Gravity is a myth.
Says who ?
Albert Einstein
The equation explains that energy is equal to mass and that there is a time frame involved. The energy inside the rock is the same energy as outside the rock but it is moving very slowly over time. If it was travelling at the same speed as the energy outside the rock then the mass would be negated and it would cease to be a rock within your relative time frame. The equation is correct its the theory built around it that isnt.
According to einstein there is still a force that pull rocks toward earth due to space time curvature. At earth scale the classic formulation and relativity are roughly equivalent.