The problem is that advanced mathematics are needed to model the world around us, and therefore to successfully explain it. When Newton was doing his experiments on gravity, he realized the existing mathematics of the day were unable to successfully model it, so he literally invented calculus. Acceleration in science is defined as a change in speed or direction, aka a change in the vector. Since gravity is continuously exerting a force on objects, the definition of free fall is constant acceleration, which is roughly 9.8 meters per second per second.
You can't escape gravity, it is simply the attraction between matter. The relativity of it (the observer thing) is "easily" accounted for, until you approach the speed of light, which starts to distort the space/ time thing, which is what Einstein discovered. Newton's formulas were modified to account for this, as they are constantly updated as we learn more. Today they are studying antimatter so the formulas don't work, so they are getting changed again.