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time and clocks...

Posted by: Ekkehard Augustin - Tue Mar 29, 2005 5:28 pm
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time and clocks... 
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Post    Posted on: Fri Apr 08, 2005 1:28 pm
Although in the UK it is uncommon to see or use 24hr clocks it is taught in pimary (I think elementary is the equivalent in the US) school and everyone is aware of them so I dont think its adoption would be a problem.

Also why change the length of an hour so that 24 of them are equal a Mars day instead of 24hr 39min? Just allow the local clocks on Mars to go to 24:39 rather than resetting at exactly 24hr they reset then, the same system could be adopted on any planet with a rotational period that was similar for longer periods then it makes sense to use something like standard GMT.

Changing the actual length of an hour would cause more problems than it would solve, a lot of scientific instruments would become inaccurate and have to be replaced or recalibrated. There would be an impact on mathematical equations that have time in them, for instance:

A Watt = Joule/Second (increasing a second's length would make a Watt smaller), Maths and engineering is littered with equations that would have to be redefined.

The speed of light would not be the nice easy figure 300,000km/s, the situation would be a nightmare.

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Post    Posted on: Fri Apr 08, 2005 1:49 pm
To me the modification seems to be required for

1. solar system-wide interplanetary flight control,
2. sloar system-wide interplanetary talk and
3. the common people and their life only.

If 24 hour-clocks would be used at Mars and if the seconds were as long as on Earth in terms of cesium oscillations - then for Mars modified clocks would be required because they had to show times like 24:23.

In the case of 12 hour-clocks such a modification wouldn't be required but instead these clocks would show or times that don't exist at Mars - like an 1:25 (PM) that really is 0:46 (AM). A 12:39 (PM) would valid... I set the "PM" between "(" and ")" because 12 hour-clocks in germany don't show any "PM" or "AM" and no substitute for them.

If no modifications would be done then the time of beginning of daylight would be shifted by the 39 minutes each day - this shift would add to the shift caused by the inclination of the Axis of the Mars towards the ecliptic.

To me nothing of this sounds good. This may be different for others and that's alright - but if such differences result in different clocks and systems between american martian stations or colonies at the Mars on one side, chinese stations or colonies on the other side and european stations or colonies on the thirs side... - then it would be going to become much more complex yet.



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Post    Posted on: Fri Apr 08, 2005 3:28 pm
Andy Hill wrote:
Changing the actual length of an hour would cause more problems than it would solve, a lot of scientific instruments would become inaccurate and have to be replaced or recalibrated.

We are really talking about two (or maybe more) different time systems that would be used for different reasons.

For most purposes, including space flight, scientific work, and time on celestial bodies where the natural day is very different from 24 hours (such as the Moon), we should use SI seconds and GMT (or UTC) as the time standard.

Mars is a special case because it has a day nearly, but not exactly, 24 hours long. All real Mars missions so far have elected to use a slow clock for scheduling activities. I am not sure I would have chosen this method of time keeping, but then again I might have if I were directly involved and knew all the problems with the different methods from first hand experience. In other words, it works for the people who actually have to use it. And they use it ONLY for scheduling activities and for no other purpose. In particular they do not use it to compute light time for radio signals or rover drive speed or any other measurement type purpose.

I do oppose all attempts to develop a new time system where it is not needed, such as for interplanetary space flight. GMT (or UTC) will work just fine in those cases. But Mars really does need a special time for normal day to day activity scheduling.


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Post    Posted on: Sat Apr 09, 2005 8:34 am
In future times when there is passenger traffic between Mars and other planets there will be unpreventable links between the time to be displayed at the martian spaceports, the time to be displayed aboard space vehciles and between this time to be displayed aboard space vehicles and the time to be displayed at the spacports at the destinatoion planet. This link requires coordination at least.This is a situation in a future let's say 50 years away. This situation I am considering in this thread .- regardless of 50 years in the future or 5ßß years in the future.

It's not the situation of unammned flights to the Mars.



