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As die heelal deur 'n oerknal-ontploffing ontstaan en ontstaan het, moet daar leë spasie in die middel van die ontploffingsterrein gelaat word, aangesien die hele saak met 'n geweldige spoed van die sentrum af wegbeweeg, en daar meer materie moet wees, sterre sterrestelsels en stof, ens. naby die huidige periferie of omtrek of horison van die huidige heelal. Aangesien die groot ontploffing ongeveer 13,7 miljard jaar terug plaasgevind het, is die buitenste grense van ons heelal 13,7 miljard ligjare weg van die middelpunt van die ontploffing van die oerknal.
Het ons sterrekundiges holheid of leegheid in die middel van die heelal ontdek of nie?
U verstaan die uitbreiding van die heelal verkeerd. Die oerknal is nie 'n ontploffing nie: dit is die oomblik in tyd dat die heelal 'n (byna) oneindige digtheid het. Daar is dus geen middelpunt in die heelal nie, aangesien daar geen middelpunt van die oppervlak van die aarde is nie (dit is die gewildste tweedimensionele analoog).
Sedert hierdie oer-ultra-hoë digtheidstoestand brei die heelal uit, atome het gevorm, sterre en sterrestelsels het gevorm en nou neem die afstand tussen twee sterrestelsels mettertyd toe op baie groot skaal as gevolg van die uitbreiding.
Ek dink u vraag is onderwerp, maar @RhysW het 'n baie nuttige boodskap gekoppel om te verstaan waarom u vraag 'n algemene wanopvatting oor die oerknal is.
Geen sentrum
Daar is geen 'middelpunt' in die heelal nie. 'N Plaaslike waarnemer sal op enige punt beweer dat hulle in die middel van die heelal is deur sterrestelsels van hulle af weg te beweeg. Hoe kan ons dit weet? Die heelal lyk asof dit homogeen is (oral dieselfde struktuur het) en isotroop (daar is geen voorkeurrigting nie). As dit inderdaad eienskappe van die heelal is, moet die uitbreiding van die heelal op alle ander plekke dieselfde wees (sien: Die kosmologiese beginsel).
Hoe die oerknal en ontploffings verskil
Daarbenewens verskil die oerknal op die volgende maniere van 'n ontploffing:
1) Deeltjies wat by 'n ontploffing betrokke is, vertraag uiteindelik as gevolg van wrywingskragte. Dink aan vuurwerke (http://www.youtube.com/watch?v=qn_tkJDFG3s). Deeltjies beweeg die vinnigste op die oomblik van ontploffing, en vertraag eentonig mettertyd. Die uitbreiding van die vroeë heelal volg nie hierdie tendens nie, hoewel mense soms die woord 'ontploffing' gebruik om die enorme volumetriese toename ('n toename met 'n faktor van $ sim10 ^ {76} $) wat tussen $ 10 ^ plaasgevind het, te beskryf - 36} - 10 ^ {- 32} $ sekondes na die oerknal, wat gepas inflasie genoem word.
2) 'n Ontploffing impliseer die bestaan van ruimte. Om 'n ontploffing te vind, moet deeltjies (of ons nou oor materie of lig praat) ruimte hê om in te ontplof. Streng gesproke is die inflasie van die heelal 'n uitbreiding van ruimtetydkoördinate, en die woord ontploffing kan dus nie regtig geld nie, want daar was niks vir ruimte-tyd om in te ontplof nie.
In een opsig is elke punt wat u kies, "in die middel" van die heelal en op enige punt in die heelal, op groot skaal, lyk die heelal dieselfde as op enige ander punt. Dit is nie dieselfde as om te sê dat die heelal oneindig is (maar dit kan wees). Die analogie met 'n ontploffing is swak, want ontploffings brei uit na die bestaande ruimte. Met die oerknal brei die ruimte self uit. Maar per definisie het ruimte nie 'n voorsprong nie (as dit wel sou gebeur, sou daar 'n 'metaruimte' wees wat die werklike ruimte sou wees, ensovoorts) en oral is die middelpunt en / of nêrens nie.
Dit is nie eintlik hoe ontploffings werk nie. Wanneer nitrogliserien ontplof, laat dit nie 'n gat in die middel nie. Net soos 'n ontploffing, werk die oerknal ook nie so nie. In enige geldige verwysingsraamwerk het die heelal met die ligspoed begin uitbrei sonder om 'n gat in die middel te laat, en die middelpunt is nie 'n spesiale plek nie. Weens vreemde wette van die heelal is daar nie net een geldige verwysingsraamwerk nie.
Die heelal volg algemene relatiwiteit wat vereenvoudig met spesiale relatiwiteit in die afwesigheid van 'n swaartekragveld en in die afwesigheid van voorwerpe met 'n ontsnappingssnelheid wat 'n beduidende fraksie van die ligsnelheid is, volg 'n weergawe van spesiale relatiwiteit waar die swaartekrag werklik is krag wat nie ruimtetyd buig nie. Raadpleeg https://physics.stackexchange.com/questions/19937/time-dilation-as-an-observer-in-special-relativity/384547#384547 om te leer hoe spesiale relatiwiteit werk.
Volgens spesiale relatiwiteit het die heelal geen middelpunt nie. Enige nie-roterende voorwerp wat teen 'n konstante snelheid wat stadiger is as die snelheid van die lig beweeg, is 'n geldige verwysingsraamwerk en in sy verwysingsraamwerk is die middelpunt van die heelal die plek waar die oerknal plaasgevind het. Daar is geen tydige lyn wat volgens alle waarnemers saamstem die middelpunt van die heelal is nie. In enige verwysingsraamwerk kan die middelpunt van die heelal in daardie verwysingsraamwerk nie 'n spesiale plek wees nie, want dit is nie die middelpunt in 'n ander verwysingsraamwerk nie. As ons na sterrestelsels naby die rand van die heelal kyk, sien ons die soortgelyk aan dié wat naby die begin van die heelal voorgekom het, maar ons kyk eintlik net terug na sterrestelsels van toe hulle ongeveer die helfte van die ouderdom van ons heelal in ons verwysingsraamwerk. Hulle is net soos baie jonger sterrestelsels net as gevolg van hul eie tydverwyding en is dit in hul eie verwysingsraamwerk baie jonger. Wat gebeur in enige verwysingsraamwerk as u naby die rand van die heelal is en stilstaan? Jy beskou jouself as naby die rand. In 'n ander verwysingsraamwerk bevind u u in die middel van die heelal en beweeg u en die afwyking van die lig wat u waarneem, laat u uself sien as nie in die sentrum nie.
