"Winter is coming"

[asterroc]

Am I the only one who is severely bothered by the seasons in "A Game of Thrones"? A big premise of the "A Song of Ice and Fire" series is that seasons last multiple years. But, at least in the first book, there isn't any explanation of this given, not even a supernatural/fantasy one.


Here's the problem. The word "year" means "the amount of time it takes for the planet to go all the way around the Sun once." By default, "year" refers to the orbital period of the Earth. A Jupiter year would be the time it takes the planet Jupiter to go around the Sun once (11.86 Earth years).

Seasons too are related to the orbit of a planet. The Earth isn't pointed straight up and down in space, it's tilted over a bit (23.5 degrees, to be precise). Let's say the Earth is tilted to the right. If you're standing in the Northern hemisphere, in December the Earth is to the right of the Sun so your part of the Earth is tilted away from the Sun and we call that Winter. (On the Winter Solstice, around Dec 21, you're pointed as far away as possible.) Three months later in March, the Earth has moved around "behind" the Sun, the Earth's still pointed to the right, so we're not really tilted away or towards, so that's Spring. Three months later in June, the Earth is on the "left" of the Sun and here in the northern hemisphere we're pointed towards the Sun: Summer. Another three months makes it September and Fall. Seasons are inextricably tied to the planet's orbit around the Sun. A planet with little or no tilt (Jupiter's is 3 degrees) won't have seasons. A planet tipped all the way on its side (Uranus's is 97 degrees) will have the most drastic seasons possible, but still spread out over that planet's year.

Therefore, according to normal astronomy, a season must be shorter than a year. And yet, "A Game of Thrones" talks about nine-year summers. So there must be some other explanation. Honestly, if Martin said in the first book that the seasons were caused by the Others (rather than implying that the seasons just happen and the Others do things as a result), I'd be satisfied, but he doesn't. So some alternate explanations that don't work.

• Distance from the Sun - the Earth's orbit is so close to a perfect circle, and the size of the Earth is so small compared to the size of its orbit, that distance from the Sun does not in any measurable way affect the seasons. That's not to say it couldn't on another planet with a highly eccentric orbit, however the seasons would still be tied to the orbit, and therefore tied to years.


• A second star - if the planet were changing its distance from a second star, this could definitely cause multi-year seasons. The scenario I'm picturing is that there's a primary star A, orbiting it is a secondary star B, and the planet orbits the secondary star (so the planet would be called Bb). The planet orbits star B in a year. Star B orbits star A in a highly eccentric orbit over approximately 30-50 years. For a quarter of that time (call it 10 years) both star B and the planet are closer to star A than usual and thus are warmer, therefore a 10-year "summer". For a quarter of that time they're farther from star A than usual and thus are cooler: "winter". This could work astronomically. The problem: Martin never mentions a second sun in the sky. If this really did happen, star A would be of comparable brightness in the sky, and you think that would be mentioned.


• Ice ages - although we don't completely understand what causes ice ages, our best guess is that there's a delicate feedback mechanism between the Earth's atmosphere, ocean, and landmasses. For example, if there's a bit more snow on the ground worldwide than usual, that means the Earth is white in color, which means more sunlight is reflected, which means the Earth cools down, presto ice age! Or if it's a bit warmer than usual this can cause more moisture in the air, water is a greenhouse gas, more heat remains trapped in the atmosphere, presto interglacial! On the Earth this process takes thousands of years to go from one extreme to the other (except for the current period of warming), but it's not impossible that it could happen in years or decades on another planet, and would also explain the apparent variability of the length of time of each season. This would be an excellent explanation of the multi-year season phenomenon except for one thing: Martin explicitly states that days are getting shorter as the world approaches winter. Since the length of the day is inherently tied to the axial tilt and orbital period (it's all geometry, for a fuller explanation see H.A.Rey's The Stars: A New Way to See Them), this really doesn't fit either.


• Variable star - (edited to add this possibility.) It's possible that their star actually changes brightness over time. There are a number of different types of variable stars, Cepheid variables are the most famous, but they tend to have periods in the order of days to weeks, not years. Other types of variable stars also have periods less than a year (this is a result of what causes the variability, so it's not possible to have periods of decades), so this would not solve the problem that we need seasons to last multiple years. It also wouldn't solve the problem of the length of the day, nor the fact that Martin doesn't report anyone commenting on changes in the star's brightness (which would definitely be visible), changes in the star's color (though not all have this), or changes in the star's size (this may not be visible to the naked eye).

