Re: Day length

From: donald_at_EtTJYCbfp0PiIIfu6yu3wiV4gGW9fUX0y7BSbFIp1-7lZc5a6OzHRn2BigvJWA796OAyH
Date: Thu, 03 Jan 2008 00:36:59 GMT

In message <> Grimmund writes:
>On Jan 1, 2008 3:10 PM, <> wrote:
>> >If it's a mythic effect, that's fine, I can just write it off by
>> >saying "oh, magic" and away we go.
>> The image I have of Glorantha on this subject doesn't have much to do
>> with real world physics.
>Yeah, that's starting to become apparent. :)
> Of course, the funny bit is, I can accept a flat, lozenge shaped
>world, but I'm having trouble with the sun being "overhead" everywhere
>on the plane.
>Oh! Glorantha is flat, not round, and that would tend to reduce the
>apparent angle of the noon sun. Your local 'up' is the same
>everywhere on Glorantha, as opposed to on a ball-shaped planet, where
>local 'up' varies.
>>The sky dome is a physical place where the
>> sun and other bodies exist. You can fly up there but you are moving
>> out of the mortal world and into another one (Heroplane? Godplane?).
>Sort of like the giants, shipping cradles down the Zola Fel. Got it.
>> Doing that involves crossing several barriers which distort distances
>> and angles. So what you see when you are up there cannot be directly
>> related to what you see from the ground. There are similar barriers
>> at the edges of the lozenge.
>OK. That helps. :) But I'm not sure it's necessary.
>And now, for the math portion of the show....
>Glorantha being flat, this is actually a pretty simple set of
>trigonometry problems. I looked around for a triangle calculator on
>the web, and found this rather handy one:
>Then I plugged in some numbers.
>Height 149,669,180 (distance, earth to sun, in km)
>Base 4,250 (estimated distance, 'equator' to northern or
>southern edge of Glorantha, in km)
>Relevant result is 89.998,373 degrees, apparent elevation of sun at
>noon from edge of world, due north or south of Magasta's pool. Not
>*quite* directly overhead, but close enough for the casual observer.
>If I had the width handy, I'd run that, too, just for giggles. I did
>some high-side guestimates, and came up with about 89.96 degrees noon
>elevation from the corners of the wold.
>So, there we go. Assuming the Gloranthan sun looks like Earth's sun,
>and assuming the same apparent distance from Glorantha to the sun as
>on earth, then the Gloranthan sun does appear to be darn near directly
>overheard at noon, pretty much everywhere, without any further
>reality-bending necessary.

Except that the Gloranthan sun is a lot nearer and a lot smaller than the Earth's. The Sky Dome is literally that. So given a normal dome shape the highest part is probably about 4,000 - 5,000 km above the surface. That would give an angle of 45 deg. at the extreme north or south. However the extremes are not habitable by ordinary folk so the lowest it would appear would be 55-60 deg. and that's in the north of the Lunar Empire while on the southern coast of Genertela it would still be at an angle of 75 deg. south.

However if the sun is directly overhead in Dara Happa (which makes mythalogical sense) it would be at an angle of 60 deg. north from the south coast and about 30 deg. over most of Pamaltela.

So we do need some explanation for why it appears directly overhead across the lozenge.

>Thanks for tolerating my wandering...

No problem, wandering discussions are what we seem to do best. :)

Donald Oddy


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