Subject: (urth) Green's diameter, angular and otherwise

From: Michael Andre-Driussi <mantis at siriusfiction.com>
Date: Wed, 13 Mar 2002 02:19:24 +0000

Another way to approach the Blue/Green conjunction is to determine the size
of Green in the sky of Blue, from its "usual" size to its greatest size at
closest approach.

For simplicity sake, let us assume that both Blue and Green have surface
gravities of 1 g.  More or less "twins" in separate orbits (and Green
having an orbital eccentricity that carries it out to a close approach with
Blue every x number of local years).

I was watching for details when I read before and I don't recall finding
any, other than "baneful eye."

OTOH, we have the happy case of an eyewitness who also sees Lune (maybe?)
and the Old Sun (definitely). The Old Sun (assumed before to have an
angular diamter of around 0.83 degrees) is "swollen" to his eyes, but iirc
he never says anything in comparison to Green's biggest size.

Using the Moon as a model.
        ORBIT      ANGULAR DIAMETER
MOON    240,000    0.52 degrees
LUNE    150,000    0.83 degrees
GREEN   105,000    1.18 degrees

So even a puny world like the Moon (diameter 2160 miles) would be more than
twice the size of the Moon in our sky when located at a distance attributed
to Green.

A twin planet would naturally be much bigger.

Based upon this, the Bluvian astronomer is quite likely to be waaaay off in
his estimate of the "closest approach" distance as being 35,000 leagues.

=mantis=

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From: Jerry Friedman <jerry_friedman at yahoo.com>
Date: Wed, 13 Mar 2002 16:50:29 +0000

> Blue every x number of local years).

I don't think the eccentricity has much to do with it.  The two
planets will come into conjunction every x number of local years.  If
Green's orbit is eccentric, then sometimes the distance at conjunction
will be greater and sometimes less.

> his estimate of the "closest approach" distance as being 35,000 leagues.

How are you thinking the Bluvian astronomer would make his estimate?
I can't think of a method that would be thrown off by Green's large
size.  The only way I know of at the Green level of technology would be
parallax, which doesn't depend on Green's angular size at all.  (Though
the parallax method would require a fair amount of work, notably
measuring the distances between widely separated cities, as well as
astronomical observations at conjunction, which is presumably the
worst possible time.  Seems unlikely during the first twenty years
of settlement.)

Maybe Gagliardo used observations made from the lander and
information from the monitors, who could at least have told him
the cruising speed of the landers.  Or maybe he's doing the same
thing we're doing and guessing that the Short Sun is the same size
and brightness as the Old Sun, which makes the radius of Blue's
orbit the same as Urth's (if he knows it); then from the time
between conjunctions he can get the radius of Green's orbit.

Anyway, the higher the true distance, the harder the problem of how
the inhumi cross.

Jerry Friedman

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From: Dan'l Danehy-Oakes <ddanehy at siebel.com>
Date: Wed, 13 Mar 2002 17:07:28 +0000

Mantis wrote:

> > So even a puny world like the Moon (diameter 2160 miles) would be more
> > than twice the size of the Moon in our sky when located at a distance
> > attributed to Green.
> > 
> > Based upon this, the Bluvian astronomer is quite likely to be waaaay off
> > in his estimate of the "closest approach" distance as being 35,000
leagues.

... for which I am frankly grateful, because it seems to me to drive the
final nail into the "Blue = Urth" theory's coffin, based on past discussions
herein.

Then Jerry F. asks:

> size.  

I don't believe Mantis is referring to the Bluvian astronomer's "method"
but simply to his result. 

At one level, Mantis refers to the description of Green, seen from Blue, 
as a "baleful eye." A twin planet, or even the moon, seen at the distance 
of 105K miles, would be rather too large for an "eye" to be, at any rate, 
the most obvious metaphor. 

More important: from present evidence, it appears that Green, Blue, and 
Urth have fairly similar surface gravity (the evidence is, admittedly, 
negative: there is no mention of a sensation of weighing more or less, 
no sense that thrown or swung objects behave differently, etc., and it
is reasonable to suspect that _something_ of the sort would be mentioned) 
-- indeed, all these seem to be fairly close to the accelerational 
"gravity" of the Whorl at "ground" level. 

(BTW, the whole issue of the Fliers in a separate thread seems to miss 
the point that they rarely - never voluntarily? - come near "ground" 
level.) 

This being the case, Green needs to be at least somewhat similar in 
mass to Urth. Such a mass passing within 105K miles of Blue would have 
effects not terribly dissimilar to the effect of the passing of the 
White Fountain on Urth. (And, of course, vice versa for Green.) The 
effects described for the conjunction do not come close: for example, 
the Narrator mentions extreme tides, but apparently they are not so 
extreme as to swamp a seaside town (New Viron) or to make a home near 
the shore of an oceanic island (Horn's hut) infeasible over a period
of decades.

