Gravity is a global setting that is applied to all physics systems in a scene. 
It can be found in the scene tab. 
This value is generally fine left at its default, -9.810 on the Z-Axis,
which is the force of gravity in the real world. 
Changing this value would simulate a lower or higher force of gravity. 
Gravity denoted g, measurement m × s-2. 

Gravity is applied in the same way to all physics systems. 

Gravity is practically the same around the entirety of planet Earth. 
For rendering scenes from the Moon, use a value six times smaller, i.e. 1.622 m × s-2. 
The planet Mars has a gravity value of 3.69. 

Note

The gravity value per physics system can be scaled down in the Field Weights tab.