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Tides of Oerth

 
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gargoyle
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PostPosted: Sat Jun 27, 2009 2:30 am    Post subject: Tides of Oerth Reply with quote

Considering the two moons of Oerth, has anyone doen any work on the tides? I don't really know much about tides myself, other than the Moon has the greatest influence. I'd guess the two moons of Oerth would create more complex and possibly higher and lower tides than here on Earth. I was reading about Turucambi, and it mentioned tides, but didn't go into detail.
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Aeolius
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PostPosted: Sat Jun 27, 2009 8:40 am    Post subject: Reply with quote

You could look here:
http://www.nirgal.com/games/rpg/greyhawk/tides
http://www.nirgal.com/games/rpg/greyhawk/tides_math

While looking over the information about the Sinking Isle, I also noted some interesting tidbits:
"...the protected inner passage between Asperd Island and the Solnor's unpredictable waves, either go the long way 'round or stay in port."

"...until one of the Solnor's strange and unpredictable great waves came questing into the strait and lifted the wounded vessel clear."

unpredictable great waves.... hrmm... elementals, perhaps?
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smillan_31
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PostPosted: Sat Jun 27, 2009 7:45 pm    Post subject: Reply with quote

Remember too that Oerth is the center of the solar system with every other body, including the sun orbiting around it, so the occurrence of tides would most likely be very different. One thing I'm pretty sure of is that it would be pretty regular with tides occurring at the same times on the same days year after year which would be a great advantage to mariners and probably give rise to salty folk sayings to help people remember when the highest and lowest tides of the year are. If I'm reading it right the most extreme tides would come around the middle of Needfest and Richfest, but then I'm no scientist.
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OleOneEye
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PostPosted: Mon Jun 29, 2009 5:45 pm    Post subject: Reply with quote

If you follow the tenets of Spelljammer's Greyspace, the 2 moons are too far away to have much impact. As such, Oerth probably does not have tides.
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gargoyle
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PostPosted: Mon Jun 29, 2009 5:57 pm    Post subject: Reply with quote

OleOneEye wrote:
If you follow the tenets of Spelljammer's Greyspace, the 2 moons are too far away to have much impact. As such, Oerth probably does not have tides.
Well now, where would the fun be in that? Besides, I personally discount Greyspace entirely.
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OleOneEye
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PostPosted: Mon Jun 29, 2009 6:16 pm    Post subject: Reply with quote

gargoyle wrote:
OleOneEye wrote:
If you follow the tenets of Spelljammer's Greyspace, the 2 moons are too far away to have much impact. As such, Oerth probably does not have tides.
Well now, where would the fun be in that? Besides, I personally discount Greyspace entirely.


I completely ignore Greyspace as well, or rather, all of Spelljammer besides using deck plans for fantastical, if waterbound, ships. Nonetheless, were one to use Greyspace and keep any semblance of Newtonian physics (which Spelljammer has already thrown out the window), than the two moons are simply too far away to cause any significant tides.
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smillan_31
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PostPosted: Mon Jun 29, 2009 6:40 pm    Post subject: Reply with quote

Yeah, according to SJ Luna (Raenei) is about 130 times as far from Oerth as the Moon is from Earth, while being of similar sizes. Celene (Kule) is about 44 times as far while being considerably smaller than the Moon. The Sun of Oerth is roughly 1/8 the diameter of Earth's Sun, a little larger than Saturn, and is a little further from Oerth than the Sun is from Earth. So as well as not exerting any significant tidal forces they also appear considerably smaller in Oerth's sky.
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gargoyle
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PostPosted: Mon Jun 29, 2009 11:09 pm    Post subject: Reply with quote

Well all that SJ/Greyspace stuff just doesn't jibe with physics to begin with, so if you're going to use that - forget about Newton. The tides are caused by Procan, Xerbo and/or Osprem farting in the ocean depths! Since Turucambi mentioned tides, I am assuming there are tides on Oerth. I like the post above; the tide calculator is really good. So that's what I'm going with.
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MToscan
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PostPosted: Mon Jun 29, 2009 11:12 pm    Post subject: Reply with quote

smillan_31 wrote:
Yeah, according to SJ Luna (Raenei) is about 130 times as far from Oerth as the Moon is from Earth, while being of similar sizes. Celene (Kule) is about 44 times as far while being considerably smaller than the Moon. The Sun of Oerth is roughly 1/8 the diameter of Earth's Sun, a little larger than Saturn, and is a little further from Oerth than the Sun is from Earth. So as well as not exerting any significant tidal forces they also appear considerably smaller in Oerth's sky.

