Editing Hydrostatics (section)

{{short description|Branch of fluid mechanics that studies fluids at rest}}
{{about|the discipline branch|the concept|Hydrostatic equilibrium}}
[[File:Table of Hydraulics and Hydrostatics, Cyclopaedia, Volume 1.jpg|thumb|right|250px|Table of Hydraulics and Hydrostatics, from the 1728 ''[[Cyclopædia, or an Universal Dictionary of Arts and Sciences|Cyclopædia]]'']]
{{Continuum mechanics|cTopic=fluid}}

'''Hydrostatics''' is the branch of [[fluid mechanics]] that studies [[fluid]]s at [[hydrostatic equilibrium]]<ref>{{Cite web|title=Fluid Mechanics/Fluid Statics/Fundamentals of Fluid Statics - Wikibooks, open books for an open world|url=https://en.wikibooks.org/wiki/Fluid_Mechanics/Fluid_Statics/Fundamentals_of_Fluid_Statics#Hydrostatic_Equilibrium|access-date=2021-04-01|website=en.wikibooks.org|language=en}}</ref> and "the pressure in a fluid or exerted by a fluid on an immersed body".<ref name="MW dictionary def">{{cite web |title=Hydrostatics |url=https://www.merriam-webster.com/dictionary/hydrostatics |website=Merriam-Webster |access-date=11 September 2018}}</ref> The word "hydrostatics" is sometimes used to refer specifically to water and other liquids, but more often it includes both gases and liquids, whether [[Compressible flow|compressible]] or [[Incompressible flow|incompressible]].

It encompasses the study of the conditions under which fluids are at rest in [[Mechanical equilibrium|stable equilibrium]]. It is opposed to ''[[fluid dynamics]]'', the study of fluids in motion. 

Hydrostatics is fundamental to ''[[hydraulics]]'', the [[engineering]] of equipment for storing, transporting and using fluids.  It is also relevant to [[geophysics]] and [[astrophysics]] (for example, in understanding [[plate tectonics]] and the anomalies of the [[Gravity of Earth|Earth's gravitational field]]), to [[meteorology]], to [[medicine]] (in the context of [[blood pressure]]), and many other fields.

Hydrostatics offers physical explanations for many phenomena of everyday life, such as why [[atmospheric pressure]] changes with [[altitude]], why wood and oil float on water, and why the surface of still water is always [[Water level|level]] according to the [[spherical Earth|curvature of the earth]].