Astronomy Paper The Celtic Calendar

Choose a historical or fictional culture which had a reasonably sophisticated way of reckoning time: a calendar. Some possible suggestions: the Julian calendar (of the Romans, named after Julius Caesar); the traditional Chinese calendar; any of the Hindu calendars of India; any of the Buddhist calendars used in Southeast Asia; the Hijra calendar (used by many Muslims); the Hebrew calendar; the Korean calendar; any of the traditional Japanese calendars; the ancient Egyptian calendar; the traditional Ethiopian calendar; the pagan/neopagan Wheel of the Year; the Zoroastrian calendar. If you choose Mayan calendar, be aware that it is somewhat complicated, and there is only speculation as to what the tzolk’in might be used for. Give me that speculation and discuss its astronomical implications.
If you have a background in a culture that uses a different calendar from the Gregorian calendar, you may write about your own culture’s calendar (and teach me something I didn’t know!)
Alternatively, you may choose to write about the reckoning of time used in any major work of speculative fiction (science fiction, fantasy). Possible choices include:
the calendar used by the Hobbits in Lord of the Rings, detailed in the appendices to Return of the King (I can get you a copy if you don’t have one, but I can’t post it here).
Game of Thrones. See below.
Any other work of fiction you are familiar with that takes place on a non-Earth cosmology. There are likely some very interesting calendars used in science fiction settings involving interplanetary/interstellar travel.
the concept of “astrological ages”; do they themselves form a very long calendar?
Write a short essay of at least a single-spaced page in 12-point font (or two double-spaced pages) about how your calendar relates to the sky. You should address:
how the calendar you have chosen is connected to the motion of the Sun, the stars, the Moon, and anything else of note. How and how well do they line up with the days, months, years, or whatever else the calendar has. Which motions in the sky are treated as more important, and which are treated as less important?
how your calendar accounts for the fact that the Earth’s rotation, the Earth’s orbit, and the Moon’s orbit don’t synch up well. I described what effects this has in the Gregorian calendar above; tell me about the one you have chosen.
any “intercalary months” or leap-whatevers needed to keep your calendar in sync with the various celestial cycles, why they are needed, and how they work
what celestial events your calendar’s reckoning predicts exactly, and which ones are only approximate (for instance, the winter solstice is sometimes 21 December and sometimes 22 December in the Gregorian calendar, because we consider the daily rotation of the Earth to be more important than the exact moment that the axis of the Earth’s tilt is maximally toward or away from the Sun.
Modifications for particular calendars
The ancient Egyptian calendar: We think that the new year in the Egyptian calendar was related to the “heliacal rising” of the star Sirius. What does that mean? Is the Egyptian year the exact same length as the modern year? Consider carefully the effect of the “precession of the equinoxes”, the fact that the tilt direction of the Earth’s rotation changes slowly over thousands of years.
The Jewish calendar or the Chinese calendar: Both of these calendars are very similar, and are based on something called the “Metonic cycle” in the Western world. They are called lunisolar calendars because they try to accurately depict both the season and the phase of the moon in their timekeeping. If you write about either of these, your paper should discuss questions like:
An “intercalary month” is an extra month that is added to the year sometimes. Why do they use intercalary months, when the Western (Gregorian) calendar does not?
How do you determine whether to add an intercalary month to any given year?
The Metonic cycle is nineteen years long, after which the pattern of intercalary months repeats. Why is this? Why nineteen?
Is the Metonic cycle “perfect”, or must a calendar based on it be modified over long periods of time to “keep in sync” with both the cycles of the Sun and the Moon?
What are the similarities between the intercalary months used in these calendars and the “leap day” added to every fourth year (or thereabouts) in the Western calendar? What are the differences?
