On youtube, I came across to one of many videos trying to explain General Relativity. One of the comments was interesting to me: "I understand how gravity causes an object with velocity to go in curves or to orbit, due to the curvature of space-time: the object thinks that it's traveling in a straight line. But how does gravity (and curved space-time) cause an object to ACCELERATE towards the gravity source? The object was stationary. Why is this g-acceleration a "straight line" to the object even though it was originally stationary. Wouldn't to remain stationary be more of a "continuous motion" for it?" And then I realized that indeed: to my very limited knowledge, many if not every textbook in a subtle manner, slips around this very simple and basic aspect: why exactly and how, does a simple fall down with the acceleration occur. Why? Is it SO OBVIOUS, that needs no words, or is it the fact, that actually many of people claiming to know RG do not actually grasp it? Any ideas how to explain it?