ABSTRACT
The Solar System a few AU in size, involves about a solar mass, and is several billion dynamical times old. Clusters of galaxies are 1012 AU in size, involve upwards of 1014 solar masses and are only a few dynamical times old. The commonality that relates these systems is gravity, and that they are both well approximated as a Hamiltonian system. In the past decade, gravitational N-body simulations have been successfully used to make discoveries in both of these regimes. The chapter focuses on modelling the Middle stage of planet formation. There are a number of observations that one would hope to explain using simulations of terrestrial planet formation. These include the size of the planets, their composition, their spin, and the amount of debris (comets and asteroids) left over. The “standard model” for planet formation is the planetesimal hypothesis where dust grains condense into kilometre-sized bodies before aggregating into planets.
