[Dragaera] Fwd: Moon(s) and Tides (was Re: Jhegaala etc.)

[Jon Lincicum]

 -------------- Original message ----------------------
From: Rebecca Harbison <beccastareyes at gmail.com>
> 
> On Jul 18, 2008, at 11:18 AM, Jon Lincicum wrote:
> 
> > Matthew Jennings wrote:
> >> Conspicious by its absence: a moon.  Is the Dragaeran 'planet'  
> >> moonless? Did
> >> we already know this. Would have been handy for Vlad.
> >>
> > In /Phoenix/, Vlad talks about the winds and tides when going to  
> > Greenare. Tides means moon. QED.
> >
> > It is somewhat curious that we do not see mention of it. But then,  
> > perhaps it is a much smaller moon, or it was a new moon during the  
> > two or three days he's in town stirring up trouble before he's...  
> > inconvenienced, and not in a position to notice anymore.  
> > Alternatively, perhaps the moon is composed of dark matter and not  
> > visible at all?
> 
> The Sun (at least on Earth), also produces tides -- they make up  
> about a third of the strength of the total tide on Earth.  Assuming  
> normal gravity, if a planet orbited a sunlike star and had no  
> satellite, the tides would be weaker than Earth's, and happen at  
> about the same time every day (high tide around midday and midnight,  
> low tide around dawn and dusk), but they would be present.  They also  
> would be nearly constant in strength at the same location -- local  
> places might have stronger effects depending on the shape of the sea  
> bottom (as, I'm sure, any sailor could tell), but there wouldn't be a  
> strong spring tide and a weak neap tide over the month.
> 
> I'd have to reread that part in /Phoenix/ to see if the tides could  
> still fit with only the Furnace in the sky.  If they change in  
> strength over the month, or occur at different times, then it implies  
> a moon or moons.  (You could also get the rough phase of the moon  
> from the tides).
> 
> -- Rebecca (Becca Stareyes)

Hrmph. I will, of course, defer to your expertise in this area. 

I hadn't thought the sun's tidal influence was that pronounced. 

The other compelling argument for a moon, however, is the presence of life on Dragaera. It is undeniably the case that without the moon on Earth, life could not have evolved here. Not just due to tides, but also because the moon helps stabilize our orbit, and maintain the planet's rotational speed. Without the moon, the axial tilt of earth would long ago have evened out to be perpendicular to the plane of the Solar system, meaning we would not have seasons. 

There are clearly seasons on Dragaera.  And from observations about planting/harvesting times and such in various books, they appear to be quite similar to ours. 

I long ago compiled a speculative list of planetary statistics for Dragaera, based on known clues from the books. See:

http://dragaera.wikia.com/wiki/Speculation:Dragaera

I guess there is more wiggle room for there possibly to not be a moon than I had thought. /Phoenix/ probably bears a closer examination for the timing of Vlad's departure, compared to when high-tide would have to be on a moonless planet.

Majikjon