ABSTRACT
This chapter introduces and discusses the concept of a system, its mathematical modelling, and the value and usefulness of the principle of dynamic consistency. It examines the concept of dominant balance and the construction of valid approximations to the original modelling equations, which for most situations are differential equations. The chapter introduces the look-up methodology using standard mathematical handbooks and Wikipedia listings. It determines what is currently known about a particular topic or issue and may point to additional sources of information. The chapter deals with additional comments on the modelling process. Most individuals would guess that the rope would lie some small fraction of a meter above the surface of the planet given the fact that the radii of planets are huge compared to the 10 meter increase in the length of the rope.
