If a world was three times as large as Earth, how long would a day be?

[St Valamir]

I have struggled with some of the same pseudo-science questions myself. I always end up going back to what works, with perhaps a 5% variable. But since you explicitly stated it was for a fantasy world, as some folks already eluded to above, you can get away with anything you want. Hell, Jules Verne had people enjoying the idea of dinosaurs and cavemen at the center of the Earth, even when it was out of the question.

I suppose what I am trying to say is, I would rather read your well written story than attend a lecture on how it is not possible.

Call me crazy.

[DaronFraley]

John,

Since you said it is fantasy, I think you can do whatever you want. Great writing will suck the reader in, and as long as your descriptions don't get super technical, your readers will be fine.

But since I like this kind of thing, I wanted to share that I am of the opinion that we just don't know much about how planetary systems work. Science is inherently arrogant about where it stands at any moment in time. And then a new discovery comes along which changes everything, and all the models are re-written.

For example, I believe we will eventually find systems with binary stars, even perhaps complex quad star systems (like Mintaka), where life is possible under certain circumstances. What those circumstances are, we just don't know yet. The universe is a very big place.

Just my two cents.

[Sunlite]

I think one important question is: Do you have to relate your planet to earth?

Is there anyone in the story, who knows earth and can relate any aspect of it to the planet they are on?

If the characters in the story are native to the planet they will probably be adapted to it. IMHO they will have to handle days differently only if the length of the day get into real extremes - lets say less than 52 days per year.

[dworth]

"For example, I believe we will eventually find systems with binary stars"

The majority of star systems are in fact binary systems. Alpha Centauri is the nearest example. (okay actually it's a widely seperated trinary system as Proxima orbits the common centre of gravity at about 900 A.U).

Whether planets are able to form in such systems is open to debate, though it's thought possible that a closely orbiting binary could possibly have planets in wide orbits. Closer in, the complex interacting forces of multiple stars would make formation more difficult, and increase the likelihood that any planets that did form would either plunge into one star or another, or be flung out of the system altogether.

Edit: Looks like planets can form in binaries, given the right circumstances:

http://www.deepfly.org/TheNeighborho...-Binaries.html

[Worldwalker]

Originally Posted by Dodge

If every fiction writer and movie maker had to be a master of their project's genre we would have very few pieces of fiction entertainment. If facts are wanted then I would suggest documentaries.

We all have questions, even the experts.

Actually, that's almost of the definition of an expert. Experts ask (and find answers for) questions. Ignorant amateurs never ask questions; they make ignorant mistakes, and put mind-burningly stupid things in their books to afflict the rest of us. Smart amateurs fit somewhere in between.

I'd like to see more fiction writers and movie makers become, if not masters of their projects' genres, at least fundamentally aware of the basic facts and premises of those genres. "It's (fill in medium or genre here) so I can do as I like" doesn't cut it with me. If, for instance, we have futuristic space troopers making human wave attacks against enemies who have no long-range weaponry, rather than standing off and filling them full of holes/grenades/rockets/antimatter, I want to know why. It wouldn't make sense to a Marine today; why does it make sense for a Space Marine hundreds of years from now? If the answer is not provided (or if it's obvious that the answer is "because the filmmaker thought that's how it works" or "because he had this awesome enemy-eating-extra scene that he wanted to put in") that completely breaks the story for me.

In short, when you tell me something or show me something, it has to be consistent with what I know of the characters and the world -- and absent other knowledge, the default is reality. If something is inconsistent with reality, its presence must be logical, I must be aware of the logic, and the author must be aware of the ramifications of it. For example, if water flows uphill on alternate Tuesdays, that's going to affect everything from pouring buckets of water for horses to drink to whether tanneries' outflow is downstream or upstream of towns' water intakes (laws on where tanneries could locate were some of the first pollution control laws). Events and people don't exist in vacuums, and trying to pretend that they do produces fundamentally bad stories.

There was an excellent example in the old MMORPG Shadowbane. The developers created a quasi-medieval world, including walled towns which could be besieged, and expected the players, their function following the form, to behave like medieval warriors. The players, on the other hand, having been given de-facto phasers, cloaking devices, and transporters with magical names, used them accordingly, and our sieges bore no resemblance to their medieval counterparts; form followed function and we slipped invisibly into town, set up the summon chain to port in our friends, and nuked the living hades out of the place while the defenders sheltered on the walls. Someone, a lot of someones, didn't think hard about the situation. It appears that they believed that the trappings of the medieval world "just happened" and people adapted their behavior to conform with them (and expected us to do the same) rather than, as was the case, the outward appearance of the medieval world being a direct and inevitable effect of its technology, and, as we demonstrated, different technology would give totally different results.

