Brendan (![[info]](http://l-stat.livejournal.com/img/userinfo.gif){kind=small} grishnash) wrote,@ 2004-02-20 22:30:00 |
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And now for something completely the same...
OK, so I decided to attempt what many have attempted previously, and come up with a feasible Martian calendar. In doing so, I've attempted to avoid the impracticalities that I've seen earlier attempts get hung up on. I hope to come up with something that could actually be used for everyday purposes, as opposed to some of the more unusual calendars I've seen that ignore some pretty basic facts and traditions of human society. Anyway, here's my attempt:
THE SOL:
A Martian sol (solar day) is roughly the same as an Earth day at roughly 24h 39m 35s, so this is already a nicely circadianly useful time period. When on Mars, use the Martian Sol as the standard unit of time when planning your daily schedule.
HOURS, MINUTES, SECONDS:
This is where the trouble begins. The second is such a basic unit of scientific timekeeping, that a standard second has to be used throughout any sort of unified human civilization. You can't very well have engineers on Mars computing Newtons of thrust using a different-length second, so seconds MUST be uniform. There's no particular reason to maintain hours and minutes, though, as these are pretty arbitrary units based on ancient hybrid base-10/12 counting anyway. The Martian sol is 88775 seconds long. This number has prime factors of 5, 5, 53, and 67. Ugh. If you were a masochist and had it in for wristwatch manufacturers, you could devise a clock with 25 "mars-hours" per sol, 53 "mars-minutes" per hour, and 67 seconds per "mars-minute", I suppose. A better suggestion would be to maintain the second for scientific measurements, and have a completely independent civil clock. Metric could be useful here, although a quasimetric might be useful as well. The metric option would be to base on the millisol would be 88.775 seconds long, which could be a useful analog to the minute. 50 millisols would be 73 minutes, which is close enough to an hour to serve the same sorts of purposes. A civil workday could be 350 millisols, with a 25 millisol lunch break.
The quasimetric solution would be to divide these units in half. Half a millisol would be still useful and minute-like at 44.3875 seconds. If this was your base unit, you could have a clock which displayed 2000 of these units per day which would look somewhat reassuringly like an Earth clock, but when you saw it reading something like 14.82, there'd be no confusion over which it was. In this clock, Martian time zones would be 18 degrees of longitude wide.
THE WEEK:
Let's face it. The seven-day week works, and is one of the few constants throughout history. The ratio of making 5 of these 7 to be work days also is about right. So with no compelling reason to change it, there should be a seven-sol week on Mars. The only thing that I think it is imperative NOT to keep are the names of the days. Those should be changed to avoid confusion with Earth days. The minimalist in me says go with Sunsol (ha!), Monsol, Tuessol, Wednesol, Thurssol, Frisol, Satursol. Those actually aren't too ludicrous. I'd avoid numbering the days of the week to avoid confusion with day numbers.
THE MONTH AND YEAR:
The Martian year is 668.6 sols long (more on this later). The month really has no meaning on Mars, since the moons of Mars are so close to the planet that their orbital periods don't mark useful amounts of time. Martian calendars that I've seen tend to try to even out the lengths of the months, or dramatically synchronize the months to the days of the week or some such, taking advantage of such numerically nice concepts as that the Martian year divides nicely into four 167 day quarters. I believe that a better argument can be made for varying the lengths of the months. I've used a few basic principles to design the months: 1) The month on Mars is really only useful for human societal reasons. It gives little astronomical insight. 2) Humans are used to timekeeping periods in the approximate range of 24-35 days. 3) The Martian orbit is far more eccentric than the Earth's. On Earth, for instance, February is the only month that has to be significantly trimmed to account for the Earth moving faster near perihelion. If Martian months are to be equalized throughout the Martian seasons, a much greater effect needs to be accounted for. 4) It really isn't THAT much of an inconvenience to have the days of the week precess throughout the year.
