A geographer is a physical scientist, social scientist or humanist whose area of study is geography, the study of Earth's natural environment and human society, including how society and nature interacts. The Greek prefix "geo" means "earth" and the Greek suffix, "graphy," meaning "description," so a geographer is someone who studies the earth. The word "geography" is a Middle French word that is believed to have been first used in 1540. Although geographers are historically known as people who make maps, map making is actually the field of study of cartography, a subset of geography. Geographers do not study only the details of the natural environment or human society, but they also study the reciprocal relationship between these two. For example, they study how the natural environment contributes to human society and how human society affects the natural environment. In particular, physical geographers study the natural environment while human geographers study human society and culture. Some geographers are practitioners of GIS (geographic information system) and are often employed by local, state, and federal government agencies as well as in the private sector by environmental and engineering firms. The paintings by Johannes Vermeer titled The Geographer and The Astronomer are both thought to represent the growing influence and rise in prominence of scientific enquiry in Europe at the time of their painting in 1668–69. Areas of study There are three major fields of study, which are further subdivided: Human geography: including urban geography, cultural geography, economic geography, political geography, historical geography, marketing geography, health geography, and social geography. Physical geography: including geomorphology, hydrology, glaciology, biogeography, climatology, meteorology, pedology, oceanography, geodesy, and environmental geography. Regional geography: including atmosphere, biosphere, and lithosphere. The National Geographic Society identifies five broad key themes for geographers: human-environment interaction location movement place regions Notable geographers Alexander von Humboldt (1769–1859) – published Cosmos and founder of the sub-field biogeography. Arnold Henry Guyot (1807–1884) – noted the structure of glaciers and advanced understanding in glacier motion, especially in fast ice flow. Carl O. Sauer (1889–1975) – cultural geographer. Carl Ritter (1779–1859) – occupied the first chair of geography at Berlin University. David Harvey (born 1935) – Marxist geographer and author of theories on spatial and urban geography, winner of the Vautrin Lud Prize. Doreen Massey (1944–2016) – scholar in the space and places of globalization and its pluralities; winner of the Vautrin Lud Prize. Edward Soja (1940–2015) – worked