Confused? Don’t worry HBO have not decided to sponsor the site, although perhaps they should. It was brought to my attention today that sometimes science meets popular culture in the most surprising ways, and that being an Earth scientist……can make you cool(?) on internet discussion boards. I swear I am not talking about myself, rather this particularly interesting piece revolving around the peculiar seasonal cycles that occur in HBO’s current hit series “Game of Thrones”. I’ll confess, I love the program, and I love it even more now somebody has attempted to explain the show’s unpredictable winter lengths using orbital theory, or Milankovitch cycles.
Game of Thrones is rather unique in that the plethora of evil spirits, white-walking ghouls, double-crossing dwarves and wicked villains are over shadowed by the pervasive threat of the winter that is coming. Summer has lasted seven years, but now the winter encroaches and it sounds more miserable than Canberra in August. Actually, it sounds more like an ice age in its severity, and its length is entirely unpredictable. The erudite gentlemen in the chat room discusses 5 different planetary mechanisms that could explain such phenomena.
1) A wobbly planetary tilt. Here on Earth the season’s are caused by our axial tilt, or obliquity, that describes the angle between our rotational axis and our orbital axis. Our season’s are driven by our current 23.4° offset that angles the hemisphere’s toward/away from the sun, depending on where we are in our orbit (see the animation here). This results in changing daylight exposure, and as you get closer to the poles produces a marked change in the intensity of sunlight reaching the Earth. This rotation is extremely stable on Earth, thanks in part to the presence of our very large moon. However, in Game of Thrones there is mention of only one small moon orbiting our mythical planet of Westeros, and therefore a wobbly planetary tilt is invoked to explain the erratic seasons.
2) Orbital eccentricity: Eccentricity refers to the shape of a planets’ orbit, or how far this shape deviates from a perfect circle. Obliquity influences climate due to the tilt toward the sun, however the shape of your planet’s orbit will dictate the distance you are from the sun. Earth’s proximity to the sun barely changes through its current orbit. However, if Westeros had a much more elongated, or eccentric orbit the aphelion (distance furthest from the sun) would bring prolonged severe winters, and conversely, the perihelion (distance closest to the sun) prolonged summers. A nice theory although the author does admit that this would not explain the unpredictability of the seasons.
The discussion goes on to explain the potential impact of complex Milankovitch cycles that combine the effects of obliquity, eccentricity, and precession (or the movement of the rotational axis), Westeros geography that would alter the effects of thermohaline circulation and wind stress and then of course, a combination of all of the above. For the complete discussion, the link is here or to sign up for a PhD in Earth sciences because you’ve just discover how awesome it is to be a climate scientist the ANU is always an option, link here!