Taking all this into account, I settled on a 22-month Martian year, beginning with the Martian northern hemisphere vernal equinox. As far as naming the months, I have no idea, although existing sequence sets such as months, planets, etc., should be avoided at all costs to prevent confusion. If I can come up with a good mythological/scientific/historical reference that contains a matching set of 22, I'd choose that, as long as a memorable order could be achieved. The interim names I'm using will correspond to the Hebrew alphabet, since that's the best set of 22 that I could come up with on short notice. It might be best in the long run to replace these with names relevant to Martian history. The months in order would be:
1 Alef (32 sols)
2 Bet (33 sols)
3 Gimel (32 sols)
4 Dalet (32 sols)
5 He (30 sols)
6 Vav (29 sols)
7 Zayin (30 sols)
8 Het (29 sols)
9 Tet (30 sols)
10 Yod (29 sols)
11 Kaf (28 sols)
12 Lamed (29 sols)
13 Mem (28 sols)
14 Nun (29 sols)
15 Samekh (28 sols)
16 Ayin (31 sols)
17 Pe (31 sols)
18 Tsadi (31 sols)
19 Qof (31 sols)
20 Resh (31/32 sols)
21 Shin (33 sols)
22 Tav (32 sols)
For purely civil reasons, I have moved the start date of the year by moving the first two spring months to the end of the calendar for timekeeping purposes, and then timeshifted the entire calendar by 20 days. The 20 day timeshift is to keep the equinox and solstice always occuring in the same month, rather than oscillating between the beginning of one month and the end of another, and around the 21st of the month for analog with Earth. The solstices and equinoxes will occur under this calendar always at around integer numbers of months from each other as well. In the northern hemisphere the dates will be approximately as follows: summer solstice: He 21st, autumnal equinox: Kaf 21st, winter solstice: Ayin 21st, vernal equinox: Shin 21st. Moving two of the spring months to the end of the calendar, and thus putting the new year's date at a totally arbitrary point was to gain an added benefit of having the first 11 months of the year and the last 11 months of the year combined both be 334 sols long. Since the Martian year is so much longer than the Earth year, it will likely be civilly useful to break it down into two equal semesters. Another added benefit of choosing this number of months per year is that it makes the 22 Earth-months between Earth to Mars launch windows, and 8 Earth-month Hohmann transfer travel time to Mars analogous to 22 Mars-months between Mars to Earth launch windows, and 8 Martian-month Hohmann transfer travel time to Earth.
INTERCALATION:
Based on the incredibly convenient Martian year length of 668.6 sols (nearly precisely), the intercalation can be a lot more simple than on earth. My first approach to this led me to rediscover the system previously developed by Aitken. Essentially, 6 extra sols must be added every 10 years. Aitken achieved this by making even years leap years of 669 sols, and every decadal year a double leap year of 670 sols. I don't like having three different year lengths, so I simply swapped the odds and evens. In my calendar, a leap year is every odd year, and every year evenly divisible by 10. Since the leap sol properly belongs to the Martian northern hemisphere winter, the leap sol will be an added Resh 32nd. No attempt is made to synchronize the calendar with Earth's. The two will simply precess against each others seasons.
THE EPOCH:
So how do the years get numbered? The most obvious way is to not yet assign a year number. The first year should be following the first manned landing on Mars. Since we now know about 0, whatever year Mars is in when the landing happens will be Martian Year (MY) 0. The next (or previous, if less than 44 sols since the last one) northern hemisphere vernal equinox would then be set as Shin 21st, MY 0. On the Alef 1st (Martian New Year) following the landing, the year will become MY 1. Years before the landing year will be designated by negative numbers (e.g. MY -16).
SO WHAT SOL IS IT ON MARS TODAY?
Because no manned landing has yet been made on Mars, the Epoch has not been set, and it is impossible to say what Martian year it would currently be under my calendar. It is also impossible to say whether or not it is a leap year right now. However, we are currently about 20 sols before the Martian northern vernal equinox, so between Midnight and the Martian Date Line, it is currently Shin 1st!
OK, so I decided to attempt what many have attempted previously, and come up with a feasible Martian calendar. In doing so, I've attempted to avoid the impracticalities that I've seen earlier attempts get hung up on. I hope to come up with something that could actually be used for everyday purposes, as opposed to some of the more unusual calendars I've seen that ignore some pretty basic facts and traditions of human society. Anyway, here's my attempt:
THE SOL:
A Martian sol (solar day) is roughly the same as an Earth day at roughly 24h 39m 35s, so this is already a nicely circadianly useful time period. When on Mars, use the Martian Sol as the standard unit of time when planning your daily schedule.
HOURS, MINUTES, SECONDS:
This is where the trouble begins. The second is such a basic unit of scientific timekeeping, that a standard second has to be used throughout any sort of unified human civilization. You can't very well have engineers on Mars computing Newtons of thrust using a different-length second, so seconds MUST be uniform. There's no particular reason to maintain hours and minutes, though, as these are pretty arbitrary units based on ancient hybrid base-10/12 counting anyway. The Martian sol is 88775 seconds long. This number has prime factors of 5, 5, 53, and 67. Ugh. If you were a masochist and had it in for wristwatch manufacturers, you could devise a clock with 25 "mars-hours" per sol, 53 "mars-minutes" per hour, and 67 seconds per "mars-minute", I suppose. A better suggestion would be to maintain the second for scientific measurements, and have a completely independent civil clock. Metric could be useful here, although a quasimetric might be useful as well. The metric option would be to base on the millisol would be 88.775 seconds long, which could be a useful analog to the minute. 50 millisols would be 73 minutes, which is close enough to an hour to serve the same sorts of purposes. A civil workday could be 350 millisols, with a 25 millisol lunch break.
The quasimetric solution would be to divide these units in half. Half a millisol would be still useful and minute-like at 44.3875 seconds. If this was your base unit, you could have a clock which displayed 2000 of these units per day which would look somewhat reassuringly like an Earth clock, but when you saw it reading something like 14.82, there'd be no confusion over which it was. In this clock, Martian time zones would be 18 degrees of longitude wide.
THE WEEK:
Let's face it. The seven-day week works, and is one of the few constants throughout history. The ratio of making 5 of these 7 to be work days also is about right. So with no compelling reason to change it, there should be a seven-sol week on Mars. The only thing that I think it is imperative NOT to keep are the names of the days. Those should be changed to avoid confusion with Earth days. The minimalist in me says go with Sunsol (ha!), Monsol, Tuessol, Wednesol, Thurssol, Frisol, Satursol. Those actually aren't too ludicrous. I'd avoid numbering the days of the week to avoid confusion with day numbers.
THE MONTH AND YEAR:
The Martian year is 668.6 sols long (more on this later). The month really has no meaning on Mars, since the moons of Mars are so close to the planet that their orbital periods don't mark useful amounts of time. Martian calendars that I've seen tend to try to even out the lengths of the months, or dramatically synchronize the months to the days of the week or some such, taking advantage of such numerically nice concepts as that the Martian year divides nicely into four 167 day quarters. I believe that a better argument can be made for varying the lengths of the months. I've used a few basic principles to design the months: 1) The month on Mars is really only useful for human societal reasons. It gives little astronomical insight. 2) Humans are used to timekeeping periods in the approximate range of 24-35 days. 3) The Martian orbit is far more eccentric than the Earth's. On Earth, for instance, February is the only month that has to be significantly trimmed to account for the Earth moving faster near perihelion. If Martian months are to be equalized throughout the Martian seasons, a much greater effect needs to be accounted for. 4) It really isn't THAT much of an inconvenience to have the days of the week precess throughout the year.
Taking all this into account, I settled on a 22-month Martian year, beginning with the Martian northern hemisphere vernal equinox. As far as naming the months, I have no idea, although existing sequence sets such as months, planets, etc., should be avoided at all costs to prevent confusion. If I can come up with a good mythological/scientific/historical reference that contains a matching set of 22, I'd choose that, as long as a memorable order could be achieved. The interim names I'm using will correspond to the Hebrew alphabet, since that's the best set of 22 that I could come up with on short notice. It might be best in the long run to replace these with names relevant to Martian history. The months in order would be:
1 Alef (32 sols)
2 Bet (33 sols)
3 Gimel (32 sols)
4 Dalet (32 sols)
5 He (30 sols)
6 Vav (29 sols)
7 Zayin (30 sols)
8 Het (29 sols)
9 Tet (30 sols)
10 Yod (29 sols)
11 Kaf (28 sols)
12 Lamed (29 sols)
13 Mem (28 sols)
14 Nun (29 sols)
15 Samekh (28 sols)
16 Ayin (31 sols)
17 Pe (31 sols)
18 Tsadi (31 sols)
19 Qof (31 sols)
20 Resh (31/32 sols)
21 Shin (33 sols)
22 Tav (32 sols)
For purely civil reasons, I have moved the start date of the year by moving the first two spring months to the end of the calendar for timekeeping purposes, and then timeshifted the entire calendar by 20 days. The 20 day timeshift is to keep the equinox and solstice always occuring in the same month, rather than oscillating between the beginning of one month and the end of another, and around the 21st of the month for analog with Earth. The solstices and equinoxes will occur under this calendar always at around integer numbers of months from each other as well. In the northern hemisphere the dates will be approximately as follows: summer solstice: He 21st, autumnal equinox: Kaf 21st, winter solstice: Ayin 21st, vernal equinox: Shin 21st. Moving two of the spring months to the end of the calendar, and thus putting the new year's date at a totally arbitrary point was to gain an added benefit of having the first 11 months of the year and the last 11 months of the year combined both be 334 sols long. Since the Martian year is so much longer than the Earth year, it will likely be civilly useful to break it down into two equal semesters. Another added benefit of choosing this number of months per year is that it makes the 22 Earth-months between Earth to Mars launch windows, and 8 Earth-month Hohmann transfer travel time to Mars analogous to 22 Mars-months between Mars to Earth launch windows, and 8 Martian-month Hohmann transfer travel time to Earth.
INTERCALATION:
Based on the incredibly convenient Martian year length of 668.6 sols (nearly precisely), the intercalation can be a lot more simple than on earth. My first approach to this led me to rediscover the system previously developed by Aitken. Essentially, 6 extra sols must be added every 10 years. Aitken achieved this by making even years leap years of 669 sols, and every decadal year a double leap year of 670 sols. I don't like having three different year lengths, so I simply swapped the odds and evens. In my calendar, a leap year is every odd year, and every year evenly divisible by 10. Since the leap sol properly belongs to the Martian northern hemisphere winter, the leap sol will be an added Resh 32nd. No attempt is made to synchronize the calendar with Earth's. The two will simply precess against each others seasons.
THE EPOCH:
So how do the years get numbered? The most obvious way is to not yet assign a year number. The first year should be following the first manned landing on Mars. Since we now know about 0, whatever year Mars is in when the landing happens will be Martian Year (MY) 0. The next (or previous, if less than 44 sols since the last one) northern hemisphere vernal equinox would then be set as Shin 21st, MY 0. On the Alef 1st (Martian New Year) following the landing, the year will become MY 1. Years before the landing year will be designated by negative numbers (e.g. MY -16).
SO WHAT SOL IS IT ON MARS TODAY?
Because no manned landing has yet been made on Mars, the Epoch has not been set, and it is impossible to say what Martian year it would currently be under my calendar. It is also impossible to say whether or not it is a leap year right now. However, we are currently about 20 sols before the Martian northern vernal equinox, so between Midnight and the Martian Date Line, it is currently Shin 1st!
