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Forum » SpaceEngine » Science and Astronomy Discussions » Timekeeping on Mars
Timekeeping on Mars
HarbingerDawnDate: Wednesday, 10.07.2013, 23:13 | Message # 1
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Now that surface exploration of Mars is a fact of everyday life and human visitation of the planet is on the horizon, the need for a system of keeping time on Mars is becoming increasingly apparent.

For convenient and practical timekeeping there are two fundamental systems which must be decided upon: a clock (how to divide the day into units of time), and a calendar (how to divide the year into units of time). Of these, the clock has a pair of possibilities: making the base unit of time equal to the SI second, as is the case with Earth's clock, or making a clock with a new base unit of time (a new 'second', if you like).

This thread is for discussing different ideas related to Martian timekeeping: clocks and calendars, month and day-of-week names, and technical or social issues related to the subject.
 
HarbingerDawnDate: Wednesday, 10.07.2013, 23:37 | Message # 2
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I'll start things off.

The clock proposal that I most favor - of the ones that I've seen at least - is this one by Dale Shultz. It retains the SI second as the base unit of time, and it also has minutes that are 60 seconds in length. Hours are 74 minutes in length, and each day contains 20 hours. Unlike most clock systems based on the SI second, this one does not require daily adjustment by adding leap seconds or similar. Instead, it can be kept accurate simply by adding an hour every 180 days. So once every 180 days, Martians would get an extra hour of sleep, or work, or whatever they wanted to do smile

I like this clock so much that I created a time zone map for it, which depicts the nominal assignment of time zones under this clock system. The boundaries would probably get increasingly irregular as people settled and developed more places on Mars' surface, but it would likely stay close to the original layout.

I have four versions of the map:

Shaded topographic map (with landing sites)
Color visible surface map (with landing sites)




The calendar proposal I most favor is the always popular Darian calendar. It divides the year into 24 months, and each month has 28 days (4 weeks), except for every 6th month (the last month of every season) which has 27 days. The exception to this is the last month of the year, which has 28 days 60% of the time and 27 days 40% of the time. It has the same purpose as a leap day on leap years, except it's probably better to call them skip years here since the skips are more infrequent than the leaps.

While I do like the Darian calendar system, I do not like the names of the months or days of the week. Nor have I been able to find any other naming convention that I like. So I'm currently working on my own set of names.





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Edited by HarbingerDawn - Wednesday, 10.07.2013, 23:37
 
SpaceEngineerDate: Thursday, 11.07.2013, 10:07 | Message # 3
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I agree that SI second should be used. Imagine a mess it measurements, science, communication, trade and all other life situation if martians start using their own time unit. And BTW here, on Earth, one solar day is not precisely 86400 seconds (or 1440 minutes or 24 hours), but 86164.08984 seconds (or 1436.068164 minutes or 23.9344694 hours). So we may just use Earth's units on Mars, rounding the martian day to 24 hours 40 minutes and leap that extra 40 minutes each 15 days or so. Or we may use different martian hour like in system you have suggested, but I suggest still divide a day into 24 hours, because a number 24 is in good relationship with a number 360, and because this martian hour will be closer to Earth's hour (61 minute vs 74 in those system). Astronauts frequently flying between Earth and Mars may still use seconds and minutes, but they may do not use hours at all, to avoid confusion. They may just say "137 minutes before landing" etc.

Edit: alternative system: make martian day of 24 martian hours, but 11 of these hours will have 61 minute (equal to Earth's minute), and 13 of them will have 62 minutes. This will give extra 37 minutes per day, leaving relatively small error in 22.6632 seconds - it is one extra day each 3910 days or one extra hour each week or one extra minute each 65 hours.

All these relatively complex system may be easily handled with electronic watch, so it will not confuse people.





