The wandering planets and the seven-day week

A waning gibbous Moon, 15 April 2016 - Lower Hutt, NZ. Photo: Louise Thomas

Celestial observations to mark the passing of time have been used since the dawn of human kind. Early humans counted off the number of Suns to mark the days, followed by the changing phases of the Moon, which repeats approximately every 30 days, to mark longer periods, after all, it was easy to count the number of full or new moons that elapsed since or leading up to some big event. We observed seasons and the changing patterns of the Sun and star movements to mark the passing of a year, and from prehistory used this not only for migration, hunting and agricultural planning, but to mark how old our children were and to record and observe their transition into adulthood. These early observations of the world around and sky above of course laid the foundations for development of the calendar, that, with some variations throughout history, we would eventually use to divide the year into months, weeks and days. But what are the origins of the seven-day week as a division of time? It seems that this too, at least in ancient European and Mesopotamian cultures, was also rooted in astronomical observations.

I'll have the pleasure of giving a talk about the origins of the seven-day week and the significance of the order of the days at an upcoming astronomy conference on 13-15 May at Stonehenge Aotearoa in New Zealand's beautiful Wairarapa. Great dark skies and plenty of chance for observing if the weather holds - it's been a beautiful autumn so far, with plenty of opportunity for observing the planets. Jupiter in particular has been holding sway in the early evening in the Northern sky. The conference will be a great opportunity for me to show off my newly developed astrophotography skills.