[nilmot]

I'm not so sure this is a scientific question. More of a philosophical question.

Tom

[NakedScientist (OP)]

No, it is definitely a scientific question, with a scientific answer, though some of the answer has its origins in philosophy.

TNS

[cuso4]

I found something on the Internet which might be what we're looking for.

Why are there 7 days in a week?

One month is roughly the time taken for the Moon to rotate the Earth once. One year is 365 days and divide this by 12, we get 30.416 days per month. One week is the time taken for the Moon the a quarter of the Earth. So divide 30.416 by 4, we get a value around 7.

I'm not sure anout the second question but I'll have a go.
Monday is named after the Moon and since ancient people use the movement of the Moon to measure time (Chinese Calender is based on this), Monday is set to be the first day of the week.

Angel

[NakedScientist (OP)]

Well done Angel, you are on the right lines. Keep going.

TNS

[neilep]

Here is something I have blatantly 'borrowed' from a website I found which I think part explains why Monday is the first day of the week.

MONDAY
There are some countries which have Monday as the first day of the week. This is in accordance with the International Standard
"ISO 8601:1988 (E)"
Which states under item:
5.4 Combinations of date and time of day representations
3.0 Terms and Definitions
3.17 Week Calendar
"A seven day period within a calendar year,
starting on Monday and identified
by the ordinal number with in a year....."

There are countries in Europe, such as Denmark, Norway and Sweden that have Monday as the first day of the week.
In the USA documents ANSI (X3.30) and NIST (FIPS 4-1) adopted ISO 8601 and list Monday as the first day of the week.
However, the calendar in USA has
Sunday as the first day of the week

'Men are the same as women...just inside out !'

[neilep]

Here is something else i have borrowed, regarding the number of days in the week.
Known as an interval between Market Days. In central Asia five days was used, Egyptians used ten days and the Babylonians like the multiple of seven because of the lunations of the moon. In Rome the eight day cycle was used for market. The orgin of the seven day week seems to be related to the four (about) seven day phases of the moon. Also the seven colors in the rainbow, and in the Babylonian times, the seven planets. By the time of the first century BC the Jewish seven-day week seems to have been put into place throughout Rome.


The calendar in the USA has Sunday as the first day of the week. The word week comes from Latin "vicis" meaning change. The week is a period of seven days and is now used throughout the world as a division of time. History seems to favor the Hebrew or Chaldean origin and the week is mentioned as a unit of time in the Bible, see the Old Testament book of Genesis 29:27. ....do me and Angel get a gold star ?

'Men are the same as women...just inside out !'

[tweener]

If you're going to insist that Monday is the first day of the week despite every calendar in the known universe, then I say Monday is the first day of the week so that everyone can get off to a really rough start every seven days. []

----
John - The Eternal Pessimist.

[neilep]

Personally..I think Mondays should be cancelled []

'Men are the same as women...just inside out !'

[Donnah]

I've got it!  It's divine intervention that caused the 7 day week and the week to begin with Monday.  We're told that God made the world in six days and took the 7th day to rest, calling it the sabath.  How do you like that?  He takes the 7th day to rest but expects us to get up on that day to go to church.  *tongue in cheek*

[nilmot]

But isn't that a religious explaination not a scientific explaination?

Tom

[tweener]

I vote for cancelling Mondays.  But everytime I try, Tuesday is worse than Monday.

----
John - The Eternal Pessimist.

[Boffy Clywd]

quote:Originally posted by NakedScientist

HERE'S THE ANSWER TO LAST WEEK'S "QUESTION OF THE WEEK", SUBMITTED BY NILMOT (Tom Lin)

The appearence of the moon in the sky depends upon the position of its orbit. There is no reason why the moon and sun should not appear together in the sky since they are totally independent of each other. The moon orbits the earth and the earth orbits the sun. Therefore sometimes the moon coincide on its orbit with the rising of he sun and hence the two will appear in the sky together.

This is precisely how an eclipse occurs, only on this occcasion the path of the moon crosses the path of the sun. But the two bodies are still in the sky at the same time.

I think most people seemed to get that one right. Good question though. By an amazing co-incidence a lady phoned the radio show a few weeks ago with the same question !

[Boffy Clywd]

The moon and sun do not very often appear near each other in the sky for a very good reason. The sun is so bright, and back lights the moon, that it can not be seen even though it is often there. Just before and after any eclipse the moon is not visable for example. Often the moon can be seen if it is over the other side of the sky from the sun, this will mean the distance from the moon to the sun is greater than the distance of the earth to the sun.
  [8D]

[NakedScientist (OP)]

Here's the answer to the last QOTW "WHY ARE THERE 7 DAYS IN A WEEK, AND WHY DO WE HAVE TO HAVE MONDAYS ?"

