What’s a Week?

When I chose Week as today’s Ragtag Daily Prompt, it was because of my surprise that it was Thursday again (that’s usually when I set up the prompt for Friday). Hadn’t I just done that? A week goes by so quickly.

As I was pondering the concept of a week, seven days, I was imagining it to be a made up concept, a somewhat arbitrary system. Useful for coordinating time, calendars, etc, but without a basis in the natural world. I was wrong. According to LiveScience.com, the week as we know it was developed by the Babylonians and was related to the changing phases of the moon. First quarter, second, etc. This makes sense to me, as a day is turn of the earth on its axis, the original (lunar) month is one full moon to the next, and a year is the time it takes the earth to make a trip around the sun. All features of the natural world and the relationship of the planet to the sky, which in earlier times was a huge source of information. The sun and stars allowed for navigation on earth as well as timing and understanding seasonal change as well.

Here on earth, the planet rotates once every 24 hours, and that’s a day. There are minor variations depending on whether its measured sunrise to sunrise or a full rotation, but 24 hours works well. A year is the time it takes the earth (or any other planet) to traverse a full orbit around the sun.  On earth, that’s 365 and a quarter days. As it turns out, our normal is not how it is on other planets. Venus takes 225 earth days to orbit the sun, and 243 earth days to rotate  just once, making a day longer than a year. By that criteria, on Venusian week takes 7.5 years. Talk about having a seemingly endless week!

And the big “gas giant” planets rotate really fast, so that a day on Jupiter is 10 earth hours and its 11 on Saturn. NASA has a site designed for kids, NASA Space Place, that has lots of easy to understand and fun info about space and science. Its an enjoyable exploration if you’re so inclined and have a little time in your week.

Enjoy your week here on earth, and who knows what may prompt my prompt next Friday.

2 thoughts on “What’s a Week?

  1. Erm, I think the basis for a week comes from the amount of time it takes to create everything… with an extra day for napping. I guess I knew that bit about the moon. Now let’s figure out how they decided how long to make each month.


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