I feel like giving up now that I think I understand it. Gravity explains the deflection of the moon towards the earth but not it's straight line velocity past the earth. That velosity is explained by how the solar system was formed from a swirling cloud and objects once set in motion keep moving forever. Gravity that can deflect planets, speed them up and slow them and turn them, but not cause any drag on the overall velocity of an orbit seems strange. However Einstein warped space-time might make it more acceptable, but we can't see or imagine, I persume, a physical expression of it. Could time and gravity be a linked mystery then?