{"id":866,"date":"2023-03-06T01:09:07","date_gmt":"2023-03-05T23:09:07","guid":{"rendered":"http:\/\/www.cosmoespai.com\/cat\/?p=866"},"modified":"2023-03-06T01:09:07","modified_gmt":"2023-03-05T23:09:07","slug":"la-velocitat-de-la-llum-per-definir-unitats-de-mesura","status":"publish","type":"post","link":"https:\/\/www.cosmoespai.com\/cat\/la-velocitat-de-la-llum-per-definir-unitats-de-mesura\/","title":{"rendered":"La velocitat de la llum per definir unitats de mesura"},"content":{"rendered":"\n<p class=\"has-text-align-justify\">Sabem exactament quina \u00e9s la velocitat de la llum: c = 299.792.458 m\/s, que sempre es refereix a la velocitat de la llum en el buit.<\/p>\n\n\n\n<p class=\"has-text-align-justify\">I aquest nombre \u00e9s 100% exacte, havent estat incl\u00f2s a l\u2019octubre de 1983 com una constant al Sistema Internacional d\u2019Unitats, el que va fer passar el metre a una unitat derivada d\u2019aquesta constant, com explicarem a continuaci\u00f3 en aquest article.<\/p>\n\n\n\n<p class=\"has-text-align-justify\">Com que la velocitat de la llum \u00e9s una constant (sempre \u00e9s la mateixa), \u00e9s una refer\u00e8ncia irrefutable a partir de la qual podem definir altres unitats de mesura.<\/p>\n\n\n\n<p class=\"has-text-align-justify\">Avui en dia, la definici\u00f3 del metre \u00e9s: \u00abla dist\u00e0ncia que la llum recorre en el buit en exactament 1\/299.792.458 segons\u00bb.<\/p>\n\n\n\n<p class=\"has-text-align-justify\">Anteriorment, el metre s\u2019havia definit com la 1\/10.000.000 part de la dist\u00e0ncia entre l\u2019equador i el pol Nord, seguint el meridi\u00e0 de Par\u00eds, al 1799, i la longitud d\u2019una barra de plat\u00ed guardada en una caixa forta a Par\u00eds, al 1889. No obstant, totes aquestes definicions del metre poden contenir errors de mesura. D\u2019aqu\u00ed prov\u00e9 la depend\u00e8ncia en la velocitat de la llum.<\/p>\n\n\n\n<p class=\"has-text-align-justify\">Els cient\u00edfics van triar 299.792.458 m\/s com la velocitat de la llum (i no un n\u00famero m\u00e9s convenient com 300.000.000 m\/s), ja que d\u2019aquesta manera la definici\u00f3 del metre nom\u00e9s es modificava per una fracci\u00f3 d\u2019una fracci\u00f3 d\u2019un percentatge. Dit en altres paraules, per intentar conservar la mesura tradicional del metre.<\/p>\n\n\n\n<p class=\"has-text-align-justify\">Una conseq\u00fc\u00e8ncia d\u2019utilitzar aquesta definici\u00f3 \u00e9s que qualsevol intent de mesurar la velocitat de la llum \u00e9s c\u00edclic. S\u2019ha d\u2019utilitzar el metre per mesurar-la en algun punt, el que a la vegada dep\u00e8n de la velocitat de la llum.<\/p>\n\n\n\n<p class=\"has-text-align-justify\">En conclusi\u00f3, la constant de velocitat de la llum s\u2019utilitza com una refer\u00e8ncia amb la qual \u00e9s possible mesurar altres unitats de dist\u00e0ncia.<\/p>\n\n\n\n<hr class=\"wp-block-separator\"\/>\n\n\n\n<p><strong>Entrades Similars:<\/strong><\/p>\n\n\n\n<p><a href=\"http:\/\/www.cosmoespai.com\/cat\/velocitats\/\">Velocitats<\/a><\/p>\n\n\n\n<p><a href=\"http:\/\/www.cosmoespai.com\/cat\/la-llum\/\">La llum<\/a><\/p>\n\n\n\n<p><a href=\"http:\/\/www.cosmoespai.com\/cat\/la-llum-tarda-uns-170-000-anys-en-escapar-del-sol\/\">La llum tarda uns 170 000 anys en escapar del Sol<\/a><\/p>\n\n\n\n<p><a href=\"http:\/\/www.cosmoespai.com\/cat\/que-es-lespectre-electromagnetic\/\">Qu\u00e8 \u00e9s l\u2019espectre electromagn\u00e8tic?