Topic: Where exactly is the Ceril VII Star System.

[DonMoody]

The tidal force would also be distinctly larger than the Moon's tidal force on Earth.

The Moon's [surface] gravity is 0.1654 g.

Using the suggested .4 g for Orhan and the inverse square law, the tidal force of Orhan on Ceril VII/Kulthea would be about 3 1/6 times that of the Moon's tidal force on Earth (3.1587).

Even going with Mars' actually gravity (0.376 g) instead of .4, the tidal force is still almost 3 times that of the Moon's (2.9692).

DonMoody

[Alten]

I made rough calculations back in the day. Seen from Kulthea, Orhan would have an apparent diameter of about 24 minutes of arc, or about half that of the Moon as seen from Earth. It would not be possible to get full eclipses of Ceril, only annular or partial ones. The second biggest moon would be Varin, with about 15 minutes, then Charon at 5 and a half minutes, finally Mikori at 39 or 40 seconds of arc.

I'm no scientist, though, and had to make arbitrary assumptions for a few variables.

[kmanktelow]

Hi, Terry et al,

I got the data for the Kulthean moons from the First Edition Master Atlas World Guide (pg: 17)

Yeah, I've still got it- in it's box!

"By far the largest of the Kultheam moons, Orhan also has a unique characteristic: it has an atmosphere. Just over 3,500 miles in diameter, it has a very slow rotation (70 days: the same as its orbital period around the world) It is also quite massive; Orhan's gravity is 40% of Kulthea's....

The Great Moon (as it is sometimes called) orbits nearly on the ecliptic at a distance of 270,000 miles...."

So, the data I've used is as follows:

Orhan: diameter 3,500 mi; Mean Orbit 270,000 mi; Period 70 days
Varin:  diameter 601 mi; Mean Orbit 125,000 mi; Period 10 days
Charon:diameter 350 mi; Mean Orbit 190,000 mi; Period 49 days
Mikori: diameter 99 mi; Mean Orbit 520,000 mi; No Period- guessed at 75 days
Tlilok: diameter 40 mi; Mean Orbit 8,500 mi; Period 10 days (No actual Orbital distance or Period is specified- so I guess-timated them, so that it wouldn't intersect any other orbits.)

Obviously, I've had to convert to kilometers (miles time 0.621) then for the diameters had to divide by 2 to get the radii- which is what celestia works on.

One way around it, would be to say that the 'diameters' for the moons in the first edition was a mis-print and they were actually the radii...?

I'll take it back to the Moons diameters being their radii and see how it looks.

As for the Tidal forces, mentioned by DonMoody, Kulthea doesn't possess the large contiguous landmasses that the Earth does, which are partially responsible for the height of the tides- channelling water through narrow gaps increases the apparent tidal height. The so-called Severn Bore, in Somerset, has the second largest Tidal Range in the world and can be as much as 15 metres (49 ft). Because Kulthea has much more broken landmasses, in theory, it shouldn't suffer as much as the Earth from tidal variations.

Admittedly, Kulthea suffers from the additional complication of 5 moons- all of which will have some tidal effects. Although, unless they are all in conjunction they will be trying to cancel each other out- which will further reduce the tidal range.

All the Best,

Kevin.

PS: I've uploaded a comparison between our moon and Orhan, as viewed from the surface:

http://www.flickr.com/photos/28576267@N02/2680045263/sizes/o/

Hopefully, this is a bit more like Terry's vision.

[Terry K. Amthor]

But Alten, shouldn't Orhan seem much larger than the moon, since it is about the same distance and a much larger body? And also it should be able to fully eclipse the sun.

Kevin: oops it seems that Orhan has moved about 60,000 miles closer to Kulthea between the first and third edition atlases! Hmm. That latest comparison looks good; I guess it's hard to imagine it in a real setting, cause there the moon looks teeny


I had intended for Orhan to have more severe tidal effects on Kulthea than we see on earth, though maybe not more than three times...

