*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.