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Hoe werk Hawking Radiation presies?

Hoe werk Hawking Radiation presies?


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Ek weet dat 'n deeltjie en anti-deeltjie, virtuele deeltjies, aan die rand van 'n gebeurtenishorison kuit, en een deeltjie val in die swart gat, en die ander gaan uit, maar hoe weet die ander een hoe om energie uit die swart gat te neem ? Ek bedoel hoe doen dit? Weet dit net om energie uit die swart gat te neem of val die antipartikel in, en verloor die swartgat massa?


... maar hoe weet die ander een hoe om energie uit die swart gat te haal?

Om dit te verstaan, moet u vertroud wees met die essensie van hierdie prent$^1$ insluitend negatiewe energietoestande binne die horison, skepping van virtuele deeltjie-antipartikel-pare, en behoud van energie.$^2$ Ek probeer u vraag intuïtief beantwoord met eenvoudige woorde.

Neem aan dat 'n virtuele deeltjie-antipartikel-paar naby die horison van die swart gat geskep word. Volgens die beginsel van behoud van energie moet die totale energie van die paar deeltjies nul wees. Dus, een van die deeltjies het positiewe energie en die ander een het negatiewe energie. Aan die ander kant kan aangetoon word dat daar negatiewe energie-toestande binne die horison van 'n statiese swart gat bestaan ​​en dat die deeltjies met negatiewe energie hierdie toestande kan beset. Om 'n paar werklike deeltjies met 'n totale totale energie te hê, is die enigste fisiese moontlikheid dat die deeltjie met positiewe energie tot in die oneindigheid kan ontsnap, terwyl die negatiewe-energie-deeltjie in die swart gat val. Op hierdie manier kan die sterk swaartekragveld van die swart gat 'n virtuele deeltjie-deeltjie-paar omskakel in 'n paar werklike deeltjies met geen totale energie nie. Dit is die rede waarom die ingeslote virtuele deeltjie altyd negatiewe energie kry. Op hierdie manier is dit geregverdig dat die swart gat sy massa verloor en geleidelik verdamp. (Sien die waarskuwing aan die einde van hierdie antwoord, asseblief.)

Weet dit net om energie uit die swart gat te neem of val die antipartikel in, en verloor die swartgat massa?

Let daarop dat in hierdie prentjie, wanneer 'n virtuele deeltjie-deeltjie-paar naby die horison van die swart gat geskep word, elkeen in die horison kan val of tot in die oneindigheid kan ontsnap (een van hulle val altyd in en die ander een ontsnap.) , is dit nie korrek dat slegs die antipartikel in die swart gat val nie. Dit beteken dat 'n statiese waarnemer buite die gebeurtenishorison sowel die deeltjie- as die deeltjiespektrum sal waarneem.


Waarskuwing: Myns insiens moet u bogenoemde argument oor virtuele deeltjie-anti-deeltjiepaar ensovoorts nie te ernstig opneem nie, aangesien hierdie prentjie naïef 'n intuïtiewe begrip het. 'N Streng behandeling van Hawking-bestraling deur kwantisering van kwantumvelde op 'n geboë swartgat-agtergrond te gebruik, het nie so 'n naïewe prentjie nodig nie.


$^1$Daar is noukeuriger behandelings vir die begrip van die Hawking-bestraling, maar ek beperk my tot hierdie raamwerk (prentjie) waarin u belangstel en waaroor u vra.

$^2$ Hier, vir die eenvoud, beperk ek hierdie bespreking tot die geval van statiese swart gate. Die algemene gevolgtrekking is steeds geldig vir die draaiende swart gate.


Hoe Hawking-straling werk

Die naam Stephen Hawking sal vir altyd geassosieer word met 'n briljante en inspirerende wetenskaplike wat gehelp het om teorieë en verklarings vir sommige van die vreemdste raaisels in die fisika uit te dink. Een so 'n teorie, bekend as Hawking Radiation, kan lig werp op voorwerpe wat ons bang maak en fassineer: swart gate. Hier is wat Hawking Radiation is en hoe dit teoreties is om te werk.

1. Volgens Hawking is swart gate nie eintlik swart nie.
Die eerste en mees noodsaaklike ding om te verstaan ​​oor Hawking-bestraling is dat dit beweer dat swart gate, die voorwerpe waaraan ons dink, alle materie rondom hulle suig en niks laat ontsnap nie, eintlik iets uitstraal — swart liggaamsstraling.

2. Die teorie stel dat deeltjies-antipartikelpare by 'n swart gat se gebeurtenishorison geskep word.
Kwantumteorie stel dat elke deeltjie 'n antipartikel het wat teenoorgestelde werk. Hierdie twee vernietig mekaar gewoonlik, maar in die geval van Hawking-bestraling, doen hulle dit nie. In plaas daarvan val die een in die swaartekrag van die swart gat, en die ander kan ontsnap. Daardie vrygestelde deeltjie het energie in die vorm van bestraling, dus blyk dit dat die swart gat bestraling uitstraal in plaas daarvan om dit net op te neem.

3. As dit die geval is, verloor swart gate massa.
Terwyl die een deeltjie deur die swart gat geabsorbeer word, ontsnap die ander een. Dit beteken dat die swart gat energie verloor, en as dit energie verloor, verloor dit massa. Daarom moet swart gate nie vir altyd aanhou nie. Op 'n stadium sal hulle al hul massa verloor en volgens die teorie uit die bestaan ​​knipoog.

William Pennat

David-J-Franks

Die naam Stephen Hawking sal vir altyd geassosieer word met 'n briljante en inspirerende wetenskaplike wat gehelp het om teorieë en verklarings vir sommige van die vreemdste raaisels in die fisika uit te dink. Een so 'n teorie, bekend as Hawking Radiation, kan lig werp op voorwerpe wat ons bang maak en fassineer: swart gate. Hier is wat Hawking Radiation is en hoe dit teoreties is om te werk.

1. Volgens Hawking is swart gate nie eintlik swart nie.
Die eerste en mees noodsaaklike ding om van Hawking Radiation te verstaan, is dat dit beweer dat swart gate, die voorwerpe wat ons beskou as suig in alle materie rondom hulle en niks laat ontsnap nie, eintlik iets uitstraal - swart liggaamsbestraling.

2. Die teorie stel dat deeltjies-antipartikelpare by 'n swart gat se gebeurtenishorison geskep word.
Kwantumteorie stel dat elke deeltjie 'n antipartikel het wat teenoorgestelde werk. Hierdie twee vernietig mekaar gewoonlik, maar in die geval van Hawking-bestraling, doen hulle dit nie. In plaas daarvan val die een in die swaartekrag van die swart gat, en die ander kan ontsnap. Daardie vrygestelde deeltjie het energie in die vorm van bestraling, dus blyk dit dat die swart gat bestraling uitstraal in plaas daarvan om dit net op te neem.

3. As dit die geval is, verloor swart gate massa.
Terwyl die een deeltjie deur die swart gat geabsorbeer word, ontsnap die ander een. Dit beteken dat die swart gat energie verloor, en as dit energie verloor, verloor dit massa. Daarom moet swart gate nie vir altyd aanhou nie. Op 'n stadium sal hulle al hul massa verloor en volgens die teorie uit die bestaan ​​knipoog.

SaraRayne, as een deeltjie in die swart gat val, verhoog dit nie die massa daarvan nie? Die ander deeltjie wat vrygestel word, is van buite die gebeurtenishorison, nie van die swart gat self nie. Dit lyk vir my asof die swart gat materie uit die ruimte onttrek (kwantumveld / skuim / skommelinge, eter, vakuumenergie, donker energie of wat ook al) en groter word, nie kleiner nie! Ek verstaan ​​nie! Help asb.

Kyk na my boek SaraRayne. Met al die ekstra onderwerpe, is my boek meer as net 'n heelal-teorie, so hopelik bied dit 'n beeld van die bestaan ​​wat volledig is, (behalwe vir die klein besonderhede van elke deeltjie, ens.) En selfvoorsienend is, wat geen skepping of evolusie en het geen begin of einde nodig nie. Met baie daarvan gebaseer op deeglike wetenskaplike beginsels en goeie redenasies.


