The velocity changes are an illusion because you're looking only at the spatial metric of distance. You have to look at temporal metrics too. The proper "a" he

The velocity changes are an illusion because you're looking only at the spatial metric of distance. You have to look at temporal metrics too. The proper "a" here in F=ma is the time derivative of four-velocity or spacetime velocity, and that is constant. It's c (the speed of light). Its time derivative is zero; hence no force and no acceleration. Yes, this gets tricky because you have to care about "the speed of time through time." Welcome to general relativity. The answer here goes into more detail: https://physics.stackexchange.com/questions/102910/why-would-spacetime-curvature-cause-gravity https://physics.stackexchange.com/questions/102910/why-would...