Gravity and inertia are two fundamental forces that work together in the universe. Inertia is the tendency of an object to resist a change in its motion, whether it be a change in speed or direction. It is the property of an object that keeps it in motion or at rest unless acted upon by an external force.
Gravity and inertia are closely related as they both affect the motion of objects. When an object is at rest, it will remain at rest unless an external force, such as gravity, acts upon it. Similarly, when an object is in motion, it will continue to move in a straight line at a constant speed unless acted upon by an external force, such as gravity.
In the case of gravity, it acts as an external force upon an object, causing it to accelerate towards the center of mass of the object it is interacting with. Inertia, on the other hand, causes the object to resist this change in motion and continue moving in a straight line at a constant speed. The combination of these two forces results in the curved trajectory of an object under the influence of gravity, such as the orbit of a planet around the sun.
In summary, gravity and inertia work together in the universe, gravity is the force that attracts any two objects with mass towards each other, and Inertia is the tendency of an object to resist a change in its motion, the combination of these two forces results in the curved trajectory of an object under the influence of gravity, such as the orbit of a planet around the sun.