Let's suppose that the humans in world are distributed symmetrical so that the centre of mass of earth lies at the very centre of earth. Now a giant car comes in with great speed that it moves down the earth's curvature very fast then you will see as its swirls around the centre of mass of the car-earth system is changing ( as the mass of the car is comparable to our earth) the centre of mass shifts .As the car rotates the center of mass shifts being at the same radial distance from the centre of earth now if no external force is acting on the car earth system as a the as the normal force is provided by the earth then how does the central mass change?

Let's suppose that the humans in world are distributed symmetrical so that the centre of mass of earth lies at the very centre of earth. Now a giant car comes in with great speed that it moves down the earth's curvature very fast then you will see as its swirls around the centre of mass of the car-earth system is changing ( as the mass of the car is comparable to our earth) the centre of mass shifts .As the car moves the center of mass shifts being at the same radial distance from the centre of earth now if no external force is acting on the car earth system as a the as the normal force is provided by the earth then how does the central mass change its position without any external forces acting on earth?