Slide Rule
"We went to the Moon with slide rules." —Norman Chaffee, NASA Astronaut
The Apollo astronauts carried a slide rule on board to calculate as needed. Also, many of the calculations necessary for the technical details of the launching, landing, and lunar or Earth interception were carried out on slide rules.
The spacing on the scale is not uniform, but rather logarithmic. A uniform scale would permit addition and subtraction.
The logarithmic scale transforms multiplication (division) to addition (subtraction), allowing these operations to be rapidly calculated to three or four digits
Logarithms were invented in 1614 by John Napier.
Slide rules allow for many operations including multiplication, division, powers and roots, exponentials, logarithms (naturally) and trigonometry.
Additionally, there were scales for calculations and unit conversions in areas such as thermodynamics, heat flow, electricity and magnetism, and statistics.
It was the standard calculating tool in all areas requiring mathematics.
There were different designs, including circular and cylindrical slide rules.
The hairline was intended to allow for more precise estimating between the marks as well and to read across various scales.
This demonstration is currently displayed in the Hallway on the 2nd Floor in Manning Hall.