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Did I missed something in angular momentum definition? Two identical bodies rotate around mass center. Now I invented anti-gravity and turning gravitational switch off. Those two bodies will move now in straight line with constant velocity and angular momentum conservation is compromised. Turning the gravitation off does not provide any external torque to the system. I also could not find any example when angular momentum is conserved and no internal forces (i.e. gravitation, Coulomb, tension) exist in the system. The definition of angular momentum does not said that existing of internal forces are necessary.