The geology consists of the sciences of mathematics, physics (geophysics and seismology), and chemistry (petrology and geochemistry); these are the sciences that set the general principles for all the other sciences. Additionally, geology is composed of or interrelated to the sciences that describe the great systems that make up the universe: astronomy (planetary geology) and biology (paleontology). Some geologists are specialists who deal with very narrow parts of geology including mineralogy, meteorology, botany, zoology, and others. Geological science also includes exposure to the principles of sociology and psychology. In a nutshell and based on personal experience, it can be said with some certainty that the practicing geologist, whether a specialist or not, should and must be a generalist. That is, to be effective in practice, the geologist must have a well-rounded exposure to and some knowledge of just about everything related to the other scientific disciplines.