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Bots sommige sterrestelsels vinniger as die ligsnelheid?

Bots sommige sterrestelsels vinniger as die ligsnelheid?


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As sommige sterrestelsels vinniger as die ligspoed van mekaar af uitbrei, bots hulle dan vinniger as die ligspoed?

Opdatering 1:

  • Ek dink my vraag is wat is die maksimum snelheid / snelheid waarmee sterrestelsels na mekaar toe kan beweeg?
  • Hoe lank neem dit om sterrestelsels te bots?

As u hierdie voorbeeld kan gebruik, sal dit wonderlik wees. Melkweg A: deursnee van 3 000 ligjare Melkweg B: deursnee van 300 000 ligjare

As Galaxy A met Galaxy B sou bots, wat sou die snelheid tydens die botsing wees? Ek het geen idee oor wat die tyd en afstand sou wees nie.


As sommige sterrestelsels vinniger as die ligspoed van mekaar af uitbrei, bots hulle dan vinniger as die ligspoed?

Die kort antwoord is "nee".

Die uitbreiding van die ver heelal teen skynbare snelhede vinniger as lig as gevolg van die uitbreiding van die ruimte. Maar die snelheid van die uitbreiding hang af van hoe ver die waarnemer en voorwerp van mekaar af is. As daar twee voorwerpe A en B is wat ons blykbaar vinniger as die ligspoed van ons af wegbeweeg weens die uitbreiding van die ruimtetyd, dan is dit nie hoe die voorwerpe mekaar sal sien. Hulle sal naby mekaar wees, dus is die uitbreiding van die ruimtetyd vanaf hul verwysingsraamwerke weglaatbaar (net soos vir ons en ons 'plaaslike' sterrestelsels).

Op 'n sekere tydstip dink ons ​​dat die heelal op 'klein' reekse nog vinniger kan uitbrei, maar in daardie geval kon die twee voorwerpe nie bots nie. Sodra hulle in staat is om te bots, is hulle naby genoeg sodat die gevolge van die uitbreiding van die heelal hulle nie vinniger as lig uitmekaar gaan laat beweeg nie. Sodra voorwerpe vinniger as lig uitmekaar beweeg, kan hulle nie bots nie (tensy die hele heelal begin saamtrek).

As hulle vinniger as lig van mekaar uitbrei (as gevolg van die uitbreiding van ruimtetyd), kan hulle nie bots nie. Geen aantrekkingskrag kan die uitbreiding van die ruimtetyd oorkom as dit reeds die punt bereik het dat hulle vinniger as lig beweeg nie. Dit sou vereis dat die hele heelal begin kontrakteer om dit te doen.

As dit dus met u gaan bots, kan 'n voorwerp nie vinniger as die lig teenoor u beweeg nie.

Hoe lank neem dit om sterrestelsels te bots?

Dit hang af van hoe vinnig hulle mekaar nader. In teorie kan hulle nie vinniger as lig benader nie, dus is die boonste grens (eenvoudig) die afstand gedeel deur die snelheid van die lig.

'N Meer realistiese voorbeeld is Andromeda en die Melkweg wat mekaar teen 'n relatiewe snelheid van 300 km / s nader. Andromeda is ongeveer 2,5 miljoen ligjare weg en die huidige ramings is vir 'n botsing oor ongeveer 4,5 miljard jaar, so dit beweeg baie, baie stadiger as die snelheid van die lig.


Ons weet dat sommige sterrestelsels vinniger van ons af wegbeweeg as die snelheid van die lig, en ons weet dit deur die rooi skuif te meet, maar hoe is dit moontlik?

Die volgende vraestelle gee goeie verduidelikings:

Samevattend, Hubble Law: $ v = H (t) D $, waar $ v $ resessiesnelheid is, $ D $ afstand is en $ H (t) $ die Hubble "konstante" op 'n gegewe tydstip, vereis dat buite 'n sekere afstand is die snelheid groter as die snelheid van die lig. As die resessiesnelheid op die plek van 'n bewegende foton groter was as die ligspoed gedurende die hele tyd wat die foton uit 'n afstandstelsel gereis het, sou ons die foton nooit waarneem nie. 'N Foton wat uit 'n sterrestelsel uitgestraal word wat vinniger van ons af wegbeweeg as lig, is aanvanklik ook besig om van ons af te neem. Die foton kan egter uiteindelik in 'n gebied van ruimtetyd kom waar die resessie van ons ltc $ is. In hierdie geval kan die foton ons bereik. Die presiese verband tussen rooi verskuiwing en snelheid hang af van die kosmologiese model, maar volgens bogenoemde verwysings is sterrestelsels met rooi verskuiwings groter as

3 was en is vinniger van ons af as lig.

As hulle wegbeweeg, sê teen 2c, hoe sou die sterrestelsel se lig wees? ons selfs bereik?

Slegs as die fotone uit die sterrestelsel 'n gebied van ruimtetyd bereik waar die resessiesnelheid ltc $ is.

Hoe meet ons 'rooi verskuiwing' vir iets vinniger as lig?

Rooi-skuif word gemeet as die verandering in golflengte van die lig, maar eerder as om die resultate te interpreteer met behulp van spesiale relatiwiteit (wat $ v & ltc $ tot gevolg het vir alle rooi verskuiwings), word die resultate geïnterpreteer in die konteks van 'n kosmologiese model en algemene relatiwiteit.

Lig van buite die Hubble-sfeer (die plek waar resessiesnelheid gelyk is aan die ligspoed) bereik ons ​​daagliks.

Ek is nie 'n fisikus genoeg om 'n mooi leek se verklaring hiervoor uit te dink nie, maar dit kan help om te dink aan koördinate: Dit is 'n spesiale koördinaatstelsel waar die koördinaatrooster met ruimte uitbrei, dws al is die regte afstand tussen sterrestelsels sal toeneem, sal hul koördinate nie verander nie.

In hierdie koördinaatstelsel word lig nie gevries by die Hubble-sfeer nie (soos 'n mens kan verwag), maar beweeg dit konstant van emitter na uiteindelike waarnemer, ongeag die verandering in die regte afstand.

Die beweging wat geleidelik na ons toe beweeg, moet eintlik ook geld vir lig wat van buite die kosmiese gebeurtenishorison uitgegee word (die ding wat die waarnemingsuniversum afbaken) - dit neem die lig net langer as oneindige tyd om ons te bereik)

Wat die tweede deel van u vraag oor die rooi verskuiwing betref: Dit hang nie af van resessiesnelhede nie, maar eerder van relatiewe snelhede soos bereken deur parallelle vervoer langs die ligpad (en moet onder $ c $ bly totdat u die gebeurtenishorison bereik) .

Ek is geen spesialis in swaartekrag of kosmologie nie. Alhoewel, weet ek (sonder besonderhede) dat A. Peres bewys het dat die ligsnelheid nie dieselfde was gedurende die geskiedenis van die heelal nie. Die verwysing is

Int. J. Mod. Fis. D, 12, 1751 (2003). DOI: 10.1142 / S0218271803004043

International Journal of Modern Physics D (Gravitasie Astrofisika en Kosmologie)

Jaargang 12, uitgawe 09, Oktober 2003

VERANDERLIKHEID VAN FUNDAMENTALE KONSTANTE

ASHER PERES, hierdie opstel ontvang 'n "eervolle vermelding" in die 2003-opstelkompetisie van die Gravity Research Foundation.

Hulle gaan eenvoudig nie vinniger terug as lig nie.

Resessiesnelhede word gedefinieer soos snelheid in spesiale relatiwiteit. As A, B,. Z beweeg almal in 'n lyn van mekaar af, en A en C trek van B af met 'n snelheid $ v $ wat klein genoeg is om die Newtonse relatiewe snelheid 'n redelike benadering is, en B en D op dieselfde tyd van C afneem. snelheid, ensovoorts, dan is die relatiewe snelheid van A en Z per definisie $ 25v $. As $ v = 0.05c $ dan is die relatiewe snelheid $ 1.25c $, terwyl die relatiewe spoed $ dx / dt $ .85c $ is. Niks gaan vinniger as lig nie. Die spoed $ c $ het geen spesiale betekenis as ons oor snelhede praat nie.

Dit alles geld ook vir kosmologiese resessiesnelhede. Dit het geen sin om dit met die snelheid van die lig te vergelyk nie, want dit is so gedefinieër dat daar geen waarde is wat die snelheid van die lig voorstel nie - beslis nie $ c $ nie.