 
HarbingerDawnDate: Thursday, 11.07.2013, 10:19 | Message # 4
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Quote (SpaceEngineer)
rounding the martian day to 24 hours 40 minutes

I used to favor a system like this until I started researching the subject more. The problem with this is that it does not divide the day equally, and not everyone's "time slip" (as Kim Stanley Robinson named it) would happen simultaneously. So it would be inconvenient when trying to figure out what time it is in other time zones, and just making time zones would be hard. So it is important to divide the day equally into whole hours. So far the only system I have seen which keeps the SI second, and divides the day into an even number of hours, is the system I mentioned in my previous post.

The only way to get a 24 hour clock that does not require frequent adjustment is to not use the SI second.

Quote (SpaceEngineer)
one solar day is not precisely 86400 seconds (or 1440 minutes or 24 hours), but 86164.08984 seconds (or 1436.068164 minutes or 23.9344694 hours).

That is not a solar day, that is a sidereal day (rotation period). Solar day is almost exactly 86400 seconds (actually it is very slightly longer and is getting longer all the time, which is why leap seconds are sometimes added to UTC time).





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SpaceEngineerDate: Thursday, 11.07.2013, 10:29 | Message # 5
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Quote (HarbingerDawn)
That is not a solar day, that is a sidereal day (rotation period). Solar day is almost exactly 86400 seconds (actually it is very slightly longer and is getting longer all the time, which is why leap seconds are sometimes added to UTC time).

Sorry, my bad. Anyway, read my previous post again, I edit it a bit.





 
HarbingerDawnDate: Thursday, 11.07.2013, 10:46 | Message # 6
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Quote (SpaceEngineer)
a number 24 is in good relationship with a number 360

Why is this important? Also, 20*18=360, which works almost as well as 24*15.

Quote (SpaceEngineer)
make martian day of 24 martian hours, but 11 of these hours will have 61 minute (equal to Earth's minute), and 13 of them will have 62 minutes.

This is still a problem because not all hours are equal, so times will not convert well between time zones (it could be 15:12 in one time zone and 16:13 in the next, or even 17:61 and 19:00). This may not cause many problems for computers, but it will cause some inconvenience for people.

Quote (SpaceEngineer)
one extra hour each week

Adapting to an extra hour each week is not bad, but one extra hour each 180 days is easier. The main problem is still the unequal dividing of the day into segments (hours) of different length.

Quote (SpaceEngineer)
All these relatively complex system may be easily handled with electronic watch, so it will not confuse people.

I think it is still important for people to be able to calculate time as easily as they do now, since having to check a clock or time chart all the time is slightly inconvenient.





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midtskogenDate: Thursday, 11.07.2013, 11:04 | Message # 7
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Quote (HarbingerDawn)
While I do like the Darian calendar system, I do not like the names of the months or days of the week. Nor have I been able to find any other naming convention that I like. So I'm currently working on my own set of names.

How about simple counting based names, which is what we have today, except the first months (January - August). In the Roman republic August was called named sextilis and July quintilis. Since the last months are intact, an extension should be no problem. Nor does it matter that the counting is relative to March.

What would it look like? After December we get:
Undecimber
Duodecimber
Tredecimber
Quattourdecimber
Quindecimber
Sedecimber
Septendecimber
Duodevigintiber
Undevigintiber
Vigintiber
Unvigintiber
Duovigintiber

(The last two have slightly contracted forms, as in unvigintillion, duovigintillion, not Unusetvigintiber etc).

Some possible modifications:
* -cember instead of -cimber might catch on more easily
* So also Septemdecember
* Perhaps also Octodecember and Novemdecember

The names look as alien as anything else, but they follow at least a very simple pattern.





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VoekoevakaDate: Thursday, 11.07.2013, 11:16 | Message # 8
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One aspect of timekeeping I found interesting on Earth's timekeeping is that the number of hours in half a day divides the number of minutes in an hour, which is equal from the number of seconds is a minute. So I suggest to take the number of SI seconds in a martian day (88642.663), take a near integer, and factorise it in prime numbers.