[kmanktelow]

Hi, Terry et al,

But Alten, shouldn't Orhan seem much larger than the moon, since it is about the same distance and a much larger body? And also it should be able to fully eclipse the sun.

Kevin: oops it seems that Orhan has moved about 60,000 miles closer to Kulthea between the first and third edition atlases! Hmm. That latest comparison looks good; I guess it's hard to imagine it in a real setting, cause there the moon looks teeny


I had intended for Orhan to have more severe tidal effects on Kulthea than we see on earth, though maybe not more than three times...

Oh, bugger!

Does this mean that I've got to throw my first Edition Atlas away??

I've corrected the distances to those given in the third Edition Atlas- I notice that some of the moon sizes have changed as well- but, I still took the 'diameter' to be the radius, when converted to km.

I've uploaded two more grabs, with the camera set at about 2 metres above sea-level- looking towards the Horizon. One shows Orhan, whilst the other shows Varin relative to the sun- and even Varin will cause total eclipses....

(Yeah, I know, there's still no Kulthean textures. I am working on it, honest!)

http://www.flickr.com/photos/28576267@N02/2681146524/sizes/o/
http://www.flickr.com/photos/28576267@N02/2681146422/sizes/o/ (I must apologise, as I managed to turn asterisms on, whilst trying to get a shot of one of the moons and the sun together. The time and constellation controls are too close together- particularly when you've got a full day whipping by in less than a second.)

As for the moon looking small, the Celestia manual states that a field of view of between 35 and 45 simulates what the average person would 'see' in real life- using the averages for peoples' fields of view. The problem is, is the image is being squashed into a monitor that only covers a quarter- or less- of your actual view. (Trouble is you look a bit daft with your nose virtually touching the monitor trying to squint at the image! Literally, with my 19 inch monitor, my nose is about 1 inch away, before I can't see the monitor surround- by which time I can't focus on the image anyway.)

Hopefully, the new distances and sizes is a bit more like it.

As for the Orhan tidal issue- the other moons will tend to reduce the severity of the tides- except in the times of a conjunction. OK, Orhan will generally have quite an effect- and the tides will be larger than on Earth- but the other moons positions and the more broken landscape will tend to soften the effects.

But, conversely, look out, during a conjunction- the Lords of Orhan would probably be getting their feet wet!!!!

All the Best,

Kevin.

[DonMoody]

As for the Tidal forces, mentioned by DonMoody, Kulthea doesn't possess the large contiguous landmasses that the Earth does, which are partially responsible for the height of the tides- channelling water through narrow gaps increases the apparent tidal height. The so-called Severn Bore, in Somerset, has the second largest Tidal Range in the world and can be as much as 15 metres (49 ft). Because Kulthea has much more broken landmasses, in theory, it shouldn't suffer as much as the Earth from tidal variations.

I am not sure this is correct.

On Earth, the main (larger than any other factor) tidal constituent is the Moon (via its gravitational force relative to its distance from the earth); the second largest tidal constituent (less than half that of the Moon's) is the Sun.
On Kulthea, even with its multiple moons, the main tidal constituent would be Orhan (compare the mass of Orhan to the total combined mass of *all* of Kulthea's other moons).

When the Sun/Earth/Moon are in a line, tidal amplitude is the greatest (spring tide).
When the Earth/Moon line is perpendicular to the Sun/Earth line, tidal amplitude is the least (neap tide).

In theory, if the Earth:
- was tide locked (i.e. the same side always facing the Sun)
- had no above water land surfaces
- was completely covered with water
- and the water covering had a uniform depth
[i.e. if the Earth was a 'round ball of rock' evenly covered with water]

the theoretical amplitude of oceanic tides caused by the Moon would be a bit more than half a meter and that caused by the Sun would be about a quarter of a meter.
In theory, this means spring tide amplitude would be a little more than three-quarters of a meter and neap tide amplitude would be a little more than one-quarter of a meter.