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Post    Posted on: Sat Apr 09, 2005 2:36 pm
Yes, we are talking about the same thing. Current unmanned practice is just a precursor to the future.


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Post    Posted on: Thu Dec 08, 2005 8:18 am
In the last few days I read an article under www.welt.de saying that a white dwarf with an extremely constant period of pulses has been found.

Today now a longer and more detailed article about it is to be read under www.astro.uni-bonn.de/~dfischer/suw-news/ .

The article says that the white dwarf needs 8.9 mio. years until the period is increased by one second while an atomic clocks needs only 300,000 years for that increase.

That white dwarf is already called the most precise clock ever found. The article explicitly says that it is imaginable to create a new Universal Time by that white dwarf combined with a few special pulsars not only but a time of the universe too.

This seems to fit into the thought I discuss(ed) in this thread - the white dwarf can be observed from nearly all locations in the solar system and it would mean to be one and a single clock for all locations together instaed of needing several atomic clocks which will have to be adjusted to each other.

The white dwarf is G 117-B15A while the pulsars mentioned are two millisecond-pulsars not listed.



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Post    Posted on: Thu Dec 08, 2005 1:21 pm
I read an article the other day of an interview with one of the ISS astronauts and he mentioned that they use GMT on the space station. I guess that this practice will spread to a moon base and by then it will be pretty much established as the norm.

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Post    Posted on: Thu Dec 08, 2005 2:45 pm
Ekkehard Augustin, I posted the news December 2 - http://www.spacefellowship.com/News/?p=1286
and in english (so others can read it as well).

There're 2 to 10 new articles on our own front page, so a good place to read news as well :idea: (yes that's advertisement lol)

http://www.spacefellowship.com/News/ - (a new advanced news system coming in "a few weeks").

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Post    Posted on: Thu Dec 08, 2005 3:14 pm
Yes, now I seem to rember having read that article - but didn't recognize obviously that it is relevant in this thread.

Andy, the post wasn't meant as an argument against GMt or the like but as a hint to a "tool" to measure time independently of rotation periods not only but by one and the same tool for very very much locations in parallel: not many atomic clocks are required but only this one single white dwarf together with two pulsars.

It could also free vehicles from the requirement to carry their own clocks and it could be a way to get rid of problems caused by relativistic effects which would occur during use of vehicles going by velocities that are significant fractions of c.

It would be more reliable than atomic clocks.



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Post    Posted on: Thu Dec 08, 2005 4:11 pm
I read about this a few days ago and thought of this thread immediately, but didn't want to start the old argument again. But since you have, I must say that even if it becomes the new time standard it will never replace clocks. Clocks will simply be set to a pulsar based standard instead of an atomic clock based standard. Observing a pulsar is not so simple and it does not tell the current time anyway. It only tells you if your clock is ticking at the right speed.


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Post    Posted on: Sat Dec 10, 2005 1:36 pm
This would be valid for rotation-based clocks like the very old sun clocks too.

I don't restrict the term "clock" to mechanical clocks, disks with pointers and so on. The time is nothing else than a repitition of units and the time expressed by seconds, minutes and hours is rotation-based.

The technology to wtach white dwarfs and pulsars eexists and may be going to be improved if and when it is cosnidered to be advantegous to watch them to get the current time

Which is required is at least one telescope to watch the white dwarf as well as the pulsars and links and connections to that telescope for each one who wants to use it. It may be used to adjust clocks like it is done with the atomic clock of the Physikalische Bundesanstalt in Braunschweig too - that Bundesanstalt tells the official time by law here in Germany - and all clocks in Germany are adjusted to that clock. Some by wire - others by radio. This could be done with a white-dwarf-based clock too.

For these reasons the white dwarf would be a clock.

May be you and me use different definitions of the term "clock" - don't start to insist on me having to use a definition according to yours: there is a large danger of this causing this thread spirally. Plus remeber the lot of PMs we excahnged and you didn't read two of them...



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