88640=2*2*2*2*2*2*5*277
88641=3*3*3*7*7*67
88642=2*23*41*47
88643 is prime
88644=2*2*3*83*89

I'll make further investigations in it.

About the number of days and months, suggest the number of months yo be a multiple of four, to respect the seasons, and the monthe to have an approximatively equal number of days. If there is a correction to do on a year (for exeample a leap year), i suggest to add days on the shorter month, or to remove days on the longer month.





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HarbingerDawnDate: Thursday, 11.07.2013, 11:32 | Message # 9
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Quote (midtskogen)
How about simple counting based names

I've considered this, but some of the names get pretty cumbersome. If a system like this is used then one which combines the season with the number of the month would make for a nicer system (see the column here marked Darian Hensel for example).

Quote (Voekoevaka)
About the number of days and months, suggest the number of months yo be a multiple of four, to respect the seasons, and the monthe to have an approximatively equal number of days. If there is a correction to do on a year (for exeample a leap year), i suggest to add days on the shorter month, or to remove days on the longer month.

The Darian calendar that I mentioned satisfies all of these criteria.





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midtskogenDate: Thursday, 11.07.2013, 12:29 | Message # 10
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Quote (HarbingerDawn)
If a system like this is used then one which combines the season with the number of the month would make for a nicer system (see the column here marked Darian Hensel for example).

I find it a bit odd in that system to switch from Latin to Greek numbers between 4 and 5, and the -ember for marking winter seems somewhat constructed.

While the concept of months makes some sense on Earth, it's totally meaningless on Mars, so why have months at all? Mars has seasons. So why not just do away with months and have four seasons, each 167 (168) days long? The names can be as on Earth. If it's impractical to have that many days in a season, then simply add a few seasons. The number of seasons is pretty arbitrary anyway (English used to have three, not four).





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HarbingerDawnDate: Thursday, 11.07.2013, 12:53 | Message # 11
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Quote (midtskogen)
While the concept of months makes some sense on Earth, it's totally meaningless on Mars

It's a convenient way to break up time and aid in scheduling, and it's something familiar which we and our languages are very well adapted to. If the system can be kept with little difficulty, then why not keep it?

Quote (midtskogen)
The number of seasons is pretty arbitrary anyway

Not really. Four seasons because there are two equinoxes and two solstices, each (approximately) marking a transition from one climate to another over the course of the seasonal cycle. The number of seasons makes most sense if it is two or four.

Quote (midtskogen)
I find it a bit odd in that system to switch from Latin to Greek numbers between 4 and 5, and the -ember for marking winter seems somewhat constructed.

I agree that it has problems, I was pointing it out only as an example.

Quote (midtskogen)
then simply add a few seasons

If you're going to do that, then we're back where we started and might as well call them months.





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midtskogenDate: Thursday, 11.07.2013, 13:43 | Message # 12
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Quote (HarbingerDawn)
It's a convenient way to break up time and aid in scheduling, and it's something familiar which we and our languages are very well adapted to. If the system can be kept with little difficulty, then why not keep it?

So is just day counting as well. The thing that a month adds is that it roughly corresponds to a full cycle of the Moon's phases (and related matters such as tides), which is irrelevant on Mars.

Quote (HarbingerDawn)
Not really. Four seasons because there are two equinoxes and two solstices, each (approximately) marking a transition from one climate to another over the course of the seasonal cycle. The number of seasons makes most sense if it is two or four.

I think the origin of seasons is to be found in weather rather than directly from astronomy. And then a different number of seasons might fit better in some parts of the world than others (or on Mars). So clearly such things rather than astronomy explain why we only counted three seasons here in northern Europe still surviving in the languages as a missing proper word for "autumn". But since we feel the effects of weather less these days, I suppose the astronomical argument is better for new calendars.

