On Creating an Earthlike Planet

8/7/2019 On Creating an Earthlike Planet

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On Creating an Earthlike Planet

Geoff's homepage -> Creating Planets

Last updated: 7 April 2006

[Brian Davis, if you're reading this and wondering why you haven't heard from me: I lost

your email address and all your emails when my computer died. Aargh.]

This page is intended to help role-players and authors of sci-fi and fantasy to, as the title

suggests, create a world which resembles the Earth - that is, a world in which humans could

live and develop societies similar to those with which we are familiar.

The key ingredient here is familiarity. Worlds which are substantially different from the

Earth are certainly interesting, but they need more effort and imagination to create, and I'd

personally prefer to channel my imagination into the story rather than the setting. People withalien tastes may nevertheless find some material of interest here anyway, particularly in the

Astronomy and Geology sections.

The wildly different lengths of the sections reflect three factors:

What I know and have got around to writing;

How much freedom the subject allows you;

The amount of relevant information elsewhere on the Web which I see no point in

repeating here.

Thus Astronomy is very long, but Flora and faunais short. Further contributions, particularly

to the shorter sections, are actively sought and will be gratefully received.

Contents

Introduction

The Easy Way

Astronomy

o The Stars

o The Sun

o The Solar System

o Moons

o The day

Geology

o Gravity

o Surface composition

The Map

Climate

o Establishing your climates

o Effects

o Local Winds Flora and fauna

o Flora
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o Fauna

Culture

Languages

o Place-names

o Language creation

o Dialects Other pages

Credits

Introduction, or Why I Wrote This

This page originated in discussions I had with various people, both online and offline, about

the world I was creating for my novel-in-progress. It emerged quite clearly that you can't

create your world at random; there are a lot of interacting scientific principles you need to

know to guide you, and if you're not careful you could end up making careless yet avoidablemistakes which a pedantic reader will take great pleasure in pointing out later. I am an

(aspiring!) author rather than a role-player, for which reason role-players should substitute

players where I say readers.

There is plenty of relevant information out there on the World Wide Web, but of course you

need to find it first, which takes time and effort; moreover, I'm not aware of any source which

contains everything you need to know in sufficient detail. This page is ultimately intended as

a source of enough information, or failing that, pointers to further information, to take the

hassle and effort out of finding and using it. Most of the page is based on my experiences and

discoveries while creating my own world. Some of you will no doubt find some sections

irrelevant, while others may well find these same sections to be a source of hithertounsuspected interesting ideas.

I can't claim to know everything about every subject I touch on here; the sign "[*]" indicates

that, due to such a gap in my knowledge, I'm soliciting for more information from someone

who knows more. Nor can I in all conscience claim infallibility; for which reasons I will

gratefully accept corrections of errors. All contributions will be appropriately credited.

Note: to simplify the maths, all equations are given using normalised quantities, where the

quantities are relative to the Earth, the Sun or the Moon as appropriate. This gets rid of several

universal constants.

The Easy Way, or Things You Can Assume To Start With

Robert Louis Stevenson once said that every adventure should start with a Map. If, like him,

you're assuming a planet similar to the Earth in size, composition and density which orbits

around a Sun-like sun at more or less the same distance and has days of approximately the

same length and similar seasons, you can skip the mathematically-oriented parts of the

Astronomy and Geology sections and start drawing yourMap.

On the other hand, particularly if you're writing sci-fi, you might well want to consider what

happens if you have a different type of Sun, or a planet with the average density of foam

rubber. In this case, carry straight on; there are a lot of surprising restrictions which crop up
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where you might not expect them. Certain calculations have been simplified, although their

conclusions are not particularly affected; there's little point in trying to be too exact.

Astronomy, or Your Universe and What You Can See In ItThis is the subject with the most material, and the most mathematics; be warned!

I'll start this section big and steadily work inwards. The first assumption is that your world

will be set in either this universe or one with the same laws of physics; if it isn't, many of the

following equations will need to be changed.

Useful astronomy-related links include Curious about Astronomy,Phil Plait's Bad Astronomy

site and thePlanetary Society. TheVoyager Project website (one of many, so I believe) has

lots of stuff about our own Solar System. For further equations pelating to planetary

mechanics, don't miss The World Builders' Cookbook.

My source for all these links also adds that "A good reference on resonance effects in

planetary mechanics is at http://history.nasa.gov/SP-345/ch8.htm which is part of a very good

online book on the Solar System formation and state athttp://history.nasa.gov/SP-

345/sp345.htm which is in turn from the NASA online histories page at

http://www.hq.nasa.gov/office/pao/History/on-line.html -- this has so much good stuff that

space history geeks (that'd be me) could be there for weeks." What you make of all these is up

to you, but if you're paranoid about violating the laws of physics, they're well worth reading.

The Stars

From the point of view of an Earth-bound observer, the stars remain fixed with respect to each

other but appear to move en masse across the sky as if fixed to the inside of a celestial

sphere. The exact locations and brightnesses of the stars will matter more if you're writing SF

than if you're writing fantasy; but, if you want to randomly generate an interesting night sky

resembling the Earth's, you could do worse than the following equation, which I empirically

found to be useful:

magi = 2 * log10i + B - R * rand(100) / i

where magi is the magnitude of the i'th brightest star, Ris a randomizing factor (the larger it

is, the greater the deviation from a true logarithmic scale), and B is the magnitude of the

brightest star in the sky. For Earth, R = 1 and B = -1.4.

This should give you a naturalistic distribution of the stars by brightness; now you need to

place them on your celestial sphere. The right ascension (the celestial equivalent of longitude)

can be totally random; the declination (analogous to latitude) should be the inverse cosine of a

random number between -1 and +1.

Another addition to the celestial sphere is the Milky Way; as visible from the Earth, it forms

a great circle in the celestial sphere because the Earth is in the galactic plane. If your planet is

some way removed from the galactic plane, the Milky Way will form a smaller circle. Ingeneral, the density of stars will be greater closer to the Milky Way and less further away

from it; the area looking towards the galactic centre (on Earth, this is in the direction of
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Sagittarius) will be particularly rich. This does not preclude placing bright constellations away

from the Milky Way; you can place the brighter stars where you like, so the above equations

should still apply.

Bear in mind that constellations are apparent groupings of stars which are really at widely

differing distances; this is why it's meaningless to talk about "the Sagittarian Sector" (sci-fiwriters please note), since in any given constellation there are stars which are closer to Earth

than to the other stars in that constellation.

As far as other night-sky objects are concerned, external galaxies are more visible when

you're looking away from the galactic plane; naked-eye galaxies are thus most commonly

found far from the Milky Way. Globular clusters are generally found within or near to the

galactic plane.