The Islamic calendar: Compare the Islamic calendar to the Jewish calendar. The Jewish calendar uses intercalation, but the Islamic calendar does not. What are the consequences of this? As inspiration, compare the (Gregorian) dates of Rosh Hashanah and Eid al-Fitr over the last decade. Relate the pattern you see to the fact that the Jewish year sometimes has an intercalary month, but the Islamic year does not. (You can find these tabulated online – see https://www(dot)timeanddate(dot)com/holidays/us/eid-al-fitr#obs for Eid al-Fitr and https://www(dot)timeanddate(dot)com/holidays/us/rosh-hashana#obs for Rosh Hashanah.
Lord of the Rings: What are these funny Yule and Lithe things? Why are they there, what function do they serve in the Hobbits’ calendar (which is otherwise pretty normal), and why do they have those names? Why is Lithe sometimes extended? Tolkien wanted to write “a mythology for the British people”, blending both their Christian and pagan heritage. If the Hobbits are the Britons of Middle-Earth, does this fit? Additionally, if you are familiar with these elements from the setting, you might address in addition or instead: how do you expect the Star of Eärendil to move in the night sky? Do you expect the Undying Lands (Tol Eressëa and Valinor) to experience days, nights, and seasons in the same way as the rest of Middle-Earth? (If you’ve not read the Silmarillion, this might not make sense. Your professor is a Tolkien fan, and I know many of you probably are too!)
Game of Thrones: In Game of Thrones, the seasons are quite extreme, last for a long time, and don’t have regular cycles. Assuming that the seasons in this world are caused by the same things as they are caused in ours (changes in the amount of sunlight reaching the ground), consider what sorts of physical mechanisms might cause this. (You can propose anything you want: irregular orbits for the planet that Westeros resides on, variations of the axial tilt, etc.) Explain what other consequences this would have for Westeros: what else would a Westerosian astronomer see as a consequence? Would Westeros experience solstices and equinoxes? Would it have tropics and polar regions? Would it be summer on half of the planet, and winter on the other half? Discuss how your proposal fits with the elements in the story. (For instance, if it is summer elsewhere while it is winter in Winterfell, one might imagine shipping food back and forth.) However, you need to describe those elements; not all of your TA’s are current with the show or books (and I’m in the middle of Feast for Crows myself, but I’m not spoiler-adverse. You may hear “The Rains of Castamere” later in this class, actually!)
The Gregorian Calendar: Our own calendar is familiar to us, but for high-precision timekeeping it has to be modified. What is a “leap second”, and why do we need them? How should we adjust timekeeping if the Earth’s rotation speeds up or slows down? What are some predictable things and unpredictable things that cause this, and how should we adjust timekeeping to deal with it? What about people who need to measure time to one-second precision (the Internet). What about people who need time measurements to one-thousandth of a second (scientists). What about things that need timing precision that’s even smaller than that (GPS satellites)? You may either discuss what people currently do, or make your own proposal for accommodating the needs of people who need to keep time in different ways across the Earth’s surface. Comment on the philosophical implications on our ideas of time itself. A good place to start reading is this article.
Any culture, real or fictional, that emphasizes solstice celebrations (many forms of paganism, for instance): Some cultures, historical and fictional, hold celebrations with particular symbolic significance on the Longest Day or Shortest Night (summer solstice), or Longest Night or Shortest Day (winter solstice). Suppose that the calendar says that the “date of the Winter Solstice is December 21”. Speaking extremely precisely, is the solstice a particular day, or something more narrow than that? Suppose your tradition celebrates the Longest Night rather than the Shortest Day, and believes that getting the exact Longest Night right, even if it is longer just by a few seconds, is important. Should you celebrate on the night spanning the 20th-21st, or the 21st-22nd? What astronomical phenomenon (having to do with the placement and orientation of the Earth and the Sun) is important, and how do you know which night will truly be the Longest? If you choose to write about the neopagan Wheel of the Year, then this may occupy a large portion of your paper, even though many Neopagans don’t emphasize getting the exact date right for their observances. This is okay, as it’s an interesting problem. (This question was inspired by a conversation I had with several friends years ago, some of whom recognize the Longest Night on its astronomically-correct date, on a year when the date of the Longest Night differed between regions of the USA.)