Or we can think a bit out of the box: The first settlers on Mars will probably depend a lot on Earth, and they might care more about deliveries from Earth than where the sun is in the sky. So it could be more useful to define a year and its division into seasons by the opposition of Mars (or inferior conjunction of Earth as seen from Mars). So as on Earth, the availability of many fresh goods would depend on the season. Even radio communication with Earth and its delay would depend on the season, and communication would even become difficult during some specific days of the year when the sun gets too much in the way. It might be much easier for the settlers to relate to such a calendar. And likewise for people on Earth for Mars matters. If it's ok for a Mars calendar to have geocentric baggage (e.g. months), why not keep it geocentric in nature rather than to have a clumsy adaptation?





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Edited by midtskogen - Thursday, 11.07.2013, 13:54
 
SpaceEngineerDate: Thursday, 11.07.2013, 15:35 | Message # 13
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Quote (midtskogen)
While the concept of months makes some sense on Earth, it's totally meaningless on Mars, so why have months at all? Mars has seasons. So why not just do away with months and have four seasons, each 167 (168) days long?

I have a better suggestion: why not divide a year in 12 months, but 57-58 days long each? This getting us rid of these strange month names. Just use common Earth's names. It is not so bad to have 2x times longer months, remember Mars is a different planet.
And regarding to week days, why we must bind it to months? Having 6 days in some weeks is wierd. I want to have at least 2 vacation days each week! Why do not use continous system, like here on Earth, when week days are independent on calendar date?

Quote (midtskogen)
So as on Earth, the availability of many fresh goods would depend on the season. Even radio communication with Earth and its delay would depend on the season, and communication would even become difficult during some specific days of the year when the sun gets too much in the way.

It depends not on martian seasons or day of martian year, but on Earth-Mars sinodical period, which it equal:
(TEarth-1 - TMars-1)-1 = 780 days (Earth's days).





 
HarbingerDawnDate: Thursday, 11.07.2013, 21:31 | Message # 14
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Quote (midtskogen)
The thing that a month adds is that it roughly corresponds to a full cycle of the Moon's phases (and related matters such as tides), which is irrelevant on Mars.

I could not care less about lunar cycles or tides, yet I still very much like having months. So clearly that's not a requirement. You still haven't given a good reason why we should abandon the concept.

Quote (midtskogen)
I think the origin of seasons is to be found in weather rather than directly from astronomy.

Of course it is, but the changes in weather are CAUSED by the Earth's axial tilt.

Quote (midtskogen)
The first settlers on Mars will probably depend a lot on Earth, and they might care more about deliveries from Earth than where the sun is in the sky.

No. Martian calendars should be specific to Mars, and not factor in anything to do with Earth. Mars colonists should not be forcibly tied to Earth in any way, and if colonization goes well then they will be entirely self-sufficient within a few martian years anyway. Should they have one calendar for a few years and then have to devise a new one so soon? It makes no sense. Just make a Mars calendar to start with.

Quote (SpaceEngineer)
And regarding to week days, why we must bind it to months? Having 6 days in some weeks is wierd. I want to have at least 2 vacation days each week! Why do not use continous system, like here on Earth, when week days are independent on calendar date?

There is a variant of the Darian calendar which does this.

Quote (SpaceEngineer)
why not divide a year in 12 months

Why? Just for more convenient naming? If months are going to be wildly different in length then what's the point in keeping them, since they would cease to be familiar? Also, having Earth-months and Mars-months with the same names could get confusing in some cases. Same with having days of the week with same names.

Quote (SpaceEngineer)
remember Mars is a different planet.

But we're still the same humans and still think about time in the same way. These systems are for the use of people, and must be developed with that in mind. They need to be easy and convenient.





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SpaceEngineerDate: Thursday, 11.07.2013, 23:32 | Message # 15
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Quote (HarbingerDawn)
If months are going to be wildly different in length then what's the point in keeping them, since they would cease to be familiar?

Because "January" is strongly associates with winter (or summer in southern hemisphere) and so.





 
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