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How do you go about creating a fictional planet and have most of the geological specifications right? We all know how our planet reacts to the moon and other forces in our solar system, but what about a planetary system that we've never encountered before.
That's my problem. Creating a map of a fictional planet wouldn't be the hard thing. that hard part would be in creating it that is believable to the reader when you proceed to describe the way the oceans currents flow, or the way the terrain on the surface affects the weather.
Any ideas on how to proceed with the correct description of planetary forces on a fictional world?
My current computer is a little slow, and can't read the menu bar on the site, but I've been on it before (I'm pretty sure it's this one...). Anyway, it helps you make a scientifically sound planet from scratch. It has a lot of information and articles for exactly what you're trying to do.
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If you post specific issues here, maybe someone can answer them. Miriel's link is an even better way though I think; it's got resources specifically for this!
Regarding currents: note that earth currents go against rotation at the equator, then curve north/south depending on hemisphere, and make a circle. East of a cold current at subtropical latitudes, you find desert. The only other deserts in the world are Gobi (very far from oceans) and some of Antarctica. Just a neat observation.
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One of the basic tenets of the natural sciences is "uniformitarianism." Basically, the way things work now is the way they've always worked. And if it works one way here, it works the same way everywhere.
The natural processes on your fictional planet should work the same way as the processes on earth, unless you add some factor that alters them (magic, no planetary rotation, no water, cooled planetary core, etc). Plate tectonics, ocean currents, and weather patterns will all vary depending on your placement of the plates, the size and shape of the oceans, and the temperature and makeup of the atmosphere.
There's no quick answer to your question though. You just have to draw a map of the entire planet, then apply what you know about earth's processes to it.
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I'ma geologist, so if you have some specific questions, I'll be glad to answer as best I can.
There used to be a program called SimEarth which you used to create a world from scratch. You can still find copies from time to time. It runs in DOS but there are ways around that.
Use it and base your world on the world you create and you should be fine.
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Or just learn as much as you can about our Earth and use that information as a basis for your world. In particular, there is a book out by the name of Ice Ages. It will explain the glacial cycle in terms of stronomical events such as orbital eccentricity, precession, and axial tilt. Any earth-like world will be susceptable to those kinds of cycles, and will dominate the historical climate, which will, in turn, dictate how your world looks today.
Posts: 2 | Registered: Aug 2010
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posted
Greg may be overstating the case for uniformitarianism, since so far we haven't discovered any planets with geology similar to Earth's.
But, as noted, those planets are...well, not very much like Earth. If you want a planet to be Earth-like, then probably most of the same features of geology that are found on Earth will be found there as well. For instance, you'll need to have oceans for there to be much life. If you want land, you'll need plate tectonics to build up continents and so forth by producing granite and other oxidized minerals and shoving them together. You'll want a strong magnetic field to protect you from ionizing radiation, so a nickle/iron type core and electrically charged convection currents are probably a good idea. You know, all the basics.
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I would argue (and do ) that your best bet for life is a planet like Earth in most of its characteristics. But violations of that make it interesting.
Plate tectonics: if you don't have continents, you don't get land life -- and w/o having them float on a bed of magma, erosion will destroy any static continents.
Still, we found fun variants in Niven's Known Space. Jinx, Canyon, Plateau.
1) Learn a lot about real geology. Researching can be one of the most rewarding parts of beginnig a new story, if you enjoy studying on your own and learning new things. It can also take a lot of time though, so you're second option would be...
2) Talk to someone who does. The last time I wanted to create a story with a strange new planet, I called my aunt, who has a masters degree in geology. I hadn't called her in years, so it was good to get in touch again, and she was all too happy to explain a few things for me (and save me from looking like an idiot if I had went along with some of my original ideas about how my planet's geology might work). Mikemunsil has kindly offered to help out in this way here. Take advantage of it.
3) The last (and sometimes best) option is to just not worry about it. Learn just a little bit about geology, and then be vauge about any specific references so that you haven't stated enough to actually be wrong.
