galaxies and calendars?

[shamguy4]

right, so ive learned from all this that i hate time and it hates me...

 

[Ursa major]

We mustn't let Time hate us; after all, it is hours....

 

[Darth Angelus]

This could be complex. After all, every planet would have its own years and season, so there could be as many calendars as inhabited planets in the galaxy.

In all likelyhood, however, each planet would use its own calendar for everyday purposes, and there would be one central planet whose calendar becomes the standard calendar.

Think of how the English language (in addition to the number of countries where it is the official or de facto language) is typically used for international communication as a sort of standard in our world. Then other countries communicate in their own respective languages, internally.
I am guessing one planet would get its calendar to have a similar default role in communication.

 

[Venusian Broon]

This could be complex. After all, every planet would have its own years and season, so there could be as many calendars as inhabited planets in the galaxy.

In fact, many, many times more.

This discussion so far has been, I feel, a little bit too scientific.

Currently on earth there are hundreds of working calendars. So to name a few:

Sure, Gregorian is a standard we in the west use. But what about the numerous religious calenders - Islamic, Jewish, Hindu (a great many of them I believe). Or even the Julian calendar - doesn't the orthodox church still use that? Even although it's 'wrong'.

Or the cyclical Chinese calendar (You could argue that it's not really used, but if billions of people celebrate Chinese new year on a certain day, then in my books it's in use.)

The Mayan long count, another much longer cyclical calendar, you could argue has been in use (well at least up till last year!)

And what about Regnal calendars - Egyptians (and Romans I think) favoured them, i.e. we're in the 60th year of QE2 reign. (Ok, ok, these are probably not in use much nowadays! But it's an option to use and pretty simple.)

But it doesn't stop there. As is appropriate, because today I have just finished paying my taxes for fiscal year 2012/13, there are many, many fiscal calendars, corporate and governmental.

HOWEVER

For the purposes of writing a story, if you really need to mark time in a calendar form - I can understand the lure of a monolithic time system - to stop the writer and reader going mad *. But, if you are trying to present a rich and diverse culture with many facets and different peoples, I'd have all sorts of calendars in the story.

And just to put the cat amongst the pigeons again...If I was to put a galactic calender together for my current WiP** then perhaps I'd calculate it using galactical measurements for the standard amongst all the planets, rather than rely on one planet-derived one that is likely only to have relevence for one planet and one group of beings

i.e. I'd think that a galactic calender is such so that anyone on any planet can just get out their telescope and measure it in the sky. Then say after crunching through all the angles and numbers, well it's it's 'Galactic year 1.222.23' right now, a figure everyone on every planet would derive***

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* The other way is just not to have it in your WiP, something I think is easier!

**I've taken my own advice and not tried to delve too deeply into a structured calender!

*** Not sure how many points would exactly be needed and what it would involve, but all it needs is a strict definition that is measurable - I think

 

[Darth Angelus]

In fact, many, many times more.

This discussion so far has been, I feel, a little bit too scientific.

Well, yeah, due to purely cultural reasons, there probably be many times more, at least if most planets had been inhabited for a while.

Let me rephrase it, then, will you?

What I meant was what would be the minimum requirement for convenient everyday use.
At the risk of sounding culturally insensitive (which is not how this is intend), all these earth calendars would be little more than variants of the same calendar, or perhaps I should call it supercalendar. They would belong to the same superset of calendars, with similar properties, from a galactic perspective. The year and day cycles are the same everywhere. For the most part, date and time conversion is just a matter of a couple of fairly simple arithmetic operations, maybe just adding and subtracting some fixed number offset.
There are, after all, only so many choices if you want certain requirements fullfilled. If each year is 365 days in your calendar, you have roughly 24 extra days each century to spread out across the years (hence the 366 day years), and how exactly these are spread out, is a fairly arbitrary choice. Sufficiently advanced civilisations with know astronomy (or they wouldn't be traveling between planets) and is likely to want this kind date adjustment to prevent a certain date on the calendar to float across the actual physical years (June would be in winter here on the northern hemisphere if we only went with 365 day years all the time, starting now).

Different planets is another matter. You could have a planet P such that.
1 P year = 0.85732 Earth year
1 P day = 1.28943 Earth day

Ok, these numbers I just pulled out of nowhere, but the point stands.

