In many European languages there's an obvious connection between the names of the days of the week and the planets. When we consider that the ancients divided the heavenly bodies into fixed stars (of which there are thousands) and wandering stars, of which they knew of seven, we begin to see the connection between days of the week and wandering stars.

The Wandering Stars or "planets" were as follows:

• The Sun
• The Moon
• Mercury
• Venus
• Mars
• Jupiter
• Saturn

Uranus and Neptune had not yet been discovered.

It's obvious that Sunday, Monday and Saturday are named after the Sun, the Moon and Saturn. In French, Tuesday, Wednesday and Friday are are called Mardi, Mercredi and Vendredi which clearly come from Mars, Mercury and Venus. Thursday as Jeudi is not as obviously Jupiter, but in Italian it is more evident - Thursday is Giovedi and Giove is Jove, the other name for Jupiter. So the seven days of the week are called after the seven "planets" or wandering stars.

The ancients didn't think of the Earth going around the Sun. Instead they thought that the Sun and all the other "planets" went around the Earth. They didn't have the technology to measure the distance to the planets but worked out a mathematical model to predict their positions. This put the distances of the planets from the Earth in the following order:

• 1. The Moon
• 2. Mercury
• 3. Venus
• 4. The Sun
• 5. Mars
• 6. Jupiter
• 7. Saturn

So why are the days of the week in a different order? If we use the numbers for the planets just given, we see that the days come in the order 4, 1, 5, 2, 6, 3, 7. This is not just a random scrambling of the seven numbers. If we draw a circle and write the numbers 1 to 7 around the outside of it, we can see that the pattern here is jumping around the circle in steps of 4. This can't be a coincidence.

A Theory

The Babylonians who worked out much of the theories about the movements of the planets, divided the days into twenty four hours. If you label the hours with the names of the planets, calling the first hour "Saturn", the next "Jupiter" and so on, working your way from furthest planet inwards, you run out of names after 7 hours. If you start again at "Saturn", and repeat as often as necessary, you'll find that the last hour will be called "Mars". The next day will start with "Sun". The day after this will start with Moon, then Mars, Mercury, Jupiter and Venus, exactly the order of the days of the week.

But is this actually the origin of the day order? It seems a very elaborate procedure. Is there any evidence that the hours were named in this way?