Dit is net wat spesiale relatiwiteit voorspel, maar in werklikheid volg die heelal nie spesiale relatiwiteit nie, maar sommige van die resultate wat ek reeds genoem het, is steeds waar. Die heelal versnel so sterrestelsels sal uiteindelik vinniger van ons afneem as die lig omdat die ruimte dit vinniger wegsleep as die lig. Ons leef waarskynlik in 'n De Sitter-heelal. Ons kosmiese horison, die gebied van die ruimte wat met ons ligsnelheid in ons verwysingsraamwerk van ons af wegbeweeg, gedra net soos 'n swart gat in die sin dat ons sterrestelsels eksponensieel sal sien naderkom na die kosmiese horison sonder om dit ooit te bereik en meer te kry rooi verskuif sonder gebind soos dit nader kom.
Bron: https://en.wikipedia.org/wiki/De_Sitter_universe
Die amorfe meetkunde van die Heelal word tans bestudeer, en die grootskaalse verspreiding van die sterrestelsels is soortgelyk aan 'n spons. Die maatstaf in die middel van die beeld verteenwoordig 1,5 miljard ligjare. lig reis in alle rigtings, en ten tye van die oerknal was daar geen lig om oral heen te reis nie, en vroeg in die teorie van die oerknal was daar geen 3D-aanwysings wat ons kan bedink nie, geen definisie van reguit en rand nie, geen afstand tussen iets in 'n bekende meetkunde in die superstringteorie 3D, 4D, 5D, 12D. Om die meetkunde wat u benodig te vind, kan Wiskunde dus 12D / 28D word en is dit vir ons verwarrend, die begrip middelpunt verskil in 12/20 dimensies. Die oerknal met hoë temperatuur is voorafgaande aan atome, lig, subatomiese deeltjies, materie, swaartekrag, dit gaan voor die bestaan van bekende meetkunde, die inhoud daarvan oorskry enige meetkundige of eindige maat, die enigste fokuspunt is tyd, dus om dit te meet, moet u baie uitvind nuwe afmetings en meetkundige modelle.
Die aantal leemtes in die spons kan meer as triljoen keer soveel wees as die aantal atome in die oseaan. Daar kan 'n Googolplex MPC's wees as 'n motief van die totaal. Waar is die middelpunt daarvan? Wanneer sal die tyd eindig?
Die oerknal was amorf vanuit ons oogpunt, en in daardie opsig kan jy sê dat dit 'amassief' is. Dit is kosmies, ruimte en fisiese eienskappe is ongelyk (dit is 'n mooi woord om onmeetbaar / onverwant te sê).
As u dink dat ons siening van die kosmiese agtergrondstraling (13,8 miljard LY) die deursnee van 'n atoom in die see het. Die oerknal het miskien ook in 'n ander atoom aan die ander kant van die see plaasgevind, sodat die meetkunde nie 'n mate van meting het wat binne waarneming gedefinieer kan word nie. As die groot heelal anders lyk as 'n triljoen ligjare van die Googolplex-kubus in die kubus, kan u dit moeilik vind.
'N Voorwerp sonder simmetrie of meting en sonder 'n grens kan nie 'n middelpunt hê nie. Dit het 'n kubieke googolplex-meting eerder as 'n enkele middelpunt.
U vra dus 'n meetkundige vraag soortgelyk aan 'waar is die middelpunt op die oppervlak van 'n bol en 'n ring'?
Die heelal brei nie weg van enige sentrum nie. Al die afstande brei eenvormig deur die heelal uit. Dit veroorsaak so 'n effek dat dit vir elke individuele waarnemer lyk asof die hele heelal van hulle af wegbeweeg. Dit kan met behulp van hierdie figuur (vanaf google) gedemonstreer word:
$ A $ verteenwoordig die heelal op een oomblik, $ B $ stel die heelal op 'n later tydstip voor. U kan (skaars) opmerk dat $ B $ met 'n klein bedraggie vergroot word. Dit verteenwoordig die uitbreiding van die heelal. Gestel u stel nou $ B $ oor $ A $ soos getoon in $ C $, dan lyk dit of die heelal uitgebrei het vanaf $ X $. Maar as u dit plaas soos getoon in $ D $, lyk dit asof die hele heelal van 'n ander punt uitbrei! Dit is alles te wyte aan die homogene uitbreiding van die heelal.
Wat is in die middel van die heelal?
Hierdie vraag by Physics.SE: "Het die oerknal op 'n stadium plaasgevind?", Wat 'n antwoord met meer as 300 UpVotes het, verduidelik:
"Die eenvoudige antwoord is dat nee, die oerknal op geen stadium plaasgevind het nie. In plaas daarvan het dit terselfdertyd oral in die heelal gebeur. Die gevolge hiervan sluit in:
Die heelal het nie 'n middelpunt nie: die oerknal het nie op 'n stadium plaasgevind nie, dus is daar geen sentrale punt in die heelal waaruit dit uitbrei nie. '
Die heelal brei in niks uit nie: omdat die heelal nie soos 'n bol vuur uitbrei nie, is daar geen ruimte buite die heelal waarin dit uitbrei nie.
Ons is minder as 'n spesifikasie in ons superkluster:
Daar is 'n Wikipedia-webblad: "History of the Center of the Universe - The nonexistence of a center of the Universe" wat verduidelik:
"'N Homogene, isotropiese heelal het nie 'n middelpunt nie." - Bron: Livio, Mario (2001). Die versnelde heelal: oneindige uitbreiding, die kosmologiese konstante en die skoonheid van die kosmos. John Wiley en Sons. bl. 53. Besoek op 31 Maart 2012.
Kyk ook na hierdie CalTech-video: "Waar is die middelpunt van die heelal?".
As die heelal deur 'n oerknal-ontploffing ontstaan en ontstaan het, moet daar leë spasie in die middel van die ontploffingsterrein gelaat word, aangesien die hele saak met 'n geweldige spoed van die sentrum af wegbeweeg, en daar meer materie moet wees, sterre sterrestelsels en stof, ens. naby die huidige periferie of omtrek of horison van die huidige heelal. Aangesien die groot ontploffing ongeveer 13,7 miljard jaar terug plaasgevind het, is die buitenste grense van ons heelal 13,7 miljard ligjare weg van die middelpunt van die ontploffing van die oerknal.
Het ons sterrekundiges holheid of leegheid in die middel van die heelal ontdek of nie?
As ons inkom op die Melkweg (middel van hierdie beeld, maar nie die middelpunt van die heelal nie) sien ons:
Die blou gebiede naby ons is die plaaslike leemte, terwyl die gebied aan die linkerkant die groot lokmiddel is.