Ek dink mense val in die strik om te dink dat as jy genoeg sterrestelsels in 'n ry het, moet uiteindelik op 'n punt kom waar hulle regtig vinniger as lig beweeg, maar dit is eenvoudig nie waar nie. Weereens, selfs in spesiale relatiwiteit is dit onwaar. U kan nog duisend sterrestelsels aan die einde van die lyn 26 byvoeg, sonder enige probleem op dieselfde tyd op mekaar, gemeet aan die gebruik van meterstokke en horlosies wat gesinkroniseer is toe die sterrestelsels op dieselfde punt was. Daar is 'n onbeperkte hoeveelheid kamer & quotjust kort van $ c $ & quot. U kan sê dat daar weens die lengte-inkrimping onbeperkte ruimte is, maar let op dat dit 'n heeltemal simmetriese situasie is: u kan enige sterrestelsel in die middel plaas met 'n Lorentz-hupstoot.

In die regte kosmologie kan u dink aan sterre in die verte as lengtekrimp as u wil, ten minste as die ruimtelike kromming nie positief is nie. U kan enige negatiewe-kromming-FLRW-heelal in die Minkowski-ruimte konformeel insluit, op 'n manier wat lyk soos die spesiale-relativistiese speelgoedmodel. In die kwasi-Minkowski-koördinate beweeg lig teen $ | dx / dt | = c $, al die sterrestelsels het $ | dx / dt | & ltc $, en dié met snelhede naby $ c $ is Lorentz gekontrakteer.

In ΛCDM-kosmologie het u 'n kosmologiese horison en sal u nooit weer 'n sein van 'n sterrestelsel ontvang nadat dit die horison oorsteek nie. Dit beteken nog steeds nie dat dit in enige fisiese sinvolle sin vinniger as lig terugtrek nie. By konforme inbeddings ontstaan ​​die horison omdat die heelal eindig op 'n eindige konforme tyd (wat dit 'n tydsomkeer van die oerknal-horisonprobleem maak). Ek stel nie voor dat dit die regte en korrekte verduideliking van die horison is nie, maar dit is a korrekte verduideliking. Dit is beslis nie die geval dat 'n sterrestelsel ooit 'n ligstraal sal oorskry nie, en daarom is enige verduideliking nie korrek nie.

Die aanvaarde antwoord bied hierdie verduideliking van die vermoë van lig om uitbreiding te oorskry:

'N Foton wat uit 'n sterrestelsel uitgestraal word wat vinniger van ons af wegbeweeg as lig, is aanvanklik ook besig om van ons af te neem. Die foton kan egter uiteindelik in 'n gebied van ruimtetyd kom waar die resessie van ons ltc $ is. In hierdie geval kan die foton ons bereik.

Dit is 'n korrekte verduideliking. Dit is ook 'n korrekte uiteensetting van die spesiale relativistiese geval, as u die totale afstand meet soos dit in die kosmologie gemeet word, as die som van die afstande gemeet deur plaaslike meetstokke op tye wat gelyktydig is volgens plaaslike klokke. Die koördinaatstelsel wat effektief op hierdie manier gedefinieer word, is soortgelyk aan Rindler-koördinate met ruimte en tyd omgekeer. In Rindler-koördinate is daar 'n swaartekrag-rooi verskuiwing, alhoewel die ruimtetyd Minkowski is. In hierdie kwasi-kosmologiese koördinate is daar & sitaatxpanding space & quot en kosmologiese rooi verskuiwing, alhoewel die ruimtetyd Minkowski is.


Hoe is dit moontlik dat sterrestelsels vinniger van ons af beweeg as die snelheid van die lig?

Volgens Albert Einstein is die snelheid van die lig 'n absolute konstante waarbinne niks vinniger kan beweeg nie. Dus, hoe kan sterrestelsels vinniger beweeg as die snelheid van die lig as niks veronderstel is om hierdie kosmiese spoedgrens te kan breek nie?

Ek is 'n klein wêreld van teenstrydighede. 'Nie eers lig self kan aan 'n swart gat ontsnap nie', en dan, 'swart gate is die helderste voorwerpe in die heelal.' Ek het ook gesê "niks kan vinniger as die ligspoed ry nie". En dan sal ek iets sê soos: "sterrestelsels beweeg vinniger van ons af as die snelheid van die lig." Daar is meer as 'n paar items op hierdie lys, en dit is op sy beste verwarrend. Dankie Heelal!

Hoe kan sterrestelsels dus vinniger beweeg as die ligsnelheid as niks vinniger as lig kan beweeg nie? Warp-galaksies kom op as ek praat oor die uitbreiding van die heelal. Miskien is dit donker energieversnelling, of die vroegste inflasieperiode van die heelal toe ALLES vinniger uitgebrei het as die ligspoed.

Stel jou voor ons groeiende Heelal. Dit is nie 'n ontploffing vanaf 'n spesifieke plek nie, met sterrestelsels soos kosmiese jetsam. Dit is 'n uitbreiding van die ruimte. Daar is geen sentrum nie, en die Heelal brei nie uit na iets nie.

Ek het voorgestel dat dit 'n verskriklike oorvereenvoudigde model is vir die uitbreiding van ons heelal. Ongelukkig is dit ook verskriklik gerieflik. Ek kan dit van my kinders steel wanneer ek wil.

Stel jou voor dat jy hierdie knooppunt hier is, en namate die speelding uitbrei, sien jy al hierdie ander nodusse van jou af wegbeweeg. En as u na 'n ander node sou beweeg, sou u sien dat al die ander nodusse van u af wegbeweeg.

Hier is die interessante gedeelte, dit lyk asof hierdie knope hier, twee keer so ver weg as die nader, vinniger van jou af wegbeweeg. Hoe verder die knooppunt is, hoe vinniger lyk dit asof dit van u af wegbeweeg.

Dit is ons freaky vriend, die Hubble Constant, die idee dat die spoed wat hulle skei vir elke megaparsek afstand tussen ons en 'n verre sterrestelsel met ongeveer 71 kilometer per sekonde toeneem.

Sterrestelsels wat deur 2 parseke geskei word, sal hul spoed elke sekonde met 142 kilometer verhoog. As u die marathon hardloop, sal u twee sterrestelsels sien dat hulle vinniger wegvlieg as die snelheid van die lig sodra u 4 200 megaparsek weg is. Maar hoe groot is dit, en is dit groter as die heelal?

Die eerste lig ooit, die kosmiese mikrogolf-agtergrondstraling, is 46 miljard ligjare van ons af in alle rigtings. Ek het die wiskunde gedoen en 4 200 megaparsek is 'n bietjie meer as 13,7 miljard ligjare. Daar is baie ruimte vir voorwerpe om meer as 4 200 megaparsek van mekaar af te wees.

Die grootste deel van die heelal wat ons kan sien, jaag al vinniger weg as die ligspoed. Dus hoe dit moontlik is om die lig van enige sterrestelsels vinniger as die snelheid van die lig te sien. Hoe kan ons selfs die kosmiese mikrogolf-agtergrondstraling sien?


Stadiger as die snelheid van die lig

Die volgende belangrike stel deeltjies (sover ons weet, almal wat nie bosone is nie) beweeg stadiger as die ligspoed. Relatiwiteit vertel ons dat dit fisies onmoontlik is om hierdie deeltjies ooit vinnig genoeg te versnel om die snelheid van die lig te bereik. Hoekom is dit? Dit kom eintlik neer op 'n paar basiese wiskundige konsepte.

Aangesien hierdie voorwerpe massa bevat, vertel relatiwiteit ons dat die vergelyking kinetiese energie van die voorwerp, gebaseer op sy snelheid, deur die vergelyking bepaal word:

Daar is baie aan die gang in die vergelyking hierbo, so laat ons die veranderlikes uitpak:

  • γ is die Lorentz-faktor, wat 'n skaalfaktor is wat herhaaldelik in relatiwiteit voorkom. Dit dui op die verandering in verskillende hoeveelhede, soos massa, lengte en tyd wanneer voorwerpe beweeg. Sedert γ = 1 / / vierkantswortel van (1 - v 2 /c 2), is dit wat die verskillende voorkoms van die twee vergelykings veroorsaak.
  • m0 is die rusmassa van die voorwerp, verkry as dit 'n snelheid van 0 in 'n gegewe verwysingsraamwerk het.
  • c is die spoed van lig in vrye ruimte.
  • v is die snelheid waarmee die voorwerp beweeg. Die relatiwistiese effekte is slegs merkbaar betekenisvol vir baie hoë waardes van v, daarom kan hierdie effekte lank geïgnoreer word voordat Einstein gekom het.