The colour of a star is of course a function of its temperature. The hottest stars are white or

blue-white, the coolest are orange or red, and those in between are yellowish. The colours are

actually only noticeable for the brightest stars; faint stars all look white. In general, thebrightest stars tend towards the hotter end of the temperature range (classes B and A, with

very occasional O); as the stars get fainter, types G and especially K become more common.

Because the Earth is rotating on its axis, the celestial sphere appears to rotate just over once

per day. The "just over" - a result of the Earth moving along its orbit - causes the night sky to

appear the same at any given time as it does slightly later the preceding night and slightly

earlier the following night. The difference in time is calculated by dividing the length of the

day by the length of the year; for the Earth it is 236.5 seconds per day.

The sun

Your planet will in all probability orbit round a single sun, which will essentially be a rather

ordinary star. It's very tempting to orbit your planet planet in a figure-of-eight path around a

binary star (i.e.) two suns, but unfortunately such an orbit is unstable. If you have more than

one sun, you'll encounter the "n-body problem" [*], which is insoluble; in general, an orbit

around two suns is only stable if:

The planet is at least five times as far away from both suns as they are from each

other.

The planet is at least five times as far away from one sun as it is from the other.

The two suns are in a very nearly circular orbit around their barycentre and the planetmakes an equilateral triangle with them. This is, I am informed, "the Lagrange points

L4 and L5 cases; Donald McLean provideda reference explaining Lagrange points if,

like me, you don't know what they are. The planet orbits the common centre with the

same period as the suns.

Added to which, one correspondent mentions that "binary star systems will generally have too

great a fluctuation in temperature to be habitable". For this reason I will assume one sun only

here.

Our own Sun (spelt with a capital) is a main sequence star ofspectral type G2 (yellow),

which is pretty average in star terms. Its diameter is 1.39 million km, and the Earth orbits it ata mean distance of 149 million km (1 astronomical unit, or AU) in 365.25 days (1 Earth

year) to complete one orbit. Note that 1 AU = 216 Sun radii.
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Life on Earth has evolved because the Earth is at the right distance from the Sun to ensure that

it receives the right amount of heat from the Sun. None of the other planets in the Solar

System have developed "life as we know it" because they're either too close and thus too hot,

or too far away and thus too cold. If you want your sun to be of a different spectral type from

the Sun, there will be several knock-on effects to consider. There are several physical

quantities which are relevant here, two of which are fundamental:

M, the mass of the sun.

R, the distance between the planet and the sun.

From these can be derived:

L, the sun's luminosity, i.e. how much light it gives out.

D, the diameter of the sun.

I, the insolation, or amount of heat energy the planet receives from the sun. This is

equivalent to the sun apparent brightness, i.e. how bright it appears when viewed

from the planet. T, the orbital period, or year, of the planet around the sun.

which are related as follows:

L = M3.5

D = M0.74

I = L / R2 (inverse-square law)

M T2 = R3 (Kepler's third law)

Note also:

Surface temperature = M0.505

Lifetime = M-2.5

Now, for Earthlike planets I must be close to 1; according to Brian Davis, "recent work

suggests very conservatively 1.1 > I > 0.53". Thus the feasible limits for R and T can be

calculated:

Rmin = sqrt(L / 1.1)

Rmax = sqrt(L / 0.53)

Tmin = 0.53 M2.125 Tmax = 1.1 M

2.125 From these can be calculated, for a star of any spectral

type, reasonable year-lengths for a planet with Earthlike life orbiting around it. Using data

from Norton's 2000.0 (18th edition), we get the following table. [I might redo this table

sometime when Ihave the time to bring it in line with the new equations].

Type L M D Rmin Rmax Tmin (days) Tmax (days)

(main sequence)

O5 500000 40 14.72 674.20 971.29 1010981.52 1748158.60


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B0 20000 18 6.01 134.84 194.26 134797.54 233087.81

B5 800 6.5 3.91 26.97 38.85 20063.49 34693.18

A0 80 3.2 3.02 8.53 12.29 5084.97 8792.77

A5 20 2.1 2.07 4.26 6.14 2219.26 3837.48

F0 6.3 1.7 1.53 2.39 3.45 1037.11 1793.35

F5 2.5 1.3 1.22 1.51 2.17 592.96 1025.34

G0 1.26 1.1 1.02 1.07 1.54 385.59 666.75G5 0.79 0.93 0.96 0.85 1.22 295.48 510.93

K0 0.4 0.78 0.88 0.60 0.87 193.66 334.87

K5 0.16 0.69 0.77 0.38 0.55 103.56 179.08

M0 0.06 0.47 0.68 0.23 0.34 60.13 103.98

M5 0.01 0.21 0.42 0.10 0.14 23.47 40.58

(giants)

G0 32 2.5 6.01 5.39 7.77 2893.60 5003.52

G5 50 3.2 9.34 6.74 9.71 3574.36 6180.67

K0 80 4 14.70 8.53 12.29 4548.13 7864.49

K5 200 5 32.47 13.48 19.43 8087.85 13985.27

M0 400 6.3 66.12 19.07 27.47 12117.71 20953.57

(supergiants)

B0 250000 50 18.49 476.73 686.80 537669.89 929722.47

A0 20000 16 32.69 134.84 194.26 142974.38 247226.96

F0 80000 12.5 193.19 269.68 388.51 457518.01 791126.27

G0 6300 10 80.98 75.68 109.03 76041.58 131488.79

G5 6300 12.5 112.49 75.68 109.03 68013.66 117607.15

K0 8000 12.5 177.43 85.28 122.86 81359.49 140684.36

K5 16000 16 339.94 120.60 173.75 120941.60 209128.55

Sun 1 1 1.00 0.95 1.37 340.05 588.01

So, theoretically, your year may vary over a range of 23 days to a few thousand Earth-years;

note that years of Earthlike length are only possible with Sunlike suns, and shorter yearsimply redder suns.

Brighter stars, giants and supergiants have shorter lifespans (3 billion years for F0, compared

to 10 billion for the Sun). There's presumably a lower limit for the lifetime, below which the

planet's atmosphere won't be able to become breathable before the star turns into a giant, but

nobody seems to know what it is [*]. Stars dimmer than about K2 have tidal forces strong

enough for the planet's rotation to be slowed down or stopped. This is what's happened with

Mercury and Venus, but for different reasons; research at Weather on Tide-Locked Planets

suggests that the day side might be able to support life.

A correspondent says:

"... if you want to create a group of stars with masses distributed the way you would see in a

real-world group of stars, -ln(1-x)/ln(1.35), where x is a random number between 0 and 1, will

do the trick. Most stars that come out of this are larger than the sun (2.3SM is about average),

but the larger stars die so much more quickly than the smaller ones that there are already far

more small stars in the galaxy than big ones."

