Game of Thrones.... Ever wonder why this will be a long winter???

There is a book in the restricted section of the Citadel, where we could see a a diagram of the phases of the Moon by an Iranian scholar, Al-Biruni, who was born way back in 973 AD. His diagram shows the phases of the Moon and indicates that the Moon revolves around the Earth and the Earth around the Sun.

In the world of Game of Thrones there could be a long summer after a long winter,

also a short summer after a short winter is possible, it´s always unsteady and nobody knows

really what will be next. With our common celestial mechanics there would be always same long seasons. 

But how to explain the mystic irregularity?

As a matter of fact, there is a modell of celestial mechanics which explains the unequal length of seasons:

The Sitnikov System!

http://www.ams.org/samplings/feature-column/fcarc-sitnikov

In Short: A Planet between two Stars, exactly in the mass focus, moves up and down, if this happens irregular,

you have different long seasons...