World Size Does Matter

Has anyone put any solid thought on how Athas would look if it were the same size as Toril or Oerth? The maps from the Cartographers’ Guild have been shared a lot lately, but that makes Athas smaller than small.

Given the descriptions from the 2E box set, there’s no reason to think that Athas is any smaller than the other game worlds…

It just isn’t detailed. Or wasn’t at the time.

I for one think there should be a major body of water far to the west of the Ringing Mountains that justify the forestation on the western side of the mounts. Also. where along the equator do the Tablelands lie?

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From my understanding both Toril and Oerth are similar size to Earth . If you also go with the idea that the game rules for a planet all function under the same physics and gravitational rules then I think it’s reasonable to assume Athas has similar gravity and is approximately the same size with similar geologic construction. i.e we don’t muck with the rules if a character from Athas magically appears on Toril. They hit the same, fall the same, jump the same etc.

There are differing opinions on it. I come from the mindset to treat Athas as the about the size and mass of Earth and all the other physics. We’ve discussed it a bit in the geology thread. Here. Planetary Geology of Athas - #45 by Otello

If this is the case that the size is indeed like Earth, there is a whole lot of planet left to explore and define. Is it mostly silt or is there some ocean there somewhere?


The more I think about it, the more I’m convinced that Athas is Earth size:

  • There isn’t any reference that I could find that says Athas is smaller than Earth
  • Gravity is the same as on Earth. Having the same gravity with a different size need carries a lot of problems to explain it
  • Days are 24h long. I’m not sure about this, but I think there’s a relation between the planet size and the day duration (need to investigate a bit more about this, as I’m not sure the rotation speed could be considered also the same)

The only evidence usually given to say that Athas is smaller than Earth is that it’s based on the Mars from the John Carter novels, which I think is not completely true (I think the real basis is the Counter-Earth, from the Gor books).

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Mars is 53% the diameter of Earth (c.6,800km diameter vs c.12,800km diameter for Earth), yet its sidereal day is slightly longer - 24 hours and 37 minutes. I don’t think we know enough about Athas as a planet to work out its canonical size based in sidereal days.

As you say, there’s nothing to say Athas is smaller than Earth and the gravities are the same/similar (as opposed to Mars, which has a surface gravity about 38% that of Earth).


True the size of the planet can have just about any spin regardless of size. However, I think the rules assume a day on Athas is still approximately equal to a day on Earth. 24h=24h. Which also means 1h=1h and 1m=1m. Otherwise, you’d have to make accommodations for spell durations, travel, and the like that specify durations in these game terms.

Overland Movement is expressed in how far a given race can move per day. For the mul and thri-kreen on page 87-88. DS CS it talks of being able to travel 20 hours per day. See also pg 46 of WJ.

If you assume a radius of like Earth of about 4,000 miles you get about 200 million sq miles of surface to map. Granted, a lot of that space on Eath is ocean

I haven’t looked at existing maps to do the calculation myself, but I recall a thread from somewhere that the provided map of Athas events in the campaign setting covers about the size of Colorado. Which is just over 100,000 sq miles. Which means you have 0.05 percent mapped.

It looks like this topic is related to both my planetary geology topic, and my world map topic.

I would like to suggest a reason why these things weren’t defined-- to give DMs the space to do whatever they want in uncharted regions. As it stands now, at least half the planet is not defined at all, and about 80% of what has been drawn has been left intentionally vague for DM’s benefit.

Also, this brings me to another related topic-- non-canon creations.

Maybe before we start defining any more of the world, we agree to have a separate section for non-canon creations. @Grummore - how about your new website?

I’m back online and I would be more than happy to move from a dinosaur html to a wordpress as soon as possible (with help, especially for visual).

I’ve just PM’ed you about this. I can help you get started, but won’t have time for a long time to get it running fully.

We’ll need help from other people for that anyway, so once the basic structure is set up, we’ll need to recruit Wordpress geeks from the community to help us out with this.

Your points are arbitrary.

Gravity can be totally different than another celestial body, but if a being has been on the planet long enough the body will acclimate to the gravity, and you won’t feel the difference.

Days can be 24 hours on a smaller planet, it just means that the world is spinning slower, which would make sense, given that the planet is mineral poor to begin with. If the planet core is weak it will spin slower, also the size of the Red Giant in the system may slow down the spin.

Why this topic was made into a separate post, when we were discussing the exact same things in the Geology topic is beyond me.

If gravity was different from the Earth one, the original CS would have included new rules to reflect it. You can be acclimated, but it would still affect falling and thrown objects.

Regarding the spinning, I said I wasn’t sure about it and and I was already corrected. Thank you anyway for providing extra information.

But, at the end what is for sure arbitrary is to say that Athas size is different from that of the Earth without providing any kind of reference to support it. At least if we are talking about canon, and not of what each one does on their house.

As things would be lighter due to lower gravity, it’s possible that falling and thrown would be different, but it’s also possible that it wouldn’t, depending on the density of the things falling or being thrown. It can be assumed that all matter is relative to the gravity it is influenced under.

For the topic of this thread it boils down to how much more surface area is available to define.

Surface area of a sphere = 4 x pi x r^2

An Earth sized planet has about 198.7 million sq miles vs Mars sized would be about 55.6 million square miles.

A Colorado sized campaign setting is about 104,000 square miles.

A map of Earth-sized Athas will be 3.5 bigger than the Mars-sized Athas version.

Happy mapping.


What if Athas is flat? :stuck_out_tongue:

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It could just be a disk.

Not a disk. Not flat. (Contrary to what Uncle Tontor believed) Notice language of “once held that”

Dragon Kings pg 6. In an elven legend:

“The wyrms deposited Uncle Tontor unceremoniously on the underside of Athas. (Elven folklore once held that Athas is flat.)”

Also please see Marauders of Nibenay and Nibenay’s orrery.


So, to run some calculations and build on what you’ve wrote.

We know the size of the 4e tablelands map to be 519.33 miles east to west (based on some other members’ calculations) and 261 miles north to south (by my own measurement laying the map out in CAD). For the continent to be 9 squares tall, that would make it about 2349 miles north to south (one state shy of coast to cost east to west through the middle of the USA).

So, how much bigger/smaller should the planetary view be? Or even better, can we calculate the diameter from this planetary view?


How many square miles is one of the rectangles?

Or what is a rectangle’s height and width.

We also assume the planet is roughly the same high as it is wide. Roughly uniform radius.

A bit larger than the state of Colorado given that one of the more central tiles is the Tyr region and stuff from the original CS.

I actually toyed with one of the maps uploaded earlier in one of @neujack 's topics on the world map and put in a size comparison for my own reference with the outlines of Colorado state and my own country (the Netherlands).

Remember this is on a sphere trying to be projected onto a rectangle. Which is why Greenland looks so big on a Mercator map when really it is much smaller. The rectangles at the extreme north and south actually contain less square miles in the area.

Circumference of the earth is 24,900 miles. Assuming roughly spherical planet then a line traveling from North Pole to South Pole would be half that. 12,450 miles

Colorado is 280 high x 380 wide ~106,000 sq miles.

  • Which is what you say the area on the map are about the size.

Total surface area / area of Colorado


Means you need about 2000 squares total.

Top down
12,450 / 280 = 44.5 rectangles high

total needed / high
2000 / 44.5 = 44.9 total rectangles wide about.
(One way to calc width, the one below is better)

Total circumference / width of Colorado is 24900 / 380 = 66.5 total rectangles at the equator

There’s really probably more rectangles needed than the 2000. Due to all the “wasted”area at the poles

So I have 44 high by 66 wide which gives 2.904 total. You have 24 total already mapped.

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