From Second Life Wiki
Parameter range: [-1.0 to +28.0]
1.0 is equal to normal Earth gravity (acceleration of 9.8 meters per second in a vacuum)
Considering the object alone, increasing its gravity multiplier has a similar effect as increasing the object's mass.
However, for interactions with other objects the gravity multiplier is different from increasing mass:
- a low-mass object with a high multiplier will not transfer much inertia to another object during an impact.
- a high-mass object with a low multiplier will transfer large amounts of inertia to another impacted object.
Warning, objects with the multiplier set to less than zero will repel gravity, causing the objects to "fall upward". This may result in loss of objects in the sky of a sim.