Let op die noemer wat die veranderlike bevat v (vir snelheid). Namate die snelheid nader en nader aan die snelheid van die lig kom (c), daardie v 2 /c 2 kwartaal nader en nader aan 1 sal kom. wat beteken dat die waarde van die noemer ("die vierkantswortel van 1 - v 2 /c 2 ") sal al hoe nader aan 0 kom.

Namate die noemer kleiner word, word die energie self groter en groter, wat oneindig nader. As u dus probeer om 'n deeltjie te versnel tot by die ligspoed, neem dit meer en meer energie om dit te doen. Om die snelheid van die lig self te versnel, sal 'n oneindige hoeveelheid energie verg, wat onmoontlik is.

Deur hierdie redenasie kan geen deeltjie wat stadiger beweeg as die snelheid van die lig, ooit die spoed van die lig bereik nie (of, by uitbreiding, vinniger as die ligspoed gaan nie).


Onderwerp: Kan ons sterrestelsels sien wat meer as die snelheid van die lig terugtrek?

Ek dink daardie sterrestelsels met 'n snelheid wat groter is as die snelheid van die lig, is eintlik buite die & waarneembare heelal & quot, en daarom kan ons dit nie eintlik sien nie, want hul lig sal ons nooit bereik nie - ten minste volgens die algemene wetenskap.

Hier is die 'Help George om dit te verstaan ​​& quot draad wat my geduld het om dit dood te slaan om dit uiteindelik & quotgetquot & quot.

Die miermetafoor is so gebruik dat die mier die sterrestelsel voorgestel het, waar die mier stadiger beweeg as die rekkie wat dit uitgebrei het.

Ja, ons kan sterrestelsels sien wat vinniger teruggekeer het as lig toe hulle die fotone wat ons nou sien, uitstraal en wat dit nog steeds in die huidige tydvak doen.
Lineweaver en amp Davis's Scientific American artikel, Misconceptions About The Big Bang (440KB pdf), gee 'n redelike duidelike weergawe van hoe dit werk.

Alles - ek was die een wat hierdie verklaring [verkeerd geplaas het ] in 'n ander draad. Ek sien nou die misverstand wat ek gemaak het. Wat ek moes gesê het, was: 'die lig wat hierdie sterrestelsels nou verlaat, sal nooit die aarde bereik nie, want die bron beweeg van ons af met meer as die snelheid van die lig en die lig wat ons nou sien, word deur die sterrestelsel uitgestraal toe dit nie wegbeweeg van ons groter as die snelheid van die lig. ' Jammer vir die deurmekaar spul.

Ter toeligting verstaan ​​ek dat volgens die huidige denke dat die fotone wat die genoemde sterrestelsels verlaat, die ruimte kan verbysteek wat nie so vinnig van ons afneem nie, en dus uiteindelik die ruimte sal terugneem wat minder is as die spoed van die lig en ons dus uiteindelik sal bereik en so , kan ons sterrestelsels sien wat hoër is as die snelheid van die lig. Lyk nie baie logies nie en ek weet nie of dit iets anders is as net teorie nie, maar ek verstaan ​​die konsep. Net nie seker dat ek daarmee saamstem nie.

Dit is eintlik wiskundig onvermydelik vir 'n stel modelle van uitbreidende ruimte wat ons beste huidige model insluit.

Vir die eenvoudige analogie van die wurm wat langs 'n elastiese tou kruip wat met 'n konstante tempo groter is as die kruipspoed van die wurm, is dit bewys dat die reeks 1/2 + 1/3 + 1/4 + is. 1 / n kom nooit saam nie.

(BTW: ek neem aan dat die pos nr. 5 wat ek hierbo aanhaal, eintlik die onmiddellik vorige pos nr. 4 oorheers, aangesien hulle verskillende dinge sê.)

. (BTW: ek neem aan dat die pos nr. 5 wat ek hierbo aanhaal, eintlik die onmiddellik vorige pos nr. 4 oorheers, aangesien hulle verskillende dinge sê.)

Post # 4 is wat ek logies probeer het om oorspronklik te sê.

Post 5 sê dat ek die huidige teorie verstaan, maar ek stem dit nie noodwendig saam nie.

Ek weet dat hierdie bespreking al voorheen met die & quotant en die tou & quot-analogie aan die gang was, maar daardie berig is na die tyd hersien met 'n waarskuwing dat die begrip van die pos tans moeilik sou wees as gevolg van so 'n hersiening, en daarom het ek nie die hele berig gelees nie. As dit nie te veel tyd verg nie, kan u hierdie analogie in meer besonderhede verduidelik?


Inhoud

In die konteks van hierdie artikel is FTL die oordrag van inligting of saak vinniger as c, 'n konstante gelyk aan die snelheid van die lig in vakuum, wat 299,792,458 m / s is (per definisie van die meter [7]) of ongeveer 186,282,397 myl per sekonde. Dit is nie heeltemal dieselfde as om vinniger as lig te reis nie, aangesien:

  • Sommige prosesse propageer vinniger as c, maar kan nie inligting saamdra nie (sien voorbeelde in die afdelings onmiddellik hierna).
  • In sommige materiale waar lig vinnig beweeg c / n (waar n is die brekingsindeks) ander deeltjies kan vinniger beweeg as c / n (maar steeds stadiger as c), wat lei tot Cherenkov-bestraling (sien fasesnelheid hieronder).

Nie een van hierdie verskynsels is in stryd met spesiale relatiwiteit of skep probleme met oorsaaklikheid nie, en kwalifiseer ook nie as FTL soos hier beskryf.

In die volgende voorbeelde lyk dit of sekere invloede vinniger as lig beweeg, maar dit dra nie energie of inligting vinniger as lig oor nie, en dit skend dus nie die spesiale relatiwiteit nie.

Daaglikse lugbeweging Wysig

Vir 'n aardgebonde waarnemer voltooi voorwerpe in die lug op een dag een omwenteling rondom die aarde. Proxima Centauri, die naaste ster buite die sonnestelsel, is ongeveer vier ligjare weg. [8] In hierdie verwysingsraamwerk, waarin Proxima Centauri beskou word as in 'n sirkelvormige baan met 'n radius van vier ligjare, kan dit beskryf word as 'n spoed wat baie keer groter is as c aangesien die randsnelheid van 'n voorwerp wat in 'n sirkel beweeg, 'n produk is van die radius en die hoeksnelheid. [8] Dit is ook in 'n geostatiese aansig moontlik dat voorwerpe soos komete hul spoed van subluminaal tot superluminaal kan varieer en omgekeerd, bloot omdat die afstand vanaf die aarde wissel. Komete kan bane hê wat hulle na meer as 1000 AU uitbring. [9] Die omtrek van 'n sirkel met 'n radius van 1000 AE is groter as een ligdag. Met ander woorde, 'n komeet op so 'n afstand is superluminaal in 'n geostatiese en dus nie-traagheidsraamwerk.

Ligte kolle en skaduwees

As 'n laserstraal oor 'n ver voorwerp gevee word, kan die ligvlek maklik gemaak word om oor die voorwerp te beweeg met 'n snelheid groter as c. [10] Net so kan 'n skaduwee wat op 'n ver voorwerp geprojekteer word, vinniger as die voorwerp laat beweeg c. [10] In geen geval beweeg die lig vinniger as van die bron na die voorwerp nie c, en geen inligting reis vinniger as lig nie. [10] [11] [12]

Sluitingsnelhede Wysig

Die tempo waarteen twee voorwerpe in beweging in 'n enkele verwysingsraamwerk nader aan mekaar kom, word die onderlinge of sluitingspoed genoem. Dit kan twee keer die ligspoed nader, soos in die geval van twee deeltjies wat naby die ligspoed in teenoorgestelde rigtings beweeg ten opsigte van die verwysingsraamwerk.

Stel jou voor dat twee vinnig bewegende deeltjies mekaar van weerskante van 'n deeltjieversneller van die botsertipe nader. Die sluitingsnelheid is die snelheid waarmee die afstand tussen die twee deeltjies afneem. Vanuit die oogpunt van 'n waarnemer wat in rus staan ​​in verhouding tot die versneller, sal hierdie snelheid effens minder as twee keer die ligspoed wees.

Spesiale relatiwiteit verbied dit nie. Dit vertel ons dat dit verkeerd is om die relatiwiteit van Galilea te gebruik om die snelheid van een van die deeltjies te bereken, soos gemeet sou word deur 'n waarnemer wat langs die ander deeltjie beweeg. Dit wil sê, spesiale relatiwiteit gee die korrekte formule vir toevoeging van snelheid vir die berekening van sulke relatiewe snelheid.

