Author Topic: Mars Timekeeping System  (Read 57918 times)

Offline Paul451

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Re: Mars Timekeeping System
« Reply #60 on: 11/05/2016 10:09 pm »
The 13 month calendar works on Earth because 7*4*13 is 364 days, only one day off 365, close enough to be workable.

But the closest you can get on Mars is 7*5*19, which is still 5 sols away from a Martian year. You end up with a very clumsy calendar.

Offline GORDAP

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Re: Mars Timekeeping System
« Reply #61 on: 11/05/2016 10:21 pm »
On Earth with this calendar, we'd have 1, sometimes 2 'leap days' at the end of the year.  This just gives one a looong weekend, which is just fine, and kind of lends itself to a natural 'New Years's extended holiday.

Sure, on Mars this comes out to 5, sometimes 6 extra days, but I don't think anyone would complain.  After all, the 'year' is a lot longer, so I'm sure the Martians would appreciate a nice 7 or 8 day weekend break before launching into the new year. 

Small price to pay for the nice, rational 'Fixed Calendar'.  Actually (for Earth or Mars), such a natural year ending holiday would be a feature, not a bug, in my book.


Offline Paul451

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Re: Mars Timekeeping System
« Reply #62 on: 11/05/2016 10:27 pm »
Surely the most "fixed" calendar is simply to count the sols.

Offline mark_m

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Re: Mars Timekeeping System
« Reply #63 on: 11/05/2016 10:34 pm »
Surely the most "fixed" calendar is simply to count the sols.

This seems reasonable, especially in technical applications. However, in the same way that timezones allow the various hours to correspond to traditional times of day (noon is about midday, 6 or so is sunrise, etc.) as Jim commented, the months do the same for the time of the year. Why not just have the same twelve months, just make them 57 or 58 sols long? That way, March would still mean the beginning of spring, August the middle of summer, etc.

[Edit days reference to sols.]
« Last Edit: 11/06/2016 12:55 am by mark_m »

Offline Ludus

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Re: Mars Timekeeping System
« Reply #64 on: 11/06/2016 01:49 am »
http://chapters.marssociety.org/usa/oh/zubrin/Zubrin.html
Zubrins

https://en.m.wikipedia.org/wiki/Darian_calendar
Darian

https://en.m.wikipedia.org/wiki/Timekeeping_on_Mars
Mars timekeeping conventions

https://en.m.wikipedia.org/wiki/Astronomy_on_Mars
Astronomical observation from Mars.

If I was going to live on Mars I'd prefer a calendar year based on the Mars-Earth Synodic cycle rather than Mars' orbit around the sun. That's 780 days so only about a hundred days longer, though that's based on earth days. The Mars sol concept as a basis for a day seems reasonable. I just don't see a justification from a colonist's pov to base a year on a Mars' solar year instead of a synod. That's fine for academics living on earth and is an obvious choice, but seems out of synch with what would matter to the lives of Martians living with the calendar day to day.

On earth it makes total sense that the relevant cycle of seasons that dominates people's lives be the basis of the calendar. On Mars it seems like the Mars solar orbit would be less important to people living there than the Mars-Earth synodic cycle. That's what would dictate holidays and determine the rhythm of life. Nobody is planting based on seasonal cycles or experiencing weather. Everybody is planning their life around the next wave of ships arriving and departing and the waxing and waning of communications latency.

The Martian Calendar shouldn't be arbitrarily imitative of what's important to people on Earth. This would be a "year" based on a physical orbital cycle, just not on Mars' Solar orbit, which would be less relevant to the lives of humans living there.

Numbers for a Martian Synodic Year Calendar:

The conversion is about 1.0274 days/sol (Earth days to Mars days).

So a Synod which is about 780 earth days is about 759.1 Sols.

This could allow 27.1 Martian months of 28 Sols each per Synodic year. So 27 months of a perfect 28 sols each, synched to the days of the week evenly plus a few festival days left over to even out the Synodic year (which might be styled as a very short 28th month.)

There is a pleasant symmetry in having a "year" contain as many months as a month has days, having months that are all even units (except for the last), having the days of the week synched with months and having the whole cycle reflect the orbital period that defines the coming and going of physical contact with earth which would dominate people's work and emotional lives.
« Last Edit: 11/06/2016 02:37 am by Ludus »

Offline mark_m

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Re: Mars Timekeeping System
« Reply #65 on: 11/06/2016 02:13 am »
If I was going to live on Mars I'd prefer a calendar year based on the Mars-Earth Synodic cycle rather than Mars' orbit around the sun.
That's a very interesting thought. Things to consider though: It'll certainly be a major factor for many decades at least, but how long until advances reduce the importance of the synod cycle? Similarly, how long before the Mars society isn't focused around the arrival of ships from Earth?

