Editing Earth radius (section)

==Nominal radii{{anchor|Nominal|Nominal radius}}==
In astronomy, the [[International Astronomical Union]] denotes the ''nominal equatorial Earth radius'' as <math>\mathcal{R}^\text{N}_\text{eE}</math>, which is defined to be exactly {{convert|6378.1|km|mi|abbr=on}}.<ref name = "IAU XXIX"/>{{rp|3}} The ''nominal polar Earth radius'' is defined exactly as <math>\mathcal{R}^\text{N}_\text{pE}</math> = {{convert|6356.8|km|mi|abbr=on}}. These values correspond to the zero [[Earth tide]] convention. Equatorial radius is conventionally used as the nominal value unless the polar radius is explicitly required.<ref name = "IAU XXIX"/>{{rp|4}}
The nominal radius serves as a [[unit of length]] for [[Astronomical system of units|astronomy]].
(The notation is defined such that it can be easily generalized for other [[Planet#Size and shape|planets]]; e.g., <math>\mathcal{R}^\text{N}_\text{pJ}</math> for the nominal polar [[Jupiter radius]].)