Do you know the significance of 3.14159265358…, 29.92, and 9.81?
What about 929?
If you wander the shelves at your local library looking for genealogy books, you find them under the Dewey Decimal Classification 929.
This matrix, see a full-size version at Library Thing, shows how 929, Genealogy and Heraldry, fits within 92, biography, genealogy and insignia, that within 9, history and geography.
The row below shows the sub-categories of 929 indicated by the number after the decimal. Below are the number of entries in that category saved by Library Thing users. Click on any one of them at Library Thing and scroll down to see selected works in the category. You can also click to see further sub-classifications. Go far enough and you’ll find 929.1072041 includes
Tracing Your Irish History on the Internet by Chris Paton
Researching Scots-Irish Ancestors: The Essential Genealogical Guide to Early Modern Ulster, 1600-1800 by William Roulston
Scottish Genealogy by Bruce Durie
Who Do You Think You Are? Encyclopedia of Genealogy by Nick Barratt.
What about those other numbers?
You probably recognized 3.141… I could go on …as the value of pi, the ratio of the circumference to the diameter of a circle.
A pilot would recognize 29.92 as the altimeter setting used at or above 18,000 feet. It’s the average air pressure, at sea level, the height of a barometer column of mercury in inches.
If you literally fell off your chair puzzling over these, you’d fall under gravity at an acceleration of 9.81 metres per second squared. Fortunately not too far!
Too easy? What about 1.618033988749?