The Solar System

Now it's time to consider the otherplanets which orbit your sun. Our own Sun has eight ofthese: Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto; they appear in the

sky as moving stars. There's no obvious limit to the number of planets you can have around
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your own sun, but there are limitations on where they can go. Moreover, planets too far away

will be too faint to see, and planets too close to the sun will be very hard to see in the sun's

light. Uranus, for example, is just at the edge of human visibility, but was not actually

recognised as a planet until 1781; and Mercury is very hard to see except just after sunset or

before sunrise.

I'd really like to know what effects the processes of planetary formation have on the distances

of the planets from the sun [*]. In the meantime, the best I can offer is a method based on

Bode's Law. This law relates the distances of the planets from the Sun to a simple formula,

by which the distance of the i'th planet is given by:

Ri = 0.4 + 0.3 2i - 2

i.e. the distances in AU are ideally 0.55, 0.7, 1.0, 1.6, 2.8. 5.2, 10.0, 19.6, 39.2 and so on.

Note however that Mercury's distance is 0.4, not 0.55; there is no planet at 2.8 AU from the

Sun (we have the asteroids instead); and the Law puts Pluto where Neptune should be.

Whether or not Bode's Law is a genuine physical law or the product of coincidence, you canstill use it to generate a workable set of planetary distances by twiddling the numbers to your

preferences. (I am informed that "Bode's Law works because planets tend to settle into orbits

whose periods are in simple fractional relations: e.g. Neptune:Pluto::2:3 and

Venus:Earth::8:13".) You can now work out the orbital periods of your planets with Kepler's

third law:

T2 = R3

Having done this, you will also need to re-twiddle your distances to eliminate the possibility

of two planets disturbing each other's orbits at the same point within the orbits. What this

means is that the ratio of no pair of orbital periods must be close to the ratio of two small

integers (e.g. 4/3, 3/2), unless the planets are far enough apart (how far? [*]). Once that's

done, you can work out the synodic period (S) of each planet, which is the time taken by the

planet to reach the same position relative to the sun and your own planet:

1/S = 1 - 1/T, or S = T / (T - 1)

This doesn't mean that every S years the planet returns to the same part of the sky (except as

seen from from the Sun), because the home planet has also moved in that time; instead it

means that the planet will be best visible every S years, and will have moved across the sky

by an amount equal to the fractional part of S.

For example, consider Mars as viewed from Earth. For Mars, R is 1.52; T is thus 1.877, or

685 days, or one year and 10.5 months, giving a value of S of 2.14 years, or 781 days. This

means that successive oppositions of Mars, when it is opposite the Sun as seen from the

Earth, occur every 781 days, during which time it has moved 0.14 (the fractional part of S) of

the distance across the sky from the previous opposition.

In general, it must be said that our own Solar System is believed to be typical of most solar

systems. Thus it's highly probable that the outer planets of all solar systems are gas gaints, all

with ring systems and large numbers of satellites. Note, too, that celestial mechanics dictate

that neighbouring planets cannot approach each other closer than a certain limit withoutbecoming perturbed and breaking up; this is the origin of the asteroids, and probably several

of the moons of the planets beyond Earth.


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Finally, you can work out how bright your planets will be in the sky; the equations here come

from some pages from the National Solar Observatory Sacramento Peak. First of all, calculate

M0 and M, the absolute and apparent magnitudes of your sun, from its luminosity (L) and

distance from your home planet (R, which must be in kilometres):

M0 = 4.8 - 2.5 log L

M = M0 - 5 log (R / 308.6 1015), or M0 + 5 log R - 72.447

For the Sun, these values are 4.8 and -26.8 respectively. Next calculate a useful constant C

(for the Sun, 14.10):

C = M + 5 log R, or 10 log R - 2.5 log L - 67.647

You can now calculate the magnitude m0 of a planet at 1 AU:

m0 = C - 2.5 log (a r2)

where r is the planet's radius in km and a is its albedo or reflectivity. The albedo depends on

what the planet is made of; for rocky planets a is around 0.15, and for gas giants it's between

0.4 and 0.6. Venus, which is covered in highly reflective clouds, has an albedo of 0.65; the

Earth's is about 0.4; and that of an icy planet would probably be 0.6 to 0.8.

At last! The magnitude of your planet is given by:

mmax = m0 + 5 log(d1 d2) - 2.5 log (0.5 + 0.5 cos phase)

where:

d1 is the distance from the planet to the viewer in AU

d2 is the distance from the planet to the sun in AU

phase is the phase angle of the planet, i.e. the angular proprtion of its visible disc

which is illuminated.

Forinferior planets, those closer to the sun than your planet, the phase angle is 180 degrees

at inferior conjunction, i.e. when the planet is directly in front of the sun, and zero degrees at

superior conjunction, when it's directly behind the sun. Obviously, you won't see inferior

planets at either of these times; they're best seen around greatest elongation, when they're attheir maximum distance from the sun in the sky. This distance, and the phase, are given by:

emax = sqrt(1 - d22)

phase = 180 - arccos d2

Forsuperior planets, i.e. those outside the orbit of your home planet, the phase angle is

rarely far from 180 degrees. Superior planets make complete circuits of the sky, including the

interesting phenomenon ofretrograde motion at opposition. This is particularly noticeable

with Mars; as it reaches opposition, it slows down and stops, then moves backwards through

its opposition, then stops and moves forwards again. Experimenting with a night-sky viewer,such as my Night Sky Applet, should help you to understand the process.
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Note that planets with apparent magnitudes less than 6 will be invisible without optical aid, as

is the case with Neptune and Pluto from the Earth. The value for Uranus is 5.5.

Moons

From the point of an observer on the planet, moons differ from planets in that they are larger,brighter and cross the sky more quickly. Additionally, moons orbit the planet rather than the

sun.

Earth has only one Moon; there's no reason why you can't have many more. Of all the topics

in this section, this one offers the greatest number of possibilities which are interestingly

different from the Earth.

However many moons you have, you need to know the following about each of them:

Diameter, which will affect how big they appear, and thus whether they can cause

total or annular eclipses of the sun and of each other. The Moon has a diameter of

3475 miles.

Brightness, which is similarly a function of their composition. It also determines how

many of the fainter stars will be drowned out when the moon is above the horizon.

Distance from the planet, which affects the apparent size and the orbital period,

which in turn affects the planet's tides.

Orbital inclination relative to the planet's orbit, which will affect how far from the

ecliptic (the path of the sun across the sky) the moon will appear in the sky. This in

turn affects the frequency of eclipses.