However, it may be true that the colonists won't care about the Martian seasons. I was just thinking of how the rovers have had to hunker down for the winter and assuming that they would have an impact on people's lives as well.

Offline Ludus

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Re: Mars Timekeeping System
« Reply #66 on: 11/06/2016 02:22 am »
If I was going to live on Mars I'd prefer a calendar year based on the Mars-Earth Synodic cycle rather than Mars' orbit around the sun.
That's a very interesting thought. Things to consider though: It'll certainly be a major factor for many decades at least, but how long until advances reduce the importance of the synod cycle? Similarly, how long before the Mars society isn't focused around the arrival of ships from Earth?

However, it may be true that the colonists won't care about the Martian seasons. I was just thinking of how the rovers have had to hunker down for the winter and assuming that they would have an impact on people's lives as well.

I'd think it would dominate completely for many centuries. Only on a terraformed Mars that had weather and seasons that mattered to people would there be competition from the Solar year for priority.

Offline Hyperion5

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Re: Mars Timekeeping System
« Reply #67 on: 11/06/2016 06:11 am »
People aren't going to use the 24-hour clock like the military. We could do that now, and often do for train times etc. But we don't.

Who are these people you speak of?  I've lived in Germany and traveled to much of Europe, where practically everything runs on 24-hour time, although a 12-hour clock is still more often used in colloquial conversation.  At last glance 24-hour time is used to varying degrees in Germany, Austria, Switzerland, Belgium, France, the Netherlands, Norway, Denmark, Sweden, Finland, the UK, Ireland, Italy, Poland, Spain, Portugal, Serbia, Turkey, South Korea, Japan, Australia, Cyprus, Czechia, Brazil, South Africa, Thailand (also uses 6-hour clock), Bahrain, Pakistan, and others.  India, Colombia, the US, Canada, and the Philippines are countries where 24-hour time is rarely used outside the military.  It doesn't seem like adjusting to a 24-hour clock is all that hard given its widespread use, sometimes even in colloquial speech. 


People prefer to keep the am/pm distinction. So, unless you're going to criminalise people on Mars for answering six instead of 18 to 'what's the time?', I expect it will continue. And people will want a whole, preferably even number of time units in a sol. Who wants to do complex mental arithmetic to work out what half a day is?

No one's going to criminalize anything, it's just that 24-hour time makes a lot of sense.  Obviously it's going to need some adjusting however, since we need to stuff more seconds into each hour.  A Martian Hour would therefore consist 3,698.9675 seconds in 60 Martian Minutes.  Each Martian Minute would consist of 61.649 seconds, while the SI second would be left as is.  This would probably be a good compromise at doing an early Martian timekeeping system. 





Offline Hyperion5

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Re: Mars Timekeeping System
« Reply #68 on: 11/06/2016 06:23 am »
so instead of hours, minutes and seconds, have ores, lepta and defterolepta

Gak. If you're going to change the fundamental units, why copy the base-12/base-60 conventions from Babylonian time?

Just use decimal fractions of sols. Half way through the day is 0.5. Each thousandth is nearly 90 seconds, each hundredth is nearly 15 minutes, each tenth almost 2.5hrs, so quick'n'dirty conversion isn't difficult.

Decimal Timekeeping has already been done on Earth, but it never divided up the day as you have suggested.  Instead each day consists of 10 hours, each hour consists of 100 minutes, and each minute consists of 100 seconds.  It makes calculating fractions of the day dirt-simple and you can easily have time zones.  Although it never caught on it does make a lot of sense. 

Offline Paul451

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Re: Mars Timekeeping System
« Reply #69 on: 11/06/2016 11:44 am »
Decimal Timekeeping has already been done on Earth, but it never divided up the day as you have suggested.

Swatch company tried to introduce "Swatch time", which was based on 1000th of a day.

Instead each day consists of 10 hours, each hour consists of 100 minutes, and each minute consists of 100 seconds.

