Gravity Planes

The reason everything pulls its own atmosphere along through space is the force of gravity. It’s also the reason why creatures can stand on a spacefaring ship without falling off the deck.

In Wildspace and on the Astral Plane, gravity is an accommodating force, in that the direction of its effect seems to be “that which is most convenient.” For an object the size of a planet or moon, gravity pulls everything toward the center of the body, meaning that creatures can stand upright anywhere on the surface, and dropped objects fall perpendicular to the surface they land on.

For smaller objects, such as spacecraft, gravity doesn’t radiate from a point but rather from a plane that cuts horizontally through the object and extends out as far as its air envelope. An object’s gravity plane is two-directional: a creature can stand upright on the bottom of a ship’s hull—upside down from the perspective of those elsewhere on the ship—and move around as easily as if it were walking on the top deck. Diagram 2.1 shows the location of the gravity plane of a nautiloid, by way of example, and indicates the directions in which its gravity operates.

One of the unusual properties of a gravity plane is that an object that falls off the side of a ship can end up oscillating back and forth across the gravity plane. It drops in one direction until it crosses the plane, then reverses direction back toward the plane again, continuing until something causes it to stop.

Overlapping Gravity Planes

When gravity planes intersect, such as when two ships pass close to each other and at different angles, the gravity planes of both ships remain in effect until the two ships touch one other (as often happens when they collide or when one ship lands on the other). If that happens, the gravity plane of the ship that has more hit points remaining (regardless of the ships’ actual dimensions) overrides the other ship’s gravity plane, suppressing it as long as the ships remain in contact, and the first ship’s definition of “up” becomes the other ship’s as well.

When a ship touches down on a planet (or some other enormous body), the ship’s gravity plane is suppressed. If a ship has one or more decks on the ventral side of the ship’s gravity plane (rather than its dorsal side), precautions must be taken before the ship lands to secure anyone and anything that might fall when the ship’s gravity plane is suppressed.

Falling

A floating creature that enters the air envelope of a larger body is immediately affected by the larger body’s gravity (such as that of a planet) or gravity plane (such as that of a spelljamming ship). The creature falls from where it entered the air envelope to the surface of that body, or to the gravity plane of that body, whichever is nearer. Normal damage from the fall applies if the creature hits something solid at the end of the fall. A creature or an object that falls across a gravity plane takes no damage from the fall but begins oscillating from one side of the gravity plane to the other, as described above.

Drifting

When a spelljamming ship moves in space, creatures and objects in its air envelope move with it, pulled along with the ship because of the strength of its gravity plane.

An unanchored creature or object floating in a ship’s air envelope is weightless and drifts toward the center of the air envelope at a speed of 10 feet per minute.