In my case, I wanted a planet four times the size of earth, but with earth like gravity levels. After trying several ideas to explain how this could be possible, I finally realized that the story worked best if I just didn't explain it all. I just stated that it was so as if I knew what I was talking about, and then went on to more important things. (Your case is a little different than that, but the same principle can be used.)
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I happen to know that AaronAndy, in the end, bought a really big styrofoam ball and painted it to look like a planet. But don't tell the readers. Posts: 2 | Registered: Aug 2010
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posted
Hmm...if it were only four times the size of Earth, though, it wouldn't have anywhere near the same gravity, would it?
Oh, and what do you mean by "four times the size"? Volume or diameter or mass or what(I suppose that surface area is the only one left)? If it were four times the mass, then you'd need it to be twice the diameter to have the same gravity, which would also give you four times the surface area. Doesn't sound too hard to me. It couldn't be very Earth-like, though.
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Well, this thread wasn't really supposed to be about my failed styrofoam noval project, but since you asked, the answer is four times the surface area. Now, (assuming a constant density), surface area and gravity have a direct linear relationship, meaning that an object with x times the surface area would have x times the gravity of the original. The only solution, as you figured out, is to decrease the density of the object (planet, in this case). The problem is (and this is what I found out talking to my geologist aunt) is that there pretty much is no possible way to decrease the density of an earth-like planet by that much and still have it remain earth-like.
So it doesn't work. But since it has to work for the story, you have to make up fake geological theories to make it happen, or (which is what I did) you just assume that those fake goelogical theories are there, without ever actually including them in the book.
Now, I'm not saying that you can do that in every case, and you don't want to be completely scientifically wrong in your books, but I've read far too much Sci-Fi that spends so long trying to explain why this or that is possible that the story drags along at a snail's pace. On the other hand, if the story is exciting enough your readers often won't have time (or desire) to start asking "how is that possible" questions.
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But if you write it well, you can have the information in your notebook and only refer to it as needed. Your reader will see that the world follows rules and will sense consistency, even if said reader doesn't know the rules. What's important is that YOU the writer know them.
Posts: 2 | Registered: Aug 2010
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posted
Actually, it would be very possible for an Earth-sized world to be less dense than Earth -- but probably not much. You'd have to get rid of that huge iron core.
Earth's core is bigger than that of Mars or Venus, and the moon either doesn't have one or has a very very tiny one. The best theory I know is that two planet-sized things collided, forming the earth and moon (this model also explains why the moon's orbit is so close to circular), and the bigger one got all the iron.
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Without the iron core, you have no magnetic field. Without the magnetic field, you have no protection from the solar wind (of the star in question). That also makes navigation for primitives much more difficult.
Posts: 2 | Registered: Aug 2010
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posted
Well, you'd have a weak magnetic field at best. You also probably couldn't have a dynamically stable mantle, which would mean no plate tectonics, which would mean no continents. Thus, you couldn't have both oceans and land. And the surface mineral composition would be radically different.
Like AA's aunt said, it wouldn't be very earth-like. For my part, I wonder why it would need to be four times the size of Earth. Why not just have twice the land mass? That would make the oceans too salty for most life, of course, but the salt content reaches a point where as much salt is being subducted as is being leeched from the rocks (that's not actually a point, because the salt content of the continents starts to increase too, but things slow down). Or the planet could have just started with a bit less water (or lost it somewhere along the way). True, you can't get four times the land mass without getting rid of pretty much all your water (which would be very not like Earth in important and obvious ways) but then again, I'm not clear why you want so much surface area anyway.
You might want to pick up the Special Edition of Scientific American (on stands until Sept 26 if you believe the cover). It is entitled "Our Ever Changing Earth" and looks quite interesting.
[This message has been edited by Spaceman (edited August 06, 2005).]
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If it's about living space, then increasing the raw amount of land mass is pointless. The key is to increase the amount of arable land.
Posts: 8322 | Registered: Aug 1999
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) that your best bet for life is a planet like Earth in most of its characteristics. But violations of that make it interesting.
