Post/Author/DateTime	Post
fuindordm 03-08-05, 06:16 AM	OK, since a bunch of people have been asking and to satisfy my own curiosity, here are some calculations on the moons of Eberron. Enjoy! You can trust me, I'm an astrophysicist. :D An interesting result: if all the moons were in conjunction they would exert about 80 times the gravity that our own moon does. If the moons were hollow, however, we wouldn't need to worry about coastal cities getting swallowed by the high tide. Maybe all the moons ARE hollow, and they're really the shells of eggs that Syberis laid before she died. Which dragon came from which Egg, I wonder? Our moon has a diameter of 2160 miles and a mean distance of 239000 miles, giving a diameter of 0.009 radians (about half a degree) on the sky. Zarantyr is enormous by comparison, with a diameter of 0.087 radians. It appears almost ten times as big! It's diameter is 0.57 the Moon's diameter, so if it's composition is similar it has about one-fifth the Moon's mass. It's also about sixteen times closer. This means that the force of gravity due to Zarantyr at the surface of Eberron is about 50 times that due to the Moon at the surface of the Earth. Strong tides indeed! I don't know what the relationship between the gravity and average height of tides is--it might not be a linear relationship. If these seems too high for you, then maybe this moon is hollow, with a Lost World inside? Zarantyr is an impressive sight, but for some reason it's not reckoned as bright as Barrakas. If you hold out your arm against the sky, Zarantyr would be about 2/3 the size of your closed fist. To put it another way, at 5 degrees of diameter, it covers 1/18 the distance between the horizon and the zenith. Olarune has a diameter only half the size of Zarantyr's, at 0.042 radians--still almost 5 times the size of the Moon. It exerts about 10 times the Moon's gravitational pull at the surface of Eberron. Therrendar has a diameter about 3 times the Moon's at 0.028 radians, and exerts about 5 times the Moon's gravitational pull. Eyre has a diameter of 0.023 radians, about 2.5 times the Moon's, and exerts 3.6 times the gravity. Dravago actually appears slightly larger than Eyre at 0.026 radians, and exerts 7.5 times the gravity. It's almosst as big as our moon! Nymm, Lharvion, and Barrakas all appear only slightly larger than our moon, and could eclipse the sun well enough to display the corona. They exert 0.45, 0.85, and 0.52 the Moon's gravity respectively. Finally, compared to the Moon's diameter of 0.009 radians the last four moons are (I'm tired of calculating their gravities): Rhaan has a diameter of 0.005 radians. It's described as looking more like a bright star, which isn't quite right given the data. Jupiter looks like a bright star, but the disc becomes visible even with a pair of good binoculars. Jupiter's diameter is a little less than one arcminute, about 30 times smaller than the Moon's half-degree. Sypheros has a diameter of 0.006 radians. It's described as dim and hard to find, which must mean that it's surface brightness is not much greater than that of the night sky. Of course, with all these other moons and rings around the background light is much higher than we're used to on Earth. Aryth has a diameter of 0.0045 radians Vult has a diameter of 0.007 radians. So the smallest-appearing moon is orange-red Aryth, but none of them are so tiny as to be star-like. Ben
MarkB 03-08-05, 06:59 AM	Thanks, Fuindordm - that's excellent work, and really helps me visualise how the moons would appear in Eberron's sky.
okaynowa 03-08-05, 07:50 AM	Thanks again, Ben. Your numbers mean I did the math right. The relatively low levels of brightness (magnitude) of these nearby moons would probably have to be attributed to surface composition, wouldn't they? I seem to recall reading somewhere that the night sky in Eberron isn't too much brighter than Earth's...
Host of Angels 03-08-05, 07:56 AM	Random thoughts: I guess that a lot of the time the moons will be in opposition to each other and much of the gravitational effects on the tides will cancel out. A major conjuction, with all its attendent and disasterous tidal effects must be extremely rare. So maybe we do not need to invoke non-physics to deal with the tidal issue (i.e. hollow moons). Maybe.... On another note - the night sky will be incredibly bright. In fact a dark night sky would be virtually impossible, and were it to happen it would scare the pants of the population of Khorvaire. Star gazing would also be significantly more tricky. Given the prominence of the moons, the various cultures would place great significance on the moons - I think I shall be playing up the presence of the moons in the sky in future. Thanks Fuindordm - a very useful application of your astrophysics...
AvonRekaes 03-08-05, 07:59 AM	I dunno, the ring of glowing dragonshards might have something to do with the light polution. Thanks again for the calculations. Just knowing that the closest moon is that much bigger than ours, it really makes a difference in how I picture Eberron's night skies..
Gez 03-08-05, 10:09 AM	Thanks again for the calculations. Just knowing that the closest moon is that much bigger than ours, it really makes a difference in how I picture Eberron's night skies.. With lots of shiny moons, yet as dark as Earth's own nights, like the twin suns of Tatooine that mysteriously project a single shadow? :P
fhilbrandt 03-08-05, 10:54 AM	From yet another physicist: The nearest moon would br retrograde and the next is in a nearly geosynchronous (sp?) orbit. If you downloaded the Eberron moons and calendar WE, it does not agree with Mr. Baker's Dragonshard. The WE list Nymm as the moon with the shortest period at exactly 28 days. I'll post the WE periods if I get a chance. This may be a moot point if the Eberron system does not follow conventional physics.
fhilbrandt 03-08-05, 11:26 AM	Per the Web Enhancement: Nymm - 28 days Sypheros - 35 days Therendor - 42 days Rhaan - 49 days Olarune - 56 days Eyre - 63 days Vult - 70 days Zarantyr - 77 days Aryth - 84 days Dravago - 91 days Lharvion - 98 days Barrakas - 105 days Different order than the dragonshard.
fuindordm 03-08-05, 11:38 AM	I'm glad everyone enjoyed that calculation. Bad news for the tides. I looked the formula up on the web, and the height difference between high and low tide goes as mass/distance cubed. So assuming similar composition to our moon, Zarantyr has 0.193 the Moon's mass, and is 16.7 times closer--so the tides would be 900 times higher than the ones we get on Earth. The difference between high and low tide in Hawaii is about 1.25 feet, so we're talking tides of 1125 feet, just from that moon. The interference effects from all the other moons will certainly damp this out some, but the dominant moon is going to preserve a good chunk of this effect. If, on the other hand, it were hollow with a shell, say 20 miles thick (about the thickness of the Earth's mantle)...it would only have a tenth the volume and probably a much smaller fraction of mass due to the increasing density towards the core. The tides would come down to a still high but more managable level on the order of tens of feet. When you add on the effect of the other moons, I think you could hand-wave a situation where the tides are similar to the Earth's most of the time but occasional conjunctions cause severe coastal flooding. Probably it's easier to assume that near the ring of Syberis different physics holds sway, that gravity is a purely local phenomenon and ends when you get, say, 100 miles off the ground. Still, it's a fun thought exercise, and a talented Eberron astronomer might be able to deduce that different rules hold sway up there by calculating the periods of the moons. The brightness problem is another issue altogether! Ben
Tom McCarthy 03-08-05, 12:45 PM	If one takes the Eberron calendar tool as accurate, it doesn't allow you to have a night with all the moons new. It does allow all the moons to be full at once, and this happens many years in the past, on the first day of the year when the first dragonmark appeared, and every 7500 years or so before and after that. Coincidentally, a couple of items on the Eberron timeline are 7500 years apart; they just don't also line up with the appearance of dragonmarks. For a truly curious question, in the magical physics of Eberron, would a thirteenth moon be accommodated by: i) 13th moon is never ascendant ii) lengthen the year by 28 days to allow all 13 to be ascendant 28 days iii) shorten the months/ascendant periods to less than 28 days to allow all 13 to be ascendant in a year iv) the 13th is ascendant at the same time as one or two others or some other change I'm not imagining ?
