Editing Sanity check (section)

===Physical===
*[[Dimensional analysis]] may be used as a sanity check of physical equations: the two sides of any equation must be commensurable or have the same dimensions. A person who has calculated the [[Power (physics)|power]] output of a [[automobile|car]] to be 700 [[kilojoule|kJ]] may have omitted a factor, since the unit ''joules'' is a measure of [[energy]], not power (energy per unit time). 
*When determining [[physical property|physical properties]], comparing to known or similar substances will often yield insight on whether the result is reasonable. For instance, most metals sink in water, so the [[density]] of most metals should be greater than [[density of water|that of water]] (~{{val|1000|u=kg/m3}}).
*[[Fermi estimate]]s will often provide insight on the order of magnitude of an expected value.