Waar kom Hawking-straling vandaan (in ruimtetyd)?

Volgens my begrip van die swartgat-termodinamika, as ek 'n swart gat op 'n veilige afstand waarneem, moet ek die bestraling van swart liggame daaruit waarneem, met 'n temperatuur bepaal deur die massa daarvan. Die energie van hierdie straling kom van die massa van die swart gat self.

Maar waar (in ruimtetyd) vind die proses van die opwekking van die Hawking-straling plaas? Dit wil voorkom asof dit by die geleentheidshorison self moet wees. Hier is egter 'n Penrose-diagram van 'n swart gat wat uit 'n ineenstortende ster vorm en dan verdamp, wat ek uit hierdie blogpos van Luboš Motl gekrip het.

Op die diagram het ek die wêreldlyne geteken van die ster se oppervlak (oranje) en 'n waarnemer wat op 'n veilige afstand bly en uiteindelik na die oneindigheid (groen) ontsnap. Aan die hand van die diagram kan ek sien hoe die waarnemer fotone van die ster self en enige ander valstof (oranje ligstrale) kan sien. Dit sal rooi verskuif word na onopspoorbaar lae frekwensies. Maar dit wil voorkom asof enige fotone wat uit die horison self uitgestuur word net op 'n enkele oomblik (blou ligstraal) waargeneem sal word, wat lyk asof dit waargeneem moet word as die ineenstorting van die swart gat.

Dit wil dus voorkom asof ek fotone vanaf 'n swart gat op enige tydstip voor die uiteindelike verdamping daarvan waarneem, dit moes ontstaan ​​uit 'n tyd voordat die horison werklik gevorm het. Is dit reg? Dit lyk baie in stryd met die manier waarop die onderwerp van Hawking-bestraling gewoonlik saamgevat word. Hoe is dit moontlik om die fotone uit te gee? voorheen die vorming van die horison? Speel die verband tussen energie en tyd onsekerheid hier?

Een rede waarom ek hierin belangstel, is omdat ek graag wil weet of Hawking-bestraling in wisselwerking is met die saak wat in die swart gat val. Dit lyk asof daar drie moontlikhede is:

  1. Hawking-bestraling word gegenereer in die ruimtetyd tussen die swart gat en die waarnemer, en wissel dus nie (veel of glad nie) met die valstof nie.
  2. Hawking-straling word naby die middel van die swart gat gegenereer, op 'n tydstip voordat die horison vorm, en gevolglik is dit in wisselwerking met die saak.
  3. Die Hawking-bestraling is eintlik uitgestraal deur die uitstortende saak, wat om die een of ander rede verhit word tot 'n baie hoë temperatuur wanneer dit die gebeurtenishorison nader.
  4. (Met dank aan pjcamp) kan u nie dink dat hulle van 'n spesifieke punt af kom nie, want dit is kwantumdeeltjies en het nooit 'n goed gedefinieerde plek nie.

Al hierdie moontlikhede het baie verskillende implikasies vir hoe 'n mens moet dink aan die inligtinginhoud van die bestraling wat uiteindelik die waarnemer bereik, so ek wil graag weet watter (indien enige) korrek is.

Die vierde moontlikheid doen klink na die redelikste, maar as dit die geval is, wil ek meer besonderhede hê, want wat ek regtig probeer verstaan, is of die Hawking-fotone met die valstelsel kan kommunikeer of nie. Gewoonlik, as ek 'n foton waarneem, verwag ek dat dit deur iets uitgestraal is. As ek een waarneem wat uit 'n swart gat kom, lyk dit nie onredelik om die trajek daarvan in tyd te probeer opspoor en uit te werk wanneer en waar dit vandaan kom nie, en as ek dit doen, sal dit steeds verskyn om te kom van 'n tyd voordat die horison gevorm het, en in werklikheid sal verskyn afkomstig wees van die oppervlak van die oorspronklike ineenstortende ster, net voordat dit die horison verbysteek. Ek verstaan ​​die argument dat die uitvallende saak geen Hawking-bestraling sal ervaar nie, maar ek wil graag verstaan ​​of, vanuit die perspektief van die buite-waarnemer, blyk die Hawking-bestraling in wisselwerking te wees met die saak wat in die swart gat val. Dit is duidelik doen interaksie hê met voorwerpe wat voldoende ver van die swart gat af is, selfs al val dit vrywaarts, dus as dit nie met die oppervlak van die ineenstortende ster wissel nie, waar is die afsnypunt, en waarom?

In 'n antwoord hieronder noem Ron Maimon ''n mikroskopiese punt waar die swart gat die eerste keer gevorm is', maar in hierdie diagram lyk dit asof geen straling vanaf daardie punt waargeneem sal word totdat die gat ineenstort nie. Alles wat ek oor swart gate gelees het, dui daarop dat daar waargeneem word dat Hawking-bestraling voortdurend uit die swart gat kom en nie net op die oomblik van ineenstorting nie, daarom is ek nog steeds baie verward hieroor.

As die bestraling is alles wat vanaf hierdie tydstip in ruimte-tyd uitgestraal word, lyk dit asof dit baie sterk met die in-val-saak moet saamwerk:

In hierdie geval sal die oorskryding van die geleentheidshorison tog nie 'n onvergeetlike nie-ervaring wees nie, aangesien dit gelyktydig met 'n groot deel van die Hawking-fotone moet bots. (Hou dit verband met die idee van 'n 'firewall' waarvan ek gehoor het?)

Uiteindelik besef ek dat ek net verkeerd daaroor kan dink. Ek weet dat die bestaan ​​van fotone nie onafhanklik van die waarnemer is nie, daarom kan ek dink dat die vraag waar die fotone ontstaan, nie sinvol is nie. Maar selfs in hierdie geval wil ek regtig 'n beter fisiese beeld van die situasie hê. As daar 'n goeie rede is waarom "waar en wanneer kom die fotone vandaan?" is nie die regte vraag nie, ek sal baie waardeer 'n antwoord wat dit verklaar. (pjcamp se antwoord op die oorspronklike weergawe van die vraag gaan hierdeur, maar dit behandel nie die tydsverwante aspek van die huidige weergawe nie, en dit gee ook geen insig of die Hawking-straling met die uitstortende materie, vanuit die perspektief van die waarnemer.)

Redaksionele opmerking: hierdie vraag is nogal verander sedert die weergawe wat pjcamp en Ron Maimon beantwoord het. Die ou weergawe was gebaseer op 'n tydsimmetrie-argument, wat korrek is vir 'n Schwartzchild-swart gat, maar nie vir 'n kortstondige een wat uit 'n ineenstortende ster vorm en dan verdamp nie. Ek dink die uiteensetting in terme van Penrose-diagramme is baie duideliker.


Ja, Stephen Hawking het ons alles gelieg oor hoe swartgate verval

Die fisikus en topverkoper-outeur Stephen Hawking bied 'n program in Seattle aan in 2012. Alhoewel hy. [+] het 'n geweldige bydrae tot die wetenskap gelewer, en sy analogie oor swart gate wat verval het, het bygedra tot 'n generasie verkeerde ingeligte natuurkundiges, fisikastudente en fisika-entoesiaste.

Die grootste idee van Stephen Hawking se wetenskaplike loopbaan het 'n rewolusie gemaak vir die manier waarop ons oor swart gate dink. Hulle is tog nie heeltemal swart nie, en dit was inderdaad Hawking wat die bestraling wat hulle sou uitstraal, eers verstaan ​​en voorspel het: Hawking-straling. Hy het die resultaat in 1974 afgelei, en dit is een van die diepste skakels ooit tussen die wêreld van die kwantum en ons gravitasieteorie, Einstein se algemene relatiwiteit.

En tog skets Hawking in sy besonderse boek A A Brief History of Time 'n beeld van hierdie bestraling - van spontaan geskep deeltjie-antipartikelpare waar die een lid in val en die ander ontsnap - dit is baie verkeerd. Vir 32 jaar is dit fisika-studente, leke en selfs professionele persone wat verkeerd ingelig is. Swart gate verval regtig. Laat ons vandag die dag maak waarop ons uitvind hoe hulle dit eintlik doen.

Die kenmerke van die geleentheidshorison self, geskets teen die agtergrond van die radio-uitstoot. [+] van agter af, word deur die Event Horizon Telescope in 'n sterrestelsel van ongeveer 60 miljoen ligjare hiervandaan onthul. Die stippellyn verteenwoordig die rand van die fotonfeer, terwyl die gebeurtenishorison self daaraan inwendig is. Buite die gebeurtenishorison word 'n klein hoeveelheid straling voortdurend uitgestraal: Hawking-straling, wat uiteindelik verantwoordelik sal wees vir die verval van hierdie swart gat.

Event Horizon Telescope-samewerking et al.

Wat Hawking ons sou wou voorstel, is 'n relatiewe eenvoudige prentjie. Begin met 'n swart gat: 'n gebied van die ruimte waar soveel massa in so 'n klein volume gekonsentreer is dat daar nie eers lig kan ontsnap nie. Alles wat te naby daaraan waag, sal onvermydelik in die sentrale enkelvoud ingetrek word, met die grens tussen die ontkombare en onontkombare streke wat die gebeurtenishorison genoem word.

Laat ons nou die kwantumfisika byvoeg. Ruimte, op fundamentele vlak, kan nooit heeltemal leeg wees nie. In plaas daarvan is daar entiteite inherent aan die weefsel van die Heelal self - kwantumvelde - wat altyd alomteenwoordig is. En net soos alle kwantum-entiteite, is daar onsekerhede aan hulle verbonde: die energie van elke veld op enige plek sal mettertyd wissel. Hierdie veldskommelings is baie werklik, en kom selfs voor in die afwesigheid van deeltjies.

'N Visualisering van QCD illustreer hoe deeltjie- / antipartikelpare uit die kwantumvakuum spring. [+] baie klein tydjies as gevolg van Heisenberg-onsekerheid. Die kwantumvakuum is interessant omdat dit eis dat die leë ruimte self nie so leeg is nie, maar gevul is met al die deeltjies, antipartikels en velde in verskillende toestande wat vereis word deur die kwantumveldteorie wat ons Heelal beskryf. As u dit alles saamstel, kom u agter dat leë ruimte 'n nulpunt-energie het wat eintlik groter is as nul.

In die konteks van die kwantumveldteorie stem die laagste energie-toestand van 'n kwantumveld ooreen met geen bestaande deeltjies nie. Maar opgewonde toestande, of toestande wat ooreenstem met hoër energieë, stem ooreen met deeltjies of antipartikels. Een visualisering wat algemeen gebruik word, is om te dink aan die leë ruimte as om leeg te wees, maar bevolk deur deeltjies-antipartikelpare (as gevolg van bewaringswette) wat kortliks ontstaan, om dan na 'n kort rukkie weer in die vakuum van niks uit te wis.

Dit is hier waar Hawking se beroemde prentjie - sy erg verkeerde prentjie - ter sprake kom. Deur die hele ruimte, beweer hy, verskyn hierdie deeltjies-antipartikelpare in en uit die bestaan. Binne die swart gat bly albei lede daar, vernietig, en niks gebeur nie. Ver buite die swart gat, is dit dieselfde. Maar net naby die gebeurtenishorison kan die een lid inval terwyl die ander ontsnap en werklike energie wegdra. En dit, verklaar hy, is die rede waarom swart gate massa verloor, verval en waar Hawking-straling vandaan kom.

In Hawking se bekendste boek, A Brief History of Time, maak hy die analogie dat die ruimte gevul is. [+] met deeltjies-deeltjies-pare en dat die een lid kan ontsnap (positiewe energie dra) terwyl die ander in val (met negatiewe energie), wat lei tot verval in swart gate. Hierdie gebrekkige analogie verwar steeds geslagte fisici en leke.

Ulf Leonhardt / Universiteit van St. Andrews

Dit was die eerste verduideliking wat ek, self 'n teoretiese astrofisikus, ooit gehoor het oor hoe swart gate verval. As die verduideliking waar was, sou dit beteken:

  1. Hawking-bestraling bestaan ​​uit 'n 50/50 mengsel van deeltjies en antipartikels, aangesien die lid val en watter een ontsnap, willekeurig sal wees,
  2. dat al die Hawking-bestraling, wat swart gate laat verval, van die gebeurtenishorison self uitgestraal sal word, en
  3. dat elke kwantum van uitgestraalde straling 'n geweldige hoeveelheid energie moet hê: genoeg om van te ontsnap amper, maar nie heeltemal nie, word ingesluk deur die swart gat.

Al drie die punte is natuurlik nie waar nie. Hawking-bestraling bestaan ​​byna uitsluitlik uit fotone, nie uit 'n mengsel van deeltjies en antipartikels nie. Dit word uitgestraal uit 'n groot streek buite die horison van die gebeurtenis, nie reg op die oppervlak nie. En die individuele kwantas wat uitgestraal word, het klein energieë oor 'n groot verskeidenheid.

Beide binne en buite die gebeurtenishorison van 'n Schwarzschild-swart gat, vloei die ruimte soos 'n a. [+] bewegende looppad of 'n waterval, afhangende van hoe u dit wil visualiseer. Maar buite die gebeurtenishorison, as gevolg van die kromming van die ruimte, word straling gegenereer wat energie wegdra en die massa van die swart gat mettertyd stadig laat krimp.

Andrew Hamilton / JILA / Universiteit van Colorado

Wat vreemd aan hierdie verduideliking is, is dat dit nie die een is wat hy in die wetenskaplike artikels wat hy oor hierdie onderwerp geskryf het, gebruik het nie. Hy het geweet dat hierdie analogie gebrekkig was en daartoe sou lei dat fisici verkeerd daaroor moes dink, maar hy het verkies om dit aan die algemene publiek voor te stel asof mense nie die werklike meganisme kon verstaan ​​nie. En dit is jammer, want die werklike wetenskaplike verhaal is nie meer kompleks nie, maar veel meer verhelderend.

Die leë ruimte het regtig dwarsdeur die kwantumvelde, en daardie velde het regtig skommelinge in hul energiewaardes. Daar is 'n kiem van waarheid in die analogie "deeltjie-antipartikelpaarproduksie", en dit is die volgende: in die kwantumveldteorie kan u die energie van die leë ruimte modelleer deur diagramme op te tel wat die produksie van hierdie deeltjies insluit. Maar dit is 'n berekeningstegniek, net die deeltjies en antipartikels is nie werklik nie, maar is eerder virtueel. Hulle word nie eintlik vervaardig nie, hulle kommunikeer nie met regte deeltjies nie en is op geen manier waarneembaar nie.

'N Paar terme wat bydra tot die nulpunt-energie in kwantum-elektrodinamika. Die ontwikkeling van. [+] hierdie teorie, vanweë Feynman, Schwinger en Tomonaga, het daartoe gelei dat hulle in 1965 die Nobelprys ontvang het. Hierdie diagramme kan toon dat deeltjies en antipartikels in en uit spring, maar dit is slegs 'n berekeningsinstrument wat hierdie deeltjies is nie eg nie.

R. L. Jaffe, van https://arxiv.org/pdf/hep-th/0503158.pdf

Vir enige waarnemer wat oral in die Heelal geleë is, blyk dit dat die "energie van die leë ruimte", wat ons die nulpunt-energie noem, dieselfde waarde het, ongeag waar hulle is. Een van die relatiwiteitsreëls is egter dat verskillende waarnemers verskillende realiteite sal waarneem: waarnemers in relatiewe beweging of in gebiede waar die ruimtetydkromming anders is, sal in die besonder nie met mekaar verskil nie.

As u dus oneindig ver van elke massa in die Heelal is en u ruimtetyd kromming weglaatbaar is, sal u 'n sekere nulpunt-energie hê. As iemand anders by die horison van 'n swart gat geleë is, sal hulle 'n sekere nulpunt-energie hê wat dieselfde meetwaarde vir hulle het as wat dit vir u oneindig ver is. Maar as u u nulpunt-energie probeer toewys aan hul nulpunt-energie (of andersom), stem die waardes nie ooreen nie. Vanuit mekaar se perspektiewe verander die nulpunt-energie in verhouding tot hoe ernstig die twee ruimtes geboë is.

'N Illustrasie van swaar geboë ruimtetyd vir 'n puntmassa, wat ooreenstem met die fisiese. [+] scenario om buite die gebeurtenishorison van 'n swart gat geleë te wees. Soos u nader en nader aan die ligging van die massa in die ruimtetyd kom, word die ruimte sterker gebuig, wat uiteindelik lei tot 'n plek van waar selfs die lig nie kan ontsnap nie: die gebeurtenishorison. Waarnemers op verskillende plekke sal nie saamstem oor wat die nulpunt-energie van die kwantumvakuum is nie.

Pixabay-gebruiker JohnsonMartin

Dit is die belangrikste punt agter Hawking-bestraling, en Stephen Hawking self het dit geweet. In 1974, toe hy Hawking-bestraling vir die eerste keer beroemd gemaak het, was dit die berekening wat hy uitgevoer het: die berekening van die verskil in die nulpunt-energie in kwantumvelde van die geboë ruimte rondom 'n swart gat tot die plat ruimte, oneindig ver weg.

Die resultate van die berekening is wat die eienskappe van die bestraling wat uit 'n swart gat voortspruit, bepaal: nie uitsluitlik vanaf die gebeurtenishorison nie, maar uit die geheel van die geboë ruimte daaromheen. Dit vertel ons die temperatuur van die straling, wat afhang van die massa van die swart gat. Dit vertel ons die spektrum van die straling: 'n perfekte swartliggaam, wat die energieverspreiding van fotone aandui en - as daar genoeg energie beskikbaar is via E = mc² - ook massiewe deeltjies en antipartikels.

Die gebeurtenishorison van 'n swart gat is 'n sferiese of sferoïedale gebied waaruit niks, selfs nie. [+] lig, kan ontsnap. Maar buite die gebeurtenishorison word voorspel dat die swart gat straling sal uitstraal. Hawking se 1974-werk was die eerste wat dit getoon het, en dit was waarskynlik sy grootste wetenskaplike prestasie.

NASA DANA BERRY, SKYWORKS DIGITAL, INC.

Dit stel ons ook in staat om 'n belangrike detail te bereken wat nie algemeen waardeer word nie: waar die bestraling vandaan kom wat swart gate uitstraal. Terwyl die meeste foto's en visualisasies 100% van die Hawking-straling van 'n swart gat uit die gebeurtenishorison self uitstraal, is dit meer akkuraat om dit uit te beeld as uitgestraal oor 'n volume wat ongeveer 10-20 Schwarzschild-radiuse strek (die radius tot by die gebeurtenishorison) , waar die bestraling geleidelik afneem, hoe verder jy kom.

Dit lei ons tot 'n fenomenale gevolgtrekking: dat alle voorwerp wat in duie stort wat ruimtetyd krom, Hawking-straling moet uitstraal. Dit kan 'n klein, onmerkbare hoeveelheid Hawking-bestraling wees, oorstroom deur termiese straling vir sover ons dit kan bereken vir selfs lang dooie wit dwerge en neutronsterre. Maar dit bestaan ​​steeds: dit is 'n positiewe, nie-nul-waarde wat berekenbaar is, afhanklik van die massa, draai en fisiese grootte van die voorwerp.

Aangesien swart gate weens Hawking-bestraling massa verloor, verhoog die verdampingstempo. Na genoeg. [+] die tyd gaan verby, 'n briljante flits van 'laaste lig' word vrygestel in 'n stroom hoë-energie swartliggaamstraling wat geen materie of antimaterie bevoordeel nie.

Die grootste probleem met Hawking se uiteensetting van sy eie teorie is dat hy 'n berekeningsinstrument gebruik - die idee van virtuele deeltjies - en dit instrument hanteer asof dit gelykstaande is aan die fisiese werklikheid. In werklikheid gebeur dit dat die geboë ruimte rondom die swart gat voortdurend straling uitstraal as gevolg van die krommingsgradiënt daaromheen, en dat die energie van die swart gat af kom, wat veroorsaak dat die gebeurtenishorison mettertyd stadig krimp.

Swart gate is nie besig om te verval nie, omdat daar 'n virtuele deeltjie is wat negatiewe energie dra, wat nog 'n fantasie is wat Hawking bedink het om sy onvoldoende analogie te "red". In plaas daarvan verval swart gate en verloor dit mettertyd massa, omdat die energie wat deur hierdie Hawking-straling vrygestel word, stadig die kromming van die ruimte in daardie streek verminder. Sodra genoeg tyd verbygaan, en die duur vir realistiese swart gate baie duur is, sal dit heeltemal verdamp het.

Die gesimuleerde verval van 'n swart gat het nie net die uitstraling van straling tot gevolg nie, maar ook die verval van. [+] die sentrale wentelmassa wat die meeste voorwerpe stabiel hou. Swartgate sal eers ernstig begin verval, maar sodra die verval die groeikoers oorskry. Vir die swart gate in ons heelal sal dit eers plaasvind voordat die heelal ongeveer tien miljard keer sy huidige ouderdom is.

Niks hiervan mag dien om Hawking se geweldige prestasies aan hierdie front weg te neem nie. Dit was hy wat die diep verband tussen swartgat-termodinamika, entropie en temperatuur besef. Dit was hy wat die wetenskap van die kwantumveldteorie en die agtergrond van die geboë ruimte naby 'n swart gat saamgestel het. En dit was hy wat - heeltemal korrek, let wel - die eienskappe en energiespektrum van die straling wat swart gate sou oplewer, uitvind. Dit is absoluut gepas dat die manier waarop swart gate verval, via Hawking-bestraling, sy naam dra.

Maar die gebrekkige analogie wat hy in sy bekendste boek, A Brief History of Time, voorgehou het, is nie korrek nie. Hawking-bestraling is nie die vrystelling van deeltjies en antipartikels vanaf die gebeurtenishorison nie. Dit behels nie dat 'n innerlike dalende paarlid negatiewe energie dra nie. En dit behoort nie eers eksklusief vir swart gate te wees nie. Stephen Hawking het geweet hoe swart gate regtig verval, maar hy het die wêreld 'n heel ander, selfs verkeerde, verhaal vertel. Dit is tyd dat ons almal eerder die waarheid weet.


Nuwe moontlikhede vir die opsporing van Hawking-straling wat deur oorspronklike swart gate uitgestraal word

Nuwe PBH-beperking gebaseer op COMPTEL-data (donkerblou), projeksies van die ontdekkingsbereik van toekomstige MeV-gammastraal-teleskope (ander gekleurde kurwes) en bestaande beperkings (skaduryke grys streke). Krediet: Coogan et al.

Terwyl baie fisici die bestaan ​​van donker materie voorspel het, 'n soort materie wat nie lig absorbeer, weerkaats of uitstraal nie, kon niemand dit tot dusver eksperimenteel waarneem of die fundamentele aard daarvan bepaal nie. Ligte oer-swart gate (PBH's), swart gate wat in die vroeë heelal gevorm is, is van die mees belowende kandidate vir donker materie. Die bestaan ​​van hierdie swart gate is egter nog nie bevestig nie.

Navorsers aan die Universiteit van Amsterdam en die Universiteit van Kalifornië-Santa Cruz het onlangs 'n studie gedoen wat daarop gemik is om die bestaande beperkings op die toegelate parameterruimte van PBH's as donker materie te verbeter. In hul referaat, gepubliseer in Fisiese oorsigbriewe, stel hulle ook 'n moontlike metode voor wat gebruik kan word om Hawking-bestraling direk in digte gebiede met donker materie op te spoor en moontlik die ontdekking van PBH-donker materie moontlik te maak.

Hawking-bestraling is die termiese bestraling wat Stephen Hawking voorspel het spontaan deur swart gate uitgestraal te word. Hierdie bestraling word veronderstel om te ontstaan ​​as gevolg van die omskakeling van kwantumvakuum-skommelinge in deeltjiespare, die een ontsnap uit die swart gat en die ander vasgevang binne die gebeurtenishorison (dit wil sê die grens rondom swart gate waaruit geen lig of straling kan ontsnap nie).

"PBH's wat meer as 'n paar persent van die donker materie bevat, moet 'n massa van tussen 10 16 gram en 10 35 gram hê," het Adam Coogan, een van die navorsers wat die studie gedoen het, aan Phys.org gesê. "Oor die grootste deel van die reeks sluit verskillende waarnemings hulle uit om 100% van die donker materie uit te maak. Daar is egter 'n noemenswaardige gaping in die beperkings: PBH's met massas rondom die van 'n asteroïde (

10 17 gram tot 10 22 gram) kan nog steeds al die donker materie uitmaak. '

Die identifisering van metodes om die toegelate parameterruimte van PBH's te beperk of die Hawking-straling wat daaruit voortspruit, op te spoor, kan 'n belangrike stap in die rigting van die waarneming of ontdekking van PBH-donker materie wees. Coogan, in samewerking met sy kollegas Logan Morrison en Stefano Profumo, het dus die potensiaal van MeV gammastraal-teleskope ondersoek as instrumente om PBH Hawking-straling op te spoor.

"Die hoofgedagte agter ons werk was om na te dink oor 'n spesifieke manier om na asteroïedmassa's te soek," het Coogan verduidelik. "Daar word verwag dat ligte PBH's Hawking-straling sal uitstraal wat bestaan ​​uit 'n mengsel van fotone en ander ligdeeltjies, soos elektrone en pione. Teleskope kan dan hierdie straling soek deur ons sterrestelsel of ander sterrestelsels waar te neem. Die doel van ons referaat was om te verstaan ​​hoe wel komende teleskope sou hierdie bestraling kon waarneem en gevolglik hoeveel van die asteroïedmassa PBH-parameterruimte hulle kon ondersoek. '

Terwyl hulle probeer om die massas PBH's te skat wat opkomende teleskope kan help om te beperk, ontdek Coogan en sy kollegas dat vorige studies nog nie die data wat deur die COMPTEL-teleskoop versamel is, ontleed het nie, 'n gammastraal-teleskoop wat deur NASA aan boord van die Compton Gamma Ray Observatory gelanseer is (CGRO). Hierdie gegewens kan egter help om die oorvloed PBH's effens onder die asteroïedemassagaping (d.w.s. onder 10 17 gram) te beperk. Alhoewel daar reeds beperkings bestaan ​​in hierdie massa-reeks danksy waarnemings van Hawking-bestraling wat deur Voyager 1 en die satelliet INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) ingesamel is, is bevind dat die nuwe beperkings wat deur die navorsers ingestel is, die sterkste tot nog toe was.

"Die belangrikste insette vir die beperking van rekenaars en die maak van projeksies is om die spektrum van Hawking-straling wat deur 'n enkele PBH geproduseer word, te bereken," het Coogan gesê. "Ons het hierdie berekening verfyn in vergelyking met die bestaande instrumente in die literatuur deur te verbeter hoe die bestraling wat deur elektrone en pione geproduseer word, in die spektrum verreken word. Die res van die berekeninge is baie tipies vir soeke na donker materie."

Assuming that PBHs of a specific mass make up a given fraction of the total dark matter in space, the calculations carried out by Coogan and his colleagues would allow researchers to compute their contribution to the spectrum of photons emitted by an astrophysical object believed to contain a substantial amount of dark matter, such as the center of the Milky Way. If the spectrum estimated by these calculations was far brighter than the observed spectrum, for instance, one could rule out the possibility that PBHs of that specific mass make up a specific fraction of dark matter.

"Making projections for the performance of future telescopes follows along similar lines, though there is no observed spectrum to compare to," Coogan explained. "In this case, the spectrum of photons emitted by PBHs is compared with a model for the expected astrophysical background of photons."

The recent study by Coogan, Morrison and Profumo set the strongest constraints on low-mass PBHs to date, using data collected as part of an experiment that was completed 20 years ago. In addition, the researchers showed that upcoming telescopes capable of observing MeV-energy gamma rays could help to probe asteroid-mass PBHs, which is a very difficult part of the PBH parameter space to probe.

"The astronomy community has been considering several proposals for such telescopes in recent years and I think our paper provides another solid motivation for constructing them," Coogan added. "Aside from PBHs, we have been studying how upcoming MeV gamma-ray telescopes could probe different models of particle dark matter. We recently finished another paper where we computed the gamma-ray spectra for a few particular such models and are working with other collaborators to refine these calculations."

Coogan, Morrison and Profumo have recently also been collaborating with Alexander Moiseev, a Research Scientist at NASA, who is developing a telescope called the Galactic Explorer with a Coded Aperture Mask Compton Telescope (GECCO). Together with Moiseev, they have been trying to map out ways in which GECCO could aid the search for dark matter.

More information: Direct detection of Hawking radiation from Asteroid-mass primordial black holes. Physical Review Letters(2021). DOI: 10.1103/PhysRevLett.126.171101.

Precision gamma-ray constraints for Sub-GeV dark matter models. arXiv:2104.06168 [hep-ph]. arxiv.org/abs/2104.06168

Hunting for dark matter and new physics with (a) GECCO. arXiv:2101.10370 [astro-ph.HE]. arxiv.org/abs/2101.10370

Citation: New possibilities for detecting Hawking radiation emitted by primordial black holes (2021, June 21) retrieved 21 June 2021 from https://phys.org/news/2021-06-possibilities-hawking-emitted-primordial-black.html

This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.


Antwoorde en antwoorde

There is a better way of thinking about it.

Quantum mechanics says that there is some inherent uncertainty about what the location of a particle is or how much energy and momentum it has. It turns out that if you ask "how many particles are in this box" that's also an number that is fuzzy. It's not that there are twenty particles in the box, it's that the exact number of particles in the box is undefined. It's "around 20-ish."

Both the particle and anti-particle have positive mass.

Also the reason that something like Hawking radiation has to exist is that if you had a black hole suck everything, it would turn into an ultimate heat sink, and you could use it to create a perpetual motion machine.

Another problem I have with it, why would such a particle be able to escape anyway?

I mean we're talking at the edge of an event horizon with an escape velocity of slightly below light speed, how does any particle get away from there? Unless its a photon or a neutrino thats not pointing toward the black hole?

Anything else with mass, I have a hard time imagining it having enough momentum to get away from the black hole.

But then again, as far as I understand there has never been any proof of hawking radiation, so it could be a wrong assumption.

The way hawking Radiation works as I understand it, a pair is created on the edge of the event horizon, and as the pair is created, and before it can annihilate, the anti-particle falls into the black hole, and the positive particle is seen by the rest of the universe as if the black hole had just expelled matter.

Now, given how the uncertainty principle will never allow for any particle to have a known position, how can the black hole only absorb the anti-particle? Why isn't the black hole sometime getting the positive particle and therefore gaining weight? While the universe gets the bad end of the deal and gets an anti-particle?

and the link to Steve Carlip's explanation that I give in this post.

sorry to bring an old thread to the top, but i've been confused about the exact same thing as the OP, and luckily i found this thread via a search before unnecessarily starting my own. at any rate, after much thought of how particle-antiparticle pair creation near an event horizon can result in Hawking Radiation (BH evaporation), the most sensible explanation i could comtemplate in my own head was more or less what was stated above. if the gravitational field near the event horizon gives up a certain quantity of mass/energy in order to create the particle-antiparticle pair, then the BH's mass/energy must decrease by that same quantity. but the BH must gain some (but not all) of that mass/energy back when it swallows either one of the two particles previously created. that's the only way i can visualize hawking radiation as the actual decrease in the mass/energy of a BH. now granted, i don't expect anyone to be able to definitively confirm or deny my analysis - after all, we won't really know the specifics of the energy exchange until we start to actually witness Hawking Radiation. but i would like to hear from others on whether they generally agree or disagree with this notion of BH evaporation.

also, this blurb is a bit off-topic, but its somewhat related, so i thought i would postulate it here. i don't know if its possible, but i was wondering if the quantities of energy involved in the minute fluctuations of the BH's gravitational field that create these particle-antiparticle pairs in the first place could be small enough that neither particle of the pair is endowed with enough energy to escape the BH. if this scenario is possible (and i have no idea if it is or isn't), then it would seem that not all particle-antiparticle pair-creating fluctuations in the gravitatonal field result in Hakwing Radiation. that is, if the entire quantity of mass/energy given up by the BH during the creation of a particle-antiparticle pair is swallowed back up by the BH, then its mass/energy is conserved, and no mass/energy is radiated away in the form of Hakwing Radiation.


The origin of Hawking radiation

Let us now explain the mechanism that is responsible for this thermal flux. It is to be found in the redshifting effect of Eq. (2) and the associated tearing apart of the light rays across the horizon of Eq. (). The exponential redshifting applies individually and universally to all light waves irrespectively of their initial frequency (Omega_0 .) A closer examination shows that every wave, in addition of being redshifted, is slightly amplified by this redshift. Moreover, it can be also shown that this amplification is necessarily accompanied by a correspondingly small production of a partner wave of opposite frequency. In classical terms, these two effects have no significant consequences because they are weighted by the amplitude of the partner wave (the coefficient ( eta_omega ) in Eq. (8) below) which is in general extremely small. On the contrary, in quantum mechanical terms this small amplification accompanied by the production of a partner wave is of uppermost importance as it is directly responsible for the Hawking effect. In quantum terms indeed, in the vacuum, the state of minimal energy, nothing would have happened without this amplification, i.e. black holes would have remained black.

Given the importance of this amplification, let us describe it with more precision. When considering the propagation of light in the static spacetime obtained after the collapse, one finds that outgoing wave packets initially localized very near the horizon split into two waves: one with positive frequency that escapes and a partner wave ( phi_ <-omega>) of negative frequency which is trapped inside the horizon: 2

There is a conservation law associated with the splitting that takes the form [ ag <9>vert alpha_omega vert^2 = 1 + vert eta_omega vert^2. ]

This law relates ( alpha_omega ,) the amplification factor of the escaping wave, to ( eta_omega ,) the amplitude of the partner wave which is trapped. Hawking showed that these coefficients obey [ ag <10>left| <eta_omega over alpha_omega > ight|^2 = e^ <- 2pi omega au_kappa >= e^<- hbar omega /k_B T_< m Hawking>>. ]

Recalling that the Boltzmann law of thermal equilibrium takes the form ( e^ <-E/k_BT> ,) and re-using the relation ( E = hbar omega ,) one can read from Eq. (10) the Hawking temperature of Eq. (5).

It now remains to understand what happens to the vacuum state when the amplification factor ( vert alpha_omega vert^2 > 1 ,) i.e. when ( eta_omega ) does not vanish. To this end, one must recall that the field describing quantum light does not strictly vanish in the vacuum. In fact, the field steadily fluctuates around a vanishing mean value. 3 In usual circumstances, these vacuum fluctuations remain unchanged, thereby expressing the stability of the vacuum state. However, when they are excited by some external agent, there can be a quantum transition which is accompanied by the emission of a photon, i.e. an excitation of the quantum field of light. For instance, when the light field is coupled to an excited atom, this causes the spontaneous decay of the atom and the emission of a photon. Similarly here, the redshifting effect of Eq. (2) excites some vacuum fluctuations and this leads to the steady production of photons. As for the spontaneous decay of atoms, the moments when the production occurs are randomly distributed. Indeed quantum mechanics only fixes the mean rate of their occurrence. A detailed calculation shows that this production rate is constant and fixed by ( vert eta_omegavert^2 ,) the squared norm of the partner wave coefficient that appears in Eqs. (8,9,10). For more details on this correspondence we refer to the review article [5].

Two important differences between atomic transitions and black hole radiation should be underlined. The first difference between coupling light to atoms and to the gravitational black hole field is that the latter necessarily leads to the production of pairs of photons. It can also be shown that in each pair, one photon escapes to spatial infinity and carries a positive energy ( hbar omega ,) whereas its partner carries a negative energy ( - hbar omega ,) and remains trapped inside the horizon. Moreover, in each pair, the two photons are "entangled", i.e. correlated with each other. Their entangled character can be revealed by studying non-local correlations across the black hole horizon. Doing so one obtains a spacetime pattern which is similar to that associated with the splitting of Eq. (8), see Figure 2. A second difference is that these pairs are steadily produced, one after the other, at the expense of the black hole mass. The black hole effectively behaves as an extremely excited atom that would have stored a huge amount of energy and would release it extremely slowly, as can be seen from Eq. (7) which gives the enormous lifetime of black holes. Taken together the escaping members of these pairs form a thermal flux at the Hawking temperature.


How Stephen Hawking's Greatest Discovery Revolutionized Black Holes

The event horizon of a black hole is a spherical or spheroidal region from which nothing, not even . [+] light, can escape. But outside the event horizon, the black hole is predicted to emit radiation. Hawking's 1974 work was the first to demonstrate this, and it was arguably his greatest scientific achievement.

NASA DANA BERRY, SKYWORKS DIGITAL, INC.

In 1915, Albert Einstein published his General theory of Relativity, replacing our old Newtonian worldview with a unified concept of spacetime. On one side of Einstein's equations, the matter and energy in the Universe told spacetime how to curve on the other side, the curved fabric of spacetime told matter and energy how to move. The complicated nature of these equations ensured that exact solutions would be hard to find, as Einstein himself only ever found two: one for completely empty space and one for a single mass in the weak-field limit. The next year, Karl Schwarzschild found the first interesting solution, for a point mass over all of space. We now recognize this as the solution for a black hole, one of the few exact solutions known even today. While in Schwarzschild's formulation, black holes were static objects, Hawking was the first to prove that it isn't so. Black holes radiate over time, and as such, aren't even completely black.

The mass of a black hole is the sole determining factor of the radius of the event horizon, for a . [+] non-rotating, isolated black hole. For a long time, it was thought that black holes were static objects in the spacetime of the Universe.

It's been known for a long time that there are only a few properties that can describe a black hole. In Schwarzschild's case, he simply assigned it mass, and solved for the curvature of spacetime. It was shown by others that you could add a charge (Reissner–Nordström black holes) or a spin (Kerr black holes), but that was it. What you couldn't do was add information into a black hole: an electrically neutral, non-rotating human being contained as much information as an equivalent cloud of hydrogen gas once it entered a black hole. From a thermodynamic point-of-view, this was a disaster. You could throw a cloud of hydrogen gas with a temperature of absolute zero, and hence an entropy of zero, into the black hole, and it would have the same effect on the black hole as throwing an equivalent-energy human being in there. This simply didn't make sense.

When a mass gets devoured by a black hole, the amount of entropy the matter has is determined by its . [+] physical properties. But inside a black hole, only properties like mass, charge, and angular momentum matter. This poses a big conundrum if the second law of thermodynamics must remain true.

Illustration: NASA/CXC/M.Weiss X-ray (top): NASA/CXC/MPE/S.Komossa et al. (L) Optical: ESO/MPE/S.Komossa (R)

It meant that, contrary to the second law of thermodynamics, it meant we suddenly had a way to arbitrarily decrease the entropy of the Universe. A black hole, classically, should have an entropy of zero. If you could throw objects with real, positive, and large amounts of entropy into a black hole, you'd have a way to violate that law. Entropy always increases, as far as we know, and this was one of the things Hawking was thinking about when he was considering what was puzzling about black holes. There must be some way to define it for black holes, and that value ought to be both positive and large. Increasing entropy, over time, should be okay, but decreasing it should be forbidden. The only way to ensure that would be by forcing an increase in the black hole's mass to cause entropy to go up by at least the largest amount you can imagine.

Encoded on the surface of the black hole can be bits of information, proportional to the event . [+] horizon's surface area.

T.B. Bakker / Dr. J.P. van der Schaar, Universiteit van Amsterdam

The way that people working on that problem – including Hawking – assigned an answer was to make entropy proportional to the surface area of a black hole. The more quantum bits of information you can fit on a black hole, the greater its entropy was. But that brought up a new problem: if you have entropy, then that means you have a temperature. And if you have a temperature, you have to radiate energy away. Originally called "black" because nothing, not even light, can escape, now it became clear it had to emit something after all. All of a sudden, a black hole isn't a static system anymore it's one that changes over time.

The simulated decay of a black hole not only results in the emission of radiation, but the decay of . [+] the central orbiting mass that keeps most objects stable. Black holes are not static objects, but rather change over time.

So if a black hole isn't so black, and if it's radiating, the big question now becomes how. How does a black hole radiate? Figuring out the answer to this conundrum was Hawking's biggest contribution to physics. We know how to calculate, in quantum field theory, how the vacuum of empty space behaves when space is flat. That is, we can tell you properties of empty space when you're very far away from any masses, like a black hole. What Hawking showed, for the first time, is how to do this in curved space: within a few radii of the event horizon. And what he found was that there was a marked difference in the behavior of the quantum vacuum when a mass was near.

Quantum gravity tries to combine Einstein’s general theory of relativity with quantum mechanics. . [+] Quantum corrections to classical gravity are visualized as loop diagrams, as the one shown here in white. The semiclassical approximation that Hawking used involved calculating the quantum field theoretic effects of the vacuum in the background of curved space.

SLAC National Accelerator Lab

When he ran through the math, he found the following properties:

  • When you're far from the black hole, it looks like you get the thermal emission of blackbody radiation.
  • The temperature of the emission is dependent on the black hole's mass: the lower the mass, the higher the temperature.
  • As the black hole emits radiation, it decreases in mass, in exact accord with Einstein's E = mc 2 . The higher the rate of radiation, the faster the mass loss.
  • And as the black hole loses mass, it shrinks and radiates faster. The time a black hole can live is proportional to its mass cubed: the black hole at the Milky Way's center will live some 10 20 times longer than a black hole of the Sun's mass.

If you visualize empty space as frothing with particle/antiparticle pairs that pop in-and-out of . [+] existence, you'll see radiation coming from the black hole. This visualization is not quite correct, but the fact that it's easy to visualize has its benefits.

Ulf Leonhardt of the University of St. Andrews

Originally, Hawking visualized this as particle/antiparticle pairs popping in-and-out of existence, annihilating away to produce radiation. That oversimplified picture was qualitatively good enough to describe the radiation far from the black hole, but it turns out to be incorrect close to the event horizon. It's more accurate to think of the vacuum changing, and of the radiation as being emitted from wherever the curvature of space is relatively large: within a few radii of the black hole itself. Once you get far away, though, everything just appears to be this thermal, blackbody radiation.

Hawking radiation is what inevitably results from the predictions of quantum physics in the curved . [+] spacetime surrounding a black hole's event horizon. This visualization is more accurate than the above, since it shows photons as the primary source of radiation rather than particles. However, the emission is due to the curvature of space, not the individual particles, and doesn't all trace back to the event horizon itself.

All at once, there was a revolution in black holes, and in understanding how quantum fields behave in highly curved space. It opened up the black hole information paradox, as we're now asking where the information encoded on the black hole's event horizon goes when a black hole evaporates? It opens up the (related) problem of black hole firewalls, asking why don't objects get fried by radiation as they cross the event horizon, or whether they in fact do? It tells us there's a relationship between what happens within a volume (in the space enclosed by the event horizon) and the surface encapsulating it (the event horizon itself), which is a potential example of the holographic principle in real life. And it opens the door to additional subtleties that may allow us, for the first time, to probe the effects of quantum gravity if there are any departures from the predictions of General Relativity.

Against a seemingly eternal backdrop of everlasting darkness, a single flash of light will emerge: . [+] the evaporation of the final black hole in the Universe.

The paper that led to all this was simply titled Black Hole Explosions? and was published in Nature back in 1974. It would have been the crowning achievement of a lifetime of research, and Hawking published it when he was merely 32 years old. He had been researching singularities, black holes, baby universes, and the Big Bang for many years, having collaborated with titans like Gary Gibbons, George Ellis, Dennis Sciama, Jim Bardeen, Roger Penrose, Bernard Carr, and Brandon Carter, to name a few. His brilliant work didn't come out of nowhere, but arose out of a combination of a brilliant mind thriving in a fertile academic environment. It's a lesson to us all in how important it is, if we want to have these titanic theoretical advances, to create (and fund) these quality environments where research like this can come to life.

Outside the event horizon of a black hole, General Relativity and quantum field theory are . [+] completely sufficient for understanding the physics of what occurs that is what Hawking radiation is.

Nearly half a century later, the world mourns his passing, but the legacy of his research lives on. Perhaps this will be the century where there paradoxes are resolved, and the next titanic leaps forward in physics are taken. Regardless of what the future holds, Hawking's legacy is secure, and the most any theorist can hope for is that their theories will be improved in time. As Hawking himself stated:

Any physical theory is always provisional, in the sense that it is only a hypothesis: you can never prove it. No matter how many times the results of experiments agree with some theory, you can never be sure that the next time the result will not contradict the theory.

While the world may have lost one of its great scientific luminaries with Hawking's demise, his impact on our knowledge, understanding, and curiosity will echo throughout the ages.


STEPHEN HAWKING

Stephen Hawking is a world-renowned British theoretical physicist, known for his contributions to the fields of cosmology, general relativity and quantum gravity, especially in the context of black holes. In the 1960s and 1970s, he worked on ground-breaking theorems regarding singularities within the framework of general relativity, and made the theoretical prediction that black holes should emit radiation (known today as Hawking radiation). He has also published several works of popular science in which he discusses his own theories and cosmology in general, including the runaway bestseller “A Brief History of Time”, and has come to be thought of as one of the greatest minds in physics since Albert Einstein. In his own words: “My goal is simple. It is complete understanding of the universe, why it is as it is and why it exists at all”.

Stephen William Hawking was born on 8 January 1942 in Oxford, England, in the middle of World War II. After his birth in the relative safety of Oxford, the family moved back to London, where his father headed the division of parasitology at the National Institute for Medical Research, despite the continued risk of bombing from the German air forces. In 1950, Hawking moved with his family to St. Albans, where he attended St. Albans High School for Girls from 1950 to 1953 (boys could attend until the age of 10), and from the age of 11, he attended St. Albans School, where he was a good, but not an exceptional, student.

In 1959, he won a scholarship to University College, Oxford, his father's old college, where he studied physics under Robert Berman (mainly because his own preference, mathematics, was not offered there), where he pursued his particular interests in thermodynamics, relativity, and quantum mechanics. Despite his sometimes lax study habits and his boredom with university life, he graduated in 1962 with a First Class BA degree.

After graduating from Oxford, he spent a short time studying sunspots at Oxford University’s observatory. However, he soon realized that he was more interested in theory than in observation, and left Oxford for Trinity Hall, Cambridge, where he studied for a time under Fred Hoyle, the most distinguished English astronomer of the time.

Soon after arriving at Cambridge, at the age of 21, Hawking started to develop the first symptoms of amyotrophic lateral sclerosis (ALS or “Lou Gehrig's disease”), a type of motor neurone disease which would eventually cost him almost all neuromuscular control. Although doctors predicted (incorrectly, as it turned out) that Hawking would not survive more than two or three years, he did gradually lose the use of his arms, legs and voice, until he was almost completely paralysed and quadriplegic.

Crucially, in 1965, he attended a lecture by the English mathematician Roger Penrose, who had recently produced a ground-breaking paper on space-time singularities (events in which the laws of physics seem to break down). Hawking became re-energized and engaged with renewed vigour in the study of theoretical astronomy and cosmology, particularly in the area of black holes and singularities. He would later collaborate with Penrose on several important papers on these subjects.

Another turning point in his life also occurred in 1965, with his marriage to a language student, Jane Wilde. With her help, and that of his doctoral tutor, Dennis Sciama, Hawking went on to complete his PhD and to become a Research Fellow and, later, a Professorial Fellow at Gonville and Caius College, Cambridge.

In 1968, he joined the staff of the Institute of Astronomy in Cambridge, where he remained until 1973, and began to apply the laws of thermodynamics to black holes by means of very complicated mathematics. In the late 1960s, he and his Cambridge friend and colleague, Roger Penrose, applied a new, complex mathematical model they had created from Albert Einstein's General Theory of Relativity which led, in 1970, to Hawking proving the first of many singularity theorems. This theorem provided a set of sufficient conditions for the existence of a singularity in space-time, and also implied that space and time would indeed have had a beginning in a Big Bang event, and would end in black holes. In effect, he had reversed Penrose's idea that the creation of a black hole would necessarily lead to a singularity, proving that it was a singularity that led to the creation of the universe itself.

In collaboration with Brandon Carter, Werner Israel and David Robinson, he provided a mathematical proof of John Wheeler's so-called "No-Hair Theorem", that any black hole is fully described by the three properties of mass, angular momentum and electric charge, and proposed the four laws of black hole mechanics, similar to the four classical Laws of Thermodynamics. From analysis of gamma ray emissions, he also suggested that primordial or “mini black holes” would have been formed after the Big Bang.

In 1974, Hawking and Jacob Bekenstein showed that black holes are not actually completely black, but that they should thermally create and emit sub-atomic particles, known today as Hawking radiation, until they eventually exhaust their energy and evaporate. This also resulted in the so-called “Information Paradox” or “Hawking Paradox”, whereby physical information (which roughly means the distinct identity and properties of particles) appears to be completely lost to the universe, in contravention of the accepted laws of physics. Hawking defended this paradox against the arguments of Leonard Susskind and others for thirty years, until famously retracting his claim in 2004.

These cutting edge achievements were made despite the increasing paralysis caused by Hawking's ALS. By 1974, he was unable to feed himself or get out of bed, and his speech became so slurred that he could only be understood by people who knew him well. In 1985, he caught pneumonia and had to have a tracheotomy, which left him unable to speak at all, although although a variety of friends and well-wishers collaborated in building him a device that enabled him to write onto a computer with small movements of his body, and then to speak what he had written using a voice synthesizer.

In 1973, he left the Institute of Astronomy for the Department of Applied Mathematics and Theoretical Physics and, in 1979, he was appointed Lucasian Professor of Mathematics at Cambridge University, a post he was to retain for 30 years until his retirement in 2009. He had three children with Jane Wilde: Robert (1967), Lucy (1969) and Timothy (1979), but the couple finally separated in 1991, reportedly due to the pressures of Hawking’s fame and his increasing disability.

Hawking’s ground-breaking research resulted in considerable fame and celebrity. In 1974, at the age of 32, he was elected as one of the youngest ever Fellows of the Royal Society. He was created a Commander of the Order of the British Empire (CBE) in 1982, and became a Companion of Honour in 1989. He has accumulated twelve honorary degrees, as well as many other awards, medals and prizes, including the Albert Einstein Award, the most prestigious in theoretical physics. He also became well-known among a wider audience, especially after his 1988 international bestselling book “A Brief History of Time”, and its follow ups “The Universe in a Nutshell” (2001) and “A Briefer History of Time” (2005).

He continued lines of research into exploding black holes, string theory, and the birth of black holes in our own galaxy. His work also increasingly indicated the necessity of unifying general relativity and quantum theory in an all-encompassing theory of quantum gravity, a so-called "theory of everything", particularly if we are explain what really happened at the moment of the Big Bang. As early as 1974, his theory of the emission of Hawking radiation from black holes was perhaps one of the first ever examples of a theory which synthesized, at least to some extent, quantum mechanics and general relativity

Among the myriad other scientific investigations pursued by Hawking over the years are the study of quantum cosmology, cosmic inflation, helium production in anisotropic Big Bang universes, "large N" cosmology, the density matrix of the universe, the topology and structure of the universe, baby universes, Yang-Mills instantons and the S matrix, anti-de Sitter space, quantum entanglement and entropy, the nature of space and time and the arrow of time, spacetime foam, string theory, supergravity, Euclidean quantum gravity, the gravitational Hamiltonian, the Brans-Dicke and Hoyle-Narlikar theories of gravitation, gravitational radiation, holography, time symmetry and wormholes.

Never afraid to court controversy, he even began to question the Big Bang theory itself in the 1980s, suggesting that perhaps there never was a start and would be no end, but just change, a constant transition of one "universe" giving way to another through glitches in space-time. He developed his "No Boundary Proposal" in collaboration with the Amercian physicist Jim Hartle. Under classical general relativity, the universe either has to be infinitely old or had to have started at a singularity, but Hawking and Hartle’s proposal raises a third possibility: that the universe is finite but had no initial singularity to produce a boundary. The history of this no-boundary universe in "imaginary time" can perhaps be best envisaged using the analogy of the surface of Earth, with the Big Bang equivalent to Earth’s North Pole, and the size of the universe increasing with imaginary time as you head south toward the equator.

In 1995, Hawking married his nurse, Elaine Mason, although they divorced in 2006 amid unconfirmed rumours of physical abuse, and he has since made up his differences with his first wife, Jane. In 2003, Hawking became dangerously ill with pneumonia, before confounding his doctors once again by recovering and throwing himself ever more emphatically into his work.

In 2004, he dramatically reversed one of his earlier controversial claims about black holes (that they destroy everything that falls into them and that no information is ever retrieveable from a black hole), claiming new findings that could help solve the so-called “black hole information paradox”. In his new definition of black holes, the event horizon is not so well-delineated and may not completely hide everything within it from the outside, and he has embraced the concept of the multiverse to help explain the conservation of information in black holes.

Hawking's views on the existence of God have been the subject of much debate, especially since his 1988 "A Brief History of Time" in which he mused that the discovery of an overarching theory of everything would allow us to "know the mind of God", which some people have interpreted as literal and some as literary. However, in his 2010 book "The Grand Design" he states unequivocally that "spontaneous creation is the reason there is something rather than nothing, why the universe exists, why we exist. It is not necessary to invoke God. to set the universe going".

Hawking retired from his position as Lucasian Professor of Mathematics at Cambridge in 2009, in accordance with the University's retirement policy, and accepted a Distinguished Research Chair at the Perimeter Institute for Theoretical Physics in Waterloo, Canada. In the same year, he was awarded the Presidential Medal of Freedom, the highest civilian award in the United States.

Stephen Hawking died at age 76 on March 13, 2018.


Confused about Hawking Radiation

Hawking Radiation says that an antiparticle and particle spontaneously appear and annihilate each other everywhere, but at the horizon, if the antiparticle appearing inside the horizon and the particle appears outside, then the antiparticle is sucked in and the particle is emitted outward. Hawking radiation would be the particles being emitted away. The antiparticles are sucked in and, if the black hole is small enough, all the antiparticles will eventually completely annihilate the black hole.

What I am confused about is why would the black hole lose any mass at all. This relies on the premise that more often than not, the antiparticle will be the particle that appears on the inside of the horizon while the (regular) particle will be the particle to appear on the outside.
Intuitively, it would seem to me that 50% of the time, the antiparticle would appear on the inside while the other 50% of the time the (regular) particle would be the one to appear on the inside.
Why is it that the antiparticle is assumed to be the one appearing inside the horizon more than the (regular) particle?


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