Beleriphon 03-08-05, 01:53 PM	If one takes the Eberron calendar tool as accurate, it doesn't allow you to have a night with all the moons new. It does allow all the moons to be full at once, and this happens many years in the past, on the first day of the year when the first dragonmark appeared, and every 7500 years or so before and after that. Coincidentally, a couple of items on the Eberron timeline are 7500 years apart; they just don't also line up with the appearance of dragonmarks. For a truly curious question, in the magical physics of Eberron, would a thirteenth moon be accommodated by: i) 13th moon is never ascendant ii) lengthen the year by 28 days to allow all 13 to be ascendant 28 days iii) shorten the months/ascendant periods to less than 28 days to allow all 13 to be ascendant in a year iv) the 13th is ascendant at the same time as one or two others or some other change I'm not imagining ? Or maybe Eberron is the 13th "moon" and nobody thinks about it that way.
ekomega 03-08-05, 03:29 PM	fuindordm, thanks for putting all of that up. I almost got my classical dynamics textbook out for the tides equation and was about to do the other calculations this morning. I'm interested to know how you figured out about the gravitational forces. Did you just assume the same gravitational constant or something else? There are several ways to do it, but I couldn't think of one to give exact information without iterating a lot. Also, the moons don't have to be hollow. They could be made of different materials that are lighter, and this could also give reasons for their different colors. Although I think with the Ring of Siberys and regular meteoric activity, the moons would be pounded to diffuse grey dust just like our moon. The tides question bothers me a lot. Keith said in the article something about conjunction of moons and ancient Xen'drik ruins becoming uncovered from the low tide. How much of a tidal decrease would that be? 40 feet? 100 feet? If the tide ever changed 100 feet, that would be intense for all of Eberron. Conventional ideas like "ships" and "docks" and "coastal cities" wouldn't be able to exist if the tides were very severe, even 20 feet. If the tide did regularly cycle up and down 20 feet, that means the water level would change 3.333 feet per hour (assuming a 12 hour tidal cycle, high to low to high, like on earth). How would you dock a boat? You'd have to plan arriving at port in daily increments to make sure your ship could actually dock or to keep it from beaching. And the coasts would be significantly different than anything we're used to. It's insane. Clearly, the answer is "magic".
ieattrollsforbreakfast 03-08-05, 04:35 PM	I've done a quick picture showing the relative sizes of the moons of Eberron compared with our own moon (in the top middle). You can find the image here: http://www.geocities.com/ieattrollsforbreakfast/ebmoons.txt Zarantyr really is enormous!
Thaddeus P. Swift 03-08-05, 04:55 PM	Well, the problem with the sky being too bright may be partially offset by eclipses. If Zarantyr is only 14,000 miles away from Eberron, it seems like it will be in Eberron's shadow a lot, thus there will be frequent lunar eclipses. Personally, I think Keith messed up his numbers by a factor of ten. If you increase the distances by a factor of ten, then Zarantyr is about the same size as our moon in the sky. Four of the other moons are significant in size and the remaining 7 are only 3-5 times as big as stars. Zarantyr has 67% as much lunar pull as the moon, and when all the moons are in conjunction the tide is only slightly higher than an earth tide. For my campaign, this is what I choose to do..
Naudachu 03-08-05, 06:09 PM	I know very little (if anything) about this, but its has been said before that Eberron is much larger than Earth. Would this affect the calculations, gravity?
Purple Yin 03-08-05, 06:35 PM	its larger because its ment to have miles of open area in the crust empty, making up khyber, so the overall mass of the planet can be assumed to be the same (or else things like 'how fast a falling object falls' and 'how much muscle mass a bone can support before breaking'.. that kinda stuff would be off.. but probably only by a small amount)
ekomega 03-08-05, 07:00 PM	If we consider the map on the back of the ECS as the entire circumference of Eberron, then we can get somewhere. The map is 16.25" wide, with 5" = 5000 miles. This makes the circumference of Eberron 16250 miles. This makes Eberron's radius 2586 miles. Earth's equatorial radius is approximately 3950 miles, making Eberron 43% as large as Earth. Based on this, Eberron is a lot smaller than Earth. If Eberron is this much smaller than Earth, than the size of the moons is even more significant. The size of the moons is almost unbelievable. Another question that is brought up is the location of the Ring of Siberys, and if it could actually exist around Eberron. I think I'll take the "factor of 10" approach, since that makes more sense than the "everything is magic" approach. The magic approach fails to explain things like why Eberron has the same gravity as Earth without becoming ridiculous.
zambuka 03-08-05, 07:04 PM	There is an alternate way to look at the moons. There are 13 moons, each one representing one of the planes. We don't really have to worry about the physical size of the moons if we look at them as windows into their associated plane. More than just a manifest zone these moons are direct gateways to the appropriate plane of existance. The phases of the moons can be the result of these windows rotating away from the prime material and then back again as a natural part of the cosmic harmonics that drive Eberron and its universe. This way we don't have to worry about the overwhelming tides these many moons would cause, or any other issues of physical size. The larger "moon" can now get as close to Eberron as it wants without any serious gravitational issues. Manifest zones could be the result of ancient times when the orbits were a little unstable and the moons briefly touched Eberron leaving a tenuous link to the planes. We can say that it is the ebb and flow of the Ring of Syberis that gives Eberron its tibes and maybe even influences its seasons. The ring also protects Eberron, to a degree, from things coming through these windows. Basically I suggest removing physic from discussion on the moons of Eberron. Look for a more fantastic explaination that fits better with Eberron than it does with our world..
ekomega 03-08-05, 07:50 PM	...making Eberron 43% as large as Earth. Based on this, Eberron is a lot smaller than Earth. I actually fudged that a little bit. Eberron is actually 28% the size of Earth. The last statement was surface area, not volume. So Eberron is significantly smaller than Earth.
Ponderosa 03-08-05, 07:55 PM	Basically I suggest removing physic from discussion on the moons of Eberron. Look for a more fantastic explaination that fits better with Eberron than it does with our world. I would have to disagree. First of all, it makes sense for us to view Eberron the same way we view our own in these kinds of natural phenomenom. (sp?) Plus, if you correct the numbers as Thaddeus P. Swift suggested, then it all works out very neatly. I don't think it's a coincidence that the numbers Keith provided (when fixed) make this complex series of moons function just like our own, especially the way that they can occasionally conjoin to create abnormally high or low tides. I don't want to delve into the astrophysics of Eberron either, but for this example, it works perfectly.
stone_dog 03-08-05, 09:52 PM	I actually fudged that a little bit. Eberron is actually 28% the size of Earth. The last statement was surface area, not volume. So Eberron is significantly smaller than Earth. But that isn't the whole of the map. Just the bits that are important to the campaign world as a whole. There are landmasses north of Khorvaire and South of Xen'Drik that are only glimpsed at on the map on the inside covers and they might be pretty big. Look at the Pacific Ocean after all. That thing is pretty huge and there is hardly anything in most of it. It isn't all that hard to imagine that there is vast stretches of water to the left and right of that map.
patsmiley 03-09-05, 12:24 AM	Given what little I know on the subject I would have to say that Eberron would be significantly larger than Earth, else the gravitational effects from that many moons would have ripped the planet apart long ago.
Vharuck 03-09-05, 01:33 AM	1. It is a separate universe. 2. The laws of physics are only ones which we have viewed in this universe. 3. Different universes may exist because of the multiple differences between them at certain intervals of time (beginning counting as an interval) 4. The gravitational constant is a number we have noticed using physics. Dunno why I numbered them, but physics may work out the speed of light and the gravitational constant just so perfectly that Eberron's gravitational field functions exactly similar to Earth's. Or it's creepy dragon magic, and when the Siberys ring goes away all the moons will crash into Eberron.
Masterful_Norg 03-09-05, 02:04 AM	I for one like the idea of the insanely high and low tides and will be keeping them. The docks will start at the points where the tides are highest and have multiple levels that progress downward into the ocean so that timing wouldn't be such a big deal.
fuindordm 03-09-05, 05:09 AM	fuindordm, thanks for putting all of that up. I almost got my classical dynamics textbook out for the tides equation and was about to do the other calculations this morning. I'm interested to know how you figured out about the gravitational forces. Did you just assume the same gravitational constant or something else? There are several ways to do it, but I couldn't think of one to give exact information without iterating a lot. I just assumed the moons have the same density as our moon, so that their mass is proportional to their volume. The force of gravity is proportional to m/R². You can play with different moon compositions too, but this would change the mass by a factor of a few at most. And in answer to another question, the mass of Eberron doesn't play a role in the influence of the moons on Eberron. Ben
MarkB 03-09-05, 05:26 AM	Here's an idea for explaining the inconsistencies in brightness and tidal influence of the moons: What are commonly seen as the moons are actually massive projections - optical illusions around the far smaller real moons at their centres, generated by magic but not magical in nature, so that they appear the same even to True Seeing. So what is the nature and purpose of these projections? Dragonmarks. Each moon is actually a massive, natural dragonmark that forms a part of the Draconic Prophecy, which is why sages and dragons study them so assiduously. The illumination they provide is not reflected sunlight but their own glow, which also explains their ability to wax in luminosity for 28 days per year. They do maintain phases which generally match their orbital position, but in unusual circumstances such as planar conjunctions, a moon might alter its phase out of sequence.
nyysjan 03-09-05, 05:31 AM	or the moons might be hollow
HunterViper 03-09-05, 08:00 AM	And in answer to another question, the mass of Eberron doesn't play a role in the influence of the moons on Eberron. Ben Okay, I was actually going to post about viewing size of the moons but was beaten to it. Actually the planets density does matter, because of the Roche limit. without making assumptions, just using the map in the cover, the planet Eberron would have a density of 7.9, the equivalent of soft steel, much denser then our Earth, and for the first moon to exist where it does, it needs to have a density of almost 6.5, still much more then Earth, to revent being ripped apart. Increase the size of Eberron, and you decrease the density of the planet but increase the density needed to stay where it is, but remain the same if the distance is propotionally changed as the cube root of the radius of the planet. This would make the tides really bad, to the point that islands like Hawaii could come and go on a monthly basis. Just goes to show you that you have to add a bit of magic in there or else ignore laws of physics. I go with the magic, because with the information that we know the system is unstable and dangerous. I prefer to go with mysterious and mystical. -HV
ekomega 03-09-05, 01:15 PM	But that isn't the whole of the map. Just the bits that are important to the campaign world as a whole. There are landmasses north of Khorvaire and South of Xen'Drik that are only glimpsed at on the map on the inside covers and they might be pretty big. Look at the Pacific Ocean after all. That thing is pretty huge and there is hardly anything in most of it. It isn't all that hard to imagine that there is vast stretches of water to the left and right of that map. This is true, and I'm sure there is more ocean, but it's the only map we've got. Also, I used the "equatorial radius" which is the middle of the map on the book, which more than accounts for any North/South extras. This is because flat maps inherently distort spherical surfaces. The equatorial radius is the most accurate, or at least the largest one. And remember that the map is 16.25 inches wide, but probably only 11 inches tall (it's not near me). The map would have to be square and Eberron would need 5000 more miles of North/South to have a square map, which would be an even more distorted map. But if we take the map to be square, and assume the north/south length has an additional 5000 miles, that's plenty of extra ocean for everyone.
