Slide Rules facts

While investigating facts about Slide Rules, I found out little known, but curios details like:

On NASA's Gemini XII flight, the computer docking system failed and Buzz Aldrin successfully calculated the docking trajectory using a sextant and a slide rule.

IBM bragged in 1952 that each of their computers were equivalent to having 150 extra engineers with slide rules

In my opinion, it is useful to put together a list of the most interesting details from trusted sources that I've come across. Here are 17 of the best facts about Slide Rules I managed to collect.

1. Buzz Aldrin brought a slide rule with him aboard Apollo 11 in the event of a computer malfunction

2. There are advanced slide rules that can calculate cube roots, sine values for trigonometry, and raised numbers to various powers

3. In 2006, Scientific American published an issue that included blueprints on how to make a do it yourself paper Slide Rule calculator

4. The slide rule is an early computer invented in the 17th century. It is made from two logarithmic scales put next to each other. If you put 1 (the multiplicative identity) of one scale against any number on the other scale, you can see all the multiples of that number down the scales

5. NASA engineers used slide rules to build the rockets and plan the mission that landed Apollo 11 on the moon. It's said that Buzz Aldrin needed his pocket slide rule for last-minute calculations before landing

6. There are International Slide Rule championships where where you have to quickly solve a list of equations and math problems using only a slide rule

7. Before logarithms were used for easier multiplication and division (on devices like slide rules), mathematicians used a trigonometric algorithm known as Prosthaphaeresis to simplify complex arithmetic

8. The last slide rule calculator manufactured in the United States was in 1976. Slide rules fell out of favor to pocket calculators, which, by the mid 1970s, had become affordable and were considered significantly easier to use

9. During the Apollo missions Moon-bound astronauts carried slide rules as backup to electronic calculators

10. Peter Mark Roget (of thesaurus fame) also invented the slide rule

What is true about slide rules?

You can easily fact check it by examining the linked well-known sources.

We could argue that the first computer was the abacus or the slide rule, in 1622. But the first computer resembling computers we know today was the Analytical Engine, a device designed by British mathematician Charles Babbage between 1833 and 1871.

Slide rules used the concept of logarithms to make complex calculations as simple as sliding a ruler and finding the value. You just had to remember where the decimal point would be involved at the end. - source

It wasn't the slide rule that got a man on the moon but several sophisticated computers - source

Engineers used to rely on imprecise calculations with slide rules that only showed three decimal points and designed the Empire State Building, Saturn V rocket with them. As a result, they designed conservatively by making walls thicker and bridges stronger than needed