Date XX10-04-13 on one planet can be expected to be at the same point of the year, ten years later, than XX00-04-13, on the same calendar and for the very planet for which that calendar was made. However, if that calendar is applied to another planet, that will probably not be the case. If this is a calendar from planet P above and is applied to Earth, 8.5732 years would have passed here, making it another season entirely (due to the .5732-part)
The day cycle would be screwed up, the same way, which would probably be even more problematic.

The point is that we expect certain things out of your calendar to stay the same. We expect the time when the year begins (January 1st) to be in the winter season, on the northern hemisphere. We expect 9:30 AM to be somewhere in the middle of the morning. If the calendar weren't designed to keep these things constant, it would be of limited use.

So yes, the calendars on Earth may vary, but on different planets they will do so more fundamentally.

Sorry if this was too scientific, but it is how the subject is.


Another, related issue is whether a species colonising a planet they didn't evolve on, with a very different length of the day cycle, would have disturbed sleep, because the conditions in that regard on their new home would not match their biological clock. That is, would they fall into a permanent jet lag-like state, because the daylight outside would say one thing, and their biological clock something else? Let us leave that for now, though.

 

[Venusian Broon]

The point is that we expect certain things out of your calendar to stay the same.

Actually in general....not really , calendars have a number of functions, but the basic one is just to mark out time - with the day as the basic unit.

If 'we' are of European stock - the basis of western culture - then our calendar is tied to the variance of the solar cycle caused by the axial tilt. Therefore it was probably a good idea to mark time aligned to the northern growing seasons. Hence our cultural convention is to make our calendar follow the real, actual solar cycle.

But my point here would be that if observance of northern hemisphere's growing season is not important for you then the fact that July is said to be a summer month and January a winter month is purely artificial. i.e. why care if January 'turns up physically' in summer?* Ramadan is a good example of a very big human behaviour that is just not tied to a solar calendar, but a lunar one instead.

If you go closer to the equator, the effect of the earth's orbit via axial tilt just becomes less relevant. Hence the peoples of central america used a short count calendar (52 years for one full cycle) and a long count calendar (approximately 5,100 years for one cycle, very roughly!)

It's not that they didn't know about they length of the solar year - they had a period of 365 days called a Haab, and it's clear that the Maya were fully aware that this is shorter than the real year by about a quarter day. But they didn't care and did not make any corrections. (The Haab is meshed together with a 260 day cycle to make the short count.)

Hence this raises an interesting issue in that, if we have a fictional alien world, civilisation included, with no axial tilt, then their orbital year may be of no interest to them in an everyday calendar.

If the calendar weren't designed to keep these things constant, it would be of limited use.

The problem is of course that you can't really define a good universal system on things like days and years - they're bad things to try base time on - because they just aren't constant! Especially if you are looking at very long time scales. i.e. The earth's rotation is slowing down and is influenced by things that happen in it (e.g. earthquakes and large scale tidal hydroelectric schemes) And the annual orbit I'm sure, can be influenced as well by forces outside as well.

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* Actually of course this does occur anyway, but in the Southern hemisphere

 

[Mirannan]

Jewish holidays are tied to a lunar calendar, or so I understand, and so is the traditional Chinese year - which is why the Chinese New Year occurs at odd times.

On the subject of whether years actually matter to an alien civilisation (if there aren't any seasons then the year is rather unimportant except to people navigating by the stars); this situation requires a low orbital eccentricity as well as low axial tilt. I haven't seen it discussed, but in the Solar System Mars might well have seasons even if had no axial tilt. This is apparently true for Pluto, also, which has a very eccentric orbit.

Just to really muck things up; the progress of the seasons might well be rather complicated in a binary system. For example, Alpha Centauri B has a rather eccentric orbit with an average separation about that of Uranus from the Sun; if there were any planets in the Goldilocks zone of either star, their seasons would be hellishly complicated.

 

[Darth Angelus]

Actually in general....not really , calendars have a number of functions, but the basic one is just to mark out time - with the day as the basic unit.

If 'we' are of European stock - the basis of western culture - then our calendar is tied to the variance of the solar cycle caused by the axial tilt. Therefore it was probably a good idea to mark time aligned to the northern growing seasons. Hence our cultural convention is to make our calendar follow the real, actual solar cycle.