Vharuck 03-09-05, 02:02 PM	And in answer to another question, the mass of Eberron doesn't play a role in the influence of the moons on Eberron. Ben It does, as the equation for gravity is G(m1+m2)/(r^2)
Naudachu 03-09-05, 02:41 PM	Personally, I think Keith messed up his numbers by a factor of ten. If you increase the distances by a factor of ten, then Zarantyr is about the same size as our moon in the sky. Four of the other moons are significant in size and the remaining 7 are only 3-5 times as big as stars. Zarantyr has 67% as much lunar pull as the moon, and when all the moons are in conjunction the tide is only slightly higher than an earth tide. For my campaign, this is what I choose to do.. So, this is probably too simple, but does this mean we could shrink this image relative moon sizes (http://www.geocities.com/ieattrollsforbreakfast/ebmoons.txt) by 10 and have a plausible picture of the night sky (on that fictional night when all the moons are full and in the sky together)? I have a feeling there is more math involved, but please enlighten us. Thanks.
Purple Yin 03-09-05, 03:51 PM	but then even the furthest moon and smallest moons would be ten times as far away, and the gravitational pull expressed towards eberron would be even smaller... maning an asteroid impact could potentionally make the moons go rogue.
Thaddeus P. Swift 03-09-05, 04:58 PM	So, this is probably too simple, but does this mean we could shrink this image relative moon sizes (http://www.geocities.com/ieattrollsforbreakfast/ebmoons.txt) by 10 and have a plausible picture of the night sky (on that fictional night when all the moons are full and in the sky together)? I have a feeling there is more math involved, but please enlighten us. Thanks. Yes, that's right. 10 times as far away means it would appear one-tenth of the diameter in the sky.
Thaddeus P. Swift 03-09-05, 05:06 PM	but then even the furthest moon and smallest moons would be ten times as far away, and the gravitational pull expressed towards eberron would be even smaller... maning an asteroid impact could potentionally make the moons go rogue. Well, sure. An asteroid could knock our moon out of its orbit next week. Anything's possible. Of course, there may not be any asteroids in the Eberron universe. Gravity may not be the force that makes the moons circle, maybe it's aether or magic or destiny or maybe the moons are living creatures. Anything's possible.
scwolf 03-09-05, 09:42 PM	So, this is probably too simple, but does this mean we could shrink this image relative moon sizes (http://www.geocities.com/ieattrollsforbreakfast/ebmoons.txt) by 10 and have a plausible picture of the night sky (on that fictional night when all the moons are full and in the sky together)? I have a feeling there is more math involved, but please enlighten us. Thanks. You woudn't want to shrink the whole image by 10. The one labeled Luna, which is just Earth's moon thrown in for reference, shouldn't be shrunk. And if you want an Eberron night sky picture, you'd have to remove it entirely.
fuindordm 03-10-05, 04:58 AM	It does, as the equation for gravity is G(m1+m2)/(r^2) Actually, it's m1 times m2 rather than plus. The force of gravity causes the same acceleration on all objects regardless of their mass; the acceleration due to the influence of a moon at the surface of Eberron is given by G M_moon/D^2, where D is the distance between the center of the moon and the surface of Eberron. The height of the tides are similarly dependent only on the acceleration due to the moons, not on the absolute value of the force between the moon and Eberron. Good catch on the Roche limit too, HunterViper--I never studied planetary physics personally. And it's all too easy to say "it's just magic". If you say that then you can make the moons do whatever you want. It's obvious there's some magic going on because of their 28-day ascendancy, which clearly has nothing to do with reflected sunlight. Their influence on tides, however, implies gravity or something kind of like it. Khorvaire has a tradition of rational thought evident in the ECS book, and these are the kind of questions that Morgrave university scholars could be asking as well. If they're smart enough to figure out how Eberron's gravity works, and realize that the moons don't follow the same rules--this will teach them something new about magic. I still like the hollow moon theory myself, but the idea of smaller moons inside a magical projection is also pretty interesting. Ben
okaynowa 03-10-05, 08:24 AM	Forgive me if this has been covered elsewhere (that phrase should be a standard acronym by now), and forgive me for astrophysical naivete, but... is it even possible for moons orbiting the same planet to have wildly different phases? It's a nice image, but (and I'm only a student of literature, here) it feels counterintuitive. If it is possible, what basic explanation am I overlooking?
fhilbrandt 03-10-05, 09:57 AM	I asked Keith about the differences between the Web Enh. calculators periods for the moons and the distances listed in the dragonshard article. His responce: that he didn't write the calculator or choose the distances but his first cut would be that 'our world physics doesn't apply.' The Rings being highly magical, etc. As to the previous question, Orbiting in the same plane has nothing to do with the phase of the moon. It's determined by the relative angle to the sun. In other words, if the two (or more) moons are near each other in the sky, then they'll have about the same phase.
MarkB 03-10-05, 11:13 AM	I still like the hollow moon theory myself, but the idea of smaller moons inside a magical projection is also pretty interesting. Actually, I'm going back to 'hollow' myself, because it fits my new Crazy TheoryTM: The moons are actually progenitor-dragon-eggs. The thirteenth moon didn't simply disappear millenia ago - it hatched; and Sypheros is just now starting to crack. Of course, this means that somewhere out there, a baby progenitor-dragon is growing to maturity without its parents (how long would a progenitor-dragon's wyrmling phase last, I wonder), and within just a few centuries it will acquire a sibling. What happens if they come looking for their mommy?
Siran Dunmorgan 03-10-05, 11:42 AM	Looking at the relative moon size image mentioned above (http://www.geocities.com/ieattrollsforbreakfast/ebmoons.txt), I'm struck by the effectiveness of the idea of really huge moons... it's very fantasy, very other-world imagery; take this example: http://www.memory-alpha.org/en/wiki/Image:RigelVII2254.jpg I believe that's about the right size for Zarantyr, yes? So this image could be similar to something we'd see on Eberron, perhaps a Valenar stronghold on the edge of the Blade. —Siran Dunmorgan
Purple Yin 03-10-05, 02:52 PM	his first cut would be that 'our world physics doesn't apply.' is it just me, or does that line bug anyone else? so ligh under normal conditions travels on curved paths? a heavy object falls the fastest? solubility is not dependant on bonding, but a predetermined function? good greif! this statement really has to be defined clearer. what ruled dont apply? what is altered? all the laws interact to form the perceived universe, so altering one alters them all. by leaving it wide open like that we may as well be describing absolutes in kythri!
ekomega 03-10-05, 03:55 PM	Regardless of what Keith said, our world physics has to apply regarding gravity. As I mentioned earlier, here are plenty of reasons gravity has to work the same way, regardless of the moons. Look at non-magical flight (by creatures), look at the Feather Fall spell, look at the amount of time it took the airship to crash in WotVB, look at the damage from falling, etc. Gravity has to operate the same way, otherwise there is a lot of things to be changed in Eberron from many other books, rather than just one Dragonshard article. You can't just just throw statements like that around, and expect people to rationalize these things that don't make sense. The fundamentals of DnD are based on real world things, like physics, and it means a lot to just say "oh, it doesn't work that way". lots of things are dependent on it working "that way".
Urko 03-10-05, 04:15 PM	Yeah, I'm disappointed in Hellcow's response, but not particularly surprised. When the world maps first became available people asked a lot of questions about the planet's size and what kind of distortion was used in creating the maps - how this affected the actual size of the continents, etc. Hellcow basically responded that he's not a simulationist, but more interested in story telling. And, to my thinking, he has done a fantastic job at that, so I'm not going to get too bent out of shape when he doesn't want to delve too closely into the astrophysics of the world. On the one hand, I find the "it works by magic" line to be a copout, but on the other hand, just how much detail can one person work out? I prefer more realism, as apparently a lot of others do, but I'm willing to cut Hellcow some slack - his cultural details have always been fantastic. Which means that those of us who aren't satisfied with "it works by magic" need to come up with some solutions ourselves. I had been holding off thinking about the moons too much until the long-awaited astrology Dragonshard appeared. It gives a great place to start from, and there's no doubt that all the cultural fluff is fantastic. I personally will be tweaking the spots where it fails the reality test. For example, I think the idea of multiplying all of the orbital distances by ten is a good one - it lessens the problem of the tides, as well as making actual dark nights possible on Eberron, not to mention the bizarre orbital periods. Speaking of which, I think they need to be lined up with the orbital distances - shortest period is the closest moon and so on. I haven't decided which list to change. Rearranging the orbital periods means reworking the calendar and rearranging the orbital distances means reworking the apparent sizes. Any thoughts? By the way, I'm not sure I agree with the argument that all phases would be in snyc. Each moon would rise at a different time of night, so a waxing and waning moon could theoretically be in sky at the same time (one in the extreme west, one in the extreme east), but be illuminated from opposite sides due to their respective positions relative to the sun. Never having lived on a planet with multiple moons, this is not an argument I'd stake my life on, but the logic works for me (even if I may not be explaining myself well). Any astronomers who can further enlighten us?
Siran Dunmorgan 03-10-05, 04:44 PM	Regardless of what Keith said, our world physics has to apply regarding gravity... look at the damage from falling, etc. Gravity has to operate the same way, otherwise there is a lot of things to be changed in Eberron from many other books, rather than just one Dragonshard article. You can't just just throw statements like that around, and expect people to rationalize these things that don't make sense. The fundamentals of DnD are based on real world things, like physics, and it means a lot to just say "oh, it doesn't work that way". lots of things are dependent on it working "that way". Well, aye—but by that measure, physics is already out the window in Dungeons & Dragons. I am looking at the damage from falling—DMG p. 303—and I see a basic rule of 1d6 damage per 10 feet fallen, to a maximum of 20d6. Now, in the real world, damage from falling isn't linear: it's proportional to the square of the distance fallen, since damage per se is based on the kinetic energy absorbed by the body at the end of the fall, so the progression should be something like:Distance Damage -------- ------ 10-20 1d6 21-30 2d6 31-40 4d6 41-50 8d6 51-60 16d6 61-70 32d6 and so on. But it's not. Your damage from falling 70 feet is only 7d6. So right there, right in the falling damage rules, I can see that the force of gravity in a Dungeons & Dragons environment doesn't have much to do with real-world physics. Dungeons & Dragons is a set of game mechanics intended to resolve uncertain events in a narrative setting. There are simplifications and simplifying assumptions made as concessions to gameplay everywhere, even where the "real world" rules are easy to apply. Dungeons & Dragons is a collection of game mechanisms intended to resolve uncertain events in the context of a narrative, not as a physics simulation. What if, for example, I told you that in a Dungeons & Dragons environment, light travels instantaneously from point to point? What would that change about the game? What if I told you that in a Dungeons & Dragons environment, gravity only applies for about a hundred kilometers from the surface of the gravitating body, and drops off rapidly thereafter, and that the moons were actually held in orbit by an astral "silver cord" similar to that seen in the astral projection spell, only considerably mightier? What would that change about the way you play the game?[1] —Siran Dunmorgan [1] If the first thing that comes to mind is that you should be able to de-orbit a moon by using a Githyanki-style silver sword the size of Scion Sound, you're on the right track: thinking of it as a narrative device, and only secondarily as physics.
MarkB 03-10-05, 04:49 PM	By the way, I'm not sure I agree with the argument that all phases would be in snyc. Each moon would rise at a different time of night, so a waxing and waning moon could theoretically be in sky at the same time (one in the extreme west, one in the extreme east), but be illuminated from opposite sides due to their respective positions relative to the sun. Never having lived on a planet with multiple moons, this is not an argument I'd stake my life on, but the logic works for me (even if I may not be explaining myself well). Any astronomers who can further enlighten us? In real-world terms, you are indeed correct. A moon whose orbital position puts it at the zenith (due south if you're in the northern hemisphere, directly overhead from the equator) at midnight will be full, one which is on the horizon at that time will be waxing or waning (depending on whether it's to east or west), and a new moon will be visible between early morning and late evening, in nearly the same direction as the sun. Given Eberron's cosmology, there are likely to be moons in several of these stages visible at the same time.
Masterful_Norg 03-10-05, 07:12 PM	Sometimes I use the formula E(g)= m*g*h or in other words Gravitational Energy = [mass (of object in Kg)] * [strength of gravity on planet or planetesimal in question (roughly 9.8 N on earth, 1.6 N on the moon and 10 N on planet "Multiplying by ten is easier")] * [height (distance from the ground in meters)]... I then divide that number by what I think is appropriate to determine dammage. I understand that this is linear so perhaps I could go by E(k) = 1/2m*v^2 but then I would have to work out the velocity at impact and I'm too lazy (my players fall from high places a lot). So yeah D&D physics describes a world which functions quite differently from the way we think our world functions. If you find that excuse a lame then you're next option would be too add a force which keeps everything functioning in harmony with what you believe to be the "correct" state of reality. This force could be "magic" or it could be something else. If you find that lame as well you might just want to do something like making water heavier to counter the high tides issue or perhaps the moons radiate a special form of energy (that can't penetrate organic matter) which causes the hydrogen bonds in the water (but nothing else) to become stronger so that the ocean contracts as it rises. Though strictly speaking change one of the alleged "constants" in the universe (such as the gravitational constant or the charge of a proton) and the result is a world in which life as we experience it can't exist, so I think magic is our best option. Consider the fact that the moons are obviously magical or at least related to the magical dragonmarks. Just suppose that the more magical a significantly large amount of mass becomes the less it is effected by the gravity of non magical material (though equally affected by the gravitation of magical material) and vice versa. Perhaps this magical effect could be related to the existance a new particle called the Deus Ex Machinon. I ascribe to the idea that magic is just really advanced technology (read Arthur C. Clark) and that what is commonly described as the paranormal (a misnomer cause if it exists its normal) is perfectly allowable and possible (quantum mechanics anyone?), but I can hardly see how that enters into this conversation (I just like saying it). In fact no one can rightly say that the universe does indeed have laws or that we can even define what those may be if any exist. As Einstein put it the universe is like an unopenable clock to which we can only apply models that describe the means by which it works but never identify the real mechanisms responsible for the things we see it do. However I will grudgingly admit that science has been pretty successful at microwaving my pizza thus destroying many of the valuable flavanoids but providing me a quick way to have lunch. So if you don't like any of these options then you may as well go jump off a cliff and receive 7d6 dammage. ;) Edit: V^2 = Vo + 2AD D = distance from start V = velocity at specific time or position Vo= starting velocity A = acceleration (just set this to 10 m/s) Just in case you want to do falling dammage the harder way.
ekomega 03-10-05, 10:46 PM	Well, aye—but by that measure, physics is already out the window in Dungeons & Dragons. I am looking at the damage from falling—DMG p. 303—and I see a basic rule of 1d6 damage per 10 feet fallen, to a maximum of 20d6. Now, in the real world, damage from falling isn't linear: it's proportional to the square of the distance fallen, since damage per se is based on the kinetic energy absorbed by the body at the end of the fall, so the progression should be something like... I meant that in the ECS they never indicate that the damage from falling is different from that described in the DMG. Since the DMG is based on "real world physics" therefore the ECS must also be. The argument wasn't that real world physics and DnD physics are the same, it was that DnD physics are set up a certain way based on real world physics, and nothing has indicated that Eberron is different except for Keith's last article and statement. Cleary damaged sustained from falling is far more complicated than solely looking at kinetic energy. Simplifying an example to the point that it is worthless does not prove an argument. As for light traveling instantaneously from point to point, then darkness spells would not make a difference. The light could travel directly to your retina. That's only one example. Changing fundamentals of the universe does have an impact on the game, no matter how you look at it. Just because you can't think of how it would change things doesn't mean someone else can't or that it's not a bad idea for them to say stupid things and make stupid rulings. Is it so hard for them to come up with something that is consistent, rather than throwing the "it's magic" line around? They could've just given qualitative descriptions of the moons instead of made-up data and everyone would be happy and there'd be no problems. That was my original assertion (in another thread), that this was too much info that is unnecessary.
scwolf 03-10-05, 11:12 PM	From what I remember Spelljammer did some really odd things with how gravity was defined that still mantained an internal consistancy. It shouldn't be too hard to adapt to ECS, if needed.
