Speculation on the Fall of Night

[Valyirian Aurochs]

Night and day are determined by a planet's spin, and I see no reason why the WOIAF is any different. If I were to speculate on how something like the long night happened, I would guess that Planetos' spin is manipulated by magic. There is evidence that magic can do world-shattering things; the arm of Dorne was broken by powerful magic, and the neck is a bog because of magic.

This speculation leads me to ask how large Planetos is. The Long Night is said to affect lands as far east as Yi Ti, and there is no certain distance given to us on how far Yi Ti or Asshai is from Westeros. With more speculation, I would guess that when it's day in Westeros, it's also daytime in Asshai. What I'm getting at is that maybe as the Others use their magic to stop the planet's spin so their side of the world is forever facing away from the sun. We aren't sure what the rest of the world looks like, but maybe the other side of the planet will then be in eternal daytime.

This theory has a lot of problems, I know. Like I've said, there is no definitive number given to us to what the distance is from Westeros to the far east. Magic is a mysterious force in the world, but maybe it isn't powerful to stop planetary spins. Why would the Other's tolerate daytime if they had that kind of power? That's another question the looms above all of this.

If this is true it would be symbolic to the title of the series. Maybe the battle between ice and fire is a battle for the spin of the planet. One side of the planet can fight for eternal night, and other side can fight for eternal day. Balance comes when you avoid both extremes and night and day follow each other every day.