And, of course, there's the moon's colour, which is largely a function of what the moon ismade of. Moons may be:

Rocky, like the Moon and several other moons in the Solar System. Rocky moons

appear greyish and cratered.

Icy, like Jupiter's Europa. Icy moons will be white and bright, since ice reflects light

much better than rocks.

Volcanic, like Jupiter's Io. These moons will be red, orange and yellow.

Gaseous, like Saturn's Titan. Titan itself is orange, although most other colours are

possible.

Additionally, the moons will have gravitational effects on each other, which means thatcertain combinations of distances from the planet will be impossible. The unsolvable n-body

problem rears its ugly head here again, and it's difficult to give precise details; as an example,

though, the four main moons of Jupiter can never form a line on the same side of the planet.

The apparent diameter of a moon (i.e. its diameter as seen from the planet) is proportional to

its actual diameter and inversely proportional to its distance from the planet; thus a moon half

the size of the Moon and twice as far away will appear one-quarter the apparent diameter.

This is why the Sun and the Moon appear about the same size: the Sun is roughly 400 times

the diameter of the Moon, but also about 400 times further away.

Kepler's third law can be used to calculate the moon's distance from the planet given thelength of the moon's orbital period, or vice versa. The formula here needs to be used in its full

form:


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Tides are caused by the gravitational pull of the sun and moons on the planet; more moons

will produce more complicated tides. Here's a good page explaining how tides work. The

magnitude of the tide a body causes at a point equals:

t = D3 P

where:

t = magnitude of tide

D = apparent diameter of body as viewed from the point

P = density of body.

To finish with, here are some interesting phenomena of some moons in the Solar System,

which you might want to emulate:

Phobos, the larger moon of Mars, is so close in that it has an orbital period of 7.7

hours. Since a Martian day is about 24.5 hours, this means that, to a Martian, Phobos

would rise in the west, race across the sky in 3.85 hours and set in the east, rising

again 3.85 hours later and repeating the process just over 3 times every day. During

each passage across the sky, it would go through half a complete cycle of phases, and

you could even see it moving.

Triton, Netpune's largest moon, has a retrograde orbit; i.e. it would also rise in the

west and set in the east, but of course over a longer period of time (5.8 days) and for

different reasons from Phobos.

Nereid, another moon of Neptune, has a highly eccentric (non-circular) orbit which

takes it alternately close to and far away from Neptune. This would cause its

appearance to change from very small and faint to large and bright.

Pluto's moon Charon has an orbital period equal to one Plutonian day, and thus

appears in the same place in the sky at all times. This is because Pluto and Charon are

so close together that they are tidelocked.

Retrograde orbits are unstable; a satellite in one will steadily orbit closer to its primary until it

either breaks up or crashes into it.

The day

An Earth day is the length of time it takes the Sun to make one complete journey across the

sky; it is divided into, of course, 24 hours. Dividing this by 365.25 days gives 236.5 seconds,

which is the extra time added to the length of the day by the Earth orbiting the Sun; this

means that the Earth rotates on its axis in 23 hours and 56 minutes. The Earth's axis of

rotation is inclined at an angle of 23.5 degrees to the plane of its orbit around the Sun. The

direction of rotation is from west to east, which means that the Sun and other celestial objects

appear to move from east to west.

The length of the day on your planet is affected by one factor only, the speed of the planet's

rotation about its axis; faster rotation results in shorter days, and slower rotation causes longer

days. The speed of rotation has several other knock-on effects; for example, faster rotationwill have the following effects, which I am unable to provide equations for all of as yet [*]:
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Faster winds.

More atmospheric cells, which affect theclimate. Jupiter, for example, rotates on its

axis in less than 10 hours, and has several clearly visible bands in its atmosphere.

A greateroblateness, or flattening at the poles. The Earth, for example, has a polar

diameter of 26 miles less than its equatorial diameter, an oblateness of about 1/300.

Some effect on the gravity; see below. The nightly views of the sky will change more slowly. In general, the night sky

presents the same appearance slightly earlier each night; the time difference is the

"extra time" calculated earlier - 236.5 seconds for the Earth.

Since the days will be shorter, the amount of sunlight per day will be less, which will

affect anything which needs sunlight to live (i.e. plants and animals).

Moreover, there's a lower limit to the length of your day; below this limit the planet will be

spinning too fast and will thus disintegrate. TheAlien Planet Designergives an equation for

this. Elizabeth Viau's online course mentions about 3 hours; this limit is, I suppose, unlikely

to be a problem in practice. One correspondent suggests "about 84 minutes for earth density;

somewhat higher if you want to hold an atmosphere". The upper limit of the rotation speedincreases with the planet's density, which is why neutron stars can rotate so fast.

For longer days, of course, all of these effects are reversed; Jordi Mas informs me that there is

no upper limit to the length of the day. In particular, days which are too long will produce

enough heat from the sun to kill off certain flora and fauna.

If you want to be precise, here's the maths. ob, the oblateness, is:

ob = (re - rp) / re

where re is the equatorial radius and rp is the polar radius. The upper limit forob is:

obmax = (5 pi2 r3) / (G M x T2)

where:

pi is, of course, 3.14159

r is the equatorial radius of the planet in metres

G is the universal gravitational constant, 6.67 x 10-11

M is the planet's mass in kilograms T is the length of the planet's day in seconds

The lower limit forob is:

obmin = obmax 0.315

You may want to experiment with retrograde rotation - i.e. what happens when the planet

rotates "backwards" with respect to its orbit around the sun. Aside from making the sun and

other objects move in the opposite direction, this would mean that the night sky would repeat

its appearance slightly later each night, not earlier.
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The axial inclination affects the heights above the horizon of all heavenly bodies; the greater

the angle, the greater the variation in their positions. If the axial inclination is i degrees, at

latitude L the height of the sun above the horizon will vary between i-L degrees and i+L

degrees. Its maximum height in summer will also be i+L, while on the shortest day its

maximum height will be L-i. The sun's changing height has a significant effect onclimate, for

which see later.

Geology, or What Your Planet Is Made Of

The Earth has a diameter of nearly 8000 miles and thus a circumference of nearly 25000

miles. Roughly 70% of its surface is covered with water. The acceleration due to gravity,

i.e. how fast things speed up when falling freely, is 9.8 metres (32 feet) per second per

second. The mean relative density, i.e. the density relative to that of water, is about 5.5.

Gravity

The surface gravity of your planet will affect everything which moves upon it and around it;

in particular Brian Davis says that surface gravities greater than 3 times Earth's are "probably

not long-term survivable from a biomechanics viewpoint".

Gravity also affects the atmosphere, but here the upper atmosphere temperature is also

important; Saturn's moon Titan, for example, has an atmosphere with a surface pressure 1.5

times that of the Earth. The surface pressure of a breathable atmosphere should probably be

within 0.1 and 4 times that of the Earth.