<\/a><\/p>\n\n\n\n<p><strong>Entrades Populars:<\/strong><\/p>\n\n\n\n<p><a href=\"http:\/\/www.cosmoespai.com\/cat\/perque-la-lluna-nomes-ens-ensenya-una-cara\/\">Perqu\u00e8 la Lluna nom\u00e9s ens ensenya una cara?<\/a><\/p>\n\n\n\n<p><a href=\"http:\/\/www.cosmoespai.com\/cat\/stephenson-2-18-lestrella-mes-gran-coneguda-a-lunivers\/\">Stephenson 2-18, l\u2019estrella m\u00e9s gran coneguda a l\u2019univers<\/a><\/p>\n\n\n\n<p><a href=\"http:\/\/www.cosmoespai.com\/cat\/lexplotacio-minera-al-cinturo-dasteroides-una-font-de-recursos\/\">L\u2019explotaci\u00f3 minera al cintur\u00f3 d\u2019asteroides, una font de recursos<\/a><\/p>\n\n\n\n<p><a href=\"http:\/\/www.cosmoespai.com\/cat\/la-brossa-espacial-un-gran-problema\/\">La brossa espacial, un gran problema<\/a><\/p>\n\n\n\n<p><a href=\"http:\/\/www.cosmoespai.com\/cat\/com-es-van-extingir-els-dinosaures\/\">Com es van extingir els dinosaures?<\/a><\/p>\n\n\n\n<p><a href=\"http:\/\/www.cosmoespai.com\/cat\/que-passaria-si-la-terra-deixes-de-rotar\/\">Qu\u00e8 passaria si la Terra deix\u00e9s de rotar?<\/a><\/p>\n\n\n\n<p><a href=\"http:\/\/www.cosmoespai.com\/cat\/la-missio-a-venus-de-la-sonda-venus-express-per-la-esa\/\">La missi\u00f3 a Venus de la sonda Venus Express per la ESA<\/a><\/p>\n\n\n\n<p><a href=\"http:\/\/www.cosmoespai.com\/cat\/quins-son-els-requisits-per-a-ser-un-planeta\/\">Quins s\u00f3n els requisits per a ser un planeta?<\/a><\/p>\n\n\n\n<p><a href=\"http:\/\/www.cosmoespai.com\/cat\/perque-no-es-poden-sentir-sons-a-lespai\/\">Perqu\u00e8 no es poden sentir sons a l\u2019espai?<\/a><\/p>\n\n\n\n<p><a href=\"http:\/\/www.cosmoespai.com\/cat\/quina-mida-i-forma-tindrien-els-extraterrestres\/\">Quina mida i forma tindrien els extraterrestres?<\/a><\/p>\n\n\n\n<p><a href=\"http:\/\/www.cosmoespai.com\/cat\/les-unitats-de-mesura-que-fem-servir-en-astronomia\/\">Les unitats de mesura que fem servir en astronomia<\/a><\/p>\n\n\n\n<p><strong>Entrades Recents:<\/strong><\/p>\n\n\n<ul class=\"wp-block-latest-posts__list is-grid columns-3 wp-block-latest-posts\"><li><a class=\"wp-block-latest-posts__post-title\" href=\"https:\/\/www.cosmoespai.com\/cat\/com-viatjar-al-futur-sense-violar-les-lleis-de-la-fisica\/\">Com Viatjar al Futur Sense Violar les Lleis de la F\u00edsica<\/a><\/li>\n<li><a class=\"wp-block-latest-posts__post-title\" href=\"https:\/\/www.cosmoespai.com\/cat\/que-es-la-gravetat\/\">Qu\u00e8 \u00e9s la gravetat?<\/a><\/li>\n<li><a class=\"wp-block-latest-posts__post-title\" href=\"https:\/\/www.cosmoespai.com\/cat\/per-que-hi-ha-mes-materia-que-antimateria-a-lunivers\/\">Per qu\u00e8 hi ha m\u00e9s mat\u00e8ria que antimat\u00e8ria a l\u2019univers?<\/a><\/li>\n<li><a class=\"wp-block-latest-posts__post-title\" href=\"https:\/\/www.cosmoespai.com\/cat\/que-es-lantimateria\/\">Qu\u00e8 \u00e9s l\u2019antimat\u00e8ria?<\/a><\/li>\n<li><a class=\"wp-block-latest-posts__post-title\" href=\"https:\/\/www.cosmoespai.com\/cat\/per-que-els-centres-de-les-galaxies-contenen-forats-negres\/\">Per qu\u00e8 els centres de les gal\u00e0xies contenen forats negres?