That kind of stupidity is precisely what I'm trying to avoid. Blindly mimicking hours/minutes/seconds. It's the kind of thing the metric system was intended to eliminate. Different countries (or parts of a country, or trades within a country) using different length feet or miles, different sized ounces or pounds, etc. "New Seconds", "Mars Seconds". Blah.

(IMO, one of the worst mistakes in the metric system was deci/deca/centi/hecta prefixes, in order to create sub-units sort-of/kind-of similar to imperial units, giving in to the urge to mimic those old units. Centimetre, which is not even close to an inch. Decilitres, nearly but not three fluid ounces. Hectare, nothing like an acre. Hectapascal, which.. okay, it is a millibar, but still, blah, blah I say.)

[Edit: All of that said, it is interesting how easily the mission operators at NASA adopted a Mars clock by changing the length of the second, and hence minute/hour, even though the second is a metric unit, scientifically important.]
« Last Edit: 11/06/2016 11:52 am by Paul451 »

Offline Paul451

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Re: Mars Timekeeping System
« Reply #70 on: 11/06/2016 11:45 am »
Surely the most "fixed" calendar is simply to count the sols.
This seems reasonable, especially in technical applications. However, in the same way that timezones allow the various hours to correspond to traditional times of day (noon is about midday, 6 or so is sunrise, etc.) as Jim commented, the months do the same for the time of the year. Why not just have the same twelve months, just make them 57 or 58 sols long? That way, March would still mean the beginning of spring, August the middle of summer, etc.

How would that not apply to a simple sol-count? Remembering that winter starts around Sol 400, etc, is easier to remember than the kind of arbitrary calendars proposed so far.

If I was going to live on Mars I'd prefer a calendar year based on the Mars-Earth Synodic cycle rather than Mars' orbit around the sun.
That's a very interesting thought. Things to consider though: It'll certainly be a major factor for many decades at least, but how long until advances reduce the importance of the synod cycle? Similarly, how long before the Mars society isn't focused around the arrival of ships from Earth?

By which time it is a tradition, around which the Mars culture has evolved, hence very hard to shift.

Offline Jim

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Re: Mars Timekeeping System
« Reply #71 on: 11/06/2016 12:24 pm »

So a Synod which is about 780 earth days is about 759.1 Sols.


Synod is not applicable.  Musk intends to use fast transit which negates the need to launch at that specific time.

Offline Hyperion5

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Re: Mars Timekeeping System
« Reply #72 on: 11/06/2016 03:43 pm »
Decimal Timekeeping has already been done on Earth, but it never divided up the day as you have suggested.

Swatch company tried to introduce "Swatch time", which was based on 1000th of a day.

Instead each day consists of 10 hours, each hour consists of 100 minutes, and each minute consists of 100 seconds.

That kind of stupidity is precisely what I'm trying to avoid. Blindly mimicking hours/minutes/seconds. It's the kind of thing the metric system was intended to eliminate. Different countries (or parts of a country, or trades within a country) using different length feet or miles, different sized ounces or pounds, etc. "New Seconds", "Mars Seconds". Blah.

Given the distances involved, there is no way to have near-instantaneous communication with Earth, nor to have large scale trade.  Thus the barriers to implementing a more Mars-centric timekeeping system are not especially high. 


(IMO, one of the worst mistakes in the metric system was deci/deca/centi/hecta prefixes, in order to create sub-units sort-of/kind-of similar to imperial units, giving in to the urge to mimic those old units. Centimetre, which is not even close to an inch. Decilitres, nearly but not three fluid ounces. Hectare, nothing like an acre. Hectapascal, which.. okay, it is a millibar, but still, blah, blah I say.)

[Edit: All of that said, it is interesting how easily the mission operators at NASA adopted a Mars clock by changing the length of the second, and hence minute/hour, even though the second is a metric unit, scientifically important.]

I don't think you'll find many people who believe the prefix system in metric is a mistake.  It certainly hasn't hurt its worldwide acceptance, which increasingly is trending towards the US being the sole holdout against it and its prefix system.  With regards to the adoption of a Mars clock by NASA, it doesn't shock me, as some form of timekeeping adaptation will be needed.  I'd advocate keeping the SI second as is but simply modifying the minute or the hour for Mars local use. 

Offline Robotbeat

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Re: Mars Timekeeping System
« Reply #73 on: 11/06/2016 06:01 pm »

So a Synod which is about 780 earth days is about 759.1 Sols.


Synod is not applicable.  Musk intends to use fast transit which negates the need to launch at that specific time.
While true, launches ARE still going to be clustered around the Mars launch window.