Die vorm van die heelal, wat ons kan bespeur / sien, is ingewikkeld - dit is nie 'n eenvoudige sfeer of voetbalvormig nie, wat vanuit 'n sentrale punt uitstraal. Die huidige meting van die ouderdom van die heelal is 13.799 ± 0,021 miljard ($10^9$) jaar binne die Lambda-CDM-ooreenstemmingsmodel. Ons kan tot dusver net sien en meet, en die afgelope ongeveer 14 miljard jaar het dele van die heelal digter geword en dele het versprei.
Sien hierdie Wikipedia-webbladsye: "Waarneembare heelal" en "Waarnemingskosmologie", dit kom uit "Grootte en streke":
Die grootte van die heelal is ietwat moeilik om te definieer. Volgens die algemene relatiwiteitsteorie, kan sommige streke van die ruimte nooit met ons s'n interaksie hê nie, selfs gedurende die leeftyd van die Heelal, weens die eindige snelheid van die lig en die voortdurende uitbreiding van die ruimte. Radioboodskappe wat van die aarde af gestuur word, sal byvoorbeeld nooit in sommige streke van die ruimte kan kom nie, selfs al sou die heelal vir ewig bestaan: die ruimte kan vinniger uitbrei as wat lig dit kan deurkruis.
Daar word veronderstel dat daar verafgeleë streke bestaan en dat ons net so deel van die werklikheid is, alhoewel ons nooit daarmee kan kommunikeer nie. Die ruimtelike streek wat ons kan beïnvloed en beïnvloed word, is die waarneembare heelal.
Die waarneembare heelal hang af van die ligging van die waarnemer. Deur te reis, kan 'n waarnemer in aanraking kom met 'n groter ruimtetydperk as 'n waarnemer wat stilbly. Nietemin sal selfs die vinnigste reisiger nie met die hele ruimte kan kommunikeer nie. In die waarneembare heelal word gewoonlik die gedeelte van die heelal beteken wat vanaf ons uitkykpunt in die Melkweg waarneembaar is.
Die regte afstand - die afstand soos op 'n spesifieke tydstip gemeet, insluitend die huidige tussen die aarde en die rand van die waarneembare heelal is 46 miljard ligjare (14 miljard parsek), wat die deursnee van die waarneembare heelal ongeveer 91 miljard maak ligjare ($28×10^9$ rekenaar). Die afstand wat die lig vanaf die rand van die waarneembare heelal afgelê het, is baie naby aan die ouderdom van die heelal maal die snelheid van die lig, 13,8 miljard ligjare ($4.2×10^9$ parsecs), maar dit stel nie die afstand op enige gegewe tyd voor nie omdat die rand van die waarneembare heelal en die aarde sedertdien verder van mekaar af beweeg het. Ter vergelyking is die deursnee van 'n tipiese sterrestelsel 30 000 ligjaar (9,198 parsek) en die tipiese afstand tussen twee aangrensende sterrestelsels is 3 miljoen ligjaar (919,8 kiloparsek). As voorbeeld is die Melkweg ongeveer 100.000-180.000 ligjare in deursnee, en die naaste susterstelsel aan die Melkweg, die Andromedastelsel, is ongeveer 2,5 miljoen ligjare weg.
Omdat ons nie die ruimte buite die rand van die waarneembare heelal kan waarneem nie, is dit onbekend of die grootte van die heelal in sy geheel eindig of oneindig is.
Skattings vir die totale grootte van die heelal, indien dit eindig, bereik so hoog as $10^{{10}^{{10}^{122}}}$ megaparsek, geïmpliseer deur een resolusie van die No-Boundary-voorstel.
Volgens die voorstel sê Hartle-Hawking: "Die heelal het geen aanvanklike grense in tyd of ruimte nie".
Dr Brent Tulley publiseer 'n artikel: "The Laniakea supercluster of galaxies" (gratis arXiv-preprint) en gepaardgaande aanvullende video, saam met Dr. Daniel Pomarède se Vimeo-gids, spesifiek hierdie video: Cosmography of the Local Universe (FullHD-weergawe) waaruit hierdie daar is beelde geteken wat die vorm van 'n deel van die heelal soos ons dit ken, toon:
- Neem die WMAP-data en projekteer alle sterrestelsels binne 8K km / s (1:18 op die video) op 'n 3D-ruimte:
Klik op die prent om te animasie
'N Close-up van ons ligging toon die groot plaaslike leemte:
Om uit te zoem, onthul 'n deel van die heelal. Kyk na die video hierbo vir meer inligting:
Die oog van God
[/ onderskrif]
Daar was 'n paar jaar gelede 'n e-pos wat praat oor & # 8220the Eye of God & # 8221. Hierdie foto was eintlik 'n beeld van die Helixnevel wat deur die Hubble-ruimteteleskoop geneem is.
Die Eye of God-newel is 'n helder planetêre newel wat ongeveer 700 ligjaar weg in die sterrebeeld Waterdraer geleë is. Dit staan ook bekend as NGC 7293. In werklikheid is die Helix-newel waarskynlik die naaste planetêre newel wat ons in die lug kan sien, en dit wys die toekoms waardeur sterre soos ons son gaan as hulle brandstof opraak en hul buitenste lae uitpof.
Dit het gedink dat die Helix-newel eintlik silindries gevorm is. Vanuit ons perspektief kyk ons af in die silinder om die sentrale ster te sien. Sterrekundiges skat dat die Helixnevel ongeveer 10 600 jaar oud is, gebaseer op die tempo van uitbreiding van die newel.
Met die krag van die Hubble-ruimteteleskoop kon sterrekundiges materiaalknope in die newel sien. Hulle het nou meer as 20 000 van hierdie kometêre knope in die newel ontdek. Hierdie knope het kometiese sterte, en daar is ontdek dat dit met mekaar kan bots.
Hier is die e-pos wat u kan kry:
Onderwerp: Fw: Oog van God
Dit is 'n foto wat deur NASA met die Hubble-teleskoop geneem is. Hulle verwys daarna as die & # 8220Eye of God & # 8221. Ek het gedink dit was pragtig en die moeite werd om te deel.
Sommige e-posse sê selfs dat dit 'n seldsame gebeurtenis is wat net een keer elke 3000 jaar plaasvind. Die werklikheid is dat dit net 'n pragtige foto is wat deur die Hubble-ruimteteleskoop geneem is. Daar is ander beelde wat deur ander teleskope geneem is, en dit lyk ook mooi.
Ons het verskeie artikels oor die Helixnevel vir Heelal Vandag geskryf. Hier is 'n artikel oor 'n nuwe blik op die Helixnevel, en hier is 'n artikel oor komete wat in die Helixnevel bots.
As u meer inligting oor die Helixnevel wil hê, is hier 'n mooi prentjie van die La Silla-sterrewag by Astronomy Picture of the Day.