But the Earth does rotate, is not a perfectly round ball and is not evenly covered with water.
In addition, coastal characteristics - such as underwater topography and coastline shape - effect the amount of difference between the higher high water and the lower low water (and are the cause tidal bores, which are fairly rare).
These are, in general, localized effects whereas the main driving forces of tides (the Moon then a not too close second, the Sun) are worldwide.


Even in areas where coastal characteristics are not such that the amplitude of the tide is increased, the difference between high and low tides is easily noticed.
If the main force behind the tidal effect was tripled, one would think it would be even more so.

DonMoody

[kmanktelow]

Hi, Don,

I'm not trying to say that there won't be tides on Kulthea- there's got to be tides, simply because there are massive bodies around the Solar System.

As Terry has presented the moons, Orhan would have a much greater effect on the tidal amplitude, than our moon has ever had on the Earths' tides.

Acting on it's own it would probably be pretty catastrophic.

(Assuming that Orhan doesn't get pulled apart by the sun/Kulthean tidal forces acting on it, of course- when it's on the sunward side of Kulthea.)

But, there's effectively three other moons (we can pretty much ignore Tlilok- that's effectively part of Orhan's gravity) that are all pulling in different directions on Kulthea's seas. OK, Individually their Gravity is probably pretty small compared to Orhan's, but their combined masses could be equal to Orhan's. in which case you would be left with the Sun acting as your sole effect on the tides.

Admittedly, that would need a pretty darned unlikely orbital scenario to completely cancel out Orhans' tidal force- and I'd hate to have to try to work out the maths involved.

Basically, I'm trying to rationalise how there is still even a planet left, for the Players to wander around on- getting up the noses of Dragonlords, stepping on Priests' Arnak toes and generally upsetting all the forces of darkness that we know and love.

The Atlases all state how the sea depth is pretty uniform, and that the ocean area is much larger on Kulthea than it is on Earth- because the landmasses are far more fragmentary. These tend to mean, that overall the tidal amplitude shouldn't be too much worse than on the Earth.

However, in certain areas- due to the shape of the land formations, etc, there will be tidal bores that put the Bay of Fundy to shame- and these areas will be pretty much uninhabitable, because of it.

Hopefully, that all makes sense- I'm tired and it's late!

All the best,

Kevin.

[Alten]

Re: orbits, the one I had calculated put Orhan much farther away. But once again I'll be the first to admit I'm no authority on the subjects of celestial mechanics...

[kmanktelow]

Hi, Alten, et al,

Yes, you are right, in 'reality' Orhan should be significantly further away than is stated.

For Orhan's orbit, using the 'System Maker for Celestia's' Orbital Stability Calculator and Terry's value of a 70 day Orbital Period, then Orhan's orbit- to be stable- has to have a semi-major (Mean distance) axis of 80,2258.53840548 km, or for the Orbital Distance as stated, then the Rotational Period must be 19.1565835265318 days!

So, in reality it does have to be significantly further away- over double the distance away- to keep to the stated 70 day Orbital Period.

Alternatively, the mass has to drop- taking it down by 50% only reduces the orbital distance to 76,2177.370198947 km. Even taking the Great Moons mass down to 0.1 (another 50%) of Earths, still only drops the orbital distance to 740450.982889717 which still doesn't help us very much.

And, this doesn't take into account the other moons, orbiting Kulthea. NASA could probably work out that particular Orbital Dance, even taking into account things like Frame Dragging and Time Dilation- but we don't need that level of accuracy.

So, we've got a choice- either go with Classical Physics- or go with what Terry's actually written. I'm pretty sure that a little judicious application of the Essaence can solve some of the problems!

All the Best,

Kevin.

[Alten]

Mmmm just a few ideas.

At the beginning there was no Essaence in the Kulthean system, but the Lords only arrived on Orhan afterwards. So Orhan may have started on an orbit farther than it is now, but after their arrival the Lords moved it (for their own reasons: watching over Kulthea ? Easier Channeling  or ferrying souls ?) closer to its current orbit, which is only possible due to Essaence manipulation.

