Does the 'Center of mass' make sense in a $0g$ environment? Center of mass is as if where the entire mass of a body is located, here on earth there is this intuition of the object balancing at a pivot point, is there a better intuition for this applicable everywhere?
 A: The center of mass of a rigid object absolutely makes sense in a zero-g environment.
Most importantly, the entire motion of a rigid body can be fully explained as the direct combination of


*

*the motion of the center of mass, together with

*rigid rotations around the center of mass.


If you want to calculate the motion of the body under a combination of external forces, then you simply


*

*take the total vector sum of the forces, independently of where they're acting, and that will act as a single force on the center of mass, and

*you take the total torque of the forces about the center of mass, and this total torque will then influence the rigid rotations of the body about that point.


The center of mass is the unique point with all of these properties.
A: Mass is independent of gravity, so it does make sense to define a center of mass of a body.
It seems like you are instead thinking about center of gravity, which turns out to be the same thing if we are within a uniform gravitational field, but in general they are not the same thing. In terms of balancing a body in a gravitational field, the center of gravity is what we would look at to balance the object, even if the field was non-uniform.
If there is no gravitational force, then there isn't really any sense of balancing to begin with. 
