What would living on a toroid planet be like?

Because I’ve been playing way too many Square-Enix games that feature the double-wrap* map and have been wondering.

  • What would gravity be like?
  • What would the day/night cycle be like? (Obviously would depend on how the thing rotated, but I’m not very good at visualizing in 3-D space.)
  • Standing on the inner diameter, would you be able to see the other part of the planet?

…of course, realistically, a toroidal planet probably wouldn’t be able to survive long enough for anybody to live on it, but play along for the sake of this thread, would ya?

*One that wraps North-South as well as East-West. Our spherical Earth only wraps East-West


What exactly do you mean by “wrap”?

I think dotchan means a planet shaped like a donut.

Something like this

Everybody would have to live on the equator (the outer equator I guess), because everywhere else gravity doesn’t point toward the ground.

On a 2-D map of the Earth, if you head east (or west) in one direction long enough you’ll “disappear” off one edge of the map and “appear” on the other.

Nearly all of Squeenix’ Final Fantasy titles have maps that not only do this for East-West directions, but for North-South (and yet, on games with a quasi-3D view, it shows the world below as round!).


I keep imagining that the oceans would all flow into the hole, so that you’d end up with a dry donut encircling a blob of water and confused fish. The air would follow the water.

While you’re correct about the gravitational situation - the outer and inner equators will have the highest and the lowest surface gravity, respectively, and the radius that corresponds roughly analogously to the North Pole, at 90 degrees between the equators, it would feel as though the ground was slanted somewhat, with downward being toward the outer equator. However, it does not follow that therefore everyone would live at the equators. It is perfectly possible to live on a hillside, and this occurs in many place on earth, such as these places:

I’ve not worked out the numbers yet, but my gut tells me the apparent “slant” would not be very steep, perhaps similar to a hill with a 15-20 degree slope.

Wouldn’t that depend on the two radii* of the doughnut?

  • Radius from the middle of the hole to the center of the dirt on the loop, and the radius from the center of the dirt to the surface

Pretty much, hence the range.

Oh and I want to correct myself. Thinking further, I realize that at the “north pole”, the ground would seem to slant down towards the inner diameter, not the outer. If you placed a ball on the ground there, it would roll towards the inner equator, with a relatively small acceleration, because the center of gravity would lie in that direction.

Could you stand at the inner equator? My guess would be that you could. I’m also betting that the gravity from the other side of the donut hole would create some pretty wicked tidal forces.

There would be six points on the compass: East, West, North, South, Up, and Down.

Creation myths would involve an unimaginably vast cauldron of boiling fat.

3/4 of the planet’s surface would be covered by Maple Glaze.

Since magic is the only force that could create, or maintain such a planet, it obviously would be the ruling force of the entire region of space. Given that explanation, down can be arbitrary for any point on the surface, and the weather would be as the spell caster desired.

I imagine that day and night would be an “on/off” sort of thing, that being the simplest solution. Or, rotate the torus around the perpendicular axis through the hole. This leaves the center facing surface dark, unless the axis is inclined to the ecliptic enough to allow day night cycles. Given that gravity, and astronomic phenomenon must be magically controlled, I suggest that they be constrained to act in accordance with the book by Newton, except that Up and down be perpendicular to the plane tangent with the circular cross section of the local tubular region, not the body as a whole. (This has the advantage of matching the peculiarities of your mapping convention.)


I helped build a world like this, once.

Larry Niven built one in the sixties:

Ooops, that coding obviously doesn’t work here.


Looks better

Ringworld isn’t toroidal, it’s a ring. There’s no gentle curve from the inner surface to the outer surface. It’s more like a rectangular prism that’s been curved around into a circle. The walls are flat.

That’s not necessarily true. As long as the interior of the ring was sufficiently rigid to prevent collapsing, it would maintain itself. The water and atmosphere aren’t going to migrate into the “donut hole”. The gravity for their area of the ring would overrule the gravity of the other side since it’s closer. You could have a rigid core covered with dirt, water, and whatever else you wanted and it would maintain its shape.

Creating such a planet would be far beyond our technology and probably will be for hundreds of years at least, but it is technically possible.

A level of technology sufficiently advanced is indecipherable from magic.


So there would be Day/Night materia?

Good question, dotchan. I never thought of it that way.

: Uses EXIT materia. : MISS