It's a Cycle of (dot) (dot) (dot) ?

Today, is the day when Venus crosses the sun. Some astro scientists said that it's the second coming of its twin-like cycle of appearance after June 2004 transit, the next one sould be 105 years from now.

The importance of the event varies amongst the observer. But Surely, it helps us to understand of how big is big, and how small is small through this once (or probably twice) in a life time chance to directly compare the size of a planet next to us to the sun. Venus is said to be about the same size as earth by radius. And yet how lucky we are to be 'placed' here on earth. And it gives a sense of gratitude to be here at the right distance, as compared to being in unimaginably hot Venus. And that we could imagine how small the earth could be, seen from Mars and other planets further from the sun. and how 'insignificant' we (the human) are.

It's interesting when scientist could predict the cycle of planetary objects to appear and to where its course is heading. Yet, still, no one knows what cycle 'a week' represents. As we know, a month is a cycle of moon re-appearing in its original phase. A year is said to be the time when the earth completes its course around the sun. and a day is a cycle of sun rising and setting. If a month is not entirely made of similar amount of days. and thus a year does not always consists of an exact 365 cycles of sunrise and sunsets, and that a year is when the moon has changed its phase 12 times. and yet a year is not always made of 52 weeks as 365 (366 on leap year) could not be evenly devided by 52. Should they then be considered as separate measures? Still, what is a week? What inspires the 7-day count? Who started it? If some religious activities carried out in 7 day interval within a week, does 'A Week' originate from a religious trait then? Still, of what?

This may sound differently to different readers, but i just want to make sure the emphasis is that there are probably a lot more things around us that we have no idea what it is, and it's not about something unusual, it's about something as casual as 'a week'.

This is only a ponder. no other means intended.