Ons het ook 'n hele episode van Astronomy Cast opgeneem, net oor newels. Luister hier, Episode 111: Nebulae.
Wat staan in die middel van die heelal?
daar is geen middelpunt nie, of jy kan sê dat alles in die middelpunt is .. Omdat die heelal in 'n enkele punt begin het, is die hele heelal en sy middelpunt dieselfde punt, so nou is alles in die middel van die heelal.
Dit is ook die rede waarom dit nie saak waar in die heelal u is nie, dit lyk asof elke ding van u af wegbeweeg, soos u in die middel was. As gevolg van die uitbreiding van die heelal.
Die agbare ballon-analogie:
Stel u voor 'n kolonie miere wat op die oppervlak van 'n ballon woon wat aanhoudend uitbrei. Watter mier is die naaste aan die middel van die oppervlak van die ballon?
Elke mier sien elke ander mier daarvan wegbeweeg. Vanuit sy oogpunt is dit in die middel van die heelal - dieselfde as elke ander mier. Hulle staan ALMAL in die middelpunt!
Ek glo dat die voorbeeld van ballonne en miere 'n swak analogie is. In hierdie analogie sou mier slegs ander miere sien wegbeweeg in 'n tweedimensionele ruimte. Maar in die werklike heelal sou u sien dat materie in drie dimensies wegbeweeg. Die werklike vorm van die heelal word altyd bespreek en 'n duidelike beeld is nog nie beskikbaar nie. Mier- en ballonvoorbeeld sou die lesers net meer verwar as om hulle te help om die vorm van die heelal te visualiseer.
Nee kan met 100% vertroue sê dat die heelal nie 'n middelpunt het nie. U kan met reg sê dat waar u ook al gaan, u sal sien dat materie van u wegbeweeg, maar dit beteken nie dat daar geen middelpunt in die heelal is nie.
As daar middelpunt op 'n sekere plek is, sou u sien dat materie in alle rigtings met dieselfde snelheid beweeg (afhangend van afstand), maar
konsentrasie van materie sou aan die een kant hoër wees.
As daar geen middelpunt is nie, sal al die sterrestelsels ewe veel aangetrek word deur die omliggende sterrestelsels. Daar sal dus geen groot gravitasie-effek op enige Galaxy op groot skaal wees nie (ignoreer kortafstand soos Andromeda). Maar steeds
die meeste sterrekundiges glo in 'n groot verknorsing as gevolg van gravitasie-aantrekking, mits die materie-digtheid in die heelal minder is as die kritieke digtheid en dat daar ook gesê word dat donker energie swaartekrag kan oorkom. Hier aanvaar ons dus duidelik swaartekrag op groot skale, wat nie moontlik is as die heelal nie 'n middelpunt het nie.
Ek sê nie dat daar 'n middelpunt vir 'n heelal is nie, maar tog is dit nie duidelik nie.
Dankie
Gespreksabcd (basiese beginsels van gesprekke)
Daar is geen probleem om tweedimensionele analogie te gebruik as dieselfde op drie-dimensionele toegepas kan word nie, maar hierdie analogie misluk heeltemal as dit by driedimensioneel kom om te bewys dat daar geen middelpunt is nie.
Sien my tweede paragraaf in pos # 4
As daar geen middelpunt is nie, sal al die sterrestelsels ewe veel aangetrek word deur die omliggende sterrestelsels. Daar sal dus geen groot gravitasie-effek op enige Galaxy op groot skaal wees nie (ignoreer kortafstand soos Andromeda). Maar steeds
die meeste sterrekundiges glo in 'n groot verknorsing as gevolg van gravitasie-aantrekking, mits die materie-digtheid in die heelal minder is as die kritieke digtheid en dat daar ook gesê word dat donker energie swaartekrag kan oorkom. Hier aanvaar ons dus duidelik swaartekrag op groot skale, wat nie moontlik is as die heelal nie 'n middelpunt het nie.
Ek sê nie dat daar 'n middelpunt vir 'n heelal is nie, maar tog is dit nie duidelik nie.
Jammer, maar dit is alles verkeerd. Die oplossing vir die vergelykings van algemene relatiwiteit wat 'n homogene, isotropiese en oneindig is heeltemal tevrede met die huidige waarnemings. U hoef nie 'n middelpunt van die heelal te hê waaruit alles anders beweeg nie. Daar is geen netto gravitasiekrag op enigiets in die heelal nie, want in die algemeen is swaartekrag nie 'n krag nie. In plaas daarvan volg al die materie in die heelal geo-desiese bane wat bepaal word deur die vergelykings op te los. Die oplossings vertel ons dat alles uitmekaar beweeg al is die oneindige heelal homogeen.
Dit kom alles neer op die aanvanklike toestande. Die oerknal het veroorsaak dat alles uitmekaar begin beweeg het, en daarom gaan hulle voort. Dit is 'n algemene wanopvatting dat die oerknal op 'n stadium plaasgevind het. Dit is nie die geval nie. Dit het oral gebeur. Daar is geen punt waarna u al die materie in die heelal kan herlei as u tyd agteruit loop nie.
Terloops, die Big Crunch beskou niemand as 'n redelike voorspelling van die heelal se toekoms nie. Dit word tans nie ondersteun deur die waarnemings nie. Selfs al was dit nodig, hoef dit nie 'n sentrum van die Heelal te bestaan om te kan voorkom nie. 'N Groot geknak is NIE waar al die materiaal in die heelal na 'n enkele punt beweeg nie. Wat dit is, is dat die digtheid van die heelal oneindig is, maar dat daar steeds 'n oneindige (of inderdaad eindige) afstand tussen punte in die oneindig digte heelal kan wees.
daar is geen middelpunt nie, of jy kan sê dat alles in die middelpunt is .. Omdat die heelal in 'n enkele punt begin het, is die hele heelal en sy middelpunt dieselfde punt, so nou is alles in die middel van die heelal.
Dit is ook die rede waarom dit nie saak waar in die heelal u is nie, dit lyk asof elke ding van u af wegbeweeg, soos u in die middel was. As gevolg van die uitbreiding van die heelal.
Beteken dit dat die heelal konstant is? Beteken dit terwyl die buitenste dop uitbrei? die heelal ook in die sentrum saamtrek?
Is daar nie 'n oortreding van die bewaring van die massa tydens die oerknal nie?
Beteken dit dat die heelal konstant is? Beteken dit terwyl die buitenste dop uitbrei? die heelal ook in die sentrum saamtrek?
Is daar nie 'n oortreding van die bewaring van die massa tydens die oerknal nie?
Nee, nee en nee is die antwoorde waarvoor ek bang is.
