I explain why we need to take an ad-hoc approach to gravity. It is not possible at this time to create a simple and elegent force law that applies to all contexts and all scales. I explain that cosmological expansion is actually the product of repulsive gravity. I also explain that the universe is forever gently alternating between periods of expansion and contraction. I look forward to the next episode wherein I will explain how CGC deals with the deflection of light, time dilation, and the increase of momentum at relativisitic velocities.