<\/a><\/li>\n<\/ul>","protected":false},"excerpt":{"rendered":"<p>Sabem exactament quina \u00e9s la velocitat de la llum: c = 299.792.458 m\/s, que sempre es refereix a la velocitat de la llum en el<span class=\"read-more-link\"><a class=\"read-more\" href=\"https:\/\/www.cosmoespai.com\/cat\/la-velocitat-de-la-llum-per-definir-unitats-de-mesura\/\">Continuar llegint<\/a><\/span><\/p>\n","protected":false},"author":1,"featured_media":868,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_mi_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":""},"categories":[1,6],"tags":[224,711,474,713,712,710],"jetpack_featured_media_url":"https:\/\/i0.wp.com\/www.cosmoespai.com\/cat\/wp-content\/uploads\/2023\/03\/Mesurar_VelocitatLlum.jpg?fit=720%2C405","jetpack_sharing_enabled":true,"jetpack_likes_enabled":true,"jetpack-related-posts":[{"id":886,"url":"https:\/\/www.cosmoespai.com\/cat\/que-sabem-sobre-la-velocitat-de-la-llum\/","url_meta":{"origin":866,"position":0},"title":"Qu\u00e8 sabem sobre la velocitat de la llum?","author":"Ferran","date":"2 d'abril de 2023","format":false,"excerpt":"La velocitat de la llum al buit \u00e9s d\u2019exactament de 299.792.458 metres per segon, arrodonida normalment a 300.000.000 metres per segon. Aquesta \u00e9s una constant universal, simbolitzada per la lletra \u00abc\u00bb a les equacions. Segons la relativitat especial d\u2019Albert Einstein, la velocitat de la llum funciona com un l\u00edmit de\u2026","rel":"","context":"A &quot;General&quot;","block_context":{"text":"General","link":"https:\/\/www.cosmoespai.com\/cat\/category\/general\/"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.cosmoespai.com\/cat\/wp-content\/uploads\/2023\/04\/Velocitat_Llum.jpg?fit=720%2C405&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.cosmoespai.com\/cat\/wp-content\/uploads\/2023\/04\/Velocitat_Llum.jpg?fit=720%2C405&resize=350%2C200 1x, https:\/\/i0.wp.com\/www.cosmoespai.com\/cat\/wp-content\/uploads\/2023\/04\/Velocitat_Llum.jpg?fit=720%2C405&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/www.cosmoespai.com\/cat\/wp-content\/uploads\/2023\/04\/Velocitat_Llum.jpg?fit=720%2C405&resize=700%2C400 2x"},"classes":[]},{"id":293,"url":"https:\/\/www.cosmoespai.com\/cat\/les-unitats-de-mesura-que-fem-servir-en-astronomia\/","url_meta":{"origin":866,"position":1},"title":"Les unitats de mesura que fem servir en astronomia","author":"Ferran","date":"2 d'abril de 2021","format":false,"excerpt":"Les dist\u00e0ncies a l\u2019univers s\u00f3n tan grans, que ni tan sols les mesures m\u00e9s grans que utilitzem al Sistema Internacional, ens serveixen per a poder expressar les dist\u00e0ncies amb n\u00fameros que siguin raonablement manejables. Per poder fer-nos una idea d\u2019aquestes enormes dist\u00e0ncies hem de rec\u00f3rrer a noves mesures. L\u2019espai \u00e9s\u2026","rel":"","context":"A &quot;Univers&quot;","block_context":{"text":"Univers","link":"https:\/\/www.cosmoespai.com\/cat\/category\/univers\/"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.cosmoespai.com\/cat\/wp-content\/uploads\/2021\/03\/Dist\u00e0ncies_Univers.jpg?fit=720%2C405&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.cosmoespai.com\/cat\/wp-content\/uploads\/2021\/03\/Dist\u00e0ncies_Univers.jpg?fit=720%2C405&resize=350%2C200 1x, https:\/\/i0.wp.com\/www.cosmoespai.com\/cat\/wp-content\/uploads\/2021\/03\/Dist\u00e0ncies_Univers.jpg?fit=720%2C405&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/www.cosmoespai.com\/cat\/wp-content\/uploads\/2021\/03\/Dist\u00e0ncies_Univers.jpg?fit=720%2C405&resize=700%2C400 