Die boodskap wat u aanhaal, was byna korrek, hoewel dit ook die algemene fout gemaak het deur te dink dat die oerknal op 'n enkele punt plaasgevind het.
Die heelal is homogeen (op groot genoeg skale) en doen dus dieselfde dans op alle plekke tegelyk. As die heelal dus uitbrei, doen die hele heelal dit, as die heelal versnel of vertraag, dan doen dit dit weer op alle plekke op dieselfde tyd. Daar is geen binneste of buitenste dop nie.
Daar is geen oortreding van die massa-bewaring in die Oerknal nie, aangesien bewaringswette die konstantheid van iets met tyd beskryf. Aangesien die tyd met die oerknal begin, is daar niks om voorheen mee te vergelyk nie! Massa word bewaar namate die heelal uitbrei aangesien die digtheid afneem. As die heelal in volume verdubbel, dan halveer die digtheid van die massa.
Jammer, maar dit is alles verkeerd. Die oplossing vir die vergelykings van algemene relatiwiteit wat 'n homogene, isotropiese en oneindig is heeltemal tevrede met die huidige waarnemings. U hoef nie 'n middelpunt van die heelal te hê waaruit alles anders beweeg nie. Daar is geen netto gravitasiekrag op enigiets in die heelal nie, aangesien gravitasie in die algemeen nie 'n krag is nie. In plaas daarvan volg al die materie in die heelal geo-desiese paaie wat bepaal word deur die vergelykings op te los. Die oplossings vertel ons dat alles uitmekaar beweeg al is die oneindige heelal homogeen.
Dit kom alles neer op die aanvanklike toestande. Die oerknal het veroorsaak dat alles uitmekaar begin beweeg het, en daarom gaan hulle voort om dit te doen. Dit is 'n algemene wanopvatting dat die oerknal op 'n stadium plaasgevind het. Dit is nie die geval nie. Dit het oral gebeur. Daar is geen punt waarna u al die materie in die heelal kan herlei as u tyd agteruit loop nie.
Terloops, die Big Crunch beskou niemand as 'n redelike voorspelling van die heelal se toekoms nie. Dit word tans nie ondersteun deur die waarnemings nie. Selfs al was dit nodig, hoef dit nie 'n sentrum van die Heelal te bestaan om te kan voorkom nie. 'N Groot geknak is NIE waar al die materiaal in die heelal na 'n enkele punt beweeg nie. Wat dit is, is dat die digtheid van die heelal oneindig is, maar dat daar steeds 'n oneindige (of inderdaad eindige) afstand tussen punte in die oneindig digte heelal kan wees.
Ek sal nie met die algemene relatiwiteitsteorie redeneer nie. Hier beskou u die heelal as oneindig. Soveel dinge is moontlik in die oneindige heelal. As die heelal oneindig is, durf niemand sê dat daar 'n middelpunt in die heelal is nie. Maar hoe kan iemand so seker wees dat die heelal oneindig is? en nie eindig nie? Is daar goeie praktiese bewyse dat die heelal oneindig is? Oneindige heelal sou ook oneindige energie beteken wat my nie te bowe kan kom nie. Verduidelik asseblief.
U sê dat oerknal oral gebeur het. Hoe kan dit wees?
Kan u 'n kort uiteensetting gee of my na 'n skakel stuur? Ek het nog nooit hiervan gehoor nie ..
U sê dat die digtheid van die heelal onder groot verknorsing oneindig is.
Ons weet dat daar niks hoër as oneindig is nie. Hoe kan u afstande meet in 'n oneindige digte heelal? Verduidelik asseblief. Oneindige digtheid beteken nul volume. Hoe kan 'n mens afstande in nul volume meet? Praat u van ekstra afmetings?
Waar is die sentrum van die heelal?
In 'n vorige episode het ons te kenne gegee dat elke plek in die middel van die heelal is. Maar hoekom? Dit blyk dat elke manier waarop u daarna kyk, u in die middel van alles staan. En so ook almal anders.
Ons het 'n vorige episode beëindig met hoe die middelpunt van die heelal oral is, en daarna vinnig oorgegaan na "Dankie vir die kyk" sonder om enige ander besonderhede te verskaf as 'n knipoog en knik.
Goeie nuus, hier kom u besonderhede. Stel u eers die groeiende heelal voor. U kan dalk 'n opblaasbal voorstel wat in alle rigtings uitstoot. Miskien sien u 'n soort reuse-uitbreidende hemelpampoen. Ongelukkig is die idee nie korrek nie. Maar moenie sleg voel nie, ons denkende vleisdele is net nie gebou om hierdie soort dinge te doen nie.
Die ruimte wat ons kan sien, is die waarneembare heelal. As ons in enige rigting kyk, sien ons die lig wat miljoene en selfs miljarde jare gelede sterre gelaat het. As u by die 13,8 miljard ligjaarmylmerker uitkom, sien u die lig wat kort na die oerknal uitgestraal is, toe die heelal afgekoel het tot op die punt dat dit deursigtig geword het. Die waarneembare heelal is dus 'n sfeer rondom jou, dit is relatief tot jou posisie.
My waarneembare heelal is 'n sfeer rondom my, relatief tot my posisie. As ek dus 10 meter van jou af is, kan ek 'n bietjie verder in die heelal in daardie rigting sien. As jy agter jou kyk, sien jy die waarneembare heelal 'n bietjie verder in die rigting.
Stel jou voor dat jy in 'n donker kamer staan en kers vashou. U kan in 'n sfeer rondom u sien. U is in die middel van u waarneembare ruimte. En as ek op 'n ander plek is, sal ek 'n ander waarneembare sfeer hê. Dit is die rede waarom ons sê dat elkeen in die middel van sy eie waarneembare heelal is.
Dit het wenke van pedantry en dit is 'n bietjie onbevredigend, so laat ons 'n bietjie dieper delf. Waar is die werklike middelpunt van die Heelal, ongeag wie dit waarneem? Ons heelal kan eindig of oneindig wees. Sterrekundiges weet dit nie eintlik nie. Volgens hul akkuraatste berekeninge is die waarneembare heelal 93 miljard ligjare breed.
Onthou u die lig van die oerknal wat 13,8 miljard ligjare geneem het om by u uit te kom? Wel, die uitbreiding van die heelal het die streek tot meer as 46 miljard ligjare ver weggestoot. Kyk so ver as wat jy kan na regs en so ver as wat jy kan na links. Hierdie twee plekke is tans 93 miljard ligjare van mekaar af. Ons kan dus nie sien hoe groot die Heelal regtig is nie. Dit moet groter as 93 miljard ligjare wees. Alles buite die streek kan ons nog net nie sien nie ... Dit kan oneindig wees.
