{"url":"https:\/\/siunits.stuchalk.domains.unf.edu\/api\/baseunit\/meter","pid":"si:unit:meter:2019","name":"meter","urlname":"meter","definition":"The metre, symbol *m<\/em>, is the SI unit of length. It is defined by taking the fixed numerical value of the speed of light in vacuum, **c<\/em>, to be 299 792 458 when expressed in the unit **m s*^{-1<\/sup><\/em>, where the second is defined in terms of the caesium frequency Δν<\/em>Cs<\/sub>.","source":"SI Brochure 9th Ed. 2019, p 131","source_url":null,"siunit":null,"startdate":"2019-05-20","enddate":null,"status":"Valid","reference":"CGPM Resolution 1 of the 26th CGPM (2018) \"On the revision of the International System of Units (SI)<\/a>\"","reference_url":null,"year":2019,"names":"meter:meter","pinfo":null,"notes":{"1":"This definition implies the exact relation \\(c = {\\rm{299\\ 792\\ 458\\ m\\ s}^{-1}}\\). Inverting this relation gives an exact expression for the metre in terms of the defining constants \\(c\\) and \\(\\Delta\\nu_{\\rm{Cs}}\\):\r\n$$1\\ {\\rm{m}} = ( \\frac{c}{299\\:792\\:458} )\\ {\\rm{s}} = \\frac{9\\:192\\:631\\:770}{299\\:792\\:458} \\frac{c}{\\Delta\\nu_{\\rm{Cs}}} \\approx 30.663\\:319 \\frac{c}{\\Delta\\nu_{\\rm{Cs}}}$$","2":"The effect of this definition is that one metre is the length of the path travelled by light in vacuum during a time interval with duration of \\(1\/299\\:792\\:458\\) of a second."},"related":[{"relationship":"hasUnitSymbol","weburl":"https:\/\/siunits.stuchalk.domains.unf.edu\/si\/definition\/unitsymbol\/m","apurl":"https:\/\/siunits.stuchalk.domains.unf.edu\/api\/unitsymbol\/m"},{"relationship":"hasDefiningEquation","weburl":"https:\/\/siunits.stuchalk.domains.unf.edu\/si\/definition\/definingequation\/meter_equation","apurl":"https:\/\/siunits.stuchalk.domains.unf.edu\/api\/definingequation\/meter_equation"}],"date":"2024-07-24T06:08:31+00:00"}}