2x"},"classes":[]},{"id":891,"url":"https:\/\/www.cosmoespai.com\/cat\/viatjar-en-el-temps-es-possible\/","url_meta":{"origin":866,"position":2},"title":"Viatjar en el temps \u00e9s possible","author":"Ferran","date":"9 d'abril de 2023","format":false,"excerpt":"La idea de viatjar en el temps ha fascinat a la humanitat durant segles, amb incomptables obres de ci\u00e8ncia ficci\u00f3 explorant el concepte dels viatges entre diferents \u00e8poques en el temps. No obstant, des de la publicaci\u00f3 de la teoria de la relativitat general d\u2019Albert Einstein al 1915, el viatge\u2026","rel":"","context":"A &quot;Univers&quot;","block_context":{"text":"Univers","link":"https:\/\/www.cosmoespai.com\/cat\/category\/univers\/"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.cosmoespai.com\/cat\/wp-content\/uploads\/2023\/04\/Viatjar_Futur.jpg?fit=720%2C405&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.cosmoespai.com\/cat\/wp-content\/uploads\/2023\/04\/Viatjar_Futur.jpg?fit=720%2C405&resize=350%2C200 1x, https:\/\/i0.wp.com\/www.cosmoespai.com\/cat\/wp-content\/uploads\/2023\/04\/Viatjar_Futur.jpg?fit=720%2C405&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/www.cosmoespai.com\/cat\/wp-content\/uploads\/2023\/04\/Viatjar_Futur.jpg?fit=720%2C405&resize=700%2C400 2x"},"classes":[]},{"id":895,"url":"https:\/\/www.cosmoespai.com\/cat\/existeixen-els-forats-negres-no-rotatoris\/","url_meta":{"origin":866,"position":3},"title":"Existeixen els forats negres no rotatoris?","author":"Ferran","date":"15 d'abril de 2023","format":false,"excerpt":"Els forats negres s\u00f3n un dels cossos m\u00e9s fascinants i misteriosos de l\u2019univers. S\u00f3n regions de l\u2019espai amb una densitat tan elevada que ni tan sols la llum en pot escapar. Per molt que els forats negres semblin cossos molt complexos i diferents entre ells, la veritat \u00e9s que no\u2026","rel":"","context":"A &quot;General&quot;","block_context":{"text":"General","link":"https:\/\/www.cosmoespai.com\/cat\/category\/general\/"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.cosmoespai.com\/cat\/wp-content\/uploads\/2023\/04\/ForatsNegres_No_Rotatoris.jpg?fit=720%2C405&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.cosmoespai.com\/cat\/wp-content\/uploads\/2023\/04\/ForatsNegres_No_Rotatoris.jpg?fit=720%2C405&resize=350%2C200 1x, https:\/\/i0.wp.com\/www.cosmoespai.com\/cat\/wp-content\/uploads\/2023\/04\/ForatsNegres_No_Rotatoris.jpg?fit=720%2C405&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/www.cosmoespai.com\/cat\/wp-content\/uploads\/2023\/04\/ForatsNegres_No_Rotatoris.jpg?fit=720%2C405&resize=700%2C400 2x"},"classes":[]},{"id":965,"url":"https:\/\/www.cosmoespai.com\/cat\/com-viatjar-al-futur-sense-violar-les-lleis-de-la-fisica\/","url_meta":{"origin":866,"position":4},"title":"Com Viatjar al Futur Sense Violar les Lleis de la F\u00edsica","author":"Ferran","date":"14 de setembre de 2023","format":false,"excerpt":"La veritat \u00e9s que tots estem viatjant en el temps a cada instant! I ho fem a un ritme constant de 1 segon per segon. En un primer moment podr\u00edeu pensar que aix\u00f2 \u00e9s totalment diferent que viatjar a trav\u00e9s d\u2019una de les tres dimensions espacials a, per exemple, un\u2026","rel":"","context":"A &quot;Univers&quot;","block_context":{"text":"Univers","link":"https:\/\/www.cosmoespai.com\/cat\/category\/univers\/"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.cosmoespai.com\/cat\/wp-content\/uploads\/2023\/09\/ViatgesTemps_Futur.jpg?fit=720%2C405&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.cosmoespai.com\/cat\/wp-content\/uploads\/2023\/09\/ViatgesTemps_Futur.jpg?fit=720%2C405&resize=350%2C200 1x, https:\/\/i0.wp.com\/www.cosmoespai.com\/cat\/wp-content\/uploads\/2023\/09\/ViatgesTemps_Futur.jpg?fit=720%2C405&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/www.cosmoespai.com\/cat\/wp-content\/uploads\/2023\/09\/ViatgesTemps_Futur.jpg?fit=720%2C405&resize=700%2C400 2x"},"classes":[]},{"id":807,"url":"https:\/\/www.cosmoespai.com\/cat\/deteccio-dexoplanetes-el-metode-de-la-velocitat-radial\/","url_meta":{"origin":866,"position":5},"title":"Detecci\u00f3 d\u2019exoplanetes: el m\u00e8tode de la velocitat radial","author":"Ferran","date":"6 de desembre de 2022","format":false,"excerpt":"La detecci\u00f3 d\u2019exoplanetes s\u2019ha desenvolupat en gran mesura durant les \u00faltimes d\u00e8cades. Des de la primera detecci\u00f3 d\u2019un exoplaneta al 1994, s\u2019han anat posant en pr\u00e0ctica diversos m\u00e8todes per descobrir exoplanetes. A causa de les enormes dificultats per observar planetes directament, quasi totes les deteccions d\u2019exoplanetes s\u2019han efectuat mitjan\u00e7ant m\u00e8todes\u2026","rel":"","context":"A &quot;General&quot;","block_context":{"text":"General","link":"https:\/\/www.cosmoespai.com\/cat\/category\/general\/"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.cosmoespai.com\/cat\/wp-content\/uploads\/2022\/12\/Velocitat_Radialexoplanetes.jpg?fit=720%2C405&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.cosmoespai.com\/cat\/wp-content\/uploads\/2022\/12\/Velocitat_Radialexoplanetes.jpg?fit=720%2C405&resize=350%2C200 1x, https:\/\/i0.wp.com\/www.cosmoespai.com\/cat\/wp-content\/uploads\/2022\/12\/Velocitat_Radialexoplanetes.jpg?fit=720%2C405&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/www.cosmoespai.com\/cat\/wp-content\/uploads\/2022\/12\/Velocitat_Radialexoplanetes.jpg?fit=720%2C405&resize=700%2C400 2x"},"classes":[]}],"_links":{"self":[{"href":"https:\/\/www.cosmoespai.com\/cat\/wp-json\/wp\/v2\/posts\/866"}],"collection":[{"href":"https:\/\/www.cosmoespai.com\/cat\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.cosmoespai.com\/cat\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.cosmoespai.com\/cat\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.cosmoespai.com\/cat\/wp-json\/wp\/v2\/comments?post=866"}],"version-history":[{"count":2,"href":"https:\/\/www.cosmoespai.com\/cat\/wp-json\/wp\/v2\/posts\/866\/revisions"}],"predecessor-version":[{"id":869,"href":"https:\/\/www.cosmoespai.com\/cat\/wp-json\/wp\/v2\/posts\/866\/revisions\/869"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.cosmoespai.com\/cat\/wp-json\/wp\/v2\/media\/868"}],"wp:attachment":[{"href":"https:\/\/www.cosmoespai.com\/cat\/wp-json\/wp\/v2\/media?parent=866"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.cosmoespai.com\/cat\/wp-json\/wp\/v2\/categories?post=866"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.cosmoespai.com\/cat\/wp-json\/wp\/v2\/tags?post=866"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}