UIC Solar Nebula Theory Discussion

You are describing the solar nebula theory to a friend. You point out that it provides an explanation for the regular motion in our solar system, the division of the planets into terrestrial and Jovian types, and an explanation for the origin and nature of comets and asteroids. Your friend agrees that this is all very nice, but that it seems that the solar nebula theory fails the basic criteria for a scientific theory, to make predictions about the natural world that can be observationally tested. In her opinion, all the solar nebula theory does is explain known facts, albeit in a compelling and economical way. How would you answer your friend and make the case that the solar nebula theory is indeed a scientific theory that has passed many observational tests? Can you think of any predictions that the solar nebula theory has made that were confirmed only within the last decade or so?