Dit is insiggewend om die relatiewe snelheid van deeltjies wat beweeg, te bereken v en -v in die versnellerraam, wat ooreenstem met die sluitingsnelheid van 2v & gt c. Druk die spoed in eenhede van c, β = v/c:

Behoorlike snelhede Wysig

As 'n ruimteskip teen 'n hoë spoed na 'n planeet beweeg (soos gemeet in die aarde se rusraam), kan die tyd wat dit neem om daardie planeet te bereik, minder as een jaar wees, gemeet aan die horlosie van die reisiger (alhoewel dit moet altyd meer as een jaar wees, gemeet aan 'n horlosie op aarde). Die waarde wat verkry word deur die afgelegde afstand, soos bepaal in die raam van die aarde, te deel deur die tyd wat geneem word, gemeet aan die reisklok, staan ​​bekend as 'n regte spoed of 'n behoorlike snelheid. Daar is geen beperking op die waarde van 'n regte spoed nie, aangesien 'n regte spoed nie 'n spoed verteenwoordig wat in 'n enkele traagheidsraam gemeet word nie. 'N Ligte sein wat die aarde verlaat het terselfdertyd as die reisiger altyd voor die reisiger na die bestemming sou kom.

Moontlike afstand weg van die aarde Edit

Aangesien 'n mens dalk nie vinniger as die lig reis nie, kan jy aflei dat 'n mens nooit verder van die aarde af kan reis as 40 ligjare as die reisiger tussen die ouderdom van 20 en 60 jaar aktief is nie. 'N Reisiger sou dan nooit meer kon bereik nie as die min sterrestelsels wat binne die limiet van 20–40 ligjare vanaf die aarde bestaan. Dit is 'n verkeerde gevolgtrekking: as gevolg van tydsverspreiding kan die reisiger duisende ligjare reis gedurende hul 40 aktiewe jare. As die ruimteskip konstant met 1 g versnel (in sy eie veranderende verwysingsraamwerk), sal dit na 354 dae 'n bietjie onder die snelheid van die lig bereik (vir 'n waarnemer op Aarde), en die tydverwyding sal die reisiger verhoog lewensduur tot duisende Aardejare, gesien vanuit die verwysingstelsel van die Sonnestelsel ⁠ - maar die reisiger se subjektiewe lewensduur sal hierdeur nie verander nie. As hulle dan na die aarde sou terugkeer, sou die reisiger duisende jare in die toekoms op aarde aankom. Hulle reissnelheid sou van die aarde af nie gesien word as supraluminaal nie - ook vir die saak lyk dit nie so vanuit die perspektief van die reisiger nie - maar die reisiger sou in plaas daarvan 'n lengte-inkrimping van die heelal in hul reisrigting ervaar het. Nadat die reisiger van koers omgekeer het, lyk dit asof die aarde baie meer tyd verbygaan as wat die reisiger dit doen. Alhoewel die (gewone) koördinaatspoed van die reisiger nie kan oorskry nie c, kan hul regte spoed, of afstand afgelê vanaf die Aarde se verwysingspunt gedeel deur die regte tyd, veel groter wees as c. Dit word gesien in statistiese studies van muone wat baie verder reis as c keer hul halfleeftyd (in rus) as hulle naby reis c. [13]

Fasesnelhede hierbo c Wysig

Die fasesnelheid van 'n elektromagnetiese golf, as dit deur 'n medium beweeg, kan gereeld oorskry c, die vakuumsnelheid van die lig. Dit kom byvoorbeeld in die meeste bril teen X-straalfrekwensies voor. [14] Die fasesnelheid van 'n golf stem egter ooreen met die voortplantingsnelheid van 'n teoretiese enkelfrekwensie (suiwer monochromatiese) komponent van die golf teen daardie frekwensie. So 'n golfkomponent moet oneindig in omvang en konstante amplitude hê (anders is dit nie regtig monochromaties nie) en kan dus geen inligting oordra nie. [15] Dus 'n fasesnelheid hierbo c impliseer nie die voortplanting van seine met 'n snelheid hierbo nie c. [16]

Groepsnelhede hierbo c Wysig

Die groepsnelheid van 'n golf kan ook oorskry c in sommige omstandighede. [17] [18] In sulke gevalle, wat gewoonlik terselfdertyd 'n vinnige verswakking van die intensiteit behels, kan die maksimum van die omhulsel van 'n pols met 'n snelheid bo beweeg c. Selfs hierdie situasie impliseer egter nie die voortplanting van seine met 'n snelheid hierbo nie c, [19] alhoewel 'n mens in die versoeking kan kom om polsmaksima met seine te assosieer. Laasgenoemde assosiasie is misleidend omdat die inligting oor die aankoms van 'n pols verkry kan word voordat die polsmaksimum bereik word. As een meganisme byvoorbeeld die volle oordrag van die voorste deel van 'n pols toelaat, terwyl die polsmaksimum en alles daaragter verswak word (vervorming), word die polsmaksimum effektief in die tyd vorentoe geskuif, terwyl die inligting op die pols nie vinniger kom nie as c sonder hierdie effek. [20] Groepsnelheid kan egter oorskry c in sommige dele van 'n Gaussiese balk in vakuum (sonder verswakking). Die diffraksie laat die piek van die pols vinniger voortplant, terwyl die totale krag nie. [21]

Universele uitbreiding Wysig

Die uitbreiding van die heelal veroorsaak dat sterrestelsels in die verte vinniger van ons afneem as die spoed van die lig as die regte afstand en kosmologiese tyd gebruik word om die snelhede van hierdie sterrestelsels te bereken. In die algemene relatiwiteit is snelheid egter 'n plaaslike begrip, dus snelheid wat bereken word deur gebruik te maak van koördinate, het geen eenvoudige verband met die plaaslike plaaslike berekening nie. [25] (Kyk Komoving en behoorlike afstande vir 'n bespreking van verskillende begrippe 'snelheid' in die kosmologie.) Reëls wat van toepassing is op relatiewe snelhede in spesiale relatiwiteit, soos die reël dat relatiewe snelhede nie meer as die snelheid van die lig kan verhoog nie, hoef nie van toepassing op relatiewe snelhede in koördinate wat kom, wat dikwels beskryf word in terme van die "uitbreiding van die ruimte" tussen sterrestelsels. Daar word vermoed dat hierdie uitbreidingsyfer op die hoogtepunt was gedurende die inflasie-tydperk in 'n klein fraksie van die sekonde ná die oerknal (modelle dui aan dat die tydperk ongeveer 10 - 36 sekondes na die oerknal sou wees tot ongeveer 10 −33 sekondes), wanneer die heelal vinnig met 'n faktor van ongeveer 10 20 tot 10 30 uitgebrei het. [26]

Daar is baie sterrestelsels sigbaar in teleskope met 'n rooi skuifgetal van 1,4 of hoër. Al hierdie dinge beweeg tans van ons af teen snelhede wat groter is as die ligspoed. Omdat die Hubble-parameter mettertyd afneem, kan daar wel gevalle wees waar 'n sterrestelsel wat vinniger van ons afneem as die lig, daarin slaag om 'n sein uit te gee wat ons uiteindelik bereik. [27] [28] [29]

Omdat die uitbreiding van die heelal egter versnel, word daar voorspel dat die meeste sterrestelsels uiteindelik 'n tipe kosmologiese gebeurtenishorison sal oorsteek waar enige lig wat hulle verby daardie punt uitstraal, ons nooit op enige tydstip in die oneindige toekoms sal kan bereik nie, [ 30] omdat die lig nooit 'n punt bereik waar sy "eienaardige snelheid" teenoor ons die uitbreidingsnelheid van ons af oorskry nie (hierdie twee begrippe snelheid word ook bespreek in Komoving en behoorlike afstande # Gebruik van die regte afstand). Die huidige afstand tot hierdie kosmologiese gebeurtenishorison is ongeveer 16 miljard ligjare, wat beteken dat 'n sein van 'n gebeurtenis wat tans plaasvind, uiteindelik in die toekoms ons sal kan bereik as die gebeurtenis minder as 16 miljard ligjare weg is, maar die sein sou ons nooit bereik as die gebeurtenis meer as 16 miljard ligjare ver was nie. [28]

Astronomiese waarnemings

Skynbare superluminale beweging word waargeneem in baie radiostelsels, blazars, kwasars en onlangs ook in mikroquasars. Die effek is voorspel voordat dit deur Martin Rees waargeneem is [ opheldering nodig ] en kan verklaar word as 'n optiese illusie wat veroorsaak word deur die voorwerp wat gedeeltelik in die rigting van die waarnemer beweeg, [31] wanneer die snelheidsberekeninge aanvaar dat dit nie is nie. Die verskynsel weerspreek nie die teorie van spesiale relatiwiteit nie. Gekorrigeerde berekeninge wys dat hierdie voorwerpe snelhede naby die ligsnelheid het (relatief tot ons verwysingsraamwerk). Dit is die eerste voorbeelde van groot hoeveelhede massa wat naby die snelheid van die lig beweeg. [32] Aardgebonde laboratoriums kon slegs klein getalle elementêre deeltjies tot sulke snelhede versnel.

Kwantummeganika Edit

Sekere verskynsels in die kwantummeganika, soos kwantumverstrengeling, kan die oppervlakkige indruk skep dat kommunikasie van inligting vinniger as lig moontlik is. Volgens die stelling sonder kommunikasie laat hierdie verskynsels nie ware kommunikasie toe nie, maar laat slegs twee waarnemers op verskillende plekke dieselfde stelsel gelyktydig sien, sonder om enige manier te beheer. Golffunksie-ineenstorting kan beskou word as 'n epifenomeen van kwantum-dekoherensie, wat op sy beurt niks anders is as 'n effek van die onderliggende plaaslike tydsevolusie van die golffunksie van 'n stelsel en almal van sy omgewing. Aangesien die onderliggende gedrag nie die plaaslike oorsaaklikheid skend of FTL-kommunikasie toelaat nie, volg dit ook dat die bykomende effek van golffunksie nie ineenstort nie, hetsy werklik of oënskynlike.

Die onsekerheidsbeginsel impliseer dat individuele fotone vir kort afstande kan beweeg teen snelhede wat ietwat vinniger (of stadiger) is as c, selfs in vakuum moet hierdie moontlikheid in ag geneem word wanneer Feynman-diagramme vir 'n deeltjie-interaksie opgesom word. [33] Daar is egter in 2011 aangetoon dat 'n enkele foton dalk nie vinniger as c. [34] In kwantummeganika kan virtuele deeltjies vinniger beweeg as lig, en hierdie verskynsel hou verband met die feit dat statiese veldeffekte (wat in kwantumterme deur virtuele deeltjies bemiddel word) vinniger as lig kan beweeg (sien afdeling oor statiese velde hierbo. ). Makroskopies is hierdie skommelinge egter gemiddeld so dat fotone in reguit lyne oor lang (dws nie-kwantum) afstande beweeg en gemiddeld teen die snelheid van die lig beweeg. Dit impliseer dus nie die moontlikheid van oordrag van 'n superluminale inligting nie.

Daar is verskillende berigte in die gewilde pers van eksperimente oor vinniger as-lig-oordrag in die optika, meestal in die konteks van 'n soort kwantumtunnelverskynsel. Gewoonlik handel sulke verslae oor 'n fasesnelheid of groepsnelheid vinniger as die vakuumsnelheid van die lig. [35] [36] However, as stated above, a superluminal phase velocity cannot be used for faster-than-light transmission of information. [37] [38]

Hartman effect Edit

The Hartman effect is the tunneling effect through a barrier where the tunneling time tends to a constant for large barriers. [39] [40] This could, for instance, be the gap between two prisms. When the prisms are in contact, the light passes straight through, but when there is a gap, the light is refracted. There is a non-zero probability that the photon will tunnel across the gap rather than follow the refracted path. For large gaps between the prisms the tunnelling time approaches a constant and thus the photons appear to have crossed with a superluminal speed. [41]

However, the Hartman effect cannot actually be used to violate relativity by transmitting signals faster than c, because the tunnelling time "should not be linked to a velocity since evanescent waves do not propagate". [42] The evanescent waves in the Hartman effect are due to virtual particles and a non-propagating static field, as mentioned in the sections above for gravity and electromagnetism.

Casimir effect Edit

In physics, the Casimir–Polder force is a physical force exerted between separate objects due to resonance of vacuum energy in the intervening space between the objects. This is sometimes described in terms of virtual particles interacting with the objects, owing to the mathematical form of one possible way of calculating the strength of the effect. Because the strength of the force falls off rapidly with distance, it is only measurable when the distance between the objects is extremely small. Because the effect is due to virtual particles mediating a static field effect, it is subject to the comments about static fields discussed above.

EPR paradox Edit

The EPR paradox refers to a famous thought experiment of Albert Einstein, Boris Podolsky and Nathan Rosen that was realized experimentally for the first time by Alain Aspect in 1981 and 1982 in the Aspect experiment. In this experiment, the measurement of the state of one of the quantum systems of an entangled pair apparently instantaneously forces the other system (which may be distant) to be measured in the complementary state. However, no information can be transmitted this way the answer to whether or not the measurement actually affects the other quantum system comes down to which interpretation of quantum mechanics one subscribes to.

An experiment performed in 1997 by Nicolas Gisin has demonstrated non-local quantum correlations between particles separated by over 10 kilometers. [43] But as noted earlier, the non-local correlations seen in entanglement cannot actually be used to transmit classical information faster than light, so that relativistic causality is preserved. The situation is akin to sharing a synchronized coin flip, where the second person to flip their coin will always see the opposite of what the first person sees, but neither has any way of knowing whether they were the first or second flipper, without communicating classically. See No-communication theorem for further information. A 2008 quantum physics experiment also performed by Nicolas Gisin and his colleagues has determined that in any hypothetical non-local hidden-variable theory, the speed of the quantum non-local connection (what Einstein called "spooky action at a distance") is at least 10,000 times the speed of light. [44]

Delayed choice quantum eraser Edit

The delayed-choice quantum eraser is a version of the EPR paradox in which the observation (or not) of interference after the passage of a photon through a double slit experiment depends on the conditions of observation of a second photon entangled with the first. The characteristic of this experiment is that the observation of the second photon can take place at a later time than the observation of the first photon, [45] which may give the impression that the measurement of the later photons "retroactively" determines whether the earlier photons show interference or not, although the interference pattern can only be seen by correlating the measurements of both members of every pair and so it can't be observed until both photons have been measured, ensuring that an experimenter watching only the photons going through the slit does not obtain information about the other photons in an FTL or backwards-in-time manner. [46] [47]

Faster-than-light communication is, according to relativity, equivalent to time travel. What we measure as the speed of light in vacuum (or near vacuum) is actually the fundamental physical constant c. This means that all inertial and, for the coordinate speed of light, non-inertial observers, regardless of their relative velocity, will always measure zero-mass particles such as photons traveling at c in vacuum. This result means that measurements of time and velocity in different frames are no longer related simply by constant shifts, but are instead related by Poincaré transformations. These transformations have important implications:

  • The relativistic momentum of a massive particle would increase with speed in such a way that at the speed of light an object would have infinite momentum.
  • To accelerate an object of non-zero rest mass to c would require infinite time with any finite acceleration, or infinite acceleration for a finite amount of time.
  • Either way, such acceleration requires infinite energy.
  • Some observers with sub-light relative motion will disagree about which occurs first of any two events that are separated by a space-like interval. [48] In other words, any travel that is faster-than-light will be seen as traveling backwards in time in some other, equally valid, frames of reference, [49] or need to assume the speculative hypothesis of possible Lorentz violations at a presently unobserved scale (for instance the Planck scale). [aanhaling nodig] Therefore, any theory which permits "true" FTL also has to cope with time travel and all its associated paradoxes, [50] or else to assume the Lorentz invariance to be a symmetry of thermodynamical statistical nature (hence a symmetry broken at some presently unobserved scale).
  • In special relativity the coordinate speed of light is only guaranteed to be c in an inertial frame in a non-inertial frame the coordinate speed may be different from c. [51] In general relativity no coordinate system on a large region of curved spacetime is "inertial", so it is permissible to use a global coordinate system where objects travel faster than c, but in the local neighborhood of any point in curved spacetime we can define a "local inertial frame" and the local speed of light will be c in this frame, [52] with massive objects moving through this local neighborhood always having a speed less than c in the local inertial frame.

Casimir vacuum and quantum tunnelling Edit

Special relativity postulates that the speed of light in vacuum is invariant in inertial frames. That is, it will be the same from any frame of reference moving at a constant speed. The equations do not specify any particular value for the speed of light, which is an experimentally determined quantity for a fixed unit of length. Since 1983, the SI unit of length (the meter) has been defined using the speed of light.