Thramzorean 03-10-05, 11:38 PM	I for one like the idea of the insanely high and low tides and will be keeping them. The docks will start at the points where the tides are highest and have multiple levels that progress downward into the ocean so that timing wouldn't be such a big deal. Actually a very wide tidal range would work well with the depictions of Sharn. The docks sticking out from the cliff face would be floating, thus the whole rationale of having the cranes and warehoused perched up so high or tacked onto the cliff face rather than down by the water's edge.
fuindordm 03-11-05, 09:45 AM	Hum! First, some physics: Falling damage, like ballistic damage, is generally proportional to the kinetic energy of the impact but also highly variable. It can be considerably mitigated by spreading the impact out over a longer period of time (thus the Tumble skill, which would represent allowing your body to collapse and roll onto the floor over a period of say, 0.5 seconds rather than 0.01 seconds for a hard landing), or by a bit of luck with the surface you happen to land on. However, the kinetic energy that you have at the time of impact *is* directly proportional to the height at which you start falling. From that standpoint 1d6 per 10 feet is reasonable; the failure of the system to model reality comes in because there's a certain threshold where the body's vital systems completely fail. In a VP/WP system, with falling damage going directly to WP, 1d6 per 10' and allowing tumble checks to convert some portion to subdual damage would probably be pretty realistic. And as for the whole "it's just magic" thing--despite being a physicist by trade this doesn't bother me. Some changes, such as Siran's suggestion that gravity simply ends a few thousand feet above the earth but behaves normally below it, certainly can be accomadated in a fantasy world. I personally have no problem saying that the moons of Eberron are sheparded along their orbits by the magic of the ring of Syberis, and that their brightness is also a function of this magic. That's a pretty cool bit of flavor, it really is! Some changes are harder to accommodate, however. If light propagated instantaneously, compasses and lightning wouldn't work the same way. The wave nature of light is part and parcel of the whole theory of electricity and magnetism. Eberron is founded on a magical, but recognizable, version of our own world, and the players have a right to expect that everyday phenomena work in much the same way--this means that at least within the boundaries of their experience then the basic rules of physics should be the same. At least in the absence of active magic violating these rules. Changing the fundamental constants and rules of physics, even by a little bit, quickly leads to a universe that is unrecognizable, and more often than not uninhabitable. Eberron and Khyber, at least, have to support those rules. The tides are a little problematic because they do imply the existence of something like gravity that acts on those scales, but one can get around this any number of ways, by invoking the influence of the ring, hollow moons, the moons actually being nonphysical, etc. I still emphasize that the scholars of Eberron will be asking these questions too, and the rational answers you as the DM provide can lead to interesting plot hooks. The night sky is another problem altogether. If you multiply the distances by ten you get a night sky not terribly different from our own, where the closest moon appears about the size of Luna and the others are all considerably smaller and dimmer (except, presumably, Barrakas which is unnaturally bright given its size and distance). You get a less fantastic sky (but you still have the Ring), but dark nights are more plausible. If you keep the distances as is, the nights would almost never be dark--I would be inclined to say that the most common midnight light condition is more like our twilight. One can actually see pretty well on a full moon, and at half-phase the biggest moon would provide 50 times the illumination. The evolution of low-light vision hardly seems necessary! Personally, as cool as a many-mooned sky is I think I prefer the darker sky, with telescopes and observatories and scary midnight encounters. It's all about the atmosphere you want to engender in your games. Ben
Gez 03-11-05, 10:16 AM	But that isn't the whole of the map. Just the bits that are important to the campaign world as a whole. There are landmasses north of Khorvaire and South of Xen'Drik that are only glimpsed at on the map on the inside covers and they might be pretty big. True, it doesn't show the Frostfell nor Southern Xen'drik. And maybe they're an unknown fifth continent deep in the south, an Eberronian Antarctica...
greedo99 03-11-05, 10:49 AM	wow....it seems everyone who plays Eberron is now an astrophysicist. Does that mean i should put my application in at NASA? :thinks:
Host of Angels 03-11-05, 11:29 AM	Ah yes - the death of the author. What Keith says now is irrelevant. The article has been published and is now canon. Baring retraction by WOTC, the world of Eberron has these mighty moons. At least it does if we choose to interpret the data given (size and orbital radius) using our own physics laws and formula. And who is to say that we need to do that? Personally I will be taking the line used in the source book with reference to planes of existance - if the needs of the story demand it, then as GM I make it so.
Purple Yin 03-11-05, 12:17 PM	wow....it seems everyone who plays Eberron is now an astrophysicist. Does that mean i should put my application in at NASA? :thinks: dont forget to mention you play a level 6 bard!
Siran Dunmorgan 03-11-05, 01:06 PM	I meant that in the ECS they never indicate that the damage from falling is different from that described in the DMG. Since the DMG is based on "real world physics" therefore the ECS must also be. The argument wasn't that real world physics and DnD physics are the same, it was that DnD physics are set up a certain way based on real world physics, and nothing has indicated that Eberron is different except for Keith's last article and statement. Cleary damaged sustained from falling is far more complicated than solely looking at kinetic energy. Simplifying an example to the point that it is worthless does not prove an argument. I don't believe it's an oversimplification. The only other principal factor is which part of the body strikes first, but for any fall more than about fifty meters, it doesn't make much difference: it's enough to shatter any bone in the body.[1] The reason it's different in Dungeons & Dragons is because people in Dungeons & Dragons don't have internal organs per se; they have hit points, levels, and abilities. As for light traveling instantaneously from point to point, then darkness spells would not make a difference. The light could travel directly to your retina. That's only one example. Changing fundamentals of the universe does have an impact on the game, no matter how you look at it. Apologies: :embarrass I should have said 'the speed of light is infinite'; I didn't mean to imply that the light does not traverse the intervening distance, only that it does so infinitely quickly. The point I was going for is that for millenia people in the real world did assume an infinite speed of light, and it made no difference in their ability to cognate about the world. We still generally treat the speed of light as infinite for all but the most esoteric applications[2]. Just because you can't think of how it would change things doesn't mean someone else can't or that it's not a bad idea for them to say stupid things and make stupid rulings. Aye. As it happens, I know how it would change things: an infinite speed of light would collapse time, so that the entire universe happened in an instant. While this would be potentially amusing from the perspective of an external observer, it wouldn't make the universe very playable. My point is that making assumptions about quantitative physics in a Dungeons & Dragons environment is an odd thing to do on its face. My understanding is that you're upset because the issue of the positions and gravities of the moons are inconsistent with the extent to which the rest of the setting 'harmonizes' with itself: they've done such a good job of putting together a 'believable' world up to this point, why introduce such a jarring inconsistency? Well, as far as I can tell, the answer is because Wizards of the Coast in general and Keith Baker in particular wanted a setting that looks good. See my example from Star Trek, above, for the sort of effect they were going for. They wanted to have a gigantic moon filling the sky: it's an awesome image, and more than any other single factor, Eberron is about image, or attitude, if you prefer. If you want it to be about physics, well, check the math for the changes in density the moons would have to have to cause more rational tides, for example. It's quite possible for the moons to have mithral, rather than iron, cores which would lower their mass considerably without having to hollow them out. We already have mithral in the setting: let's use it. Or use the planes; in conventional occult terms, our moon is a tremendous presence on the Astral; perhaps this is even more true in situations where astrology does in fact apply? In these terms, our moon is held in orbit by the realization of the Thirty-second Path, astrally manifest between Malkuth and Yesod. On Eberron, the presence of multiple moons and the Ring of Siberys leads to a re-assignment of the Correspondences of each Sephirot. For example, we can safely assert that the correspondences of Yesod are ruled in Eberron by Zarantyr; the realizations of the Paths would have to change accordingly, but working out the tables for it would take more time than I have right now. My point is that even in the so-called 'real' world, conventional, mundane physics isn't the only available perspective. Is it so hard for them to come up with something that is consistent, rather than throwing the "it's magic" line around? They could've just given qualitative descriptions of the moons instead of made-up data and everyone would be happy and there'd be no problems. That was my original assertion (in another thread), that this was too much info that is unnecessary. They didn't say "it's magic:" they said that "our world physics doesn't apply," which is not the same thing, and isn't really telling us anything we didn't already know. They gave us the sizes and distances precisely so that someone would do the calculations and come up with the notion that the sky put on an awesome show around Eberron. No data revealed—and I am using this term in the sense of divine revelation—should be considered wrong unless errata is issued for it. Asking questions of the designers is the fantasy equivalent of physical experimentation in our world. A lot of people didn't like it when the Michaelson-Morley experiment disproved luminiferous ether: it was a tremendous, near-lethal blow to the 'fluid' models that pervaded physics in the eighteenth and nineteenth centuries. But they didn't generally declare the new physics "stupid" and refuse to accept it.[3] —Siran Dunmorgan [1] There are other factors involved than 'merely' the distance of the fall, yes, but all that those other factors do is change the kinetic energy. If you fall far enough—about nine hundred fifty meters, more or less—your velocity will stabilize at a bit over fifty meters per second, due to resistance from the air around you, so you won't be gaining any more energy simply from falling. The 'hardness' of the surface you land on is simply a way of speaking about how much of your kinetic energy is lost to that surface, and not absorbed by you. Then there's your mass: this changes from person to person, of course, but again, all it does is affect your kinetic energy. The direction you land can be important, e.g. landing on your head is generally more instantly lethal than landing on your knees, but the actual damage, to wit, the actual structural deformation of the body, is, in fact, dependent on the absorbed kinetic energy, so I'm happy to stand by my original assertion. [2] Chip design pops to mind here; speed of light is a limiting factor on how fast information can get from one component to another. Very long distance communications systems are another: we know it takes a noticeable amount of time to get a signal to a communications satellite and back. Radar depends on a principle of self-interference related to the time it takes a signal to return. But the vast majority of people in our world live their lives as if the speed of light were infinite, and don't generally care that it isn't. [3] Well, Tesla did, but he was in a profound minority.
