When most of us learn about the solar system, it seems like a pretty well-ordered place. Our sun formed first, about five billion years ago, and the planets appeared a little later. As a very general trend, these planets grew larger and less dense the farther from the sun they formed.  

But this story leaves out the chaotic dynamics and frenetic reshuffling that occurred when our solar system was young. Nature may like order eventually, but that order evolves out of pure chance. Our solar