Geophysics: study of the physical Earth, its structure and environment

Geophysics is the application of the principles and methods of physics to study the Earth and its surrounding space environment. It combines quantitative measurement, physical modeling and observational surveys to infer properties that cannot be seen directly. Modern geophysicists investigate processes ranging from the motion of tectonic plates to the behaviour of the ionosphere, using tools and theory drawn from mechanics, electromagnetism, thermodynamics and fluid dynamics. The field sits at the intersection of physical science and Earth science, translating measurements into models of structure, composition and dynamics. physics of the Earth and its environment in space are central concerns.

Core targets of geophysical study include rock and crustal structures, mass distribution and the fields that arise from them. Geophysicists commonly address geological problems (geology), the planet's external form (shape), and its gravitational and magnetic field. They probe the internal structure and composition of the crust, mantle and core to explain thermal evolution and convective patterns that drive surface change. This understanding links to large-scale processes such as plate tectonics, the production and movement of magma, and the occurrence of volcanism. Increasingly, studies also encompass the water cycle and cryosphere by measuring snow and ice, and they treat electromagnetic behaviour from near-surface currents to upper-atmosphere electricity and magnetism within the magnetosphere and ionosphere (magnetosphere).

History and development. Although scientific geophysics emerged as a distinct discipline in the nineteenth century, practical and observational roots extend far earlier. Instruments and techniques for sensing Earth processes appear in antiquity; for example, early magnetic compasses and devices to detect ground motion are recorded in ancient history. Later, the application of classical mechanics by figures such as Isaac Newton clarified gravitational influences on ocean tides and axial precession, aiding the study of tides. Over the nineteenth and twentieth centuries researchers developed precise instruments to measure the planet's shape, density and gravity, and to monitor components of the water cycle. In the twentieth century the expansion of electronic sensors, computing and remote methods transformed geophysics and enabled systematic subsurface imaging and global-scale studies.