Subject: (urth) Leagues and gravity

From: Jerry Friedman <jerry_friedman at yahoo.com>
Date: Mon, 11 Mar 2002 23:52:42 +0000

--- Michael Andre-Driussi <mantis at siriusfiction.com> wrote:
> Assuming that Lune Diameter = 2160 miles, and Orbit = 150,000 miles . .
> .
...

Where did you get 150,000 miles?

Anyway, you got me thinking about Green-Blue celestial mechanics.  Stop
me if this has all been done.

We're pretty sure Green is not a satellite but rather another planet
with a slightly smaller orbit, so that it comes into conjunction
every six years (if I remember correctly), right?  Also, Green has
higher gravity than the moon--otherwise the narrator would have told
us at least once how the first thing he as Horn noticed was floating
every time he tried to take a step.  I can hardly imagine Green has
less than half the gravity of Earth and the same density.  Using those
assumptions gives it 1/8 the Earth's mass.  (Calculations available on
request.)

Let's also believe Incanto quoting one Gagliardo when he says the
closest approach of Green to Blue is 35,000 leagues.  If these are
the same leagues in the afterword to _The Sword of Lictor_, namely
about three miles, then that's 105,000 miles.  For comparison,
somebody on the first visit to the Red Sun Whorl says a league is
7000 steps.  If these are half the Roman pace of which the 5000-foot
Roman mile was a thousand, then that's 7000*2.5 = 17,500 feet ~ 3.31
miles.  Using that latter number, Green's closest approach is about
1.87 x 10^8 meters.

We can now determine that the maximum force that Green exerts on Blue
at conjunction is about 8.5 x 10^21 N.  For comparison, the force the
sun exerts on the Earth is about 35.3 * 10^21 N.  In other words,
Green is going to mess up Blue's orbit something fierce--and much
more if it has more than half the Earth's gravity.  Mere storms and
tides are nothing.  Blue is going to mess up Green's orbit even more.
I doubt the system would be stable for more than one or two
conjunctions.

So did I make a mistake?  Are we supposed to infer something from this
discrepancy?  Or is this another case of Wolfe's not letting science
get in the way of the story?  The problem with the latter is that if
he can get away with anything, the kind of deductions he apparently
expects readers to make become problematic--which is the difficulty
we're having with the Blue/Ushas conjecture.

Jerry Friedman

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From: Dan'l Danehy-Oakes <ddanehy at siebel.com>
Date: Tue, 12 Mar 2002 00:10:49 +0000

Jerry Friedman wrote, and I'm going to snip and cut mercilessly to
avoid a 90% quoted posting...

> I can hardly imagine Green has less than half the gravity of Earth
> and the same density ... 1/8 the Earth's mass.  

> closest approach of Green to Blue is 35,000 leagues.  ... that's 
> 105,000 miles ... Green's closest approach is about 1.87 x 10^8 m.

> ... the maximum force that Green exerts on Blue at conjunction is about
> 8.5 x 10^21 N. Green is going to mess up Blue's orbit something fierce

> So did I make a mistake?  

Not, so far as I can tell, in your math.

> Are we supposed to infer something from this discrepancy?  

Possibly. My immediate guess would be that Gagliardo was actually
clueless about the actual distance between the two worlds at, uh,
perigreen. (No falcon around about this.) It's probably safe to 
guess that the astronomy and astrophysics of the Short Sun
colonists is pretty primitive.

> Or is this another case of Wolfe's not letting science get in
> the way of the story?  

This is probably heretical, given his engineering background and
almost fanatical attention to detail, but ... I have never really 
thought of Wolfe as the kind of Clement-ish worldbuilder who sits 
down and calculates all the astrophysics of a system before he 
starts writing. In fact, I could be wrong, but I'm pretty sure 
that this is the first Lupine text where the actual mechanics of a 
star system really affected the plot in any significant way - 
certainly the mechanics of the St Croix system isn't very germane 
to the plot of _Fifth Head_!) 

> The problem with the latter is that if he can get away with
> anything, the kind of deductions he apparently expects readers
> to make become problematic--which is the difficulty we're
> having with the Blue/Ushas conjecture.

The problem we're having with the Blue/Ushas conjecture is that
some people on this list, who shall go nameless, like the idea
so much that they will hang on to it in the face of any amount
of contradictory evidence. Heck, _I_ like this theory. It would
resolve a number of irritating problems in the Sun books. But
in fact it simply does not work for eighty-'leven reasons.

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From: Andy Robertson <andywrobertson at clara.co.uk>
Date: Mon, 11 Mar 2002 20:08:14 +0000

----- Original Message -----
From: "Jerry Friedman" <jerry_friedman at yahoo.com>
> discrepancy?

