Please help me understand the notion of force when it is applied to Newtonian gravity. From my understanding forces in physics involve interactions with at least 2 objects and can cause an acceleration. From this perspective gravity as Newton explained would be considered a force, be it, "action at a distance". Einstein explained gravity as the warping of space-time and not a force. So I would like clarity or corrections of my misunderstanding of when is it appropriate to say gravity is a force (and why), and also when it isn't appropriate to say it isn't a force (and why).
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$\begingroup$ It is two different theories, in one it is a force, in the other one it is not. In a future more advanced theory, who knows? $\endgroup$– Pato GalmariniCommented Jun 13 at 22:00
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1$\begingroup$ There is a Newton–Cartan theory of gravity that has the same physical contents as the usual textbook formulation of Newtonian gravity. In Newton–Cartan theory gravity is most definitely not a force but a geometry. So this question is not about personal opinions but about logical structure of the theory. Voting to reopen. $\endgroup$– A.V.S.Commented Jun 14 at 7:41
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Newtonian gravity is always a force. Einsteinian - general relativity - gravity is never a force.
The reason gravity isn't always called a "force" is because in general relativity, the most accurate to-date representation of gravity by most standards, no force is imparted on anything at all, and objects simply follow "geodesics", which is essentially the straightest line an object can follow: the path it would follow if no forces were impressed upon it.
However, in general relativity, geodesics aren't necessarily straight, and may appear to curve. It just so happens that, for objects with weak gravitational fields (like small asteroids, moons, etc.), geodesics curve in a way that makes objects' behaviors identical to those which do have an inverse-square mass-proportional force applied to them. However, near black holes and other such supermassive objects, the model of Newtonian gravity starts breaking down and disagreeing with observations, whereas general relativity works plenty fine.
Ultimately it's just that one model says it's a force and one model says that it's because geodesics aren't always "straight". Of course most physicists will tell you gravity isn't a force because general relativity is more accurate than Newtonian gravity in many circumstances.