Time for some more equations. The values here, all taken relative to the Earth, are:

g, the acceleration due to gravity at the surface at the equator.

M, the planet's mass.

R, the planet's radius.

P, the planet's density. This is determined by what the planet is made of.

Density is defined as the mass per unit volume, and volume is proportional to the cube of the

radius, therefore:

M = P R3

while surface gravity is related to mass and radius thus:

g = M / R2

Eliminating M, we get:

g = P R

In other words, a planet with a radius twice the radius of the Earth will have to be half as

dense to have the same gravity, and vice versa. An Earth-sized planet made of polystyrenewill have a relative density of about 1, and thus a surface gravity one 5.5th that of the Earth's.
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If you were to jump on such a planet, you'd rise and fall very slowly. You'd also probably die

trying to breathe the tenuous atmosphere, but that's another matter.

Here's a gravity-related mistake in a popular work of fiction, which only a pedant like me

would notice. According to Karen Wynn Fonstadt's excellent Atlas of Pern, which

accompanies the books written by Anne McCaffrey, ten degrees of latitude on the planet Pernequals about 80 miles, which indicates an equatorial circumference of 80 times 36 = 2880

miles, or a radius of 917 miles - 1/8.64 that of the Earth. Assuming that Pern has the same

surface gravity as the Earth, this indicates that Pern has a density of about 43, twice the

density of the densest known element, osmium, and thus physically impossible. Oops!

The gravity at the poles is always greater than that at the equator. For Earthlike planets, Jordi

Mas provides the following information.

The variables, again normalised relative to the Earth, are:

P = density of planet, as above T = period of rotation (i.e. length of day) in Earth days

re = equatorial diameter

rp = polar diameter

ge = gravity at the equator

gp = gravity at the poles

K= tweak factor; see below.

The value ofKdepends on the composition of the planet, and can be interpolated from this

list:

0.5: bodies with their mass concentrated at the centre, such as supergiant stars (or,

interestingly, bodies with mass distributions like a chunk of rock surrounded by many

expanded polystyrene balls)

0.73: gas giants, such as Jupiter

1.0: Earthlike planets (actually, Earth = 0.97; Mars = 1.09)

1.25: planets with uniform density

Then the oblateness is given by:

ob = K 0.00346 / (T2 P).

If this is greater than 0.2, you have a very oblate planet for which the following formulae are

not appropriate.

The polar radius and gravity are thus:

rp = re (1 - ob)

gp = ge (2.5 - K) (1 - ob)

You can also work out the shape your planet will have, although it gets complicated! First of

all, calculate its angular momentum using a formula somewhere within this paper. There are

four cases to consider, based upon the momentum relative to two values X and Y:

Zero momentum: the planet is spherical. This only happens if the planet isn't rotating.
http://www.ifa.hawaii.edu/~jewitt/papers/VARUNA2/Jewitt_Sheppard_2002%20.pdfhttp://www.ifa.hawaii.edu/~jewitt/papers/VARUNA2/Jewitt_Sheppard_2002%20.pdf


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Momentum less than X: the planet is an ellipsoid with the two greater axes equal, and

will rotate around the shortest axis. The Earth is an example of this.

Momentum greater than X and less than Y: an ellipsoid with three different axes. The

relative sizes of the axes depend on the momentum.

Greater than Y: the mass will split in two egg-shaped pieces called Roche lobes.

So you can work out the upper limit for the rotation speed, and you can calculate the planet's

shape as a function of its rotation speed if the density is uniform.

Surface composition

This heading refers to the proportion of the planet's surface which is covered by water. This

affects quite a number of factors, such asclimate and culture; a planet with no water at all,

such as Frank Herbert's classic Dune, will consist entirely of desert, since it won't rain. Going

to the opposite extreme, a planet whose surface is almost entirely water will have very small

continents and very little opportunities for different cultures to advance by sharing ideas.

(Think of Polynesia, for example.)

The proportion of water to land on a planet's surface affects the carbonate-silicate cycle. Too

much or too little water will cause this cycle to be unstable, which in turn will decrease the

likelihood of a stable climate over geologic time, and thus the likelihood of Earthlike life.

Plate tectonics come into play here, too, although you don't need to worry about them too

much. The areas where two plates meet are highly likely to feature mountain ranges (e.g. the

Himalayas or Andes), volcanoes (the Mediterranean, Japan) and earthquakes (California). A

correspondent points out that: "plate tectonics has one result worth remembering: you can

only get high mountains on one side of a continent, since the newest mountains will be on the'leading edge': compare the Rockies and the Appalachians".

The Map, or What Your World Looks Like

The Map is the most important element in the creation of your world; it tells you, and your

readers, where everything is in relation to everything else. Opinions differ widely concerning

how much freedom you have in designing your Map; at one extreme is "anything you do can

be explained in some way", while the other has "things can only happen in a limited number

of ways". The best compromise seems to be "you can do what you want as long as it's

explicable and not too far-fetched".

If you haven't already done so, decide on a scale, so you know the size of the area the Map is

supposed to represent. Start with yourcoastlines and the neighbouring islands, if you have

them; offshore islands are usually formed by the same processes as the nearby coast, and so

should have roughly similar-looking coastlines.

Next, draw yourmountains and rivers. Unless you've got a good reason to do otherwise,

mountains form irregular parallel chains, and are often continued offshore as islands. And

don't forget that rivers always start high and flow downhill; and that most rivers are created by

rainfall, which is highest on the windward sides of mountains.
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For supplementary reading, author Holly Lisle has aworkshop about mapmaking; it's oriented

towards expediency rather than scientific accuracy and rigour, but might be useful if you're in

a hurry. Take a look at her ownMap, too. Mark Rosenfelder has created some lovely Maps

forVirtual Verduria, with instructions for drawing Maps of similar quality; if this seems too

much like like work, have a look at my3d mapping toolkit.

Once you've decided on the shapes of the land and sea, virtually everything else on your Map

is dictated by theclimate. Climates are affected by both large-scale and small-scale factors,

for which reason it's probably a good idea to establish what the major land masses and seas

are in the areas adjacent to your Map.

Climate, or What Weather You Should Expect

"Climate is what we expect; weather is what we get." - unknown wit.

The climate of an area is defined as the weather conditions experienced by the area averaged

over a long period of time; it is most conveniently described in terms of the yearly amount

and patterns of two important and easily-observed factors, rainfall and temperature. These

factors dictate the plants which grow, and in turn the animals which are found; these factors

influence what kind of human cultures develop in the area. A desert society will be very

different from one which inhabits a region with a cool temperate climate, for example.