> Anyway, the higher the true distance, the harder the problem of how

True, but in any event the problem of how the inhumi cross between
Bleen and Grue is trivial next to the problem of how Remora (and,
apparently, other inhumi) achieved the crossing to the Whorl. If I
recall correctly, a Neighbor mentions to Horn that they (the Neighbors)
sent them (the inhumi) - but does not describe how this was done. 

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From: Jerry Friedman <jerry_friedman at yahoo.com>
Date: Thu, 14 Mar 2002 22:02:27 +0000

> final nail into the "Blue = Urth" theory's coffin, based on past

Okay, how?  I too would be relieved, but I don't see the connection.

> but simply to his result. 

Ah, got it.

> the most obvious metaphor. 

Au contraire, mon frere.  Sundogs (mock suns, parhelia) have a good
deal more than twice the angular diameter of the moon, and one person
who talked to me about seeing one compared it repeatedly to God's eye
looking at her, perhaps accusingly.  Anyway, the 105K miles is the
closest approach; most of the time Green looks much smaller.  (Or was
that "baleful" eye right at conjunction?)
 
> "gravity" of the Whorl at "ground" level. 

I think Marc just presented, not for the first time, cogent reasons
to think that Green's gravity is less than the Earth's.  I argued
a couple of days ago that nonetheless Green's gravity should be much
greater than the moon's, more or less for the reason you mention.  I
agree with you and him that there's no trace of any difference between
Earth's gravity, Urth's, Blue's, and the _Whorl's_ "gravity".

> the point that they rarely - never voluntarily? - come near "ground" 

But they're capable of flying near ground level, at least for a little
while.  See Sciathan's discussion of his capture, if I remember it
correctly.

> Bleen and Grue

(or Blee and Groon, for King Crimson fans)

> is trivial next to the problem of how Remora (and,

I don't see that.  It's one of the problems the Blue=Ushas theory is
supposed to solve, and for those of us who don't believe that, there
was plenty of space travel before Typhon.  The problem of how inhumi
got onto the _Whorl_ is no harder than the problem of how the averns'
and the alzabo's ancestors got to Urth.

On the other hand, I think you could make a good case that it's not
much easier for the inhumi to cross 35,000 leagues of space than ten
times that distance.

Jerry Friedman

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From: Dan'l Danehy-Oakes <ddanehy at siebel.com>
Date: Thu, 14 Mar 2002 22:27:38 +0000

Jerry F., responding to me...

> > final nail into the "Blue = Urth" theory's coffin, based on past
> > discussions herein.

> Okay, how?  I too would be relieved, but I don't see the connection.

Well, maybe I was wrong from that perspective. I think the gravity issue
does it, though...

> > A twin planet, or even the moon, seen at the distance of 105K
> > miles, would be rather too large for an "eye" to be, at any
> > rate, the most obvious metaphor. 

> looking at her, perhaps accusingly.  

I can weasel this a bit, by observing that the ring makes the sundog _look_
much more like an eye than a bright glowing round thing in the sky does,
but I accept your basic point.

> to think that Green's gravity is less than the Earth's.  

I disagree. I suggest that the "climbing with one arm while fighting with
the other" bit is possible due to one or both of two things:

1) This happens when the Narr is astrally travelling, not physical present
   on Green; and
2) Dramatic/narrative convention; how many times have you seen this in
   the movies?

> I argued a couple of days ago that nonetheless Green's gravity should be
> much greater than the moon's, more or less for the reason you mention.  I

Nor do I see any real evidence that Green's is any different.

> while.  See Sciathan's discussion of his capture, if I remember it

Maybe I'm wrong, but I seem to recall his saying it's much more difficult
near the ground. 

> (or Blee and Groon, for King Crimson fans)

Well, I confess that I'm a 21st Century Schizoid Fan... 

> and the alzabo's ancestors got to Urth.

That seems to be based on an assumption that they were on the _Whorl_ 
from the time it left Urth, and I see no basis for that claim whatever. 
The Neighbor's comment about sending the inhumi to the _Whorl_ seems to 
me to refer to a time after (probably just after) the _Whorl_'s arrival 
in the Glune system.

> much easier for the inhumi to cross 35,000 leagues of space than ten

Shrug. Possibly. And actually, the distance to the _Whorl_ can't be
_too_ much greater than the distance between the two planets, since the
_Whorl_, which is certainly smaller than either of them, is plainly visible
in the Bluvian night sky.

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