In the end, I think I have to conclude that Martin doesn't know jack about astronomy, even what they teach you about the seasons in elementary school, and just move on and try my best to stop gritting my teeth every time he refers to multi-year seasons.

And I'll leave you with this.

Comments

[benndragon.livejournal.com]

Is it possible for a planet to wobble rather than have a fixed axial tilt? Probably not without a moon or three that are massive enough to pull it about (and that would be rather massive, IIRC), though if the material composition of the moon(s) isn't stated it's vaguely possible they're made of something terrifyingly dense and thus would actually be massive enough for such an effect. . .

Which makes me wonder, do we know what causes axial tilt in the first place?

[zandperl.livejournal.com]

Axial tilt does precess, over a time period of some 40,000 years. In order to have a season lasting multiple years though, the precession would have to have a period of approximately a year. Explanation: Let's say you're living in the northern hemisphere, it's December, the Earth's axis is tilted to the right in space, and the Earth is located on the right of the Sun in space. Therefore it's winter where you are because the northern hemisphere is tilted away from the Sun. Six months later it's June and the Earth is on the left of the Sun in space, and you want it to still be winter. Therefore you need to still be tilted away from the Sun, so now the Earth's axis has to be tilted to the left. Repeat. Such a fast precession is highly unlikely physically, and would probably require something awkward like multiple moons, a single huge moon with an impossibly high density, or another planet's orbit being close to the main planet's.

You're right that precession (the wobble of the tilt) is caused by gravity from another body such as our moon. As for what causes the tilt in the first place, it depends upon the planet. For the Earth, we think it's the same collision with a Mars-sized body that created Earth's Moon. I'm not sure for Venus (177 degrees) or Uranus (97 degrees), but I'm guessing a collision too. Smaller tilts such as Jupiter's 3 degrees probably were just a result of eddies in the cloud from which the planets and Sun all formed.

[q10.livejournal.com]

i would assume that ‘nine year’ in ‘the summer lasts nine years’ should be regarded as a translation artifact, intended to make things readable for an Earth-based audience, so that the characters were probably originally referring to some other unit of time, and it was translated into Earth years for our benefit, and their planet still makes one complete circuit around its sun per seasonal cycle.

[sildra.livejournal.com]

That becomes a lot harder when you try (like I did) to read the book as literally taking place in alternate-reality England, France, and the Mongolian Empire.

[q10.livejournal.com]

okay, if you also have those commitments then it just gets unwieldy.

[q10.livejournal.com]

to clarify what i'm getting at - suppose, say, that this planet's year is about 36 Earth years. suppose further that, since 36-year chunks are sort of a coarse-grained calendrical measure, the cultures that have evolved there usually measure long temporal durations in shorter units of about a twelfth of a year (three Earth years). call these units ‘gleebs’. if you're writing a book for English-speaking, Earth-based audiences, you'll translate every reference to ‘n gleebs’ with a reference to ‘3n years’, because your audience won't know what gleebs are. so just imagine the original said something about a summer three gleebs long.

[sildra.livejournal.com]

It doesn't have to be read that way. I just happened to be reading it with/on the recommendation of two history-major friends of ours, back in college, so I was predisposed to try to read it that way.

[q10.livejournal.com]

also note that there are cultures with calendars where the major year-like unit, sometimes referred to as a ‘year’ conspicuously doesn't line up with the solar year. the standard Muslim calendar has a year of 12 lunar months, with no reference to solar time, with the result that its consistently shorter than a real solar year.* but even though the sun features in nowhere in the definition or use of this unit, people still call it a ‘year&squo; when talking about them in English.

one of the two calendrical systems associated with Mayan civilization is based on 260-day tzolk'in cycles (nobody seems to know where the number 260 came from here). we don't call these years, but i suspect we might if it weren't for the fact that the same culture also used a Solar calendar.

*the Jewish and Chinese lunar calendars have compensating mechanisms to keep them in rough solar alignment.

[sildra.livejournal.com]

Also, I may be misremembering (it's been a very long time, and I didn't get far enough in the series to see winter happen), but I think only the England-type-area had these weird seasons, perhaps due to being closer to the magical evil wintery place beyond what, for the sake of clarity since you haven't read the book, I'm going to call alternate-reality Hadrian's wall. The Mongolian Empire area either had regular seasons or no seasons, I don't remember.