Fiction not set in the modern, familiar world (SF, fantasy, historical fiction, etc.) is not, unlike what many amateurs believe, easier to write than its modern-realistic equivalent. It's harder. It's a lot harder. If you're writing something set in the present day, you and your readers all know everything they need about the fundamentals of society, its social interactions, and its technology. You don't have to explain much, if anything. For example, even if we personally don't own cell phones, we know how they work well enough to know that a phone has to be financially sound, has to be within range of a tower, and has to be contacting someone else with a viable phone of some type. We don't know that (and in the case of fantasy or SF, can't know that) about telepathy, crystal balls, or town criers; the author has to sneak that information in somehow. We would never write a story where the reader says "why didn't she just call him?" when it's obvious she could have, since it's equally obvious to us as writers.

Picking on MMORPGs again, in World of Warcraft there is a quest where someone wants you to take a letter to a person who is less than two minutes' walk away and says it's too far for her to go, and they haven't been in touch in decades. There might be a million reasons why that person from the farm couldn't travel two minutes to the adjacent town (yes, it's so close that in the real world it would be on the farm) but "it's too far" isn't one, and it rings false to the reader. It breaks the immersion, and makes us say "oh, that's just quest text; never mind what it says, just do it and get the experience points." We can deal with that in a game because, for most of us, it is "just quest text" and it could say "take this widget to Foozle and collect 2,000 experience" and we wouldn't care; it's the game mechanics, in this case the exp, that matters. But in a book or movie, what matters is the story; if the story is no good, then nothing is, because that's all that's there.

How much you tell your readers about any given situation depends on the story, its tone, the author, and so on. But the reader should never ask the equivalent of "why didn't she just call him?" Not every reader will ask, of course, even mentally, but enough will to think poorly of the book and the author, and they'll tell their friends; even the ones who don't ask that question will feel there's something wrong, and won't think as positively about the story as they otherwise would have. Everyone who says "well, that was lame" is a lost customer for your next story, and everyone who hears it is a sale that will never happen for this one. If you're writing for yourself, that might not mean much. But most of us want other people to read what we write (and most of those want them to pay for it) and therefore it's our readers, not ourselves, whom we need to satisfy. So, yes, if we're writing a genre story, we'd better be masters of our genre. If we're not, there are bargain bins ready and waiting.

[John Carroll]

*grin* This created a lot bigger response than I expected. The truth is, I don't know a lot about the physics of the universe or many scientific matters. I know many of the basics I've been taught in school and learned at museums, but that's about it. At the same time, I don't want my books to be completely implausable, improbable is okay, but not so much as to break the reader's attention.

I saw a quote that said "I'm willing to suspend my disbelief, not hang it by the neck until dead"

I've been reading the responses and considering them this weekend. Thank you all for the information and ideas. This is what I've decided:

The world is going to be about twice as large. I have dragons and like the idea of epic battles and vast unexplored regions.

That said, this is for my knowledge only . . . umm . . . shhhhhh, k? . . . anyway, I don't actually state that in the book. I say at one point that it's a "large world" and that it's a "vast world" at another point. I think that's vague enough to give the reader an impression that the world is larger than Earth without having to explain how large or justify scientifically how that can be.

As far as the days go, I've decided not to define that in the book either. In my mind, I'm making the days a bit longer, though I don't know how much. It will be proportionate day and night cycles (not quite the 32hrs of sleep DixieGal mentioned) and the characters won't know that it's different than Earth. . . . shhhhh again, k? . . .

ardeegee's information and links show me that there are definitely flaws with some of the things I've pictured. However, in the book, I give as little detail as possible while still describing it well enough for the reader to imagine themself there. (much like Stephen Lake suggested)

As far as the metals go, I need lots of precious metals and gems for treasure. There are dragons after all. I also make much of the rock more dense than Earth, which will add more mass to the world I believe. On this point, I'm hoping that only 2.5% of my readers know any details about world mass. It will be another thing I'm going to keep out of the book. The reader will know that there's lots of gold to be had, especially for dragons.

The good thing is that most of the book is centered on the characters; their interactions, feelings and adventures. The world they play in is defined only as much as it needs to be. I know there will be aspects that can be picked apart by scientists, and that's fine. I hope to learn from any details given, but it won't stop me from writing.

There won't be any water flowing uphill (even though I've seen it at Knotts Berry Farm). Nothing will be so unreal as to make the reader give up. It's a world of magic and fascination with awe inspiring sights. I believe what I've written is believable and interesting so far.

