First, note that this question consists of lots of short
more-or-less independent sections. This means
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Briefly explain the difficulties facing ancient agricultural societies
when defining a formal administrative calendar.
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[2] |
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Note that all you're being asked to do here is list the problems -
not explain the solutions.
The basic argument is:
- The essential period for agriculture is the solar year.
- This is too long to expect a non-literate population to keep track of it
directly, so you need to subdivide it.
- However, the obvious smaller unit - the synodic lunar month, which is
very easy to keep track of using the lunar phase - is far from being an
integral subdivision of the solar year.
- Therefore, simply counting lunar months will not provide a usable calendar
for agriculture.
It would be good, but is not essential, if you could put numbers into this argument
(e.g. synodic month ~ 29.5 days, so 12 synodic months ~ 354 days - lunar calendar
will get a whole season (90 days) out of step in only 8 years).
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Distinguish between lunar, solar and lunisolar calendars.
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[1.5] |
Note the wording here: you need to focus on the differences between
the three systems.
- Lunar calendar: counts lunar months, not synchronised with solar year.
- Solar calendar: based on solar year, does not keep track of lunar phase.
- Lunisolar calendar: counts lunar months, but uses intercalation of
extra months to maintain (on average) synchronisation with solar year.
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Explain, giving examples, the astronomical methods that
can be used to regulate lunisolar calendars.
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[3] |
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This section gets the most marks, so you need to give it the most time and space.
Note that you are asked for astronomical methods, so you won't get any marks
for "royal decree". You are also asked for methods, plural, so you need more
than one, and for examples, so you need to provide some.
From the notes, the two astronomical methods are:
- "observational: use a solar-year marker,
e.g. the heliacal rising of a star, and apply a rule of the form
"if this event occurs close to the beginning of the appropriate lunar month,
the year has 12 months; if it occurs near the end, it has 13 months";
- systematic: determine the true lengths of the lunar month
and the solar year as accurately as possible, and find a good common multiple –
then use this to design a pattern of intercalations."
The examples mentioned in the notes are the heliacal rising of Sirius (used
to regulate the Egyptian lunisolar calendar) and the Metonic cycle (used by the
Babylonians and the Chinese). As this is a 3-mark question, you probably need to
go into more detail here, or to describe an additional example (the obvious one is the
Indian calendar, regulated directly by the position of the Sun).
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What is the saros cycle? Explain the relevance of the saros
to the regulation of lunisolar calendars.
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[1.5] |
Be sure to answer both parts of this question:
- What is the saros?
The saros is an eclipse cycle. From the notes, eclipse cycles are
"common multiples of the synodic month and half the nodal month ...
The most commonly used cycle in ancient times was the
saros of 223 synodic months (= 242 nodal months)."
- How is it used in calendar regulation?
Again, from the notes, "eclipses have the advantage that the central moment
of the eclipse fixes precisely the instant of Full Moon (lunar eclipse) ...
Recording the precise times of eclipses in successive saros cycles therefore
allowed ancient astronomers to refine their value of the length of the month."
In other words, using the saros helps astronomers to define the synodic month more
precisely, which is useful if you are using a calculated cyclic rule to
regulate your calendar.
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Explain carefully any one of the following:
- the origins of our own (Gregorian) calendar;
- the Islamic calendar;
- the Persian solar calendar.
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[2] |
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Note that you are only asked to do one of these. It makes sense to choose
the easiest, which for most people would be the Islamic calendar. Note also the
difference in wording: for the Islamic and Persian calendars, you're asked to
explain the calendar, whereas for the Gregorian calendar you are asked to
explain the origins.
The answers to this are bookwork, so I'm not going to go into detail. The main
point is that you are asked to explain them carefully, which means that the
details are important. For example, for the Islamic calendar you need to explain
- it is a pure lunar calendar (no synchronisation with the solar year);
- months begin with the first visible crescent (not with the
astronomical New Moon);
- it is officially observational, not calculated, and therefore months
will vary in length irregularly as a result of both the variation in the length
of the synodic month and observational factors such as weather, altitude of the
observing point, etc.
A similar level of attention to detail is required in the other two cases.
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[2007 Q1.]
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