Now this does seem to contradict the fact that they tried to make their presence on Orhan inconscpicuous and deter the K'at'viiri to land on it. Some k'ta'viir astronom is bound to have noticed that the orbit isn't right. But maybe there are so many "inconsistencies" in the system that it was deemed no more severe than others...

On the other hand, having such a system must have caused terrible headaches to a Kulthean Kepler or Newton trying to figure out the laws of celestial mechanics...

[Alten]

Another question I'd like to have answered is that of Char?n. OK, it has a polar orbit, but the plane of that orbit must also rotate exactly as Kulthea rotates on its own axis, else there would be an apparent east-to-west movement as seen from Kulthea , wouldn't there ? Every night Charon would rise in the east and set in the west, only a bit higher or lower every time...

And if so, what longitude is the plane aligned on ? Aligned with Votania would be nice...

[DonMoody]

But, there's effectively three other moons (we can pretty much ignore Tlilok- that's effectively part of Orhan's gravity) that are all pulling in different directions on Kulthea's seas. OK, Individually their Gravity is probably pretty small compared to Orhan's, but their combined masses could be equal to Orhan's. in which case you would be left with the Sun acting as your sole effect on the tides.

I thought the numbers available showed that the mass of Orhan was a good amount more than all of the other moons combined.

Also, as you noted here:

Admittedly, that would need a pretty darned unlikely orbital scenario to completely cancel out Orhans' tidal force- and I'd hate to have to try to work out the maths involved.

it would be virtually impossible for the tidal constituents from Kulthea's moons to cancel each other out.
It is much more likely there would be times when the tidal forces of the moons [somewhat] cancel each other out and [somewhat] reinforce each other.
And a rather infrequent times when the tidal forces of all the moons and the sun reinforce each other.
And an even less frequent time when Kulthea is at or near perihelion while multiple moons are at or near perigree; in such a case, the tidal forces would be at or near their maximum.
(And equally rare/infrequent times when the positions of these bodies would cause the tidal effects to virtually cancel each other out and there would be very little tide.)

The Atlases all state how the sea depth is pretty uniform, and that the ocean area is much larger on Kulthea than it is on Earth- because the landmasses are far more fragmentary. These tend to mean, that overall the tidal amplitude shouldn't be too much worse than on the Earth.

I am not sure this is correct.
Please keep in mind I am at best a layman in this area.
As such, I am not sure what roll or to what extent the macro aspects of landmasses play in the amplitude of tides but I thought these factors were more localized.
(Although I do know that there are some interesting aspects to tides around larger islands such as New Zealand - but even that is more of a 'what is the timing and flow directions of the tide around this island' type effect.)

DonMoody

[markc]

 The other thing is to remember to take into account the effects of magic in classical physics. Just kidding.
MDC

[kmanktelow]

Hi, All,

This is getting a little heavy...

Yeah, Don- you're quite correct- using the stated mass/distances, Orhan alone would cause absolutely catastrophic tidal effects- there's also a high chance that combined with the solar wind, that it would also be stripping the Kulthean atmosphere at a quite a rate. (The Earth has very little atmospheric hydrogen for a similar reason.)

[kmanktelow]

Hi, All,

Sorry, I accidentally posted before I'd finished the message!

This is getting a little heavy...

Just quickly working out the attraction due to Gravity, F= Gravitational Constant times (Mass 1 times Mass 2) over the distance between them squared, the force of attraction between Kulthea and Orhan is 42.015 times greater than the attraction between the Earth and the Moon.

(As anyone who's fallen out of a tree will tell you, Gravity is a real pain!)

Yeah, Don- you're quite correct- using the stated mass/distances, Orhan alone would cause absolutely catastrophic tidal effects on both the seas and the Tectonic Plates- there's also a high chance that combined with the solar wind, that it would also be stripping the Kulthean atmosphere at a quite a rate. (The Earth has very little atmospheric hydrogen for a similar reason.)

(Sorry pressed the wrong button, there!)