It is clearly signalled that Green causes massive tides on Blue.

You are right in saying that such an orbital system would be unstable.

Blue would have even more massive effects on Green, of course, sending it
all over the place.

Is there a solution?

I favour the idea that Wolfe started off with Blue/Green just being two
planets in an alien system.

When his hero got to Blue, he started to play with the idea that Blue/Green
just *might* be Ushas/Lune.

It is only at this point that we learn that Green comes even closer to Blue
than the moon does to the Earth today - something which may signal that
Green is a torn-away moon.

I think Blue/Green are in such unstable, temporary, orbits because they are
a young configuration - one which was formed when Lune was torn away from
Ushas by the White Fountain.

    hartshorn

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From: Grant Peacock <grantpeacock at yahoo.com>
Date: Tue, 12 Mar 2002 00:49:37 +0000

> me if this has all been done.
Yeah I once posted some similar thoughts, although I didn't do any math.

Have you considered the possibility that the narrator is accustomed to gravity
less than 1 g?  I'm assuming the whorl was designed to prepare people for Blue. 
The fliers in the whorl are perhaps more realistic in a .5g environment.

Our moon exerts a stronger force on Earth than our Sun does.  I say this because
tides are only a bit more extreme during a full moon.  (I forget the terminology. 
What are neap tides??)  So I would guess there must be something wrong in your
calculations. 

I think you are surely right that the orbits are unstable, even if the force
exerted by Green on Blue is a small percentage of that exerted on Earth by the
moon.  This means that the arrangement is a new one.  For those who believe the
Blue=Ushas theory, what must have happened was that the white fountain grabbed
Lune out of orbit as it came lumbering in and made into a planet.

Does the white fountain literally move through space into the system, or does it
just magically appear?

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From: Roy C. Lackey <rclackey at stic.net>
Date: Tue, 12 Mar 2002 06:26:37 +0000

Andy Robertson opined:
[snip]

>Lune out of orbit as it came lumbering in and made into a planet.

I don't want to get into the Blue=Ushas debate, but Lune didn't go anywhere.
It came up as usual--only much brighter--the first night after the flood,
and seemed to behave itself in its customary manner thereafter. See the last
paragraph of Chapter XLV of URTH.

>Does the white fountain literally move through space into the system, or
does it

It moved through space--Sev watched it get brighter as it came nearer.

-Roy

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From: Michael Straight <straight at email.unc.edu>
Date: Tue, 12 Mar 2002 15:48:42 +0000

> Lune out of orbit as it came lumbering in and made into a planet.

But every version of the Blue=Ushas theory I've seen at least admits a
very long time between Severian and the Short Sun Books (long enough for
Neighbor civilization to rise and fall), which is probably too long for
such unstable orbits.

-Rostrum

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From: matthew.malthouse <matthew.malthouse at guardian.co.uk>
Date: Tue, 12 Mar 2002 17:58:19 +0000

On 12/03/2002 15:48:42 Michael Straight wrote:

>> moon.  This means that the arrangement is a new one.  For those who
believe
>the

For this it doesn't matter if Blue=Ushas or not: any of the explanations
requires a system stable enough for the history of the Neighbours etc and
so far I don;t think we've come up with a mechanical solution that would
be.

Matthew

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From: Jerry Friedman <jerry_friedman at yahoo.com>
Date: Tue, 12 Mar 2002 18:13:29 +0000

unequivocally!

--- Grant Peacock <grantpeacock at yahoo.com> wrote:
[I wrote]
> The fliers in the whorl are perhaps more realistic in a .5g environment.

Reasonable, though we can hang-glide on Earth and the Fliers'
propulsion modules could easily be far in advance of our
technology.  Anyway, wouldn't the narrator or Hoof say something about
how heavy they felt on the Red Sun Whorl?  Maybe you don't feel the
local gravity in astral projection, but if so, they should notice that
the Urth folk walk as if they were nailed to the ground (if nothing
else).

> What are neap tides??)  So I would guess there must be something wrong

Tidal force decreases as the cube of the distance, not the square, so
the gravitational force of the sun on us is almost 200 times that of
the moon, even though the tidal force of the moon is something like
three or four times stronger than that of the sun.

(Spring tides, at the full and new moon, are the strongest; neap tides,
at the quarters, are the weakest.)

> moon.

It's got to be *more*--Green comes much closer to Blue than the moon
does to Earth, and it's surely more massive.  Anyway, we agree on the
instability.

> This means that the arrangement is a new one.  For those who
> believe the

Rostrum (I think) answered that point.
...

...

Oops.  I meant Inclito, of course.

Jerry Friedman

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