As die Heelal oneindig is, dan is daar 'n oneindige hoeveelheid ruimte in daardie rigting en 'n oneindige hoeveelheid ruimte in daardie rigting, en daardie rigting. En ons is letterlik terug waar ons begin het. Weereens is u in die middel van die heelal. En ek ook.
Maar sê nou die heelal is eindig? Dit is waar dit lastig raak. Stel u voor die waarneembare heelal as 'n klein sfeer binne die veel groter werklike heelal. Miskien is dit 100 miljard ligjare oor, of miskien 'n triljoen, of 'n kwadriljoen. Wat ook al die grootte, dit is nie oneindig nie. Nou sou jy dink daar is 'n sentrum, of hoe?
Wel, sterrekundiges dink dat die topologie van 'n eindige heelal daarop dui dat as u lank genoeg in enige rigting reis, u na u beginpunt sal terugkeer. Met ander woorde, as u ver genoeg in enige rigting kon kyk, sou u die agterkant van u kop sien.
Stel u die heelal voor as 'n sfeer & # 8211 Advanced Celestial Sphere (Wolfram Project). Krediet: Jim Arlow
Ons het 'n hele aflewering hieroor gedoen, en u sal dit dalk wil gaan kyk. En u sal regtig die diepgaande verduideliking van Zogg the Aliens wil bekyk. Oorweeg 'n mier op die oppervlak van 'n sfeer as 'n analogie. As die mier verkies om in enige rigting te loop, sal hy terugkeer na sy beginpunt. Neem dit konsep en vergroot dit een dimensie. Kan u dit nie indink nie? Geen probleem. Soos ek gesê het, ons breine is nie toegerus of ervare nie. En tog lyk dit of die ekstra dimensie die aard van die heelal is. Ongeag in watter rigting u ry, as u net soveel tyd neem om terug te keer na u beginpunt. Wel ... jy is in die middel van die heelal?
Sien? Maak nie saak hoe jy daaroor dink en dit afbreek nie, jy is die middelpunt van alles. En ek ook. Wat dink jy? Is die heelal eindig of oneindig? Vertel ons waarom in die kommentaar hieronder.
Christendom en die middelpunt van die heelal
Nie lank gelede nie het iemand my gevra of ek die dokumentêr gesien het, Die God wat nie daar was nie (2005), wat die & # 8220Jesus-mite & # 8221 en die Christendom in die algemeen ondersoek. It’s been out for several years, and despite the fact that it’s viewable for free on YouTube, I haven’t bothered to watch it, because it looks like an uninspired retread of common challenges to the Christian faith that tend to be very weak. However, from what I can tell, it does perpetuate one historical distortion that is worth refuting. From a partial transcript on IMDb, TGWWT puts forth the idea that it was primarily Christians who were wrong about the Earth-centered universe:
Narrator: The Earth revolves around the Sun. But it wasn’t always that way. The Sun used to revolve around the Earth. It was like that for hundreds of years, until it was discovered to be otherwise, and even for a few hundred years after that. But, ultimately, after much kicking and screaming, the Earth did, in fact, begin to revolve around the Sun. Christianity was wrong about the solar system. What if it’s wrong about something else, too? This movie’s about what happened when I went looking for Jesus.
Or, more likely, what happened when he went looking for anything but Jesus, but never mind. The problem with this statement is that it implies only Christians were wrong about the solar system, when the truth is that just about everyone was wrong about the solar system at one time or another. So why single out Christians? Without having seen the movie, I am fairly confident of the answer (hint: look at who appears in the movie). Unfortunately, the notion that the medieval Church was scientifically ignorant and held back scientific progress is a fairly easy misconception to perpetuate, because people who believe it are usually already eager to believe misconceptions about Christianity and/or they do not know enough to evaluate its validity.
I made a point to cover geocentric theory in my astronomy 101 courses, so let’s explore what my college freshmen students knew about this subject that TGWWT‘s writer/director Brian Flemming apparently did not (or did not want you to know about).
The geocentric model of the solar system, which places the Earth at the center of the universe, is an idea that is found in nearly every ancient culture. In Western Civilization, the idea is usually attributed to the ancient Greek philosopher Aristotle (384 BC – 322 BC), and was later systematized by the Alexandrian astronomer Claudius Ptolemaeus (aka Ptolemy,
64 AD – 165 AD). The geocentric model persisted for more than 1,700 years, and while medieval interpretation of biblical scripture seemed to loosely support the idea, its formulation had nothing to do with Christianity.
To understand why the geocentric model persisted for so long, I want you to place yourself, just for a moment, in the ancient world where there is no such thing as telescopes, astronauts, or satellites. Your only notion of the Earth’s place in the universe is based on what your human senses tell you about the apparent motions of the heavens. You notice that the Sun and Moon make daily journeys across the sky from east to west, and that the stars at night travel in the same daily east-west direction. The familiar constellations also seem to drift across the sky over the course of weeks and months. To your human senses, it appears that the Earth is stationary and that objects in the heavens move about it in very predictable cycles. Armed only with these observations, it is entirely reasonable to assume that the Earth is at the center of the universe.
We owe a tremendous debt of gratitude to the Greeks, who were the first to seek natural explanations for the phenomena they observed. This reliance on natural explanations heralded the birth of science. But what is science? It is actually a difficult concept to define. Most of us understand science to be the search for knowledge, but knowledge can be acquired by other means. The scientific method works by making observations and asking questions in a very systematic way. One observes a phenomenon in nature (say, the motions of the heavens) and posits an educated guess about the nature of the phenomenon (everything in the heavens orbits the Earth, which is stationary). This educated guess is referred to as an hypothesis. The hypothesis then makes a prediction (where objects in the sky will appear on a certain date), and one carries out tests or observations to determine how well the hypothesis performs. If the hypothesis fails the test or cannot account for new observations, then it must be revised or abandoned in favor of a new hypothesis.
One such test of the geocentric model came in the form of retrograde motions of the planets. The Greeks observed that a handful of objects in the heavens moved in a way that was different from the other objects. For one thing, their positions were not fixed like the stars, but appeared to wander over a period of months. (The word “planet” comes from the Greek word for wanderer.) This retrograde motion, or apparent looping back of the planet’s path in the sky, is now understood in the context of the Sun-centered (heliocentric) model, but in ancient times it represented a significant challenge to the geocentric model. This challenge was resolved by placing each of the planets in a smaller orbit, called an epicycle, upon its larger orbit about the Earth. This was a key feature of the model put forth by Ptolemy, which is referred to as the Ptolemaic model.
