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This article uses c exclusively for the speed of light in vacuum. Use in unit systems. Since 1983, the constant c has been defined in the International System of Units (SI) as exactly 299 792 458 m/s; this relationship is used to define the metre as exactly the distance that light travels in vacuum in 1⁄299 792 458 of a second.
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The speed of sound is the distance travelled per unit of time by a sound wave as it propagates through an elastic medium. At 20 °C (68 °F), the speed of sound in air is about 343 m/s (1,125 ft/s; 1,235 km/h; 767 mph; 667 kn ), or one km in 2.91 s or one mile in 4.69 s.
Statistical subregions as defined by the United Nations Statistics Division. [1] This is a list of countries and other inhabited territories of the world by total population, based on estimates published by the United Nations in the 2022 revision of World Population Prospects. It presents population estimates from 1950 to the present. [2] List.
Kaliningrad (/ k ə ˈ l ɪ n ɪ n ɡ r æ d / kə-LIN-in-grad; Russian: Калининград, IPA: [kəlʲɪnʲɪnˈɡrat]), until 1946 known as Königsberg (German pronunciation: [ˈkøːnɪçsbɛʁk] ; Russian: Кёнигсберг, tr. Kyonigsberg, IPA: [ˈkʲɵnʲɪɡzbɛrk]; or Кенигсберг, tr.. Kenigsberg, IPA: [kʲinʲiɡzbʲˈerk]; Polish: Królewiec), is the largest city ...
Russia, [b] or the Russian Federation, [c] is a country spanning Eastern Europe and North Asia. It is the largest country in the world by area, extending across eleven time zones. It shares land boundaries with fourteen countries. [d] It is the world's ninth-most populous country and Europe's most populous country.
Copenhagen's name ( København in Danish), reflects its origin as a harbour and a place of commerce. The original designation in Old Norse, from which Danish descends, was Kaupmannahǫfn [ˈkɔupˌmɑnːɑˌhɔvn] (cf. modern Icelandic: Kaupmannahöfn [ˈkʰœipˌmanːaˌhœpn̥], Faroese: Keypmannahavn ), meaning 'merchants' harbour'.