Attention σ cadets: The game

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.