What is Geophysics?
[[File:2008 age of ocean plates.png|thumb|Map of the age of the sea floor made from data about changes in the magnetic field. |alt=false color image]] '''Geophysics''' ({{IPAc-en|dʒ|iː|oʊ|f|ɪ|z|ɪ|k|s}}) is the [[physics]] of the [[Earth]] and its environment in [[Outer space|space]]. It is also the study of the Earth by measuring things and collecting data. Sometimes ''geophysics'' means studying the [[geology]] of the earth such as its [[shape]], [[gravitational]] and [[magnetic field]], [[structure of the Earth|internal structure]] and [[Earth#Composition|composition]]. It may also mean how they create [[plate tectonics]], [[magma]], [[volcanism]] and rock formations.<ref name=Sheriff1991>{{harvnb|Sheriff|1991}}</ref> Some geophysicists now also study the [[hydrological cycle]] including [[snow]] and [[ice]]. They study how the [[oceans]] and the [[atmosphere]] move. They study [[electricity]] and [[magnetism]] in the atmosphere, [[ionosphere]], and [[magnetosphere]]. How the earth and sun affect each other is also part of geophysics.<ref name=Sheriff1991/><ref name=IUGG>{{harvnb|IUGG|2011}}</ref><ref name=AGUscience>{{harvnb|AGU|2011}}</ref> Geophysics was only recognized as a special area of study in the 19th century. But, there were geophysicists in [[ancient history]]. The first magnetic compasses were made in the fourth century BC and the first [[seismoscope]] was built in 132 BC. [[Isaac Newton]] applied his theory of mechanics to the [[tide]]s and the [[precession of the equinox]]. Instruments were developed to measure the Earth's shape, density and gravity field, as well as parts of the [[water cycle]]. In the 20th century, geophysical methods were developed for remote exploration of the solid Earth and the ocean. Studying geophysics may help with problems such as [[mineral]] resources, reducing [[natural hazard]]s, and protecting the environment.<ref name=IUGG/> Geophysical [[surveying|survey]] data help find petroleum reservoirs, mineral deposits, groundwater, and archaeological relics. Such data c