I think synods may be more important for the lives of Martians than seasons will be, at least for this century. It won't be "what year did you arrive?" It'll be "What synod? Oh really? That's a tough one. Must've been a long trip!"

I think it'll be some mix of synods and Earth years for a while. Eventually Mars years.

I also suspect Martian weeks of 7 days, probably grouped in fours like our months roughly are.
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Offline mark_m

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Re: Mars Timekeeping System
« Reply #74 on: 11/06/2016 07:10 pm »
I just wanted to summarize a little more clearly my posts. This is all-in on a Mars-centric calendar, because I'm suspecting the colonists will have a little too much of an independent streak to base their new calendar off of Earth interactions. It also retains familiar associations of the time of day (in relation to sun position) and months of the year (in relation to seasons). Also, hours, minutes, and seconds are identical or nearly so to the familiar Earth variety.

1 Earth second = 1 second on Mars
59 seconds = 1 Mars minute
60 Mars minutes = 1 Mars hour
25 Mars hours = 1 sol
12 months, January-December, 58 or 59 days each, with the summer solstice occurring around June 40th.

Certainly sols since Jan 1 or seconds since midnight could be used for more technical applications. And of course smartwatches and other devices would have no trouble converting to Earth time. Hmmm, might have to write an Apple Watch app to do that....  ;)

Online ccdengr

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Re: Mars Timekeeping System
« Reply #75 on: 11/06/2016 07:11 pm »
[Edit: All of that said, it is interesting how easily the mission operators at NASA adopted a Mars clock by changing the length of the second, and hence minute/hour, even though the second is a metric unit, scientifically important.]
If you're talking about the slowed-down wristwatches that were used on MER and MSL, those were useful for easily determining the local time on Mars with regard to sunrise, but nobody was making detailed calculations with the second hand (if they had one, I never saw one.)  SI units are still in effect.

BTW, the use of the word "synod" for an Earth-Mars synodic period is, AFAIK, unique to this forum.  Does anyone know of its use in common aerospace literature?  In all the dictionary definitions I've seen for "synod" it's a religious term, e.g., see https://en.wikipedia.org/wiki/Synod


Offline ThereIWas3

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Re: Mars Timekeeping System
« Reply #76 on: 11/06/2016 07:56 pm »
Remembering that winter starts around Sol 400, etc, is easier to remember than the kind of arbitrary calendars proposed so far.

That is exactly the system used in the Red-Green-Blue Mars books, at least at the start.  They used a term Ls, for Solar Longitude, as described here.  That particular paper used 12 variable-length months, since the seasons are of different lengths on Mars due to the eccentric orbit.  I think in the RGB books they eventually used 24 months, with an additional Mars-specific month interposed between each Earth Month.

Offline CuddlyRocket

Re: Mars Timekeeping System
« Reply #77 on: 11/06/2016 09:24 pm »
so instead of hours, minutes and seconds, have ores, lepta and defterolepta

Gak. If you're going to change the fundamental units, why copy the base-12/base-60 conventions from Babylonian time?

Because people like them! Or do you think they've survived all these millennia from sheer luck?

Quote
Just use decimal fractions of sols. Half way through the day is 0.5. Each thousandth is nearly 90 seconds, each hundredth is nearly 15 minutes, each tenth almost 2.5hrs, so quick'n'dirty conversion isn't difficult.

A yes, decimal fractions. Which most people never use, preferring rational ones like a half, etc.

I really hope they will use a logical regular calendar, such as the proposed International Fixed Calendar that we OUGHT to use here on Earth...
- Every day of the month falls on the same weekday in each month—the 17th always falls on a Tuesday, for example."

I can't think of anything more horrendous! This is a perfect example of calendar design that exalts logic over humanity. Calendars are meant to be used by people. People who have, for instance, birthdays; and we all know we prefer to celebrate our birthday on some days of the week more than others - those where we don't have to go to work the next day, for instance. Such a fixed calendar means that if you're unlucky enough to be born on a day that's a bad day for a birthday party, it will be a bad day for a birthday party your entire life. The Gregorian calendar rotates the dates through the days of the week giving everyone a shot at good and bad days.

People aren't going to use the 24-hour clock like the military. We could do that now, and often do for train times etc. But we don't.

Who are these people you speak of?

Humanity. Well, most of them.

Quote
I've lived in Germany and traveled to much of Europe, where practically everything runs on 24-hour time, although a 12-hour clock is still more often used in colloquial conversation.

