Nadir is employed during remote sensing of the atmosphere, as well as when an astronaut faces the Earth while performing a spacewalk. The term nadir can also be used to represent the lowest point reached by a celestial body during its apparent orbit around a given point of observation. This can be used to describe the location of the Sun, but it is only technically accurate for one latitude at a time and only possible at the low latitudes. The sun is said to be at the nadir at a location when it is at the zenith at the location's antipode
Preliminary Discourse to the Encyclopedia of Diderot reflection or reason, which is the basis of Philosophy; and what d'Alembert refers to as "imagination," (50) or imitation of Nature, which produces Fine Arts. From these divisions spring smaller subdivisions such as physics, poetry, music and many others. d'Alembert was also greatly influenced by the Cartesian principle of simplicity. In this first part of the book, he describes how the reduction of the principles of a certain science gives them scope and makes them more "fertile" (22). Only by reducing principles can they be understood and related to each other. Ultimately, from a high "vantage point" (47) the philosopher