Purple Yin 03-11-05, 01:42 PM	why would an infinite speed of light collapse a universe? (im a biologist, not a physicist)
Brastan 03-11-05, 01:42 PM	I will interject at this point to say you are all fools! We are held to the surface of Eberron by the great dragons themselves. Khyber pulls us down and Siberys pulls us up. Khyber is closer so its pull is stronger. Eberron provides us with a place to stand. Obviously the tides are cause by Eberron breathing not the distant(or not so distant) moons. They rise and fall in rhythm with the breath of the great wyrm. Realistically though I find how the moons are now being presented a bit off putting. Just having 12 moons would be quite a sight even if they were smaller and farther removed. I had always assumed that they were ruffly the size. I had thought that the closest and brightest moon would be the one that corresponds to the month. All of the others would be further out on their orbits and would have minimal effect on Eberron. Oh well.
Siran Dunmorgan 03-11-05, 01:50 PM	why would an infinite speed of light collapse a universe? (im a biologist, not a physicist) Because everything would happen all at once. Finite velocity is what 'smears' the events of a universe out through time. —Siran Dunmorgan
ieattrollsforbreakfast 03-11-05, 01:50 PM	Theres no reason that the night sky of Eberron cannot be dark and yet still have the enormous moons described. It all comes down to the brightness of the moons, and people here seem to be assuming that the moons will reflect the same amount of light as our own. From the ascendence patterns, we can already see this is an unsafe assumption. So, perhaps the same magic that keeps the moons ascendent dims them the rest of the time. So, Zarantyr or Olarune may be large, but they are dim, ghostly worlds, unlike our own moon.
Siran Dunmorgan 03-11-05, 02:10 PM	I will interject at this point to say you are all fools! We are held to the surface of Eberron by the great dragons themselves. Khyber pulls us down and Siberys pulls us up. Khyber is closer so its pull is stronger. Eberron provides us with a place to stand. Obviously the tides are cause by Eberron breathing not the distant(or not so distant) moons. They rise and fall in rhythm with the breath of the great wyrm. Realistically though I find how the moons are now being presented a bit off putting. Just having 12 moons would be quite a sight even if they were smaller and farther removed. I had always assumed that they were ruffly the size. I had thought that the closest and brightest moon would be the one that corresponds to the month. All of the others would be further out on their orbits and would have minimal effect on Eberron. Oh well. Yeah. Just try getting your kid's Science Fair judges to accept the kid's poster about how earthquakes are caused by Poseidon striking Gaea with his trident. Although, in restrospect, they took it pretty well... especially since she had a "backup" poster about the life-cycle of brine shrimp. :D Back on topic, the concept of ascendancy apparently has little to do with closeness as such. It's not so much that it's magic as it is a mystery. —Siran Dunmorgan
fhilbrandt 03-11-05, 02:25 PM	FYI, Keith's reply to another's comment re. the moons: The actual distance's are just something pulled out of his ... ur, ... somewhere. The only point he was trying to make was the order of the moons orbits, and their connection to the dragonmarks and Eberron's version of astrology (or is it lunology, in this case) If the actual numbers don't work for you, CHANGE THEM. You're THE DM!!! Remember rule 0. PS, I've posted a question to Master Hellcow asking the relative postion of the Rings to the various moons.
Purple Yin 03-11-05, 07:00 PM	Because everything would happen all at once. Finite velocity is what 'smears' the events of a universe out through time. but why does the maximum velocity of electromagnetic waves determine the rate a universe moves along the temporal dimention?
Siran Dunmorgan 03-11-05, 07:20 PM	but why does the maximum velocity of electromagnetic waves determine the rate a universe moves along the temporal dimention? Well, that's exactly it: we actually define "one second of time" as the time required for a certain number of e/m-based events to occur[1]. If e/m radiation were infinitely fast, there would be no time. —Siran Dunmorgan [1] Specifically, 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of cesium-133; the SI unit definition.
Purple Yin 03-11-05, 08:14 PM	:bigeyes: *protectivly hugs nice, soft, transcription factors to chest*
HunterViper 03-11-05, 09:04 PM	Well, that's exactly it: we actually define "one second of time" as the time required for a certain number of e/m-based events to occur[1]. If e/m radiation were infinitely fast, there would be no time. —Siran Dunmorgan [1] Specifically, 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of cesium-133; the SI unit definition. Truw, in a way, but we defined those times first and then redefined them by what happens during them. So, time, at least the construct that our minds use, exsits outside of what happens in them. It is only the mind that creates that idea. The speed of light may affect time, but not perceived time, as as the universe is by definition everything, there is no out side to see a change in everything at once to a slow drawn out time. -HV
Masterful_Norg 03-11-05, 11:30 PM	In other words if you doubled the speed of light everything would seem to be the same and the change in light's velocity would be undetectable. Now objects may be limited regarding the speed which they are allowed to travel, but supposing you could contract space[1] you might be able to do so in order to create the appearance of moving at a velocity faster than that of light by any abitrary value depending on the extent to which you were able to contract the region of space in question. Technically you don't go anywhere, its the space in between your origin and destination that changes shape. Your other option would be to quantum teleport yourself via the method used by the teams at the University of Innsbruck and the US National Institute of Standards and Technology. Again no mass is actually transfered just information in the form of quantum states, but you could very well construct an exact replica of a person or this faberge egg I hold in my hand instantaneously at some arbitrarily long distance. Isn't non-locality just wonderful? [1]When we say the universe is expanding we are actually refering to the expansion of the space in which the universe is situated. This expansion has no upper speed limit allowing galaxies to appear to be moving apart at what appear to be superluminal speeds.
MavrickWeirdo 03-12-05, 11:49 AM	The tides question bothers me a lot. Keith said in the article something about conjunction of moons and ancient Xen'drik ruins becoming uncovered from the low tide. How much of a tidal decrease would that be? 40 feet? 100 feet? If the tide ever changed 100 feet, that would be intense for all of Eberron. Conventional ideas like "ships" and "docks" and "coastal cities" wouldn't be able to exist if the tides were very severe, even 20 feet. If the tide did regularly cycle up and down 20 feet, that means the water level would change 3.333 feet per hour (assuming a 12 hour tidal cycle, high to low to high, like on earth). How would you dock a boat? You'd have to plan arriving at port in daily increments to make sure your ship could actually dock or to keep it from beaching. And the coasts would be significantly different than anything we're used to. It's insane. You are overlooking 2 things. 1. Tidal ranges are localized. Minas Basin in the Bay of Fundy, Canada has measured tidal ranges of over 50 feet after astronomical influences reach their peak. (Their average tidal range is 32 feet) 2. Astronomical influences do not reach their "peak" very often. The uncovering of "ancient Xen'drik ruins" may only happen once every hundred years. By the way earth's tidal cycle is 12 hours 25 minutes. :)
atanhel 03-12-05, 11:52 AM	and every day it gets longer, thanks to our own moon ;)
ieattrollsforbreakfast 03-12-05, 12:06 PM	A thought occured to me yesterday. What if the Ring of Siberys has a negative gravitational effect? The rings itself is made of dragonshards with special magical resonance, so what if a large portion carry some sort of reverse gravity effect? This would diminish the effect of the moons on the tides, and may also account for the proximity of the moons to Eberron.
MarkB 03-12-05, 12:39 PM	A thought occured to me yesterday. What if the Ring of Siberys has a negative gravitational effect? The rings itself is made of dragonshards with special magical resonance, so what if a large portion carry some sort of reverse gravity effect? This would diminish the effect of the moons on the tides, and may also account for the proximity of the moons to Eberron. Nice idea. And maybe the composition of some of the moons makes them more susceptible to this counter-force, which accounts for the discrepancies between the order of the moons and their orbital period as given in the planar calculator.
ekomega 03-12-05, 12:51 PM	What is the Ring of Siberys made of exactly? Siberys shards? I know people have tried to fly up there before, and failed, but the vast amount of shards just floating around up there would make spending lots of money on the problem worth it. Also, I think it has been mentioned that the Ring of Siberys can be seen in the night sky. How bright does everyone think it is? With all the bright space objects out there, I'm surprised it ever gets dark on Eberron.