The Ptolemaic model persisted for almost two millenia, because, clunky as it was, it made accurate predictions about the motions of the planets. Moreover, several key objections to the heliocentric model were unresolved. Centuries before Ptolemy, the Greek astronomer Aristarchus (310 BC –
230 BC) proposed a Sun-centered solar system, but was ridiculed by his peers for it. First, the idea that the Earth was moving was counterintuitive, because of the apparent motions of the heavens. But the most significant objection was that stellar parallax was not observed. This is the apparent shifting of position of closer stars relative to more distant background stars, which must occur if the Earth is moving around the Sun. As this was not observed, it was reasonable for Aristarchus’ fellow Greeks to reject his idea.
Fast-forward almost two millennia to Nicolaus Copernicus (1473 – 1543 AD), who was a true Renaissance man. In addition to being an astronomer, he was also a physician, scholar, cleric, and military leader. Like Aristarchus before him, Copernicus went against popular sentiment and proposed a heliocentric system. There is evidence that Copernicus knew he was recycling Aristarchus’ ancient model, but his genius was in recognizing its potential as a much more elegant and compelling model than the geocentric model. It is true that Copernicus’ book stirred some controversy within the Church, but contrary to popular belief, the Church was not monolithically opposed to, but rather divided on, the subject of heliocentrism. Secular scientists at the time likewise held to the Aristotelian school of thought, and mostly rejected Copernicus’ ideas. There was good reason for this, as the major objections to the heliocentric model had not yet been overcome. In particular, since Copernicus used circular orbits for the planets, instead of what we now know to be elliptical orbits, the predictions of the Copernican model were less accurate than those of the Ptolemaic model. Heliocentrists also had to contend with the lack of observed stellar parallax, and there were still more objections based on Aristotelian notions about nature. For instance, long before Newton developed his laws of motion, Aristotle held that all objects naturally come to rest, which meant that if the Earth was moving it would leave airborne objects (birds, clouds, etc.) behind. It was not until Galileo anticipated Newton’s first law (objects in motion tend to stay in motion) with simple experiments and made some key observations with his telescope—among them, that the stars are too far away to observe parallax 1 —that these objections were overcome and the Copernican Revolution was solidified.
It is important to understand that there was as much objection to the Copernican model from secular scientists as from the Church. Perhaps more. (For instance, it was supposedly a secular rival who reported Galileo to the Inquisition, illustrating that scientific enterprise has always been a little cut-throat.) The objections of the Church were only partially founded on Christian doctrine, which was based at that time on interpretation of scripture that was consistent with the Aristotelian school of thought. There is, in fact, nothing in scripture that dictates an Earth-centered system. The politics of the time also complicated things, with the Catholic Church struggling to come to grips with the tremendous effects of the Reformation. The most influential figure of the Reformation, Martin Luther, strongly objected to the ideas of the “upstart astrologer” Copernicus, and the Catholic Church was anxious to stay abreast with Protestantism on such an important issue. It is also important to understand that Copernicus was eventually shown to be incorrect in his placement of the Sun at the center of the universe we now understand that there is no ‘center’ to the universe, an idea that is difficult to accept for many people.
What can we conclude from all of this? We can conclude that the most important factor preventing wide-spread acceptance of the heliocentric model was simple human nature. As clever as we sometimes are, we are constrained by limited perspective and emotion. Limited perspective prevented scientists from perceiving the stellar parallax that was predicted by the heliocentric model. Human emotion means cherished ideas often have a powerful hold on people, especially when it comes to accepted ideas that have served mankind well for many centuries. Put these two constraints together and you have the very non-linear progression from old ideas to new ideas that is evident throughout human history.
Having not seen TGWWT, I can only surmise from the partial transcript that either Flemming knows very little about scientific history, classical thought, and theology, or he is being deliberately disingenuous to make Christians look bad. Which is unfortunate, because, with just a few changes to the quote from the transcript, I think we could have turned his movie into a much more interesting narrative on the fallibility of human reason:
Narrator: The Earth revolves around the Sun. But it wasn’t always that way. The Sun used to revolve around the Earth. It was like that for hundreds of years, until it was discovered to be otherwise, and even for a few hundred years after that. But, ultimately, after much kicking and screaming, the Earth did, in fact, begin to revolve around the Sun. Mankind was wrong about the solar system, but eventually figured it out. What is it today that we don’t yet understand that will be obvious to mankind hundreds of years from now? Let’s speculate…
[1] With the advent of larger and more sophisticated telescopes, stellar parallax was indeed observed.
What's The Largest Galaxy In The Universe?
The SDSS view in the infrared - with APOGEE - of the Milky Way galaxy as viewed towards the center.
Our Milky Way contains some 400 billion stars, spanning 100,000 light years in diameter.
Galaxies come in a variety of types and sizes. While the Milky Way may be impressive from our . [+] location within it, it barely registers at all on a list of the largest galaxies.
Yet compared to other galaxies, it's not even especially large.
The Andromeda Galaxy resides in our local group, and is perhaps twice as large in diameter as our . [+] Milky Way.
In our own local group, the Andromeda galaxy is significantly larger, reaching 220,000 light years across.
Severely disrupted galaxies, like NGC 6872, can extend for many times farther than a quiet galaxy . [+] that hasn't had a major gravitational interaction.
Interacting spiral galaxies can have their arms greatly extended and disrupted, with NGC 6872 spanning 522,000 light years from tip-to-tip.
The galaxy Malin 1 is one of the largest spiral galaxies ever discovered, at 650,000 light years . [+] (199 kpc) in diameter.
Ultra-low surface brightness galaxies can see their stars extend even farther, with Malin 1 reaching 650,000 light years across.
The low-surface-brightness galaxy UGC 2885 is also severely gravitationally disrupted, making it . [+] arguably the largest known spiral galaxy.
Kitt Peak / Zagursky & McGaugh, 2008
Unsurprisingly, a disrupted low surface brightness galaxy, UGC 2885, is the largest spiral known at 832,000 light years.
The galaxy NGC 262, at the image's center (and in detail, inset), is only about the size of the . [+] Milky Way, but its hydrogen halo extends more than 10 times as far, as shown in blue in the main image.
NRAO/AUI, with the VLA (main) SDSS (inset)
Hydrogen gas and dark matter halos can continue beyond the stars, like in NGC 262, extending over 1,000,000 light years.
The giant elliptical near the center of the Coma Cluster, NGC 4874, is typical of the largest, . [+] brightest galaxies found at the centers of the most massive galaxy clusters.
But the largest and most massive galaxies aren't spirals, but supergiant ellipticals, like NGC 4874 in the Coma Cluster.
The two bright, large galaxies at the center of the Coma Cluster, NGC 4889 (left) and the slightly . [+] smaller NGC 4874 (right), each exceed a million light years in size.
Adam Block/Mount Lemmon SkyCenter/University of Arizona
Coma has two enormous core ellipticals, with the even larger NGC 4889 reaching 1.3 million light years in diameter.