I like to know if what I'm writing is factual, plausable, imaginary, or just outright BS. *grin* I try to make it as factual or plausable as possible, but if a scientist points something out to me and I know they're right, I can at least admit that I'm trying to pull a fast one.

I really appreciate all of the information and ideas everyone gave me.

[AndrewH]

Originally Posted by John Carroll

The world is going to be about twice as large. I have dragons and like the idea of epic battles and vast unexplored regions.

...

I say at one point that it's a "large world" and that it's a "vast world" at another point. I think that's vague enough to give the reader an impression that the world is larger than Earth without having to explain how large or justify scientifically how that can be.

Why is it necessary to say that it's a 'large world'? Even with 2/3 our planet covered with water, Earth still has about 150,000,000 sq km of land. The United States, the third largest country in the world, only covers 6% of that. If I'm not mistaken, about 90% of the earth's land surface is still undeveloped.

Anecdote: I was about 10 years old, in the car with my parents driving from Montana to Oregon. Sometime during the 11-hour drive I asked, "If this is 'a small world after all', then why does it take so long to get anywhere?"

[Kemp]

Originally Posted by AndrewH

Why is it necessary to say that it's a 'large world'? Even with 2/3 our planet covered with water, Earth still has about 150,000,000 sq km of land. The United States, the third largest country in the world, only covers 6% of that. If I'm not mistaken, about 90% of the earth's land surface is still undeveloped.

Anecdote: I was about 10 years old, in the car with my parents driving from Montana to Oregon. Sometime during the 11-hour drive I asked, "If this is 'a small world after all', then why does it take so long to get anywhere?"

Though this is true, I'd suggest most folks don't really comprehend the size of the earth.

In the novel, an author says (hopefully weaved into the narrative) that the planet is about the size of Earth. People think, "Huh, okay," but maybe don't quite get the grand scope the author intended. To establish the feeling of massive spaces, it may or may not be necessary to have something simply different.

Of course, something different in and of itself is established when its known the land is not actually Earth, so how much other detail depends upon the author and the reader.

[Elfwreck]

Originally Posted by John Carroll

The world is going to be about twice as large. I have dragons and like the idea of epic battles and vast unexplored regions.

You can have vast, epic battles and huge unexplored regions on a planet 1/3 the size of ours. Especially if there's no fast travel like trains or airplanes. If most people are limited to ~30 miles/day, an expanse of a thousand miles is huge.

Earth still has vast, unexplored regions. Most of them are covered by ice. You probably need ice caps; you don't need the largest continents to be the coldest ones.

As far as the metals go, I need lots of precious metals and gems for treasure. There are dragons after all. I also make much of the rock more dense than Earth, which will add more mass to the world I believe.

The amount of metals *on the surface* and the density of rock that people have access to, doesn't necessarily directly connect to how much metal is under the crust. (Well. It sort of does, but you'd need to provide a lot more details than the average fantasy novel gives, for a geologist to be able to draw any conclusions about that. Having a lot more gold & gems than medieval Europe had floating around says absolutely nothing about the planet's composition.)

[John Carroll]

It's probably not necessary to say it's large and I don't compare it directly too earth, but . . . I want to give the reader the impression that it's a large world. Vast and large have positive connotations and I believe it adds to the atmosphere of a fantasy world. If a world is big then it can have more magic and adventures. There will be magical transportation as well, and dragons can fly great distances.

An epic battle can occur in a smaller world, but the population needed to sustain the warriors for epic battles needs to be large, especially if I want to add more civilizations. I also want vast uncharted territories with mythical beings and ruins and . . . well . . . stuff.

Basically, it's more about personal preference than need.

The amount of metals *on the surface* and the density of rock that people have access to, doesn't necessarily directly connect to how much metal is under the crust. (Well. It sort of does, but you'd need to provide a lot more details than the average fantasy novel gives, for a geologist to be able to draw any conclusions about that. Having a lot more gold & gems than medieval Europe had floating around says absolutely nothing about the planet's composition.)

Good call. That helps actually. Thank you.

[ardeegee]

As for surface metals:

http://blogs.discovermagazine.com/80...lanet-crasher/

[Steven Lake]

Originally Posted by AndrewH

Why is it necessary to say that it's a 'large world'? Even with 2/3 our planet covered with water, Earth still has about 150,000,000 sq km of land. The United States, the third largest country in the world, only covers 6% of that. If I'm not mistaken, about 90% of the earth's land surface is still undeveloped.

That's actually an excellent point. In fact, on a couple of occasions I've actually increased the land mass of the planet where 70-90% of it was land and the rest was water. However, the planet had just as much water as Earth has. The way I did that was to have vast quantities of the water stored underground in massive caverns filled with water. Sorta like natural storage tanks. The hydrological cycle worked just the same, however the water covered less of the total surface.