Anyway, the reduction in the atmospheric mass, would also reduce the boiling point of water- which with the increased volcanism, would start causing more and more water to turn to water vapour- some of which, would again, be lost to space. Then, we get into the effects of the reduced weight of water on the planets surface, which current theory seems to indicate would further increase volcanism- as seen by the increase in incidence of tectonic activity in the last few years- attributed in the Earth's case to the melting of Glaciers and the redistribution of the weight. (Although, the jury is still undecided on that one- the theory tends to support it, but there's not enough hard evidence.) If that theory is right, then we get even more water being boiled off- a lot being lost to space. This could quite quickly, in geological terms, end up with Kulthea with only some of the heavier (and generally highly toxic) gases left, very little surface water, and almost zero chance of life evolving....

(Note, the above completely ignores the other Moons and the additional tidal effect of centrifugal force, caused by Kulthea's rotation. Kulthea's diameter is larger than the earths, so it must rotate slightly faster, as well....)

Conversely, Orhan's atmosphere wouldn't have stood a chance.

Fortunately, we know that this hasn't happened- because Terry's written about it.

So, that leaves two choices, either get Terry- bless him- to re-write everything, or we ignore the extreme effects that Physics dictates.

My vote continues to go with ignoring the worst of the effects of Physics.

Part of the problem, I think is that it is very difficult for people to visualise the distances involved in Celestial Mechanics, and the fact that whilst the Gravitational Constant is very small- 6.6742 by 10 to the power of -11 metres cubed per Kilogram per second- it still works over an infinite distance.
This makes it difficult to visualise the effects of even slight deviations in distance or mass, between massive objects.

How do you visualise the fact that there's a Gravitiational attraction between you and the monitor in front of you, as you read this?
Microscopic, admittedly, but it's there.

Hell, there were people I did 'A' Level Physics with, who were still struggling with the theory after we'd finished the exams.....
Which either means that they weren't that good at Physics, or the Lecturer wasn't that good at explaining things.

Whew- hopefully that makes sense!

All the Best,

Kevin

[kmanktelow]

Another question I'd like to have answered is that of Char?n. OK, it has a polar orbit, but the plane of that orbit must also rotate exactly as Kulthea rotates on its own axis, else there would be an apparent east-to-west movement as seen from Kulthea , wouldn't there ? Every night Charon would rise in the east and set in the west, only a bit higher or lower every time...

And if so, what longitude is the plane aligned on ? Aligned with Votania would be nice...

Hi, Alten,

Yes, you are quite right, that Charon would rise towards the east and set in the west- but, it would rise higher in the sky each night- until you get it full and at Zenith on one particular night. This, is the Night of the Third Moon. And, it occurs in different places, every 149 days.

This implies that it's plane of orbit is 'fixed' in relation to a line drawn from the centre of the sun through Kulthea.

There doesn't seem to be any mechanism in Celestia, at least, to modify the 'Longitude of the ascending node' which would be what was required, to keep Charon orbiting directly over Votania. (Honest! That's what it's called! I didn't make it up!)
And, it does seem to be a set value for the Planets....

I haven't as yet, had a lot of time in the last couple of days, to try running Celestia with time sped up, to see the dynamics of the Moons around Kulthea. (I'm actually in work, and *ahem* am supposed to be more interested in Atomic Emission testing, and other terminally dull and boring stuff that a highly paid and dedicated Laboratory Technician should be interested in. Unfortunately, I'm neither highly paid, nor dedicated!)
Fortunately, I'm on Holiday for three weeks, so I'll have more time to play around then.

Hope this helps,

All the Best,

Kevin.

[vroomfogle]

This is cool!  Thanks for doing this project Kevin, good stuff!

[mathhatt]

I found this in my archive (can't remember where I found this originally) :



What do you think ?

[Terry K. Amthor]

I remember this! It's pretty close to what I'd intended. So the Emer I cover isn't TOO exaggerated...

[vroomfogle]

Terry, what about the vibrant atmosphere on Orhan....did you intend it to look so earth-like from Kulthea...or should it look more moon like?

Does anyone know who might have originally made the moon graphic above?