On Creating Imaginary Worlds: Science Fiction

[HardScienceFan]

Kasting, J. F. and D. Catling, Evolution of a habitable planet, Ann. Rev. Astron. Astrophys. 41, 429-463.
There's probably lots more

[Anthony G Williams]

A while back I wrote some very simple programmes to calculate different characteristics of planets depending on their size and average density.

For example, Mars has a surface gravity which is only 38% of Earth's, partly because it is smaller but also because it is less dense (3.9 tonnes per cubic metre cf 5.5T), due to being made more of rock and less of iron. If you wanted to design a bigger planet with the same surface gravity as Earth, then one with the same density of Mars would have a diameter of 17,900 km, twice the surface area, and an escape velocity 20% higher.

Our Moon is even less dense, at 3.3T/m3. So an Earth-gravity planet made up like the Moon (assuming that is possible) would have a diameter of 21,260 km, a surface area 2.8x larger and an escape velocity 30% higher than Earth's.

Earth is actually the most dense planet we know of, closely followed by Mercury and Venus. It will be interesting to see if the planet-hunters find rocky planets orbiting other stars which lie outside the 3.3-5.5T/m3 range.



Just a few points to bear in mind...

[pyan]

Originally Posted by mosaix

Chris, is it plausible that a Jupiter-like planet could gain the extra mass by colliding with another planetary sized body, triggering the fusion process? I know that such a collision would probably involve some changes in orbit but could a star system end up with two suns in this fashion?

I'm almost sure I've read a story where Saturn is pushed into Jupiter, igniting it as a proto-star, and with all the major moons of both planets becoming a secondary system orbiting the Sun, with all the minor stuff being added to "Jupurn" as extra mass.
Damned if I can dredge any details about the author or title, though......

[Culhwch]

Okay, I'm breaking my own rule in regards to the physical/geographic questioning limitations, but as the thread is quiet I thought I might open it up to more general world-building questions...

This one came to me after reading another thread. What kind of populations did kingdoms like England and France have during the Middle Ages? And how about cities and towns such as London or Paris, how many people would have called those home?

[Teresa Edgerton]

Originally Posted by Culhwch

What kind of populations did kingdoms like England and France have during the Middle Ages? And how about cities and towns such as London or Paris, how many people would have called those home?

Some figures quickly gleaned from Life in the Middle Ages, by Robert Delort (trans. Robert Allen):

Countries

England -- 1.5 million at the end of the eleventh century, growing to 3.5 million at the beginning of the fourteenth

France -- 5 million in the mid-ninth century, growing to 14 or 15 million at the beginning of the fourteenth

(I hadn't realized that there was such a huge difference between the populations of France and England.)

The population of the entire "West" (I'm not sure what countries he includes under this designation) was about 73 million in 1300, but the Black Death came along a few years later and reduced it by about a third -- in England it may have been as high as 40 percent.

Now to look through some of the later chapters for some figures on cities ...

[Lenny]

I think that the number of deaths from the Black Death (mid-14th Century) can give a pretty good idea:

Black Death - Wikipedia, the free encyclopedia

75 million deaths worldwide, and between a third and two-thirds of Europe's population.


In particular, this paragraph is a big help:

In Italy, Florence's population passed from 110,000 or 120,000 inhabitants in 1338 to 50,000 in 1351. Between 60 to 70% of Hamburg and Bremen's population died. In Provence, Dauphiné or Normandy, historians observe a decrease of 60% of fiscal hearths. In some regions, two thirds of the population was annihilated. In the town of Givry, in the Bourgogne region in France, the friar, who used to note 28 to 29 funerals a year, recorded 649 deaths in 1348, half of them in September. About half of Perpignan's population died in several months (only two of the eight physicians survived the plague). England lost 70% of its population, which passed from 7 million to 2 million in 1400.[13]

Note the fall of Florence's population from 120,000 to 50,000 - shows just how small the big cities were in those days.

And, of course, there's the figure at the end of the paragraph - England's population fell from 7 million to 2 million.

[Teresa Edgerton]

Cities

Avignon -- 30,000

Genoa -- 100,000

Venice -- 100,000

Ghent -- 50,000

Cologne -- 30,000

London -- 40,000

Paris -- 200,000 (!!)

Population density could be quite cramped. Genoa had over 250 inhabitants to the acre, lodged in multi-storied houses. Paris was better -- only about 130 people per acre.

Noting the discrepency between Lenny's wikipedia article and my book by Delort, obviously different sources give different figures for these things, but at least you now have a general idea.

[Lenny]

It's Wikipedia - what more can you expect?

But yeah, at least Cul has a general idea, now.

[Laerten]

Just started reading 'The Writers Complete Fantasy Reference', found it very useful when developing my world - it made me think about the little things I had missed.

Discovered this book as a recommended read in an article on worldbuilding. Just search on Google for 'Worldbuilding' and there are several good articles available.

[Culhwch]

Yeah, I've come across that book, Laerten. And many thanks, Teresa and Lenny!

[HardScienceFan]

This post is deleted by the author

[asher marquering]

just a general question

where should world building go during the writing process

before or after character fleshing

[Lenny]

Methinks that World Building is one of these things that can go anywhere.

Some people will sit down and create a whole world before starting on the story. Others will do it as they go through the story. And a few may even build the world in its entirety once they've finished their story.

I dived (or is it "dove"? Sounds like it's the past tense of "dive". Much nicer worded than "dived", at any rate) straight into the story, and stopped a bit later to start building the world it was on - before I started, though, I did have a general idea of the setting. Nothing too detailed, though. Just a couple of nams.

Completely up to you how and when you do it.

[Mammon]

I have some nice links that can help with building worlds:

1. Fantasy Worldbuilding Questions Part 1
2. Magical World Builder's Guide
3. World Builder Projects
4. World Builders Home Page Build Your Own World!!!

Hope you can use these.

[asher marquering]

made a template for world building concerning physical environment and things but i think this type of template would be concerned with mostly SF world because some of it is quite technical anyway wat you think?

Template world building

Constellation:
Galaxy:
Star:
Star classification:
Planetary system present:
Terrestrial planets:
Gas giants:
Terrestrial dwarf planets:
Ice dwarf planets:
Asteroids:
Meteoroids:
Cosmic dust:

Planet name:
Moons:
A planetary year in earth days:
Equatorial radius:
Polar radius:
Oblateness:
Surface area:
Volume:
Mass:
Density:
Equatorial surface gravity:
Escape velocity:
Planetary day in earth hours:
Albedo:
Mean temperature in degrees Celsius:
Atmospheric pressure at surface:
Atmospheric composition:

Geology detail:


Hydrology detail:


Geography detail:


Atmosphere detail:


Climate detail:


Orbit and rotation detail:


Moon detail:


Inhabitability detail:


Exploration detail: