I've been thinking about why we have a seven day week

So, I did some research and came up with these links:

http://www.webexhibits.org/calendars/week.html(a wonderful resource for all things calendar)
and http://sciencev1.orf.at/news/46545.html and http://www.friesian.com/week.htm (simply titled "Days of the Week")

which leads me to another thing: why is seven a special number?



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