Purple Yin 03-12-05, 01:53 PM	A thought occured to me yesterday. What if the Ring of Siberys has a negative gravitational effect? The rings itself is made of dragonshards with special magical resonance, so what if a large portion carry some sort of reverse gravity effect? This would diminish the effect of the moons on the tides, and may also account for the proximity of the moons to Eberron. thats assuming the 13 moons where captured in orbit around eberron after siberys died (assuming the dragons myth is true).
Masterful_Norg 03-12-05, 03:55 PM	Here's an Idea! What if the moons and perhaps the ring are partially composed of superconducting material and their powerful Meisner fields[1] repel them from Eberron with its ordinary electromagnetic field. [1]The size of a Meisner field (a form of magnetic field with no north or south pole that repels all ordinary electromagnetic fields) is preportionate to the amount of light flowing through it. Electrons will flow through a superconductor providing that conditions are met for them to become Cooper pairs. (All of this according to David Radius Hudson.)
Purple Yin 03-12-05, 05:31 PM	Here's an Idea! What if the moons and perhaps the ring are partially composed of superconducting material and their powerful Meisner fields[1] repel them from Eberron with its ordinary electromagnetic field. [1]The size of a Meisner field (a form of magnetic field with no north or south pole that repels all ordinary electromagnetic fields) is preportionate to the amount of light flowing through it. Electrons will flow through a superconductor providing that conditions are met for them to become Cooper pairs. (All of this according to David Radius Hudson.) you did what with who now?
fuindordm 03-13-05, 09:30 AM	A thought occured to me yesterday. What if the Ring of Siberys has a negative gravitational effect? The rings itself is made of dragonshards with special magical resonance, so what if a large portion carry some sort of reverse gravity effect? This would diminish the effect of the moons on the tides, and may also account for the proximity of the moons to Eberron. That's a nice thought. Maybe syberis dragonshards have the same function as Beanworld's twinks. :-) Ben
Masterful_Norg 03-13-05, 05:40 PM	Purple Yin, A superconductor is a material through which electricity can travel without being converted into another form of energy such as heat. When electricity travels through a normal conductor it produces an electromagnetic field however when electricity travels along a superconductor it produces a meisner field which repels against electromagnetic fields. That's all you really need to know. Sorry about the confusion.
RadicalTaoist 03-13-05, 09:50 PM	You know, with all these size discrepancies and gravitational problems...how do we know for sure that Ebberon is the planet and these other bodies are the moons? Who's orbiting who?
fuindordm 03-14-05, 05:27 AM	You know, with all these size discrepancies and gravitational problems...how do we know for sure that Ebberon is the planet and these other bodies are the moons? Who's orbiting who? That's another good point. The Earth and Moon actually orbit each other around their center of mass, which is at a point about one-quarter of the Earth's radius below the surface of the Earth. That point is what follows the Earth's orbit around the Sun, and if you watched the Earth from a rocket above the north pole while following the Earth's orbit, you would see the Earth making slow, one-month circles around the orbital path. Very big planets can have lots of moons because the moons are much smaller than they are. But if the Earth had a dozen moons of this size, I think the dymanics would grow too complicated to be described as a series of orbits. When the moons passed close too each other they would interact and change each other's orbits, and pretty soon some of them would either escape or crash into the Earth. Three or more bodies of comparable mass just can't achieve a stable orbit. So again, the moons of Eberron either have little mass or can't be held up by gravity.
Masterful_Norg 03-14-05, 11:35 AM	If this were the case then would the ring of Syberrys orbit the center of mass or just Eberron? Might 3 or more bodies of comparable mass maintain a stable orbit if Syberrys was holding them together? Could 3 or more bodies of comparable mass create a stable (not necessarily predictable) orbital system if each had a field of force which kept them a minimum distance from one another so as to prevent collisions? Perhaps our estimation of Eberron's size makes a stark contrast with its actual size? Has anyone considered that Eberron's atmosphere may be magnifying the moons more than the earth's atmosphere?
MarkB 03-14-05, 11:55 AM	Has anyone considered that Eberron's atmosphere may be magnifying the moons more than the earth's atmosphere? Unlikely. The Dragonshards article didn't say "the moons appear to have X diameter", it listed the diameters as a given fact.
MavrickWeirdo 03-15-05, 10:34 PM	Random thoughts: On another note - the night sky will be incredibly bright. In fact a dark night sky would be virtually impossible, and were it to happen it would scare the pants of the population of Khorvaire. Star gazing would also be significantly more tricky. Wouldn't that depend on how far away the stars are? :cool:
Masterful_Norg 03-16-05, 12:21 AM	Perhaps brightness is relative and the eyes of the people living on Eberron are less sensitive to light because there is a great deal more of it. Perhaps the sun is far enough away (or dark enough) to reduce the illumination of the moons to something that everyone else finds exceptable. Personally I actually imagined some of the moons looking about twice the size of a beach ball extended at arm's length. Can anybody tell me what the effect of one moon that size would have? Would any of the phases make sense if some of the moons orbited each other or did figure eights around Eberron and one or more other moons?
GrayS 03-16-05, 03:57 AM	I am also one of those who like the numbers to make sense. I'm not a physicist by trade, but I like to think I know my ups from my downs as-it-were. So the fact that Hellcow's numbers just don't make sense in a physical universe bugs me no end. Personally, I will probably be using the x10 rule espoused here until something better comes up. It makes the Eberron night sky slightly more boring (the same apparant size as Earth's moon & smaller + the rings of course), but at least the world "works" using standard physics. ------------------------------------------------------ However, just 'cos I want to "throw a cat amoungst the pigeons", here's a thought that I don't recall seeing mentioned anywhere yet: Who said Eberron was a sphere? :eek: Who's to say it's not actually FLAT....? :D ...and then the map on the inside covers of the ESC is actually perfectly accurate? It just extends off the edges of the page until you reach (dramatic music cue) "the edge of the world"..........
Purple Yin 03-16-05, 08:31 AM	in FR (dont hit me!) there were discrepencies that cropped up due to the different versions-1, 2, 3, 3.5... anywho, they explained the discrepancies in things stated as facts as beiong things stated by the inhabitants as facts. so the astronomers of khovore may be wrong, or the dragons may be wrong, or whoever is the one giving us the facts...
ekomega 03-16-05, 03:36 PM	Perhaps brightness is relative and the eyes of the people living on Eberron are less sensitive to light because there is a great deal more of it. Perhaps the sun is far enough away (or dark enough) to reduce the illumination of the moons to something that everyone else finds exceptable. That would work too, except that the illumination distances and visibility and everything aren't changed from the DMG, or the races aren't modified from the PHB. If the moons are super bright, like others have said, and the sky is really bright, maybe the Eberronians can't see as well, and their vision takes in a lot more light. But then they wouldn't have low light vision and nobody but dwarves, hobs, and a few others would have darkvision. You'd have to change a lot more of the other rules (like how far can you see in a cave with a torch) if you change something important like that. I haven't paid much attention to the moons in my campaign, but the idea of a bunch of gigantic moons is cool. I've settled on both the 10x distance, and that physics in space in Eberron is different. I want a bad guy to build an eldritch weapon and fire it into the Ring of Siberys to knock some shards down to Eberron, so I guess it doesn't matter how gravity works since it's an eldritch machine.
Tom McCarthy 03-16-05, 04:11 PM	Eberron isn't flat, as the migration pattern of humans was once indicated by Hellcow to have included going east and hitting the western edge of Khorvaire. It might be a cylinder, but that doesn't really simplify things. Easier to say the moons have no gravity and are unaffected by gravity (i.e. they're not really moons).
darkthought 03-16-05, 04:24 PM	Eberron isn't flat, as the migration pattern of humans was once indicated by Hellcow to have included going east and hitting the western edge of Khorvaire. It might be a cylinder, but that doesn't really simplify things. Easier to say the moons have no gravity and are unaffected by gravity (i.e. they're not really moons). OOOooo... I like that idea. They're the shadows of the planes as they orbit Eberron. They have some unknown magical mechanic behind it. I know that higher dimensional objects can cast some funky shadows in 3 dimensions, so why not the planes that orbit the material plane do the same? The shadows need not have any relation to positions of the planes in respect to the prime material.
