We understand it very well but not completely! https://beyond.asu.edu/workshop/unsolved-problems-gravity https://beyond.asu.edu/workshop/unsolved-problems-grav

We understand it very well but not completely! https://beyond.asu.edu/workshop/unsolved-problems-gravity https://beyond.asu.edu/workshop/unsolved-problems-gravity We don't go around declaring that "No talk about gravity till we know everything about it and have solved all open problems."