Which really, given the physics of water movement around the planet, including humidity, even if only 10% of the water was on the surface, you'd still have the same levels of humidity and the same types of weather, because the percentage of water in the air vs what's on the planet as a whole is minuscule. The average humidity around the world is about 60%. If you take that and do all the crazy math that goes with it (I'll spare you the algebra lesson) it accounts for about 0.001% of all the water on the planet.

So even with only 10% of the surface area covered in water, you could still maintain normal humidity levels in the air, and thus normal weather patterns such as what we see here on Earth. And yes, I'm nerd enough to have researched all this. Mostly because when I write sci-fi, I want it as scientifically accurate as I can where and when it's needed.

Originally Posted by Elfwreck

You can have vast, epic battles and huge unexplored regions on a planet 1/3 the size of ours. Especially if there's no fast travel like trains or airplanes. If most people are limited to ~30 miles/day, an expanse of a thousand miles is huge.

Agreed.

Earth still has vast, unexplored regions. Most of them are covered by ice. You probably need ice caps; you don't need the largest continents to be the coldest ones.

Again I agree. Case in point. I have one planet where I needed to do three continents for the series, and I have cooler northern regions, hotter southern regions, equatorial areas, islands, prairies, mountains, deserts, etc. Every planet will have a variety of environments on it, and if yours doesn't, things get a little awkward. Of course, as you pointed out, people with limited travel speed will see small geographical areas as massive.

The amount of metals *on the surface* and the density of rock that people have access to, doesn't necessarily directly connect to how much metal is under the crust. (Well. It sort of does, but you'd need to provide a lot more details than the average fantasy novel gives, for a geologist to be able to draw any conclusions about that. Having a lot more gold & gems than medieval Europe had floating around says absolutely nothing about the planet's composition.)

Excellent point! There's also something else people fail to consider. Gravity is inversely proportional to mass. The more heavy elements you have, the heavier the gravity will be. Why do you think Jupiter can be 11 times more massive than Earth and yet have only 2.5x's the gravity of Earth? It's because Jupiter has no heavy metals. The heaviest known elements in Jupiter's atmosphere are helium (10%) and hydrogen (90%) and given that we have elements as dense as plutonium on our planet, plus a massive sphere or iron at the planet's core, our gravity is naturally heavier.

If you go to Mars, our nearest neighbor, which is slightly over half the size of Earth, it has only about 1/3rd our gravity, and the only reason it has that is because of the very high iron and lead content on the planet. (it's not called the "red" planet for nothing) So there are a lot of factors that affect the gravity of a planet. The best thing to do in cases like that is simply to go with my first suggestion and avoid really getting into the details of the size, gravity, etc of the planet.

To the OP: As you can see, I do tons of research on any of the planets I write about, but even then less than 1% of the details that I work up on a planet go into the actual story. The primary reason for such detailed research is that I know what the boundaries are of the planet/environment I'm writing about and what I can and can't get away with. For example, if someone's living on a mars sized planet that has earth level gravity, they better sure as heck have a massive amount of heavy elements to make up for the extra gravity that would be required to create Earth like conditions. The inverse is true with larger than Earth planets, where heavy elements would have to be much, much rarer to allow for a lower than typical (ie, earth like) gravity.

[John Carroll]

Originally Posted by ardeegee

As for surface metals:

http://blogs.discovermagazine.com/80...lanet-crasher/

*grin* I bet the planet that crashed into Earth is the one that brought humans too.

In all seriousness, that's really interesting. Thank you.

[dadioflex]

You can have an Earth like planet that appears 3 or 4 or 5 times larger without having to do anything all that fancy.

Use smaller people.

[Worldwalker]

Something very important to remember: It wasn't all that long ago that maps had areas marked "here there be dragons." Nor was it all that long ago that travel from Europe to the Americas took months, few people ever went more than half a day's walk from their home town, and information moved at the speed of a horse. Look at the time the Crusades took to get from various parts of Europe to Jerusalem (even leaving out side trips to sack Byzantium). An island as small as England had strong nobles because information and orders took so long to go to and from the borders.

And that's with a planet that's mostly water. Reduce the water (or just arrange things to remove some significant deserts) and you can double the land area.

Incidentally, I would strongly recommend reading Jared Diamond's "Guns, Germs, and Steel". Not only is it a phenomenally good book, but it explains a lot about how civilizations grow and spread, and how things like available food plants and animals, climactic zones, etc., influence them. And it's a really good book. It's a ton of fun to read. I would consider it mandatory reading for a speculative fiction writer.