Establishing your climates

Climates don't occur at random, but can be predicted from a variety of factors. My Climate

Cookbookprovides a step-by-step guide to working out your climates; to learn about thetheory in more detail, have a look at this good online course, especially chapter 7, section (o)

onwards; the most relevant pages are the ones about the global circulation of the atmosphere

and climate classifications.

Effects of climate on the land

One obvious way in which the climate affects your Map is the rivers. Rivers which flow

through areas with seasonal rainfall will be much higher in wet seasons than in dry seasons; a

river which flows through a savanna climate, for example, will be low in the winter and high

in the summmer, giving rise to the possibility of seasonal flooding. Exactly this happens withthe Blue Nile.

By contrast, because there is so little rain in dry climates, rivers in areas with such climates

will have formed elsewhere. In general, too, rivers are less frequent on the drier leeward sides

of mountains.

Local Winds

Local winds are those which depend on a particular set of geographic circumstances, and it's a

good idea to be aware if your landscape will create any. For example, parts of the south of

France are subject to the Mistral, a cold wind which is caused by cold air "spilling" off thenearby Massif Central and Alps in winter and is drawn south by low-pressure areas above the

Meditterranean Sea. Similarly, wet winds from the Pacific Ocean shed their moisture on the
http://hollylisle.com/fm/Workshops/maps-workshop.htmlhttp://hollylisle.com/fm/Workshops/maps-workshop.htmlhttp://hollylisle.com/tm/maps--whole.htmlhttp://hollylisle.com/tm/maps--whole.htmlhttp://www.zompist.com/virtuver.htmhttp://www.zompist.com/howto.htmhttp://www.cix.co.uk/~morven/worldkit/3dmaps.htmlhttp://www.cix.co.uk/~morven/worldkit/3dmaps.htmlhttp://www.cix.co.uk/~morven/worldkit/index.html#climatehttp://www.cix.co.uk/~morven/worldkit/index.html#climatehttp://www.cix.co.uk/~morven/worldkit/climate.htmlhttp://www.cix.co.uk/~morven/worldkit/climate.htmlhttp://www.geog.ouc.bc.ca/physgeog/contents/table.htmlhttp://www.geog.ouc.bc.ca/physgeog/contents/7p.htmlhttp://www.geog.ouc.bc.ca/physgeog/contents/7v.htmlhttp://hollylisle.com/fm/Workshops/maps-workshop.htmlhttp://hollylisle.com/tm/maps--whole.htmlhttp://www.zompist.com/virtuver.htmhttp://www.zompist.com/howto.htmhttp://www.cix.co.uk/~morven/worldkit/3dmaps.htmlhttp://www.cix.co.uk/~morven/worldkit/index.html#climatehttp://www.cix.co.uk/~morven/worldkit/climate.htmlhttp://www.cix.co.uk/~morven/worldkit/climate.htmlhttp://www.geog.ouc.bc.ca/physgeog/contents/table.htmlhttp://www.geog.ouc.bc.ca/physgeog/contents/7p.htmlhttp://www.geog.ouc.bc.ca/physgeog/contents/7v.html


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Rocky Mountains and heat up as they descend to the Great Plains, creating the hot dry

Chinook.

Flora and Fauna, or Your Plants And Animals

Regions with similar flora and fauna constitute a biome, and biomes correspond more or less

with Kppen climate areas. More details about the fauna associated with particular biomes on

Earth may be found at the World Biomes page. Major Biomes of the World may also be of

interest.

Islands feature species typical of their climatic regions, but in fewer numbers and often with

idiosyncratic species. The absence of snakes in Ireland is due not to Saint Patrick, but to the

simple facts that snakes don't cross water and didn't reach Ireland before it became an island.

Moles and woodpeckers are other species which are absent from Ireland for the same reason;

and distinctively Antipodean birds such as the cassowary, emu and kiwi evolved in isolation

from those in the rest of the world.

Flora

You don't find cactuses growing halfway up a mountain in a snow climate, nor do you get

vast coniferous forests in the middle of a desert. The principle here is simple: the plants (and

animals) which would flourish in any given region on your planet will be similar to those

from a similar climatic region on Earth.

Taking as a starting point the obvious fact that plants need water to grow, some useful

generalisations follow. Most importantly, rainy climates will support many more species of

plants and animals than dry climates; compare a rainforest to a desert and you'll get the idea.

Plants which grow in dry climates will develop to conserve precious water; this is why cacti

are thick-skinned and why cork oak grows its thick spongy bark, for example. This fact also

explains why conifers have smaller leaves than broadleaved trees, since small leaves lose less

water through evaporation.

Coniferous trees are good examples of plants adapting to their climate for other reasons:

their conical shapes allow heavy snowfalls to slide off onto the ground, and their strong

branches are able to support the snow which remains. Their leaves, besides being small to

conserve water, are also dark to absorb as much of the Sun's light as possible; sunlight is in

much shorter supply in the cold climates in which conifers grow compared to the more

temperate climates which support broadleaved forests.

Less obvious is the effect of landscape on the variety of plant species. North America has a

much greater variety of tree species than Europe for two principal reasons: the orientation of

the mountain ranges, and the effects of past Ice Ages. Essentially, as the ice encroached

southwards during the Ice Ages, the trees in North America were able to retreat before the ice

since the north-south mountains provided no real barrier; by contrast, in Europe the east-west

mountains (the Alps and Carpathians) prevented all but the most hardy species from retreating

southwards, with the Mediterranean Sea sealing the gaps.

Fauna
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This can be used to explain, in somewhat simplified form, the animals which will inhabit a

particular biome. Obviously, biomes with a greater diversity of plant species will support a

greater variety of animal species; the rainforests are the most diverse biomes on the Earth, for

example. At the other extreme, relatively few types of animal may be found in moorland.

Like plants, animals adapt to their environment. A particularly striking example of this maybe found in snow climates (e.g. subarctic and humid continental), in which snow lies on the

ground for periods of several months at a time; animals in these climates, such as the snow

hare, ptarmigan and Arctic Fox, typically turn white in winter for camouflage. Animals in

cold climates also evolve ways of retaining heat; seals and polar bears, for example, have

layers of fat for this purpose.

Another good example is the fauna of the savannah climate. Here there are vast grasslands

punctuated with occasional trees which have adapted to store water throughout the long dry

season (when the grasslands turn to semi-desert), such as the bottle-shaped baobob tree. The

grasslands support large numbers of herd animals such as gnu, impala, wildebeest and so on;

in turn these herds support carnivores such as lions, cheetah and leopards. The wide openspaces allow the herd species and predators to evolve the ability to run fast to outrun each

other. The huge herds of buffalo of the the American Great Plains lived there for similar

reasons.

