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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
http://www.cix.co.uk/~morven/index.htmlhttp://www.cix.co.uk/~morven/worldkit/index.html#astrohttp://www.cix.co.uk/~morven/worldkit/index.html#geohttp://www.cix.co.uk/~morven/worldkit/index.html#astrohttp://www.cix.co.uk/~morven/worldkit/index.html#florafaunahttp://www.cix.co.uk/~morven/worldkit/index.html#florafaunahttp://www.cix.co.uk/~morven/worldkit/index.html#introhttp://www.cix.co.uk/~morven/worldkit/index.html#introhttp://www.cix.co.uk/~morven/worldkit/index.html#easyhttp://www.cix.co.uk/~morven/worldkit/index.html#easyhttp://www.cix.co.uk/~morven/worldkit/index.html#astrohttp://www.cix.co.uk/~morven/worldkit/index.html#astrohttp://www.cix.co.uk/~morven/worldkit/index.html#astro-starshttp://www.cix.co.uk/~morven/worldkit/index.html#astro-starshttp://www.cix.co.uk/~morven/worldkit/index.html#astro-sunhttp://www.cix.co.uk/~morven/worldkit/index.html#astro-sunhttp://www.cix.co.uk/~morven/worldkit/index.html#astro-solarsystemhttp://www.cix.co.uk/~morven/worldkit/index.html#astro-solarsystemhttp://www.cix.co.uk/~morven/worldkit/index.html#astro-moonshttp://www.cix.co.uk/~morven/worldkit/index.html#astro-moonshttp://www.cix.co.uk/~morven/worldkit/index.html#astro-dayhttp://www.cix.co.uk/~morven/worldkit/index.html#astro-dayhttp://www.cix.co.uk/~morven/worldkit/index.html#geohttp://www.cix.co.uk/~morven/worldkit/index.html#geohttp://www.cix.co.uk/~morven/worldkit/index.html#geo-gravhttp://www.cix.co.uk/~morven/worldkit/index.html#geo-gravhttp://www.cix.co.uk/~morven/worldkit/index.html#geo-comphttp://www.cix.co.uk/~morven/worldkit/index.html#geo-comphttp://www.cix.co.uk/~morven/worldkit/index.html#maphttp://www.cix.co.uk/~morven/worldkit/index.html#maphttp://www.cix.co.uk/~morven/worldkit/index.html#climatehttp://www.cix.co.uk/~morven/worldkit/index.html#climatehttp://www.cix.co.uk/~morven/worldkit/index.html#clim-estabhttp://www.cix.co.uk/~morven/worldkit/index.html#clim-estabhttp://www.cix.co.uk/~morven/worldkit/index.html#clim-effhttp://www.cix.co.uk/~morven/worldkit/index.html#clim-effhttp://www.cix.co.uk/~morven/worldkit/index.html#clim-windshttp://www.cix.co.uk/~morven/worldkit/index.html#clim-windshttp://www.cix.co.uk/~morven/worldkit/index.html#florafaunahttp://www.cix.co.uk/~morven/worldkit/index.html#florafaunahttp://www.cix.co.uk/~morven/worldkit/index.html#f-florahttp://www.cix.co.uk/~morven/worldkit/index.html#f-florahttp://www.cix.co.uk/~morven/worldkit/index.html#astrohttp://www.cix.co.uk/~morven/worldkit/index.html#geohttp://www.cix.co.uk/~morven/worldkit/index.html#astrohttp://www.cix.co.uk/~morven/worldkit/index.html#florafaunahttp://www.cix.co.uk/~morven/worldkit/index.html#introhttp://www.cix.co.uk/~morven/worldkit/index.html#easyhttp://www.cix.co.uk/~morven/worldkit/index.html#astrohttp://www.cix.co.uk/~morven/worldkit/index.html#astro-starshttp://www.cix.co.uk/~morven/worldkit/index.html#astro-sunhttp://www.cix.co.uk/~morven/worldkit/index.html#astro-solarsystemhttp://www.cix.co.uk/~morven/worldkit/index.html#astro-moonshttp://www.cix.co.uk/~morven/worldkit/index.html#astro-dayhttp://www.cix.co.uk/~morven/worldkit/index.html#geohttp://www.cix.co.uk/~morven/worldkit/index.html#geo-gravhttp://www.cix.co.uk/~morven/worldkit/index.html#geo-comphttp://www.cix.co.uk/~morven/worldkit/index.html#maphttp://www.cix.co.uk/~morven/worldkit/index.html#climatehttp://www.cix.co.uk/~morven/worldkit/index.html#clim-estabhttp://www.cix.co.uk/~morven/worldkit/index.html#clim-effhttp://www.cix.co.uk/~morven/worldkit/index.html#clim-windshttp://www.cix.co.uk/~morven/worldkit/index.html#florafaunahttp://www.cix.co.uk/~morven/worldkit/index.html#f-florahttp://www.cix.co.uk/~morven/index.html8/7/2019 On Creating an Earthlike Planet
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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
http://www.cix.co.uk/~morven/worldkit/index.html#f-faunahttp://www.cix.co.uk/~morven/worldkit/index.html#f-faunahttp://www.cix.co.uk/~morven/worldkit/index.html#culturehttp://www.cix.co.uk/~morven/worldkit/index.html#culturehttp://www.cix.co.uk/~morven/worldkit/index.html#langhttp://www.cix.co.uk/~morven/worldkit/index.html#langhttp://www.cix.co.uk/~morven/worldkit/index.html#lang-nameshttp://www.cix.co.uk/~morven/worldkit/index.html#lang-nameshttp://www.cix.co.uk/~morven/worldkit/index.html#lang-creathttp://www.cix.co.uk/~morven/worldkit/index.html#lang-creathttp://www.cix.co.uk/~morven/worldkit/index.html#lang-dialhttp://www.cix.co.uk/~morven/worldkit/index.html#lang-dialhttp://www.cix.co.uk/~morven/worldkit/index.html#otherhttp://www.cix.co.uk/~morven/worldkit/index.html#otherhttp://www.cix.co.uk/~morven/worldkit/index.html#creditshttp://www.cix.co.uk/~morven/worldkit/index.html#creditshttp://www.cix.co.uk/~morven/worldkit/index.html#creditshttp://www.cix.co.uk/~morven/worldkit/index.html#astrohttp://www.cix.co.uk/~morven/worldkit/index.html#geohttp://www.cix.co.uk/~morven/worldkit/index.html#maphttp://www.cix.co.uk/~morven/worldkit/index.html#maphttp://www.cix.co.uk/~morven/worldkit/index.html#f-faunahttp://www.cix.co.uk/~morven/worldkit/index.html#culturehttp://www.cix.co.uk/~morven/worldkit/index.html#langhttp://www.cix.co.uk/~morven/worldkit/index.html#lang-nameshttp://www.cix.co.uk/~morven/worldkit/index.html#lang-creathttp://www.cix.co.uk/~morven/worldkit/index.html#lang-dialhttp://www.cix.co.uk/~morven/worldkit/index.html#otherhttp://www.cix.co.uk/~morven/worldkit/index.html#creditshttp://www.cix.co.uk/~morven/worldkit/index.html#creditshttp://www.cix.co.uk/~morven/worldkit/index.html#astrohttp://www.cix.co.uk/~morven/worldkit/index.html#geohttp://www.cix.co.uk/~morven/worldkit/index.html#map8/7/2019 On Creating an Earthlike Planet
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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
http://curious.astro.cornell.edu/http://www.badastronomy.com/infohttp://www.badastronomy.com/infohttp://www.badastronomy.com/infohttp://www.planetarysociety.org/http://www.planetarysociety.org/http://nssdc.gsfc.nasa.gov/planetary/voyager.htmlhttp://nssdc.gsfc.nasa.gov/planetary/voyager.htmlhttp://www.geocities.com/Area51/Chamber/2838/cookbook.htmlhttp://history.nasa.gov/SP-345/ch8.htmhttp://history.nasa.gov/SP-345/sp345.htmhttp://history.nasa.gov/SP-345/sp345.htmhttp://history.nasa.gov/SP-345/sp345.htmhttp://www.hq.nasa.gov/office/pao/History/on-line.htmlhttp://curious.astro.cornell.edu/http://www.badastronomy.com/infohttp://www.badastronomy.com/infohttp://www.planetarysociety.org/http://nssdc.gsfc.nasa.gov/planetary/voyager.htmlhttp://www.geocities.com/Area51/Chamber/2838/cookbook.htmlhttp://history.nasa.gov/SP-345/ch8.htmhttp://history.nasa.gov/SP-345/sp345.htmhttp://history.nasa.gov/SP-345/sp345.htmhttp://www.hq.nasa.gov/office/pao/History/on-line.html8/7/2019 On Creating an Earthlike Planet
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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.
http://map.gsfc.nasa.gov/m_mm/ob_techorbit1.htmlhttp://map.gsfc.nasa.gov/m_mm/ob_techorbit1.htmlhttp://map.gsfc.nasa.gov/m_mm/ob_techorbit1.html8/7/2019 On Creating an Earthlike Planet
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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.
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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
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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.html8/7/2019 On Creating an Earthlike Planet
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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
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