The experimental determination has been made in vacuum. However, the vacuum we know is not the only possible vacuum which can exist. The vacuum has energy associated with it, called simply the vacuum energy, which could perhaps be altered in certain cases. [53] When vacuum energy is lowered, light itself has been predicted to go faster than the standard value c. This is known as the Scharnhorst effect. Such a vacuum can be produced by bringing two perfectly smooth metal plates together at near atomic diameter spacing. It is called a Casimir vacuum. Calculations imply that light will go faster in such a vacuum by a minuscule amount: a photon traveling between two plates that are 1 micrometer apart would increase the photon's speed by only about one part in 10 36 . [54] Accordingly, there has as yet been no experimental verification of the prediction. A recent analysis [55] argued that the Scharnhorst effect cannot be used to send information backwards in time with a single set of plates since the plates' rest frame would define a "preferred frame" for FTL signalling. However, with multiple pairs of plates in motion relative to one another the authors noted that they had no arguments that could "guarantee the total absence of causality violations", and invoked Hawking's speculative chronology protection conjecture which suggests that feedback loops of virtual particles would create "uncontrollable singularities in the renormalized quantum stress-energy" on the boundary of any potential time machine, and thus would require a theory of quantum gravity to fully analyze. Other authors argue that Scharnhorst's original analysis, which seemed to show the possibility of faster-than-c signals, involved approximations which may be incorrect, so that it is not clear whether this effect could actually increase signal speed at all. [56]

The physicists Günter Nimtz and Alfons Stahlhofen, of the University of Cologne, claim to have violated relativity experimentally by transmitting photons faster than the speed of light. [41] They say they have conducted an experiment in which microwave photons — relatively low-energy packets of light — travelled "instantaneously" between a pair of prisms that had been moved up to 3 ft (1 m) apart. Their experiment involved an optical phenomenon known as "evanescent modes", and they claim that since evanescent modes have an imaginary wave number, they represent a "mathematical analogy" to quantum tunnelling. [41] Nimtz has also claimed that "evanescent modes are not fully describable by the Maxwell equations and quantum mechanics have to be taken into consideration." [57] Other scientists such as Herbert G. Winful and Robert Helling have argued that in fact there is nothing quantum-mechanical about Nimtz's experiments, and that the results can be fully predicted by the equations of classical electromagnetism (Maxwell's equations). [58] [59]

Nimtz told Nuwe wetenskaplike magazine: "For the time being, this is the only violation of special relativity that I know of." However, other physicists say that this phenomenon does not allow information to be transmitted faster than light. Aephraim Steinberg, a quantum optics expert at the University of Toronto, Canada, uses the analogy of a train traveling from Chicago to New York, but dropping off train cars from the tail at each station along the way, so that the center of the ever-shrinking main train moves forward at each stop in this way, the speed of the center of the train exceeds the speed of any of the individual cars. [60]

Winful argues that the train analogy is a variant of the "reshaping argument" for superluminal tunneling velocities, but he goes on to say that this argument is not actually supported by experiment or simulations, which actually show that the transmitted pulse has the same length and shape as the incident pulse. [58] Instead, Winful argues that the group delay in tunneling is not actually the transit time for the pulse (whose spatial length must be greater than the barrier length in order for its spectrum to be narrow enough to allow tunneling), but is instead the lifetime of the energy stored in a standing wave which forms inside the barrier. Since the stored energy in the barrier is less than the energy stored in a barrier-free region of the same length due to destructive interference, the group delay for the energy to escape the barrier region is shorter than it would be in free space, which according to Winful is the explanation for apparently superluminal tunneling. [61] [62]

A number of authors have published papers disputing Nimtz's claim that Einstein causality is violated by his experiments, and there are many other papers in the literature discussing why quantum tunneling is not thought to violate causality. [63]

It was later claimed by Eckle et al. that particle tunneling does indeed occur in zero real time. [64] Their tests involved tunneling electrons, where the group argued a relativistic prediction for tunneling time should be 500–600 attoseconds (an attosecond is one quintillionth (10 −18 ) of a second). All that could be measured was 24 attoseconds, which is the limit of the test accuracy. Again, though, other physicists believe that tunneling experiments in which particles appear to spend anomalously short times inside the barrier are in fact fully compatible with relativity, although there is disagreement about whether the explanation involves reshaping of the wave packet or other effects. [61] [62] [65]

Give up (absolute) relativity Edit

Because of the strong empirical support for special relativity, any modifications to it must necessarily be quite subtle and difficult to measure. The best-known attempt is doubly special relativity, which posits that the Planck length is also the same in all reference frames, and is associated with the work of Giovanni Amelino-Camelia and João Magueijo. [66] [67] There are speculative theories that claim inertia is produced by the combined mass of the universe (e.g., Mach's principle), which implies that the rest frame of the universe might be preferred by conventional measurements of natural law. If confirmed, this would imply special relativity is an approximation to a more general theory, but since the relevant comparison would (by definition) be outside the observable universe, it is difficult to imagine (much less construct) experiments to test this hypothesis. Despite this difficulty, such experiments have been proposed. [68]

Spacetime distortion Edit

Although the theory of special relativity forbids objects to have a relative velocity greater than light speed, and general relativity reduces to special relativity in a local sense (in small regions of spacetime where curvature is negligible), general relativity does allow the space between distant objects to expand in such a way that they have a "recession velocity" which exceeds the speed of light, and it is thought that galaxies which are at a distance of more than about 14 billion light-years from us today have a recession velocity which is faster than light. [69] Miguel Alcubierre theorized that it would be possible to create a warp drive, in which a ship would be enclosed in a "warp bubble" where the space at the front of the bubble is rapidly contracting and the space at the back is rapidly expanding, with the result that the bubble can reach a distant destination much faster than a light beam moving outside the bubble, but without objects inside the bubble locally traveling faster than light. [70] However, several objections raised against the Alcubierre drive appear to rule out the possibility of actually using it in any practical fashion. Another possibility predicted by general relativity is the traversable wormhole, which could create a shortcut between arbitrarily distant points in space. As with the Alcubierre drive, travelers moving through the wormhole would not plaaslik move faster than light travelling through the wormhole alongside them, but they would be able to reach their destination (and return to their starting location) faster than light traveling outside the wormhole.

Gerald Cleaver and Richard Obousy, a professor and student of Baylor University, theorized that manipulating the extra spatial dimensions of string theory around a spaceship with an extremely large amount of energy would create a "bubble" that could cause the ship to travel faster than the speed of light. To create this bubble, the physicists believe manipulating the 10th spatial dimension would alter the dark energy in three large spatial dimensions: height, width and length. Cleaver said positive dark energy is currently responsible for speeding up the expansion rate of our universe as time moves on. [71]

Lorentz symmetry violation Edit

The possibility that Lorentz symmetry may be violated has been seriously considered in the last two decades, particularly after the development of a realistic effective field theory that describes this possible violation, the so-called Standard-Model Extension. [72] [73] [74] This general framework has allowed experimental searches by ultra-high energy cosmic-ray experiments [75] and a wide variety of experiments in gravity, electrons, protons, neutrons, neutrinos, mesons, and photons. [76] The breaking of rotation and boost invariance causes direction dependence in the theory as well as unconventional energy dependence that introduces novel effects, including Lorentz-violating neutrino oscillations and modifications to the dispersion relations of different particle species, which naturally could make particles move faster than light.

In some models of broken Lorentz symmetry, it is postulated that the symmetry is still built into the most fundamental laws of physics, but that spontaneous symmetry breaking of Lorentz invariance [77] shortly after the Big Bang could have left a "relic field" throughout the universe which causes particles to behave differently depending on their velocity relative to the field [78] however, there are also some models where Lorentz symmetry is broken in a more fundamental way. If Lorentz symmetry can cease to be a fundamental symmetry at the Planck scale or at some other fundamental scale, it is conceivable that particles with a critical speed different from the speed of light be the ultimate constituents of matter.

In current models of Lorentz symmetry violation, the phenomenological parameters are expected to be energy-dependent. Therefore, as widely recognized, [79] [80] existing low-energy bounds cannot be applied to high-energy phenomena however, many searches for Lorentz violation at high energies have been carried out using the Standard-Model Extension. [76] Lorentz symmetry violation is expected to become stronger as one gets closer to the fundamental scale.

