Re: Day length

From: Grimmund <grimmund_at_RG_GwtFGHnElYHu4FloFnV7dBavNugFpzxWc5aNDYKfX7n_CCdQeloufUqs1s5zVe_c>
Date: Tue, 1 Jan 2008 11:40:23 -0600

Well met!

On Dec 30, 2007 10:32 AM, jorganos <> wrote:

> > If the axis of rotation was perpendicular to the sun, we'd still
> > have longer days on the equator compared to closer to the poles,

> It would be a perpetual equinox,

Yes, it would be a perpetual equinox.

>except at the poles which would have 24 hours of light.

Yes, they would, although geography could limit that. It would not be the same sort of direct overhead light you get closer to the equator. You'd end up with a dim sort of sun-on-the-horizon perpetual twilight. Fog or bad weather would seriously cut into your available light, too. High mountains close to the pole would leave the poleward side in shadow during part of the day, too.

> >at noon, the sun would be (roughly) above Magasta's whirlpool, yes?
> Yes. However, the Gloranthan sky has no meaningful parallax towards
> the ground. That means if a stellar body is up 38 degrees north
> viewed from Pamaltela, it won't be any higher viewed from Genertela.

*Boggle* I can't quite picture that. Glorantha is small compared to Earth, but it's still big enough for there to be some noticeable differences in the sky.

For the sun to be close enough to provide useful energy, it's pretty much got to be close enough to be at a measurable angle away from directly overhead, as you move from the equator.

> > In the north, it would start in the southeast, peak, and set in the
> > southwest. In the south, the reverse.
> That doesn't seem to be the case. Both the Gates of Dawn and Dusk are
> so far outside of the "Circle of Time" that they appear directly east
> and west from anywhere within the "Circle of Time".

That's... just downright odd. My rough check against the map in RQ3 shows Glorantha roughly 8500 km north-south. That's only about 42% of earth, but it would still seem to me that for the sun to be close enough to be useful as an energy source, it's got to be close enough that there would be some meaningfully visible angle between the sunrise/sunset points on the 'equator' and the more northern and southern reaches.

If it's a mythic effect, that's fine, I can just write it off by saying "oh, magic" and away we go.

> Sundials don't really work on Glorantha.

I don't know; sundials are pretty much foolproof.

> Yelm, and in the nights
> Lightfore, move at varying angular speed across the sky.

Do you mean that they vary seasonally? Or daily? Longer days in Sea, Fire, and Earth, shorter days in Dark and Storm, and I'd expect the shortest day to be somewhere in Sacred Time, the period of rebirth. I'd always assumed that "longer days" meant longer periods of light relative to darkness with the overall, absolute length of time from noon to noon staying the same. Changing the overall absolute duration of the day just seems unreasonable, although I suppose it's possible.

Either way, I would think a sundial would still work for relative time, as long as the sun casts a shadow. You get relative time from a sundial, not mechanical time, so as long as you're simply looking for a way to break the day up into some number of divisions, a sundial works fine.

If you need regular, equal intervals, you're going to need a different, mechanical, timekeeper.

> > Using some sort of orbital mechanics to explain varying day lengths
> > vastly complicates things.
> Only if you use the sun. In a clear night, you get Mastakos/Uleria as
> a very reliable timepiece. Always visible, crossing the sun path in 8
> hours - four hours to meet Polaris, four hours down again.

when you write "8 hours" do you mean relative time, or mechanical time?

I'd always assumed longer/shorter days meant longer/shorter daylight with the difference made up by shorter/longer nights, and overall duration of a day remaining constant. Are you saying the nights are *always* 8 hours, and the overall duration of the day changes seasonally?

> > A simpler explanation is to make it
> > mythic, and the sun simply really DOES take longer or shorter times
> > to travel the same route depending on the season.
> There is room for an easier, mechanical explanation which has
> circular paths for both Yelm and Lightfore which have an opposed up-
> and-down movement and constant angular movement (wrt the circles, not
> the ground).

Sorry, I'm not visualizing that, either.



"A word to the wise ain't necessary - it's the stupid ones that need
the advice."  -Bill Cosby


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