Here you go:
“So, what good is this geodesic description of the force of gravity? Can't we just think of gravity as a force and be done with it?
It turns out that there are two cases where this description of the effect of gravity gives vastly different results compared to the concept of gravity as a force. The first is for objects moving very very fast, close to the speed of light. Newtonian gravity doesn't correctly account for the effect of the energy of the object in this case. A particularly important example is for exactly massless particles, such as photons (light). One of the first experimental confirmations of general relativity was that light can be deflected by a mass, such as the sun.”
If gravity isn't a force, how does it accelerate objects? (Advanced) - Curious About Astronomy? Ask an Astronomer
“Since then, general relativity has been acknowledged as the theory that best explains gravity. In GR, gravitation is not viewed as a force, but rather, objects moving freely in gravitational fields travel under their own inertia in straight lines through curved space-time – defined as the shortest space-time path between two space-time events.”
Fundamental Physics/Force/Gravity Force - Wikiversity
“In general relativity, gravity is not a force between masses. Instead gravity is an effect of the warping of space and time in the presence of mass. Without a force acting upon it, an object will move in a straight line. If you draw a line on a sheet of paper, and then twist or bend the paper, the line will no longer appear straight. In the same way, the straight path of an object is bent when space and time is bent. This explains why all objects fall at the same rate. The gravity warps spacetime in a particular way, so the straight paths of all objects are bent in the same way near the Earth.”
How We Know Gravity is Not (Just) a Force - Universe Today
You’ll see people talking about “the force of gravity” all over the place, but it’s a misnomer. Here in the post-Newtonian world of physics, gravitation is understood to be an acceleration field, not a force field, but old habits die hard and it’s easier to say “force of gravity” than “the acceleration field of gravity,” so it’ll probably never completely go away.
No – the equivalence principle is not simply a comparison between gravitation and an accelerated reference frame, it’s a true equivalence, and that equivalence is a fundamental postulate of general relativity. That’s why gravity is called an acceleration field: an observer at a point in spacetime cannot distinguish between an acceleration produced by the curvature of spacetime, and an acceleration of the observer’s reference frame. Even Wikipedia gets it right occasionally:
“The equivalence principle was properly introduced by Albert Einstein in 1907, when he observed that the acceleration of bodies towards the center of the Earth at a rate of 1g (g = 9.81 m/s2 being a standard reference of gravitational acceleration at the Earth's surface) is equivalent to the acceleration of an inertially moving body that would be observed on a rocket in free space being accelerated at a rate of 1g. Einstein stated it thus:
we [...] assume the complete physical equivalence of a gravitational field and a corresponding acceleration of the reference system.
— Einstein, 1907
That is, being on the surface of the Earth is equivalent to being inside a spaceship (far from any sources of gravity) that is being accelerated by its engines.”
Equivalence principle - Wikipedia
Anyway this has all gone off-topic, and debating basic undergrad physics concepts is a boring, tedious, and thankless chore. I’m done here.
