I know a similar question has been asked but i'm still kind of stumped. Imagine the earth on the left and a small mass to it's right separated by some distance h. You are in the frame of reference where the earth and the small mass are moving to your right at some speed v. So, both the earth and the ball have some initial kinetic energy (1/2)(respective mass)v^2 and the ball earth system will lose a potential energy of mgh as they come together. So the earth won't gain any significant energy since it is so massive but the ball appear to lose energy since it is accelerated to the left. How is energy conserved if the potential energy is gone and the ball earth system appears to actually lose energy? My only possible reasoning is that potential energy is somehow relative? But the equation for total potential energy being equal to -GMm/r makes it seem pretty absolute (in a non relativistic setting of course).. Thank you for any help!