Odd O'blography

Happy Venus D!

My son sent me a tongue-in-cheek text to warn of the looming danger of Friday the 13th. Being contrary in nature, I replied that the concept of Friday is merely a conceit of Judeo-Christian culture. And that the number 13 is just an accident of using base ten to count the days of the month.

Having a mind like a grasshopper, I began to think about other calendars and other number systems. Ancient calendars all seem to be based on the lunar cycle. Moon phases are obvious even to the casual observer, but the 29.53 day lunar month doesn't sync well with the 365.242 day solar year. So, you need 12.368 lunar months to equal one solar year. The Babylonians figured this out quite accurately. They used twelve 30-day months and added an additional month every few years to keep things in sync.

Pre-Babylonian calendars usually didn't name the months or days, and they didn't use the concept of weeks either. They simply counted the days from one new moon to the next. Some early cultures determined that the 1st, 7th, and 15th of each month should be a holy day. The Babylonians made every seventh day a holy day and they also named the months. The Hebrews borrowed some of the Babylonian concepts and the modern 7-day week is based on their calendar.

The Romans named the days of the week for their Gods. What English speakers call Friday was known as Venus' day to the Romans (it morphed into Viernes in Spanish). The English word 'Friday' didn't come into use until much later. The earliest references come from the 11th century CE.

The number 13 is rather arbitrary, too. It's based on humans having ten fingers to count on. But that hasn't always been the case. At least two Native American tribes counted up the spaces or along the knuckles in a base eight number system known as octal. I used octal back in 1985 when programming an early computer system. Octal uses only the digits 0 through 7. Today, computer languages use a base sixteen system known as hexadecimal. It uses A through F as digits in addition to the more familiar 0 through 9. The simplest system is base two, or binary, which uses only the digits 0 and 1.

Each digit (or bit) in binary is a power of two, 1 = 1, 10 = 2, 100 = 4, 1000 = 8 and so on. All digital information is stored in binary inside your computer and the binary representation of 13 is 1101 (8 + 4 + 1). Octal separates binary numbers into three-bit groups. So, 1101 is parsed as two digits, 001 and 101, and that's written as 15 octal. Hexadecimal separates binary numbers into four-bit groups. So, in hex, 1101 is parsed as one digit and written as simply D hex.

There are many choices from other cultures, but I can claim both Venus and D as part of my heritage.

So, happy Venus D!


p.s. My friend Gerry pointed out that we instinctively use base ten when counting on our fingers. But if we count in binary, with each finger representing one bit, then we can count up to 1023! (or up to 1,048,575 with our shoes off)