Yes but those moons are MAGICAL.
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rasgon
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PostPosted: Tue Jun 30, 2009 6:47 am    Post subject: Reply with quote

smillan_31 wrote:
Yeah, according to SJ Luna (Raenei) is about 130 times as far from Oerth as the Moon is from Earth, while being of similar sizes. Celene (Kule) is about 44 times as far while being considerably smaller than the Moon. The Sun of Oerth is roughly 1/8 the diameter of Earth's Sun, a little larger than Saturn, and is a little further from Oerth than the Sun is from Earth. So as well as not exerting any significant tidal forces they also appear considerably smaller in Oerth's sky.


That can't be right, because Greyspace says that Celene appears the same size as Oerth's sun from Oerth, and Luna seems a little bigger.

It seems obvious that to fit with both Greyhawk and Spelljammer canon, they need to be closer. If so, then they do exert tidal forces, and we're back to the original question.
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Aeolius
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PostPosted: Tue Jun 30, 2009 9:27 am    Post subject: Reply with quote

rasgon wrote:
It seems obvious that to fit with both Greyhawk and Spelljammer canon, they need to be closer. If so, then they do exert tidal forces, and we're back to the original question.


"The Turucambi reefs are among the most complex known, and present surprises at every turn. The tidal range is great, and there are shallows regularly exposed by the tides, deep unfathomed sinkholes, and complex and powerful tidal races which can toss a ship like a toy. "
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OleOneEye
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PostPosted: Tue Jun 30, 2009 3:13 pm    Post subject: Reply with quote

It seems obvious that Jeff Grubb did not worry at all about real-world physics when writing the Spelljammer boxed set. He did, however, give exact distances from Oerth for both moons and the sun. (Note that it lists Oerth's sun as significantly smaller than our own - perhaps the size of Jupiter or so). A DM has several options, including:

A. Ignore Spelljammer stuff,
B. Accept Spelljammer stuff and ignore the inverse-square law of gravity,
C. Accept Spelljammer stuff and try to apply physics as best as possible,
D. Use whatever Spelljammer stuff is appealing and ditch the rest,
E. Ignore any relevance that lunar bodies have on tides and come up with some fantastical explanation (e.g. Procan does a belly-flop in the Solnor twice a day).

In the end, I suspect most would want tides that are relatively similar to those we are familiar with here at home with perhaps a few fantastical hum-dinger tides from time to time.
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rasgon
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PostPosted: Tue Jun 30, 2009 9:38 pm    Post subject: Reply with quote

OleOneEye wrote:
I (Note that it lists Oerth's sun as significantly smaller than our own - perhaps the size of Jupiter or so).


Yeah, it's smaller than Jupiter, and it's further away than our sun, too. I don't mind (and, in fact, I like) the "fantasy physics" of Spelljammer where it's applied to gravity, air pockets, and so on, but I can't understand how even the most fantastic universe would make objects appear to recede less in the distance. Yet that's apparently what the assumption is - that the distance of a planet has nothing to do with how big it appears.
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rasgon
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PostPosted: Wed Jul 01, 2009 6:18 am    Post subject: Reply with quote

On a related note, the following website calculates Celune and Luna's sizes and distances from a more mathematical perspective, and also calculates the effect each would have on the world's tides (about equal):

http://www.nirgal.com/games/rpg/greyhawk/tides_math
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GVDammerung
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PostPosted: Wed Jul 01, 2009 7:16 am    Post subject: Reply with quote

Aeolius wrote:
"...until one of the Solnor's strange and unpredictable great waves came questing into the strait and lifted the wounded vessel clear."

unpredictable great waves.... hrmm... elementals, perhaps?


Two possible alternatives drawn from recent fair on the discovery/history/science channel:

1) Rogue waves, which can occur almost anywhere when regular waves randomly set up a particular oscillation pattern, or which occur more predictably when a strong current meets an upthrust of the ocean floor, like parts of the waters off South Africa. Rogue waves reach 80 to 120 feet, although the only known photographic evidence is of an 82 footer - still a monster that nearly swamped a supertanker.

2) Tidal waves, which while most notably associated with undersea earthquakes can also be caused by landslides. In fact, the larger recorded tidal waves in height have been the result of landslides or collapses.

So, on Oerth one would need to identify currents and upthrusts or seismically active or landslide prone areas to create regularly occuring conditions for giant waves.

Fireland would seem to offer earthquakes and landslides and with only open ocean, the waves could travel with nearly undiminished force over long distances. Not sure about the confluence of strong currents and upthrusts.
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