Culture

Individual human cultures, like the local flora and fauna, are shaped in large part by their

environment. Consider what would happen in a cold climate: the inhabitants need to have lots

of layers of clothing to keep warm, so the hunting of the appropriate furry animals (hares,bears, wolves) constitutes a major part of their lives. Conversely, desert cultures may paint

their dwellings white to reflect the sun's heat and keep the interiors cool.

Cultures develop and evolve by interacting with other cultures and borrowing their ideas and

inventions. This implies that cultures living in isolated regions, such as in mountainous areas

or on islands, won't develop at the same speed as those on large flat plains. Plains are also

easier to conquer and integrate into single cultural units; this explains not only why mountains

make good natural borders, but also why there are only three countries in North America but

over forty in Europe.

A very good read about the development of human cultures is Guns, Germs and SteelbyJared Diamond, which sets out to answer the question of why European cultures came to

dominate the world, overtaking those of China and the Middle East. To simplify the book's

main thrust somewhat drastically, the reason is ultimately down to the east-west orientation of

Eurasia compared to the north-south orientations of Africa and the Americas, which provided

Eurasia with much more land in temparate latitudes than any other landmass. This large

amount of land greatly facilitated east-west diffusion of cultural developments, since little

adjustment to different environments was necessary. By contrast, the diffusion of cultures

through Africa and the Americas was hindered by the presence of deserts, dense rainforests,

and the narrow mountainous land-bridges of Central America.

According to Diamond, China was eventually overtaken culturally by Europe because the

more mountainous regions of Europe resisted homogenisation and preserved many competing


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cultures, which developed and, from a few centuries ago, exchanged ideas and inventions at a

faster rate than in China. In particular, one reason why the Industrial Revolution began in

Britain was that Britain was able to exchange cultural ideas with mainland Europe but was not

hampered by wars on its soil. By contrast, it was easy for one culture to conquer the plains of

China; this monolithic culture was not conductive to development at the same speed.

Another effect of the interaction of cultures in Europe was that resistances to diseases were

spread quickly among the various peoples. The more isolated peoples in Central America did

not share the same resistances; as a result, when the Spanish arrived in Central America, the

native peoples suffered as much from European diseases as from their superior warcraft.

It's useful to know the populations of the places on the map. In general, the population

density - the number of people in a given area - depends primarily on the quality of the soil

and the level of farming technology; good soils in areas of reliable rainfall which can be

ploughed with horse-drawn ploughs are likely to support much higher population densities

than arid areas of steppe. Another factor is the security of the area - people don't generally

tend to live in areas of land which are regularly ravaged by war. This page should help youcalculate population densities; it's geared towards mediaeval societies and RPGs, but the basic

principles should still be valid.

Language, or How To Name Things

Two pages which are once again required reading areWords Maketh the Culture by Cheryl

Morgan, and What's in a Name? [Extreme pedantry: that should be "Makath" or just "Make";

"Maketh" is an older form of the singular, "Makes". Or you could try "The Word Maketh..."]

Place-names

Perhaps more than any other single factor, the names of the places on your Map create a lot of

its flavour and atmosphere. Consider for example the different moods conjured up by the

following lists of place-names from various parts of Great Britain:

Abertawe, Llanwrtid, Betws-y-coed, Ynys Mn

Littlehampton, Much Wenlock, Leighton Buzzard, Newport Pagnell

Satterthwaite, Kirbyunderdale, Copmanthorpe, Thirkleby

Auchtermuchty, Kilravock, Glenkindie, Abernethy

Nancledra, Tregavarah, Penderleath, Carharrack

Garthamlock, Ruchazie, Polmadie, Cowcaddens

or these, from assorted European countries:

Kortenberg, Hasselt, Nederokkerzeel, Sterrebeek

La Spezia, Palermo, Napoli, Brindisi

Gdansk, Wroclaw, Szczecin, Warszawa

Tampere, Oulu, Viipuri, Helsinki

or, from various fictional worlds:

Pelargir, Calembel, Ithilien, Emyn Arnen
http://www.io.com/~sjohn/demog.htmhttp://web.archive.org/web/20011031155110/http:/www.phantastes.com/99spring/words.htmlhttp://web.archive.org/web/20011031155110/http:/www.phantastes.com/99spring/words.htmlhttp://web.archive.org/web/20011031154102/http:/www.phantastes.com/99spring/interview.htmlhttp://www.io.com/~sjohn/demog.htmhttp://web.archive.org/web/20011031155110/http:/www.phantastes.com/99spring/words.htmlhttp://web.archive.org/web/20011031154102/http:/www.phantastes.com/99spring/interview.html


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Pyrdon, Auddglyn, Dun Deverry, Aver Peddroloc

Gethruva, Malottsa, Surrunguz, Hebrytcest

Hwitbaurg, Klenam uftra, Stainxaim, Licadal

Samhuomi, Azurmesti, Beluvaco, Trosesu

Good karma and plenty of kudos to anyone who can correctly identify all fifteen sources :-)

Place-names generally derive from local geographical features; for example Abertawe is

"mouth of the river Tawe", and Sterrebeekmeans "stream of stars". Sometimes the names

remain more or less unchanged down the centuries, as with these two. Other names change to

varying extents, as with Dunfermline, which comes from the Gaelic dun fearum linn (I'm notsure of the spelling), which means "fort by the crooked stream", and York, which results from

various types of phonetic change affecting the original Latin Eburacum.

Names ofrivers tend to be particularly conservative; the Rhne in France, for example, has

had the same name (subject to linguistic changes; the Romans knew it as the Rhodanum)

since at least pre-Roman times.

Language creation

You can go a long way with just English; if you have a river called - say - the Foo, a town

where it meets the sea could be called Foomouth. To add a bit of spice to the nomenclature of

your world, however, there's nothing to beat making up a language.

If all you want from such a language is a way of naming places, you can get away with:

a list ofnaming elements: "hill", "stream", "pool", "valley", "king", "chief" and so on; a compounding rule which specifies whether modifying words precede the words

they modify, as with Newport, or follow, as with Abertawe.

You can complicate matters a bit by adding another rule which specifies how the individual

elements change when combined; for example Penybontfawr in Wales ("the head of the

large bridge") comes from pen + y + pont + mawr. Of course, if you start down this road,

before you know it you'll be creating a grammar and syntax for your language and writing

epic prose in it; if you get caught up in this, theLanguage Construction Kit will be invaluable.

Dialects

For enhanced realism, remember that languages are rarely spoken uniformly; in any

reasonably-sized area there'll be differences in pronunciation and meaning, and you'll add a

lot to your world by allowing naming elements to take different forms in different areas.

Sterrebeek, for example, is the name of a village in Belgium; its pronunciation in one village

reflects its spelling, approximately "stare-uh-bake", but in a nearby village has been reduced

to something like "stare-beck".

The mixture of names in any given part of your world reflects the cultures which have lived

and fought there. The Great British names above, for example, come from areas settled by

Anglo-Saxons, Vikings, P-Celts and Q-Celts.
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Other pages

In no particular order, here are some links to sites too general to fit under individual

categories.

Designing a Fantasy World, from everything2, is a very fine essay which covers many points

I've skimped on above.

TheWorlds in the Net site. This contains a list of useful links about world-building, of which

Jesper Udsen's experienceof designing a world andRich Staats' essay are particularly good.

Hunting around this site turns up plenty of other goodies, too.

Mark Rosenfelder's Virtual Verduriais an impressive constructed world, complete with

attractive Maps and large amounts of absorbing detail.

Web Blackdragon is an online role-playing IRC channel. Don't miss the lovely Map.

Patricia Wrede's Worldbuilder Questions are useful pointers to things to think about.

Elizabeth Viau has an interestingonline course in world-building, which contains plenty of

scientific notes, although they aren't complete yet. The course is about creating planets in

general, not just Earthlike ones.

TheAlien Planet Designerwebpage.

TheNocturne Research world-building website has archives with lots of interesting material,

some of it relevant to the topics in this page.

The MythoPoet's Manual. Very good for culture and religion.

Epona, a planet in a constructed solar system. Very interesting and well thought out.

Here's a Quick'n'Dirty FAQabout science-related topics, some of which are relevant.

Occasionally you stumble across lecture notes for university courses which contain material

of interest;here's a set about geography.

Not related to world-building, but rather to writing, are Holly Lisle's Forward Motion pages,and the very funny "What I Would Do If" lists onChicken Soup for the Gamer's Soul.

Matthew White's websitecontains a lot of amusing and stimulating material, some of which

(such as Climate in Mediaeval America) is of particular interest to world-builders. Other bits

of it are barking mad, but good fun.

International recognition! Teresa Costa translated some of the astronomy section into

Portuguese forher own world-building pages, which contain much else of value and interest.

Two pages of useful writer's resources are this one (may be defunct) and Creating FantasyWorldsby Paul Nattress. Both have many further links, and also speak very highly of this
http://www.everything2.com/index.pl?node_id=1519418http://www.everything2.com/http://www.everything2.com/http://www.hut.fi/~vesanto/link.networld/networlds.htmlhttp://www.hut.fi/~vesanto/link.networld/networlds.htmlhttp://www.hut.fi/~vesanto/world.build.htmlhttp://web.archive.org/web/20010926185434/http:/goblinwerks.netfirms.com/gmwerks/gmwerks-worldbuilding.htmhttp://web.archive.org/web/20010926185434/http:/goblinwerks.netfirms.com/gmwerks/gmwerks-worldbuilding.htmhttp://web.archive.org/web/20020208224045/http:/www.hut.fi/~vesanto/link.useful/worlds/world.creation.htmlhttp://web.archive.org/web/20020208224045/http:/www.hut.fi/~vesanto/link.useful/worlds/world.creation.htmlhttp://www.zompist.com/virtuver.htmhttp://www.zompist.com/virtuver.htmhttp://www.blkdragon.com/http://www.blkdragon.com/aranmap2.jpghttp://www.io.com/~eighner/world_builder/world_builder_index.htmlhttp://curriculum.calstatela.edu/courses/builders/http://curriculum.calstatela.edu/courses/builders/http://curriculum.calstatela.edu/courses/builders/vlsnc.htmlhttp://curriculum.calstatela.edu/courses/builders/vlsnc.htmlhttp://www.planetdesigner.org.uk/http://www.planetdesigner.org.uk/http://www.nocturne.org/world/http://www.nocturne.org/world/http://www.rpgmud.com/WorldBuilding/Mythopoets/tmm.htmlhttp://www.rpgmud.com/WorldBuilding/Mythopoets/tmm.htmlhttp://www.eponaproject.com/http://people.netscape.com/treitel/rass/qdfaq.htmlhttp://people.netscape.com/treitel/rass/qdfaq.htmlhttp://geog-www.sbs.ohio-state.edu/courses/G120/mazzocco/notes.htmhttp://geog-www.sbs.ohio-state.edu/courses/G120/mazzocco/notes.htmhttp://hollylisle.com/fm/http://bull.dumpshock.com/humor/http://bull.dumpshock.com/humor/http://users.erols.com/mwhite28/http://users.erols.com/mwhite28/http://users.erols.com/mwhite28/medvam/climate.htmhttp://criarmundos.do.sapo.pt/http://www.dragonsquillandink.com/Resources/writing_resources.htmlhttp://www.oneofus.co.uk/features/creating_fantasy_worlds.htmhttp://www.oneofus.co.uk/features/creating_fantasy_worlds.htmhttp://www.oneofus.co.uk/features/creating_fantasy_worlds.htmhttp://www.everything2.com/index.pl?node_id=1519418http://www.everything2.com/http://www.hut.fi/~vesanto/link.networld/networlds.htmlhttp://www.hut.fi/~vesanto/world.build.htmlhttp://web.archive.org/web/20010926185434/http:/goblinwerks.netfirms.com/gmwerks/gmwerks-worldbuilding.htmhttp://web.archive.org/web/20020208224045/http:/www.hut.fi/~vesanto/link.useful/worlds/world.creation.htmlhttp://www.zompist.com/virtuver.htmhttp://www.blkdragon.com/http://www.blkdragon.com/aranmap2.jpghttp://www.io.com/~eighner/world_builder/world_builder_index.htmlhttp://curriculum.calstatela.edu/courses/builders/http://curriculum.calstatela.edu/courses/builders/vlsnc.htmlhttp://www.planetdesigner.org.uk/http://www.nocturne.org/world/http://www.rpgmud.com/WorldBuilding/Mythopoets/tmm.htmlhttp://www.eponaproject.com/http://people.netscape.com/treitel/rass/qdfaq.htmlhttp://geog-www.sbs.ohio-state.edu/courses/G120/mazzocco/notes.htmhttp://hollylisle.com/fm/http://bull.dumpshock.com/humor/http://users.erols.com/mwhite28/http://users.erols.com/mwhite28/medvam/climate.htmhttp://criarmundos.do.sapo.pt/http://www.dragonsquillandink.com/Resources/writing_resources.htmlhttp://www.oneofus.co.uk/features/creating_fantasy_worlds.htmhttp://www.oneofus.co.uk/features/creating_fantasy_worlds.htm


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Documents

On Creating an Earthlike Planet