.

~ ~ ~

A meeting of the wonderful cult of slide rule worshippers and collectors will occur later this month in Boston -- well, really in Cambridge, just over the Charles River from Boston -- at the Massachusetts Institute of Technology. (Last year's slide rule convention was at Cambridge University in UK.)

~ ~ ~

The Oughtred Society was founded in 1991 by a group of slide rule collectors and is dedicated to the preservation and history of slide rules and other calculating instruments. In the past 20 years it has evolved to an international organization with members in 22 countries. It is noted for its highly acclaimed Journal of the Oughtred Society, published twice annually.

~ ~ ~

Friday-Sunday 23-25 September 2011

The International Meeting of Collectors of Historical Calculating Instruments (IM 2011) will be hosted by the Oughtred Society at Massachusetts Institute of Technology in Cambridge, Massachusetts USA.