Oceanography (from Ancient Greek ὠκεανός (ōkeanós) ' ocean ' and γραφή (graphḗ) ' writing '), also known as oceanology, sea science, ocean science, and marine science, is the scientific study of the ocean. It is an Earth science, which covers a wide range of topics, including ecosystem dynamics; ocean currents, waves, and geophysical fluid dynamics ; plate tectonics and seabed geology; and fluxes of various chemical substances and physical properties within the ocean and across its boundaries. These diverse topics reflect multiple disciplines that oceanographers utilize to glean further knowledge of the world ocean, including astronomy, biology, chemistry, geography, geology, hydrology, meteorology and physics. Paleoceanography studies the history of the oceans in the geologic past. An oceanographer is a person who studies many matters concerned with oceans, including marine geology, physics, chemistry, and biology.