Exactly. Despite 'practically everything' running on 24-hour time, people still prefer to use the 12-hour clock.

Quote
It doesn't seem like adjusting to a 24-hour clock is all that hard given its widespread use, sometimes even in colloquial speech.

No, it's not that hard (although my mother could never get the hang of it!). Makes you wonder why it doesn't seem to prevail over the 12-hour system?

Quote
... it's just that 24-hour time makes a lot of sense.  Obviously it's going to need some adjusting however, since we need to stuff more seconds into each hour.  A Martian Hour would therefore consist 3,698.9675 seconds in 60 Martian Minutes.  Each Martian Minute would consist of 61.649 seconds, while the SI second would be left as is.  This would probably be a good compromise at doing an early Martian timekeeping system.

This is obviously a new usage of the phrase 'good compromise' that I've not previously come across before! Do you really think people are going to use 'minutes' consisting of 61.549 seconds?

People need to remember that a self-sustaining Mars colony is going to be big enough that a substantial fraction of the population won't have careers in any numerate discipline, let alone scientists and engineers (it will probably have the same proportion who are functionally innumerate!). Calendars and time-keeping have to work for everyone, not just scientists and engineers, or even just the well-educated.

Offline Ludus

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Re: Mars Timekeeping System
« Reply #78 on: 11/06/2016 09:35 pm »

So a Synod which is about 780 earth days is about 759.1 Sols.


Synod is not applicable.  Musk intends to use fast transit which negates the need to launch at that specific time.
While true, launches ARE still going to be clustered around the Mars launch window.

I think synods may be more important for the lives of Martians than seasons will be, at least for this century. It won't be "what year did you arrive?" It'll be "What synod? Oh really? That's a tough one. Must've been a long trip!"

I think it'll be some mix of synods and Earth years for a while. Eventually Mars years.

I also suspect Martian weeks of 7 days, probably grouped in fours like our months roughly are.

Everything I've read from Elon suggests he plans around the synodic cycle with a fleet building up and launching in that window regardless of transit times.

Communications latency also waxes and wanes with the synod and I think that will be a major rhythm in the life of Martians.

Offline Lumina

Re: Mars Timekeeping System
« Reply #79 on: 11/06/2016 11:10 pm »
I just wanted to summarize a little more clearly my posts. This is all-in on a Mars-centric calendar, because I'm suspecting the colonists will have a little too much of an independent streak to base their new calendar off of Earth interactions. It also retains familiar associations of the time of day (in relation to sun position) and months of the year (in relation to seasons). Also, hours, minutes, and seconds are identical or nearly so to the familiar Earth variety.

1 Earth second = 1 second on Mars
59 seconds = 1 Mars minute
60 Mars minutes = 1 Mars hour
25 Mars hours = 1 sol
12 months, January-December, 58 or 59 days each, with the summer solstice occurring around June 40th.

Certainly sols since Jan 1 or seconds since midnight could be used for more technical applications. And of course smartwatches and other devices would have no trouble converting to Earth time. Hmmm, might have to write an Apple Watch app to do that....  ;)

Pretty good actually! Workaholics will love the 25 hour sol and procrastinators will be grateful for the 58-59 day months. Something in it for everyone.

As for inconvenience of having to convert between units and so forth, not a problem. Richard Feynman once said that nearly a third of what one has to learn in physics is because historically we've used many different units for what is essentially the same thing. The silver lining is that we will have to use only per second units, so watt-seconds, metres per second etc. instead of kWh, mph and so on. Everyone working off the same per second units will be a positive development actually.

[Edit - a suggestion: since the Mars minute of 59 seconds will cause clocks to drift by about 5 minutes per day relative to solar time, is there a point in sticking to having an integer number of seconds in the Mars minute? Because if you allow decimals and make one Mars Minute equal to 61.6494751 seconds then the Mars Sol of 24 Mars hours of 60 Mars minutes each will be in sync with local solar time. Or you can make it 59.1834961 seconds for 25 hours of 60 Mars minutes and again be in sync...]

[Edit - another one: since on Earth the length of the month varies from 28 to 31 days, you could vary the length of the Martian month a little more so that the seasons at Mars Base Alpha will start in familiar months. You will also need a new rhyme for Martian schoolchildren to learn the arbitrary lengths of month by heart :)]
« Last Edit: 11/06/2016 11:38 pm by Lumina »

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