But my point here would be that if observance of northern hemisphere's growing season is not important for you then the fact that July is said to be a summer month and January a winter month is purely artificial. i.e. why care if January 'turns up physically' in summer?* Ramadan is a good example of a very big human behaviour that is just not tied to a solar calendar, but a lunar one instead.

If you go closer to the equator, the effect of the earth's orbit via axial tilt just becomes less relevant. Hence the peoples of central america used a short count calendar (52 years for one full cycle) and a long count calendar (approximately 5,100 years for one cycle, very roughly!)

It's not that they didn't know about they length of the solar year - they had a period of 365 days called a Haab, and it's clear that the Maya were fully aware that this is shorter than the real year by about a quarter day. But they didn't care and did not make any corrections. (The Haab is meshed together with a 260 day cycle to make the short count.)

Hence this raises an interesting issue in that, if we have a fictional alien world, civilisation included, with no axial tilt, then their orbital year may be of no interest to them in an everyday calendar.




The problem is of course that you can't really define a good universal system on things like days and years - they're bad things to try base time on - because they just aren't constant! Especially if you are looking at very long time scales. i.e. The earth's rotation is slowing down and is influenced by things that happen in it (e.g. earthquakes and large scale tidal hydroelectric schemes) And the annual orbit I'm sure, can be influenced as well by forces outside as well.

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* Actually of course this does occur anyway, but in the Southern hemisphere

Well, I agree with some, but not all. I suppose we approach the problem from slightly different perspectives.

Yes, the basic function is probably to mark out time with the day as the basic unit. However, the day has the exact same issue of varying cycle length as the year, which I tried to bring up.
Planning what to do when is a fairly fundamental function of calendar and time in everyday life. The clock is used for scheduling all sorts of public functions in modern society. Let's say your work starts at 8 AM. You probably want to keep that in the early morning. If that is noon one day, just before dawn another, and just after midnight a third, you would have a messy date and time system.
So keeping a certain time at a certain point in the day cycle (the exception being daylight savings time, but let us ignore that convention). Not knowing which part of the year January is may be acceptable in a lot of locations, but the corresponding uncertainty in the day cycle is more damning.

While a universal calendar (which may ignore year and day cycles, as you say) would be useful for interplanetary communication and putting events in galactic history on a timeline, I still very much think the everyday lives of the citizens would be guided by the local planetary calendar. Yes, you can have a scientific date and time format that is universal, but would likely be to cryptic to work with for everyday use.

Yes, a lot of calendars on Earth have their own cycles by convention, but most of them will be completely arbitrary, from a purely cosmological perspective. Seven days per week has a religious origin. The 52 year cycle you mention I do not know of, but it seems it could equally be any other number, as far as the Earth is concerned. The average month deviates from the moon cycle by a couple of days so as to ensure the year is twelve months (and not a decimal number).

The good news is that the conversion would be simple and instant for computers. Even creating a fair equivalent to the Gregorian calendar would not be hard. I am fairly certain it wouldn't be too hard to write a computer program that could generate such a calendar for a new planet, based on input data of year and day cycles, and when you want the new year to begin. Such a program also provide the conversion formula to standard time, of course.
Computers can easily handle this kind of number crunching.

 

[Vertigo]

One thing to watch out ofr is calendars are not purely tied to natural events (like lunar months). If you think about it the lunar 'month' is about 29.5 days; not 30 or 31 days. Now we are lucky in that our lunar month divides up into our year quite conveniently (12.37 true lunar months to the year) and so we have chosen 12 months. Now was that figure chosen because it is close to true or because 12 is one of the most convenient numbers to use as a base (usefully divides by 2, 3, 4 and 6 as opposed to ten that usefully divides by 2 and 5 only). I suspect it is probably the latter. The same goes for the number of hours in the day (2 times 12) and the number of minutes in an hour (12 times 5). The same also goes for degrees of angle; the full circle is 30 times 12. So it makes a huge amount of sense to use numbers that can be easily divided especially for something that is continually going to be so divided.

PS: on a related note do you have any idea how much easier much of our mathematics would be if our numbering system was duodecimal rather than decimal? Though it might have made the discovery of fractions somewhat slower!