Superfluid theories of physical vacuum Edit

In this approach the physical vacuum is viewed as a quantum superfluid which is essentially non-relativistic whereas Lorentz symmetry is not an exact symmetry of nature but rather the approximate description valid only for the small fluctuations of the superfluid background. [81] Within the framework of the approach a theory was proposed in which the physical vacuum is conjectured to be a quantum Bose liquid whose ground-state wavefunction is described by the logarithmic Schrödinger equation. It was shown that the relativistic gravitational interaction arises as the small-amplitude collective excitation mode [82] whereas relativistic elementary particles can be described by the particle-like modes in the limit of low momenta. [83] The important fact is that at very high velocities the behavior of the particle-like modes becomes distinct from the relativistic one - they can reach the speed of light limit at finite energy also, faster-than-light propagation is possible without requiring moving objects to have imaginary mass. [84] [85]

MINOS experiment Edit

In 2007 the MINOS collaboration reported results measuring the flight-time of 3 GeV neutrinos yielding a speed exceeding that of light by 1.8-sigma significance. [86] However, those measurements were considered to be statistically consistent with neutrinos traveling at the speed of light. [87] After the detectors for the project were upgraded in 2012, MINOS corrected their initial result and found agreement with the speed of light. Further measurements are going to be conducted. [88]

OPERA neutrino anomaly Edit

On September 22, 2011, a preprint [89] from the OPERA Collaboration indicated detection of 17 and 28 GeV muon neutrinos, sent 730 kilometers (454 miles) from CERN near Geneva, Switzerland to the Gran Sasso National Laboratory in Italy, traveling faster than light by a relative amount of 2.48 × 10 −5 (approximately 1 in 40,000), a statistic with 6.0-sigma significance. [90] On 17 November 2011, a second follow-up experiment by OPERA scientists confirmed their initial results. [91] [92] However, scientists were skeptical about the results of these experiments, the significance of which was disputed. [93] In March 2012, the ICARUS collaboration failed to reproduce the OPERA results with their equipment, detecting neutrino travel time from CERN to the Gran Sasso National Laboratory indistinguishable from the speed of light. [94] Later the OPERA team reported two flaws in their equipment set-up that had caused errors far outside their original confidence interval: a fiber optic cable attached improperly, which caused the apparently faster-than-light measurements, and a clock oscillator ticking too fast. [95]

In special relativity, it is impossible to accelerate an object aan the speed of light, or for a massive object to move at the speed of light. However, it might be possible for an object to exist which altyd moves faster than light. The hypothetical elementary particles with this property are called tachyons or tachyonic particles. Attempts to quantize them failed to produce faster-than-light particles, and instead illustrated that their presence leads to an instability. [96] [97]

Various theorists have suggested that the neutrino might have a tachyonic nature, [98] [99] [100] [101] while others have disputed the possibility. [102]

General relativity was developed after special relativity to include concepts like gravity. It maintains the principle that no object can accelerate to the speed of light in the reference frame of any coincident observer. [ aanhaling nodig ] However, it permits distortions in spacetime that allow an object to move faster than light from the point of view of a distant observer. [ aanhaling nodig ] One such distortion is the Alcubierre drive, which can be thought of as producing a ripple in spacetime that carries an object along with it. Another possible system is the wormhole, which connects two distant locations as though by a shortcut. Both distortions would need to create a very strong curvature in a highly localized region of space-time and their gravity fields would be immense. To counteract the unstable nature, and prevent the distortions from collapsing under their own 'weight', one would need to introduce hypothetical exotic matter or negative energy.

General relativity also recognizes that any means of faster-than-light travel could also be used for time travel. This raises problems with causality. Many physicists believe that the above phenomena are impossible and that future theories of gravity will prohibit them. One theory states that stable wormholes are possible, but that any attempt to use a network of wormholes to violate causality would result in their decay. [ aanhaling nodig ] In string theory, Eric G. Gimon and Petr Hořava have argued [103] that in a supersymmetric five-dimensional Gödel universe, quantum corrections to general relativity effectively cut off regions of spacetime with causality-violating closed timelike curves. In particular, in the quantum theory a smeared supertube is present that cuts the spacetime in such a way that, although in the full spacetime a closed timelike curve passed through every point, no complete curves exist on the interior region bounded by the tube.


Warp Drive Technology

Many science fiction fans, especially "Star Trek" fans, are well aware of warp drive technology. But it is nowhere near what we are technologically able to do today. However, recently a team of engineers proposed what could be a first proposal for a physical warp drive, breaking the laws of physics.

In theory, warp drives are supposed to morph, bend, and change the shape of the space-time continuum in order to exaggerate differences in distance and time, under the right conditions, this should allow space travelers to travel past the speed of light and move across distances in an instant.

More than a century ago a Mexican theoretical physicist proposed a spacecraft that would be powered by an Alcubierre drive in order to achieve faster than light travel. However, the design required an abundant amount of negative energy in one place that wasn't possible according to physics.

In the study published in the journal Classical and Quantum Gravity, entitled "Introducing physical warp drives" engineers looked into the plausibility of several other classes of warp drives. But the model has its own set of limitations.

For a warp drive to be able to generate enough negative energy, it needs a huge amount of matter. According to the Alcubierre estimations, a warp drive travelling 100-meters would require the mass of the entire visible universe to work.


Introducing Warp Drive Or Faster-Than-Light Space Travel

If we ever want to explore space or even travel seamlessly between stars, then we certainly need much faster transport, something that moves even faster than light. But so far, this has only been possible in sci-fi stories. But isn't fiction based on certain ounces of reality?

Star Trek fans know that characters here use warp drive technology to speed across galaxies and stars. But warp drive is still possible only on paper and practical enactments have been restricted to fiction only. However, back in March, researchers claimed to have overcome some of the major challenges in the theory of warp drives bringing it closer to reality.


When space expanded faster-than-light

Artist’s illustration of cosmic inflation via scienceblogs.com

From its orbit 930,000 miles (1.5 million km) above Earth, the Planck satellite spent more than four years detecting the cosmic microwave background – a fossil from the Big Bang that fills every part of the sky and offers a glimpse of what the universe looked like in its infancy. Planck’s observations of this relic radiation shed light on everything from the evolution of the universe to the nature of dark matter. In early February 2015, Planck released new maps of the cosmic microwave background supporting the theory of cosmic inflation, the idea that, in the moments following the Big Bang, space expanded faster than the speed of light, growing from smaller than a proton to an enormity that defies comprehension. Kelen Tuttle of the Kavli Foundation recently spoke with Dr. George Efstathiou, director of the Kavli Institute for Cosmology at the University of Cambridge and one of the leaders of the Planck mission, to understand Planck’s latest results and their implications for the theory of inflation. You’ll find an edited transcript of that interview below.

In addition, Kavli will offer a live webcast on February 18, 2015 with Efstathiou and two other prominent scientists on the subject of cosmic inflation. Love cosmology? Submit a question for the upcoming webcast at [email protected] or on Twitter use the hashtag #KavliLive.

George Efstathiou

THE KAVLI FOUNDATION: In 2013 and now this year, Planck provided very strong experimental evidence supporting the theory that the universe went through a mindbogglingly rapid expansion in its very first moments. Can you elaborate on the latest findings and why they’re important?

GEORGE EFSTATHIOU: Inflation – the theory that the early universe expanded incredibly rapidly in its first moments – makes a number of generic predictions. For example, the geometry of the universe should be very close to flat, and this should be reflected in fluctuations we see in the cosmic microwave background light. With the first Planck data, which we released in 2013, we verified some aspects of this model to pretty high precision by looking at the temperature of the cosmic microwave background across the sky. With the 2015 release, we improved the precision of those temperature measurements and also added accurate measurements of a twisting pattern in the cosmic microwave background called polarization. These polarization measurements are really important in telling us what the fabric of space was like in the early universe.

You see, there are several possibilities. For example, in some models motivated by higher-dimensional theories such as string theory, “cosmic strings” can be produced in the early universe, and these would generate a different type of fluctuation pattern. We see no evidence for cosmic strings or other types of cosmic defect. What we found is that everything is consistent – with a very high precision – with simple inflationary models. So, for example, we now can say that the universe is spatially flat to a precision of about half a percent. That’s a substantial improvement over what we knew before Planck.

The European Space Agency’s Planck space telescope was launched in 2009. During its four-year mission, it observed variations in the cosmic microwave background across the entire sky. The first all-sky map was released in March 2013 and the second, more detailed, map was released in February 2015. The mission’s successes include determining that the universe is slightly older than thought mapping the early universe’s subtle fluctuations in temperature and polarization, which eventually gave rise to the structure we see today and confirming that 26 percent of the universe comprises dark matter. Image via ESA

TKF: You’ve called the theory of cosmic inflation a cartoon of a theory. What did you mean by that?

EFSTATHIOU: We don’t yet understand the fundamental physics that drove inflation, and we certainly don’t understand the details of how it worked. The simplest model of inflation requires that the early universe contained what’s called a scalar field. This field permeates all of space and is responsible for causing space to expand faster than the speed of light. And, as with all quantum fields, it contains quantum fluctuations. It’s those tiny quantum fluctuations that, once they were stretched in size during inflation, generated the structure that we see across the Universe today – all of the galaxies and stars and planets. That’s a simple model of inflation.
Now, what is that field exactly? We don’t know. There are many theories out there, but really they’re all just guesses. That’s why I called it a cartoon of a theory – because we don’t understand how inflation works in any fundamental sense. What we need is better experimental data that tells us what the early universe looked like and hopefully this will point us toward a fundamental theory of inflation.

TKF: Does that mean the next steps are experimental as opposed to theoretical?

EFSTATHIOU: That is a very interesting question. In my mind, real progress will require experiments, because the very early universe involves energy scales so much higher than anything we’ve been able to test in laboratory experiments here on Earth. When you make such a very big leap, you don’t really know what things look like. That leaves open lots and lots of possibilities. For example, the extra dimensions predicted by string theory are hidden from us – so we don’t experience them. They must be very small and “compactified” in some way – but how, we don’t know. So from the theory point of view, there are just too many options right now. Also, in cosmology, we’re talking about highly dynamic situations. Everything is changing very rapidly and that’s also difficult to analyze theoretically. There’s always the possibility that some tremendous new theoretical insight will narrow down the options.

But I think that we need to do experiments – if we can – that narrow down the options experimentally. If we detected gravitational waves, which are ripples in the curvature of space-time, that measurement would narrow down the options a lot. It would tell us the energy scale of inflation. What’s more, any detectable level of gravitational waves would establish an empirical link with quantum gravity. Quantum gravity, which would align the force of gravity with the principles of quantum mechanics, is a very important experimental target, one that is possible to reach with high precision experiments. I think that would be the most likely experimental development that could actually make contact with physics at the very high energy scales of the early universe.

This map, captured by ESA’s Planck space telescope, reveals the Milky Way galaxy. Gas appears in yellow, radiation in blue and green, and several types of dust are shown in red. Image via ESA/NASA/JPL-Caltech

TKF: One of the most publicized new revelations from Planck is evidence the first stars in the universe started to shine about 550 million years after the Big Bang – which means they are younger by about 100 million years than previously thought. How could we have gotten this so wrong?

EFSTATHIOU: You know, I’m not so keen on claiming this as a great scientific achievement by Planck – but it is interesting. To explain why, I need to give you a little background. At the end of inflation, we know that the universe became very, very hot. Since then, as the universe expanded, it cooled down. And when the universe was 400,000 years old, the temperature was low enough that electrons and protons could combine to form neutral hydrogen. So at that time, the universe was neutral and pretty uniform.

We can see quasars – very bright compact regions at the centers of distant galaxies – that existed back when the universe was about 840 million years old. That’s really very young compared to its 13.8 billion years today. Back then, if the universe had been filled with neutral hydrogen, that hydrogen would have absorbed quasar light at short wavelengths and we wouldn’t be able to see it in our measurements today. So because we can see this light from these quasars, we know that when the universe was 840 million years old, it was no longer neutral. Sometime between the Universe being 400,000 years old and 840 million years old, energy must have been injected into the gas to change this. So the question is, where did that energy come from?

Well, it must be that stars formed and started to release energy. Now, looking at the deepest images from the Hubble Space Telescope, we can see some of these very early stars. But from the stars we see, it wouldn’t be possible to release enough energy to ionize the hydrogen by the time the universe was 420 million years old – as was suggested by previous measurements of the cosmic microwave background made with the Wilkinson Microwave Anisotrophy Probe – or WMAP – satellite. Now, with the Planck measurements, we’re saying that it happened a bit later, at 560 million years. That difference of about 140 million years may not sound like a lot, but it now brings all of our observations into alignment.

This is a very, very difficult measurement to make – it’s a very small signal hidden behind a lot of contamination from our own Milky Way. You have to dig out the real signal from all this noise. With Planck, we were for the first time able to make this measurement using the Planck data in two different ways. Why I’m not so keen on it as a real highlight from Planck is that there’s absolutely nothing wrong with the previous measurements. The WMAP observations are perfectly fine, but if you take their maps, and correct for contamination by the Milky Way, then you get the same answers as the Planck results. So everything is consistent in the end.

The Background Imaging of Cosmic Extragalactic Polarization 2 (BICEP2) experiment, shown here in the foreground, studies the cosmic microwave background from the South Pole, where cold, dry air allows for clear observations of the sky. In March 2014, the BICEP2 team announced that they had seen evidence of gravitational waves, offering what seemed to be “smoking gun” evidence of inflation. Although a Planck-BICEP2 joint analysis has since shown that dust in the Milky Way had mimicked the signal expected from gravitational waves, future experiments may yet discover these long-sought waves. The project was funded by $2.3 million from W. M. Keck Foundation, as well as funding from the National Science Foundation, the Gordon and Betty Moore Foundation, the James and Nelly Kilroy Foundation and the Barzan Foundation.
Image via Steffen Richter, Harvard University

TKF: The Planck results are also helping us understand dark matter, the mysterious substance that makes up 20 percent of the universe yet has yet to be well understood. What exactly have we learned about dark matter from Planck?

EFSTATHIOU: What do we know? Really, we’re still a long way from understanding dark matter. The leading candidate is a type of particle predicted by supersymmetry. That theory predicts a partner particle for each particle that we already know. But if that theory is true, supersymmetric particles should appear in collisions at the Large Hadron Collider. So far, they haven’t. So dark matter is still unknown.

Planck has detected no signal of dark matter. Supersymmetry predicts that dark matter particles should occasionally interact with other dark matter particles and produce a flash of energy – a process called annihilation. But we don’t see it. That’s really not all that surprising. It’s easy to hide. So that’s something that future cosmic microwave background experiments might be able to see. But we haven’t seen any signs of annihilating dark matter from Planck.

We have looked also very carefully at neutrinos – tiny, ubiquitous particles we know come in three types. As far as well can tell, there are no other types of neutrinos that could help account for some of the dark matter. People are also still trying to determine the mass of these three neutrinos. We know from other experiments the least mass that these three particles could have. Planck has now set a limit on the most mass that they could possibly have. We’re narrowing down the options, and will hopefully soon learn their exact mass. Neutrinos are some of the most mysterious particles in the universe, so this would be an important step toward understanding them.
Some theorists have also suggested that dark matter and dark energy could interact in some way. As far as we can tell, dark energy is completely constant – so there’s no evidence that it interacts with dark matter.

TKF: We would be remiss if we didn’t talk a bit more about gravitational waves. Last March, another experimental team called BICEP2 announced that they had seen evidence of gravitational waves in their observations of the very early universe. Then, just a few weeks ago, joint analysis of that data carried out by members of both Planck and BICEP2 revealed that unidentified gas and dust had contaminated the data, and that gravitational waves remain undiscovered. What does this mean for future hopes of discovering gravitational waves?

EFSTATHIOU: When the BICEP2 team announced their result, I was really shocked. The signal they detected was really big. We had already done an analysis based on the Planck 2013 data, and we had set a limit on how big the signal could be. And BICEP2’s measurements were about twice as big as that. So if BICEP2 really had detected gravitational waves, there would need to be some really strange and unexpected physics at work for us to get such different results.

The BICEP2 group knows what it’s doing – these guys are as good as any group in the world. And they’ve been working on various versions of this experiment for 7 or 8 years. So from the experimental side, the data is beautiful. They clearly detected something.

That something could have been gravitational waves, or it could have been intervening dust that confused their data. The BICEP2 experiment looks at a very small field of view, and Planck’s signal to noise is not very big. So we arranged to collaborate. Essentially, we improved the signal to noise on dust by cross-correlating their maps with ours. That showed that, as of yet, we still have no statistically significant evidence of gravitational waves. That resolves the conflict with the original Planck results. And, in the big picture, that’s a good thing. No really strange physics is needed to reconcile the two experiments.
So now we’re in a situation where we have a limit on the size of a gravitational wave signal, and that number is consistent with the Planck results. It doesn’t rule out gravitational waves by any means. If you look at the joint analysis, you see that there’s plenty of room for gravitational waves to be lurking there, just below the level we’ve set by combining the BICEP2 and Planck data. If that’s true, it shouldn’t take a very long time to dig it out. So there could be a very important development coming.


Kyk die video: Het Heelal: supernovas, zwarte gaten, quasars, Andromeda, Einstein en the Big Rip, Chill of Crunch (Desember 2022).