It all comes down to the ancient Greeks, Romans and Babylonians.

Early observers of the sky saw several prominent features - the Sun, the Moon, and the stars. But closer inspection of the stars showed that whilst most moved across the sky in a uniform way, some moved at different speeds and even turned back on themselves. These errant stars were named 'wanderers' which in ancient Greek is planetes, from which we get our modern word "planet". At that time early observers only found 5 'planetes' (Mars, Jupiter, Saturn, Mercury and Venus) - the discovery of the rest would have to wait for the telescope to come along.

Observations on these 'planets' showed that they take a different amount of time to complete a cycle and return to their starting position. The planets were assigned a seniority according to how long they took to complete their own cycle :

Saturn 29 years
Jupiter 12 years
Mars 687 days
Sun 365 days
Venus 225 days
Mercury 88 days
Moon 28 days

The Babylonians decided to divide a day into 24 hours (in place of the 12 used by Egyptians) and decided to name each hour of the day after each of the 'planets' in order of seniority, and startign again when you run out of planets. e.g. :

1 am - Saturn
2 am - Jupiter
3 am - Mars
4 am - Sun
5 am - Venus
6 am - Mercury
7 am - Moon ...and start again with...
8 am - Saturn
9 am - Jupiter and so on...
...10 pm Saturn
...11 pm Jupiter
...12 pm Mars

Obviously 7 doesn't divide equally into 24 so the next day starts with a new 'dominant planet' (the one at the top of the list). It was the custom to name the day after the dominant planet on that day.

Looking on the list you can see that after Mars comes "Sun" and hence the next day starts with Sun and works through the list. The day after that starts with "Moon", then "Mars", then "Mercury", then "Jupiter", then Venus and finally back to Saturn.

If you then write out these dominant planets in order you see a familiar pattern emerge :

Planet       English   French

Saturn day   Saturday  Samedi
Sun Day      Sunday    Dimanche
Moon Day     Monday    Lundi
Mars Day     Tuesday   Mardi
Mercury Day  Wednesday Mercredi
Jupiter Day  Thursday  Jeudi
Venus Day    Friday    Vendredi

This 7 day week was adopted by the Romans who spread it across their empire. The Pagan English preferred to keep Sunday for the Sun God, and also named the previous 4 days of the week after Anglo-Saxon gods - Tiw (Tuesday), Woden (Wednesday), Thor (Thursday) and Frig (Friday). The Christians wanted a different holy day to the Jews - so they took Sunday (Dimanche) which is a contraction of Dies Dominici (Day of our Lord) in Latin). Because Sunday is the Christian day of rest, we have to have Monday mornings on which to return to work...ouch.

[NakedScientist (OP)]

Here is this week's QOTW :

"IF A CAR IS DRIVING AT THE SPEED OF LIGHT AND IT TURNS ON ITS HEADLIGHTS, WILL THE WAY AHEAD BE ILLUMINATED ?"

That should keep you busy !

TNS

[tweener]

Yes.

----
John - The Eternal Pessimist.

[BlooGoo]

if the car were travelling NEAR the speed of light, and turned on its lights, the way would be lit (i think) because the photons that are emitted from the lights would a) be propelled forward (with some dopplar shifting in there) and b) would be travelling at the speed of light (just that little bit faster than the car itself).

if the car were travelling AT the speed of light ... hmmm ... i would imagine that as the lights were turned on, they would illuminate in front of the car, but as your eyes focused on the light (assuming that you're in the car too) it would look like you're going faster than the light, and would give you the warp speed look that's associated with going really really fast.

just a guess.

[tweener]

Here's the long version of my previously short answer:

Any photon emitted by your car would travel away from the car at the speed of light, relative to the car.  The photons would also be travelling at the speed of light relative to the signpost at the side of the road.  The photons reflected off the signpost back to your car would arrive at your eye travelling at the speed of light.  There would be considerable doppler shifting here, so that a mere eye would not be able to detect the photons, but with appropriate instrumentation technology, the "way ahead" would be lit.

----
John - The Eternal Pessimist.

[Rabbit]

Nice Easter question this one! Ask some of the clever boys on the autobahns in Germany, they will have real experience to share with us. No, I do not know any of these people. Come to that, travelling at this speed and messing around with the lights sounds pretty dangerous...

[gsmollin]

The speed-of-light-car question has a "no" answer, because a car can't travel at the speed of light. We don't ever see the lights come on because time dilation stops the car. All the energy in the universe is required to accelerate the car to the speed of light, and the car gets crushed to infinite density by Lorentz contraction. The light cannot escape the car because it turns into a black hole. This is not a good question.