Keeping Time: Why 60 Minutes?: Maps of Civilization

Over at LiveScience I've been writing a series on all the ways me measure time in modern times, specifically on all the names, numbers, and conventions that we associate with each:

• Years (AD/BC, and why there's no year zero)
• Leap Years (How they work and the history of the Gregorian Calendar)
• Months (Why there's 12, their names and lengths)
• Weeks (Why 7 days, names of the days)
• Hours (Why there's 24, why clocks only show 12, and time zones)
• Minutes and Seconds (Why 60?)

By far, my most favorite is the last one, because it's basically a history of civilization up until the scientific revolution: http://www.livescience.com/44964-why-60-minutes-in-an-hour.html

The best thing about this story is the maps. It's so hard to talk about the progress of knowledge before the scientific revolution because it spans the lifespan of so many civilizations. To me the key was looking at the maps and actually being able to see knowledge flow and grow over history. These maps are actually what inspired me to tell the history of sexagesimal as a single, unbroken story spanning the entire history of civilization.

Sexagesimal was invented in the 34th century BC with the first writing. It was the way all numbers were recorded for two thousand years.

Continuing to write in sexagesimal, the Babylonians also invented the degree. Most importantly, the Babylonians applied these principles to observing the sky, and took measurements that constituted the first study of astronomy. Their work would serve as the basis for another thousands years, in spite of the boom and bust of many great empires.

Alexander the Great's conquest reached India in 326 BC, spreading the knowledge of Babylonian astronomy to both Greece and India. This work created such a strong association between sexagesimal and astronomy that even though the Greeks had their own system of numerals in decimal, Greek (and later Roman scholars) kept using sexagesimal for star charts, trigonometry, and navigation.

Much of this knowledge was lost to Europe for many centuries, beginning with the fall of the West half of Rome in the 5th century AD. The Islamic-Arabian empires inherited many Roman (and later Indian) ideas starting with the Rashidun Caliphate in the seventh century. Muslims scholars, after expanding on this knowledge greatly, reintroduced it to Europe in the eighth century through the Iberian Peninsula, which was then part of the Umayyad Caliphate.

The knowledge that had been saved and enhanced by Muslim scholars found its way to Christian scholars in the 11-13th centuries. Europe and the Islamic lands had multiple points of contact during the Middle Ages. Particular points of transmission of Islamic knowledge to Europe were:

• The 1085 conquest of Toledo by Spanish Christians
• The 1091 re-conquest of Sicily by Normans (following Islamic conquest in 965)
• The Crusader battles in the Levant (1096–1303)

During the 11th and 12th centuries, many Christian scholars traveled to Muslim lands to learn sciences. Notable examples include:

• Leonardo Fibonacci (1170 – 1250)
• Adelard of Bath (1080 – 1152)
• Constantine the African (1017 – 1087)

Some other graphics I put together for each civilization:

Sumer & Akkadia:

Babylonia:

Greece & Rome: