I have a planet that has an odd pull of gravity because it’s shape is an amalgamation of large landmasses merged together, and held in place by magic forces. Aside from the fact a shape like this on a planet is hard to rationalize, it’s also difficult to imagine how you would map this planet out on a flat surface. how would you draw this on a map? an image of the planet mentioned

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    $\begingroup$ Welcome Moose. What's the actual question? Please take our tour and refer to the help center for guidance. It helps us to answer you if you make it clear what the question is. $\endgroup$ May 30, 2022 at 19:41
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    $\begingroup$ (a) Mapping software is listed on our list of Worldbuilding resources. However, (b) there won't be one for an arbitrary 3D shape. You'll end up compromising on the shape vs. your ability to comprehend the shape. However, I suspect that if you deal with it in portions, you'll do alright. (c) Finally, it should be noted that the nature of gravity (unless the planet is airless) is to wear everything down into a sphere. Your world must be very, very, very young to have this shape. Even if assumed, its spin would tumble something awful. $\endgroup$
    – JBH
    May 30, 2022 at 20:52
  • $\begingroup$ @JBH: Airlessness has nothing to do with it. Any sufficiently large body will be more-or-less spherical -- it's called hydrostatic equilibrium. $\endgroup$
    – AlexP
    May 30, 2022 at 21:44
  • $\begingroup$ Is your planet really so small as to have such a weird shape? A radius of 500 km or so is sufficient to make the planet spherical. (See Ceres for an example. Note that with a radius of 500 km, the surface area will be 160 times smaller than Earth's, and the gravitational acceleration on the surface will be wavy-hands about 12 times smaller than on Earth. Ceres is made of lightweight materials, so that the surface gravity is only 0.029 g.) $\endgroup$
    – AlexP
    May 30, 2022 at 21:50
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    $\begingroup$ Welcome Moose! The answer will depend on context. Do you want to describe that kind of mapmaking in a story, or do you need help actually making the map? If it's supposed to be an in-universe map, what level of science and technology do your fictional mapmakers have access to? What kind of art style do you want? I would recommend adding more details so we can help more. Also, it seems you aren't interested in the physics of why it's that shape, so I'd remove the geophysics tag, and ask people to disregard the plausibility of the situation. $\endgroup$
    – BoomChuck
    May 31, 2022 at 4:02

1 Answer 1


The "geophysics" tag necessitates a "frame challenge," which is a challenge to the premise of the question. If you have vaguely realistic physics in your setting, a planet that is as far from spherical as your drawings indicate can't exist.

The reason for this is simply that rock is not rigid enough for this planet to hold its shape. It will collapse, quite quickly, into a close approximation of a sphere. It won't be a perfect sphere, but it will be pretty close, as the earth is.

  • Earth has continents and oceans because it has two separate types of crust, called "continental" and "oceanic". Continental crust is less dense, and thus floats higher on the underlying mantle. It's all a matter of density and buoyancy: the apparent rigidity of rock on a human scale is irrelevant, because it isn't strong enough to resist the pressures within the earth, and behaves like a (pretty stiff) fluid.

  • The exact shape of the Earth is a bit complicated.

  • Its radius at the poles is about 0.3% less than at the equator, so a slightly flattened sphere is a good approximation. The reason for this distortion is that it spins quite fast, and is stretched, a little, by centrifugal force. If it were to stop rotating, it would slump back into a much more spherical form, involving a world-wide earthquake of unprecedented strength.

  • The earth's gravity field is not perfectly uniform, because its density doesn't increase uniformly with depth. There are some areas where gravity is a little stronger and others where it is a little weaker. The effect is far too small to notice with human senses, but is detectable with precise surveying instruments. The mathematical approximation of the earth's gravity is called the geoid.

A small enough planet will not collapse into a sphere, but that limits you to bodies too small to retain a significant atmosphere.

If you want an irregularly shaped planet, you're going to need different laws of nature, or technology advanced enough to manipulate gravity on a vast scale. When that goes wrong, the planet will slump into a sphere, destroying everything on its surface in the 'quake.

  • $\begingroup$ fortunately, there is magic keeping our planets shape intact. it’s a whole natural history thing, but there are beings before humans that had come and shapen our planet $\endgroup$ May 31, 2022 at 0:23
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    $\begingroup$ Throwing magic in completely changes your question and pretty much means the geophysics tag is not appropriate. $\endgroup$
    – Allan
    May 31, 2022 at 1:47
  • $\begingroup$ @Mooseofthemoss: If there is magic keeping the planet in shape, you should say so in the question, and remove the geophysics tag. We can't read your mind, and Worldbuilding gets used for SF as well as fantasy worldbuilding. $\endgroup$ May 31, 2022 at 7:24

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