[zandperl.livejournal.com]

Hm, I'll have to listen for that interpretation as I continue the series. I was actually pondering after I hit "post" (for the second time) whether there could be an alternate definition of year, but I was thinking more like a year based on the stars, or moon cycles (as you suggest below). It didn't occur to me that it could be a "translation" of native time units because of the ubiquity of the usage of the term "year". Had Martin intended it to be a translation of a native term, I would have expected to see *something* about that somewhere, anywhere, and I haven't. If I wanted to take the viewpoint that this narration was an infallible reporting of events in an alternate universe then yes, I'd find that translation of units hypothesis plausible, but I really don't think it's likely.

[q10.livejournal.com]

unit translations are often pretty fuzzy in non-technical translation, though. for instance, most mass-market English translations of Classical Chinese texts that measure distances in li convert into miles, sometimes picking a conversion for comparable literary effect and not for numerical accuracy.

seriously, if a summer in his fantasy world lasts nine Earth years,* and he wants us, the readers, to know this, how else would he go about telling us?

*this of course would raise some other questions, since presumably there are all sorts of complicated ecological effects of stretching out the year, not to mention some astronomy questions about how to rig everything else to work out if you want to extend the orbit by that much, but those are at least subtler complaints.

[meleah.livejournal.com]

Ohh yes this always bothers me. For the reasons you raise and the flow-on biological ones raised etc.

I suppose I've been attempting to explain it to myself in terms of ENSO cycles. Obviously, these are nowhere near as extreme but living in a country significantly affected by these gives you a slightly different perspective on 'seasons' - our weather in Oz is nowhere near as delineated by season as you see in places like the northeast of the US, and whether you're in El Nino or La Nina can be more informative than whether its winter or summer. Plus they're not regular enough for one to be sure when they are going to occur or how long they will last.

This does mess with the historical parallels that are clearly being drawn with the UK, Mongolia etc. as pointed out above, but I'm fine with a fantasy premise that goes 'what if it was Europe, but with weird full on ENSO seasonal effects, AND the supernatural/fantasy elements?'

[zandperl.livejournal.com]

Having read only the first book, my understanding is that everywhere has the super seasons, but it affects the most Northern latitudes first.

[zandperl.livejournal.com]

Rather than saying summer lasts nine years, he could describe the stages of life of the different characters and used that as a comparison. Martin does the opposite in fact, saying things like "at only seven years old, Bran had been born in summer and had never seen winter.". He could instead describe Bran in a way that could let us identify his age, and then say the second phrase.

Astronomically it'd be easy: a brighter star and a larger orbit. Astrobiologists might not like that though, as the brighter a star is the shorter it's lifespan, so the star might not have had enough time to evolve life. But to me, that's a minor detail as compared to the big picture.

I also find myself continually wondering how they stock up on enough food to last the winter. The northern kingdoms are described as having snow on the ground towards the end of summer, and these regions were once independent nations, so where did they get their food from?

[zandperl.livejournal.com]

ENSO also doesn't affect the length of the day, and I'm pretty sure Martin said the sun was setting earlier as it got on towards winter. But otherwise it's no less plausible than ice ages. Though for historical accuracy's sake, one could look up the dates of the Little Ice Age and compare them to the European historical events that Martin is supposedly drawing inspiration from, and this could inform us as to whether he might have been thinking ice ages.

[meleah.livejournal.com]

Well, independence doesnt' stop you trading and/or raiding.

[meleah.livejournal.com]

There aren't historical events, per se - at least not that i've been able to identify. Just parallels like Hadrian's Wall/The Wall, the Mongolian hordes/Dany's people etc.

[q10.livejournal.com]

i was thinking of the astrobiology issues, and thing sof that kind.

as for the other bit, couldn't you solve the problem just by substituting ‘84 months’ for ‘7 years’? (i'm assuming they have a moon with a similar orbital period, but if not, go out to ‘365 weeks’.) i think it's likely that that's what Marin wants to convey, and i don't thinking using ‘1 year’ as a substitute for ‘about 525949 minutes’ is such a terrible sin.

[q10.livejournal.com]

or is there evidence that these ‘years’ have real significance in their culture? i mean, if we see them observing annual festivals or religious observances, or celebrating birthdays or anniversaries on the basis of these ‘years’, then that there makes no sense.

[sildra.livejournal.com]

Early on in the series, at least (I think I read 2 1/2 books, but I haven't picked up this series in over 6 years), I was under the impression that it was meant to parallel the War of the Roses between the York and Lancaster branches of the British royal family (thus the Starks and the Lannisters). This impression is partly based on things my history-major friends said when they encouraged me to read the books (back when only two or three of them were out) and partly based on things I think I remember reading on the internet at the time.

That would vaguely line up with the Little Ice Age.