"Winter is coming"
Dec. 5th, 2010 10:26 am![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
asterrocAm 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.
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.
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.
