Re: Yes, I'm back
|From:||Peter Clark <peter-clark@...>|
|Date:||Monday, January 20, 2003, 3:40|
Wow, you're a little slow with your mail, aren't you? ;>
Ah, well, better late than never...
On Sunday 19 January 2003 07:14 pm, James Landau wrote:
> I've usually seen it given as "4 B.C.". (If you can think of any other way
> to express the would-be year 0 that marked the transition from B.C. to
> A.D., tell me). Of course there had to be some significance to "0" too, or
> else why would anyone have started there if they knew he wasn't born at
> that point? Or did the extra four years just come when they switched over
> from the Julian to the Gregorian, or come about because they started the
> calendar sometime after Jesus' birth and were unable to count? No, nothing interesting happened in the year 0 AD. In fact, positively
nothing happened in that year, since there never was such a year.[*] 1 BC
rolls over to 1 AD. And no, to forstall the next obvious question, nothing
particularly note-worthy happened in either of those years, either. (I now
await some historian buff to correct me. :) This is why purists argue that
2001, not 2000, was the start of the third millenium.
We have to thank a monk by the name of Dionysius Exiguus (aka Dennis the
Little), who had the task of figuring out the Easter cycles. In 525 AD,
unhappy that the current system of numbering years counted from the reign of
Diocletian, who had persecuted Christians during his reign, decided that the
Church needed a new system, and so (naturally) based it on his calculation of
Christ's birth. Unfortunately, we're a little foggy on why he chose 25
December 753 AUC[**] (ab urbe condita, i.e. since the founding of Rome);
there are a couple of theories, but I'm not aware of any that have been
decisively proven. In any case, the long and short of it is that Dennis the
Little goofed, and now it's too late to do anything about it.
[*] Note that astronomers count a year 0, which means that the year prior,
instead of being 2 BC, is really -1. I think it's because they are, at heart,
cruel and perverse beings who like to throw the calendar into confusion.
[**] The Romans, it should be noted, weren't exactly sure when Rome was
founded, so the margin of error is usually given +-1. Sloppy Roman
> > Ok, but there are 365.2422 days in a mean tropical year, which means
> > that
> > your calendar will drift about 5.25 days against the seasons every year.
> > Do you have some means of adding days to compensate for the drift?
> Well, when I say a "day", I mean the amount of time it takes for Kankonia
> to complete one full rotation on its axis. The same is true for Earth as well, when we talk about a day of 24 hours,
rather than the period of daylight.
In matching up the years I
> imagined a day would last about 1.0146 Earth days or so, supposedly trying
> to keep the years from going off. (This leads to another question: is there
> anyone here who knows how to find out how fast a planet will rotate on its
> axis or complete a year, given its volume, mass and distance from the sun?) Unfortunately, the first half of the problem is unsolvable. In theory, almost
any period is possible for a "day." For instance, a "day" on Mercury is 176
earth days, while a Mercurian year is only 88 earth days, or half the day
The second is a "simple" matter of physics. If you assume that the star has
about the same mass as the sun, you can apply Kepler's third law to its
distance from the sun and base your calculation off of Earth's orbit.
However, if the mass of the star in question is different, then you'll need
some slightly more complicated math.
> But maybe I shouldn't try to keep it matchable year-to-year. Would the
> naturalism of choosing a random year length that would make Kankonian years
> completely drift off from their Gregorian equivalents after a while be
> important for convincing fiction? Having different year and date lengths from Earth's would be almost
essential--otherwise, you'd have one astounding coincidence. The Gregorian
calendar is specifically designed around the sun. If you have an
extra-terrestrial calendar, it is better a.) to design either a calendar
based on its sun, b.) some other astronomical phenomenom that makes sense for
the planet, or c.) a neutral dating system (e.g. Star Trek's "star date").
> The word for Christmas in the Kankonian language is . . . Navidad. Heh heh
> heh. They obviously weren't exposed to Christianity when they started
> making the calendar, but I suppose now they'd try to celebrate it whenever
> December 25 was occurring on Earth. Why? No, really, why? I'm assuming, based off of your above comments, that
the Kankonians are not human. So why would they be all that keen to celebrate
Christmas? Unless they converted to Christianity (Missionaries in Outer
Space), at which point, it would be better for the budding Christian
Kankonians to pick a significant date on their calendar for Christmas. Terran
religious holidays would probably be a rather moot point.
I say, go ahead, design a calendar, but put any thought of Terran events or
holidays out of your mind. Once you have it developed, then work on some way
of bridging the two.
> The Kankonians are human, so I guess that means they'd be drawn to dates
> from the sun, moons and orbit. Wait, now I'm confused. Are they, or are they not, on Earth? If they are,
then you need to be worried about year length (365.2422 etc.) and what not
for your calendar. If not, pick a random number for the year length (to keep
yourself honest, hardworking, and pure, make sure that the year and date
lengths do not evenly match up :) and go from there. Although then the next
question would be how did they get on this other planet?