Why are the jovian planets larger than the terrestrial planets?
Almost all of the material in the inner solar system was swallowed by the sun during the accretion. Being further from the center allowed outer worlds to grow larger. In addition when the sun ignited the T-Tauri wind swept the early atmospheres of the inner planets and most of the left over gas and dust out of the inner solar system. Much of this material was captured by the jovian planets. Also it is important to understand that the outer planets are able to hold onto the lighter gasses since the temperatures in that region of space are considerably lower than in the inner system. I must admit here that this is traditionalist explanation and while partly accurate, reality seems to be more complex. Extrasolar planetary systems don’t fit our model, having giant planets in near solar orbits. How this occurs isn’t understood. It was much easier when our solar system was the only model.
