Moon, Sun, and curving light

From: ian (i.) gorlick (
Date: Wed 21 Feb 1996 - 19:15:00 EET

Nick Brooke:

Yes, Nick, I did read your discussion of the moon being in different phases
depending on where the observer stands.
It is a reasonable explanation and has
certain merits. I just don't like it. I am used to living on a world where the
moon has pretty much the same phase for all observers. So I went looking for a
way that could be true on Glorantha, and I think I came up with a clever idea
even if it is wrong. (But remember, if enough Gloranthans start to believe my
theory, then it may be true after all.)

You seem to propose that light may not curve once it is high in the Celestial
Dome. I think I must disagree. If the curvature of light is due to its affinity
with the Sky, then the effect should get STRONGER as the light approaches the
dome. In order to have the effect stronger at the surface of the planet then we
would have to attribute the curvature to a repulsion by the earth, not an
attraction by the sky. I am not aware of a good justification for the earth
repelling light.

My proposal that the red face of the moon attracts light and the black face was
only intended as a thought provoker. It seemed to me that while we were playing
with the effect of curving light we might consider localized effects near the
terminator of the moon. Such effects might create some interesting images and
suggest some interesting religious/mystical interpretations and thus contribute
to MGF. If the effects are not interesting then the whole suggestion can be

I think the curving light theory should be explored more, that is why I started
this thread. If we eventually decide the results are silly, THEN we can reject
the idea.

Consider what it does to the Sun as he tracks across the dome. He passes through
the gates of dawn and the sky lights up, but his face is not visible because the
bent light means that he is still below the optical horizon. Then the newly
risen Sun, young and vigorous, streaks upward once he becomes visible. As he
reaches a higher altitude his pace slows and becomes more sedate as he takes his
place above all of creation. Then he passes the zenith and his pace picks up
again till finally he plummets at high speed towards the gates of dusk and the
underworld. He disappears from view but the light lingers for a time till he
passes through the gates and darkness envelopes the surface world again.

Compare this description to the myths of Yelm's fall and rise. I think it fits
better than uniform motion across the sky.

The non-uniform apparent motion helps emphasize that Glorantha is not Terra.

Come on Nick, let go of your own theories for a moment a play with this one,
just for a little while. Maybe you'll like it.

Dane Johnson:
>The thing which occurs to me about this, right off the bat, is that if Light
>is really going to curve up towards the sky, then Glorantha will have a
>horizon even though it's flat.

I believe that is why Greg (and Nick) originally proposed that light does curve.
It was so there would be a horizon on a flat planet. I merely extrapolated from
that proposition. Nick seems to feel that I have extrapolated beyond reasonable
Please check your assumptions about people's feet coming into view on the
horizon while their heads aren't. Raising an object above the ground should have
a symmetrical effect with raising the observer above the ground.

Martin Crim:
>I don't think that a horizontal axis is consistent with observations of the

Sorry, what observations?

The only effect of a horizontal axis is to make the
moon look more like the one we are used to on Terra where the axis of rotation
is pretty much normal to our line of sight.

>...this topic was treated here a year or so ago...

I know. The discussion never came to a conclusion that I found satisfactory.
Eventually my bizarre imagination cooked up this latest theory of mine and I
thought I would share it.

Andrew c/o Barbara Braun:
>I loved this idea (but then it is probably the physicist in me).

I also suffer from the debilitating social and psychological hardship of being a
physicist. That is probably why I went looking for an explanation like this.


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