Purple Yin 03-16-05, 06:03 PM	an entity existing in more than three dimentions, being perceived in three dimentions, would in fact be a three dimentional cross section of said multidimentional entity. take a human for example. we function in four dimentions (though we only have limited control over the first three, and none over the fourth) at any one point in time (so we are only perceiving each other in a three dimentional context, not four) we are three dimentional objects- a mere cross section in our overall existance. i know nothing of shadows, but if the other planes penetrated the material, like studs piercing the ear of the universe, they would still be three dimentional spheroid (or some other 3D object that looks circular from the viewpoint of planet-side) objects (possibly composed of exotic matter, defying all non-mystic logic).
darkthought 03-17-05, 01:02 AM	an entity existing in more than three dimentions, being perceived in three dimentions, would in fact be a three dimentional cross section of said multidimentional entity. take a human for example. we function in four dimentions (though we only have limited control over the first three, and none over the fourth) at any one point in time (so we are only perceiving each other in a three dimentional context, not four) we are three dimentional objects- a mere cross section in our overall existance. i know nothing of shadows, but if the other planes penetrated the material, like studs piercing the ear of the universe, they would still be three dimentional spheroid (or some other 3D object that looks circular from the viewpoint of planet-side) objects (possibly composed of exotic matter, defying all non-mystic logic). You misunderstand me. I know that if we were to directly look at a 4 dimensional object, it would look like a 3 dimensional object. But the *SHADOW* would be something nifty. http://www.fortunecity.com/emachines/e11/86/tourist4b.html That is a simple description. Look at some of the pictures of the hypercube shadow (4 dim cube). http://www.math.union.edu/~dpvc/math/4D/rotation/welcome.html That has a few animations of a hypercube rotating, and what the shadow would look like. What I'm saying is that the planes cast shadows that are the moons. The moons are not the planes themselves.
fuindordm 03-17-05, 06:05 AM	Eberron isn't flat, as the migration pattern of humans was once indicated by Hellcow to have included going east and hitting the western edge of Khorvaire. It might be a cylinder, but that doesn't really simplify things. Easier to say the moons have no gravity and are unaffected by gravity (i.e. they're not really moons). If you really want to get funky, it could be a torus. That's what you get if you join the east and west edges of the map, then the top and bottom as well. Of course, the continents on the inside would have a very interesting view... Ben
Child Of Winter 03-17-05, 02:31 PM	Just a quick question Mr.fuindordm According to my calculations, Eberron's diameter is appoximatley twice as much as Earth's. If we assume Eberron has a similar composition of Earth, will gravitational strength be proportionally larger than Earths? Assuming that the people on Eberron's surface don't notice the increased G's and the fact everyone weighs four times as much as we as DMs and PCs assume they do(if my proportionality is correct, which it probably isn't), would this extra gravity have any effect on the height of the tides when it comes to trying to keep them realistically low? Heh heh, I'd hate to be anywhere but the highest peaks when spring tide comes. Of course I'm kind of fuzzy and not very confident with my understanding of Physics as of now, but I'm learning!
Purple Yin 03-17-05, 04:46 PM	how did you calculate the diameter?
fuindordm 03-18-05, 03:08 AM	Just a quick question Mr.fuindordm According to my calculations, Eberron's diameter is appoximatley twice as much as Earth's. If we assume Eberron has a similar composition of Earth, will gravitational strength be proportionally larger than Earths? Assuming that the people on Eberron's surface don't notice the increased G's and the fact everyone weighs four times as much as we as DMs and PCs assume they do(if my proportionality is correct, which it probably isn't), would this extra gravity have any effect on the height of the tides when it comes to trying to keep them realistically low? Heh heh, I'd hate to be anywhere but the highest peaks when spring tide comes. Of course I'm kind of fuzzy and not very confident with my understanding of Physics as of now, but I'm learning! Mass goes as r^3, so if you double the diameter you get eight times the mass and eight times the surface gravity; people would weigh eight times as much and would look very different. This would have the side effect of reducing the tides, which arise because of the perturbing effect of the moons on the Earth's gravitational field. Changing the surface gravity of Eberron isn't really an option; you can't alter it that much without making the species unrecognizable. Ben
nick012000 03-18-05, 08:03 AM	Mass goes as r^3, so if you double the diameter you get eight times the mass and eight times the surface gravity; people would weigh eight times as much and would look very different. This would have the side effect of reducing the tides, which arise because of the perturbing effect of the moons on the Earth's gravitational field. Changing the surface gravity of Eberron isn't really an option; you can't alter it that much without making the species unrecognizable. Ben No, because gravity if proportion to the mass an inversly proportional to distance squared. The net effect, if density remains constant, is that gravity is direcly proportional to distance.
fuindordm 03-18-05, 08:50 AM	No, because gravity if proportion to the mass an inversly proportional to distance squared. The net effect, if density remains constant, is that gravity is direcly proportional to distance. Oops. Thanks for the catch, you're absolutely right. So if Eberron were twice as big as the Earth then it would have a surface gravity of 2g. Ben
Masterful_Norg 03-18-05, 11:14 AM	If you really want to get funky, it could be a torus. How about a torus knot or even a mobius strip? darkthought, That's some interesting stuff right there. In fact, couldn't hyperdimensional physics (physics in consideration of additional spacial dimensions (not physics with more than 4 variables)) be used to describe pretty much explain the aberrant behavior of anything? One could say that spacial distortions created by the magical power of syberrys's ring bend the light of the moons such that the images appear closer and in a different possition (even to the point of appearing in front of the ring). This is of course assuming that the information Keith gave us was according to Eberron's astronomers as opposed to being the undeniable truth. Another hyperspacial possibility is that because of the magic of the moons circular troughs of varying slope at points along their paths have been permanently etched into the curvature of space so that if we take the rubber sheet analogy of General Relativity the ball (moon) speeds up and slows down in accordance to the slopes of the troughs in question. However, to this add the fact that the circular troughs look a lot like the Escher staircase sketch called "ascending" where the stairs form a circle but continue to go upward. One could presumable fall down these stairs forever and that's exactly what I intend by this metaphor except imagine a circular luge course which accomplishes the same effect. So in other words a fixed circular track of empty space around eberron has a strong localized gravitational force which constantly pulls at varying strength to account for some orbital abnormalities. The eternal downward slope effect may be accountable for by a ripple in space coming up behind the moon to make it fall forward through the track. Perhaps the moon associated with the mark of death imploded into a very small nuetron star and became a black hole or black ring?
Purple Yin 03-18-05, 12:32 PM	ooo... nifty!
darkthought 03-18-05, 01:39 PM	How about a torus knot or even a mobius strip? darkthought, That's some interesting stuff right there. In fact, couldn't hyperdimensional physics (physics in consideration of additional spacial dimensions (not physics with more than 4 variables)) be used to describe pretty much explain the aberrant behavior of anything? One could say that spacial distortions created by the magical power of syberrys's ring bend the light of the moons such that the images appear closer and in a different possition (even to the point of appearing in front of the ring). This is of course assuming that the information Keith gave us was according to Eberron's astronomers as opposed to being the undeniable truth. Another hyperspacial possibility is that because of the magic of the moons circular troughs of varying slope at points along their paths have been permanently etched into the curvature of space so that if we take the rubber sheet analogy of General Relativity the ball (moon) speeds up and slows down in accordance to the slopes of the troughs in question. However, to this add the fact that the circular troughs look a lot like the Escher staircase sketch called "ascending" where the stairs form a circle but continue to go upward. One could presumable fall down these stairs forever and that's exactly what I intend by this metaphor except imagine a circular luge course which accomplishes the same effect. So in other words a fixed circular track of empty space around eberron has a strong localized gravitational force which constantly pulls at varying strength to account for some orbital abnormalities. The eternal downward slope effect may be accountable for by a ripple in space coming up behind the moon to make it fall forward through the track. Perhaps the moon associated with the mark of death imploded into a very small nuetron star and became a black hole or black ring? Heh, glad I could help. :D That way, the 10x distance modification on the moons would still work, and the size and lighting descriptions from the Dragonshard would still work. Everybody's happy! The magic from the rings could also be the reason why no airship has left Eberron and into space, and why nobody has really Spelljammed into Eberron. The rings create a warping effect that makes it nearly impossible to go either way. Sort of like the Great Barrier in the center of the galaxy in Star Trek. :) Magic could be another one of the universal forces in Eberron too... Electromagnetic, Weak and Strong Nuclear, Gravity, and now Magic. I'd like to call it Arcanic Energy. :) I'd think it would be the trump card, falling somewhere between the electromagnetic and nuclear, with the caveat that it could overpower any of the other forces.
ieattrollsforbreakfast 03-19-05, 10:38 AM	Well, I finished some calculations last night regarding my Siberys anti-gravity theory, and the results seem to work quite well :) I modelled Eberron as being exactly the size of the Earth, and had all the moons and Eberron itself with the density of the Earth. I then modelled the ring of Siberys as a scaled down version of Saturn's rings, though not quite as wide. Ignoring any positive gravitational effect of the ring itself, the calculations showed that to bring tides down to the levels of Earth (but still with extremes when all the moons line up), the anti-gravity need not be too great. In fact, if a reverse gravity effect with infinite range is responible, roughly only 1 in 4500 Siberys shards in the ring need to be enchanted with this effect. To have Earth-like tides at the extreme and almost non-existant tides at other times, 1 in 350 need to be enchanted in a similar way.
Liane the Wayfarer 03-20-05, 12:19 PM	Would it make sense that every time one of the reverse gravity shards is ejected, a more "normal" Siberys shard falls to Eberron?