The brightest cluster galaxy of the Phoenix cluster, shown at left from the South Pole Telescope and . [+] at right from Blanco/MOSAIC-II optical/infrared imagery, is one of the largest galaxies of all, still rapidly forming stars at hundreds of times the rate of our own Milky Way.
R. Williamson et al., Astrophysical Journal 738(2):139 · August 2011
Even larger ones reside inside more massive galaxy clusters, like the brightest galaxy in the Phoenix cluster, at 2.2 million light years.
The giant galaxy cluster, Abell 2029, houses galaxy IC 1101 at its core. At 5.5 million light years . [+] across, over 100 trillion stars and the mass of nearly a quadrillion suns, it's the largest known galaxy of all.
Digitized Sky Survey 2, NASA
Still, IC 1101 beats them all, extending for 5.5 million light years.
Early, intense star forming galaxies, like the Baby Boom galaxy shown in green/red here and imaged . [+] in the infrared, can form up to 4,000 new Sun-like stars every year. This behavior, from more than 12 billion years ago, can lead to the largest galaxies of all by present times.
NASA/JPL-Caltech/P. Capak (Spitzer Science Center)
Periodic star formation, mergers, and gravitational growth over time inevitably lead to these cosmic behemoths.
Mostly Mute Monday tells the scientific story of an astronomical object, class or phenomenon in visuals, images and no more than 200 words.
Astronomers agree: Universe is nearly 14 billion years old
From an observatory high above Chile’s Atacama Desert, astronomers have taken a new look at the oldest light in the universe.
Their observations, plus a bit of cosmic geometry, suggest that the universe is 13.77 billion years old – give or take 40 million years. A Cornell researcher co-authored one of two papers about the findings, which add a fresh twist to an ongoing debate in the astrophysics community.
The new estimate, using data gathered at the National Science Foundation’s Atacama Cosmology Telescope (ACT), matches the one provided by the standard model of the universe, as well as measurements of the same light made by the European Space Agency’s Planck satellite, which measured remnants of the Big Bang from 2009 to ’13.
The research was published Dec. 30 in the Journal of Cosmology and Astroparticle Physics.
The lead author of “The Atacama Cosmology Telescope: A Measurement of the Cosmic Microwave Background Power Spectra at 98 and 150 GHz” is Steve Choi, NSF Astronomy and Astrophysics Postdoctoral Fellow at the Cornell Center for Astrophysics and Planetary Science, in the College of Arts and Sciences.
In 2019, a research team measuring the movements of galaxies calculated that the universe is hundreds of millions of years younger than the Planck team predicted. That discrepancy suggested a new model for the universe might be needed and sparked concerns that one of the sets of measurements might be incorrect.
“Now we’ve come up with an answer where Planck and ACT agree,” said Simone Aiola, a researcher at the Flatiron Institute’s Center for Computational Astrophysics and first author of one of two papers. “It speaks to the fact that these difficult measurements are reliable.”
Linda B. Glaser is the news and media relations manager for the College of Arts and Sciences
Where is the center of the universe?
We can easily pinpoint the center of a circle or the center of a cube. With the ability to mark the center of objects and places, you may often wonder, “Where is the center of our universe?” Unlike pinpointing the center of geometric shapes, there isn’t exactly a center of the universe to pinpoint. Let’s try to understand why there is no center of the universe.
Scientists explain the that universe began with a the Big Bang. During this cosmic event, space itself began to expand outward. While you might think that there is a single point where this expansion happened, the expansion of space actually happened everywhere. Everything moved and is moving away from everything else, instead of everything moving away from a single point or object in space.
Many scientists like to use a balloon as an example. Imagine that you draw lots of dots on a deflated balloon. The dots represent galaxies. Once you blow the balloon up, the dots begin to mover further and further away from each other. Now, if you asked one dot if they were the center of the universe, they would say yes. However, if you asked another dot, they would also say they are the center of the universe. However, we know that the dots are just small specks on the large balloon, and they are not the center.
The expansion of galaxies is not like an explosion, where you can trace the source of the explosion to once object or cause at the center. Instead, the universe expands everywhere, meaning every object will think other objects are moving away from it during expansion.
The real answer to this question is that there is no center of the universe. The universe does not expand from a single, fixed point, nor does it sit around a single point. Instead, it is more like a balloon that is being blown up bigger and bigger, which makes galaxies and objects constantly move further apart. Therefore, if you are searching for the center of the universe, then you will unfortunately not find it.
Is there a hole in the universe?
In August 2007, scientists from the University of Minnesota published an astonishing finding in the Astrophysical Journal. The universe, they declared, had a hole in it -- a hole far bigger than anything scientists have ever seen or expected. This "hole" spans almost one billion light years and is six to 10 billion light years from Earth, in the Eridanus constellation [source: Daily Tech]. (For reference, one light year measures about six trillion miles.)
Space Dust Image Gallery
What makes this vast area of the universe a hole? The area shows almost no signs of cosmic matter, meaning no stars, planets, solar systems or clouds of cosmic dust. Researchers couldn't even find donker materie, which is invisible but measurable by its gravitational pull. There were also no signs of black holes that might have gobbled up the matter once present in the region.
The hole was initially detected by a NASA program studying the spread of radiation emitted from the Big Bang, which scientists believe spawned our universe. It was then further examined using information gleaned from the Very Large Array (VLA) telescope, used in the NRAO VLA Sky Survey Project to study large sections of the visible sky.
One researcher described the find as "not normal," going against computer simulations and past studies [source: Yahoo News]. Other such holes, also known as voids, have been found before, but this find is by far the largest. Other voids amount to around 1/1000th the size of this one, while scientists once observed a void as close as two million light years away -- practically down the street in cosmic terms [source: CNN.com].
Astronomer Brent Tully told the Associated Press that galactic voids in all likelihood develop because regions of space with high mass pull matter from less massive areas [source: CNN.com]. Over billions of years, a region can lose most of its mass to a massive neighbor. In the case of this giant void, further studies may reveal some matter in the region, but it would still be far less than what is found in "normal" parts of space.
Earlier we said that the void was first discovered through a NASA program examining radiation stemming from the Big Bang. On the next page, we'll take a closer look at that program and how scientists can look far back into the universe's history -- almost to its beginnings -- in order to make discoveries like this one.
Dark Energy and Mapping the Universe
On June 30, 2001, NASA launched the Wilkinson Microwave Anisotropy Probe (WMAP), a satellite that has since been used to map cosmic microwave background (CMB) radiation. CMB radiation is billions of years old, a byproduct of the Big Bang that scientists detect in the form of radio waves. CMB radiation yields insights into the early history of the universe, showing what it looked like when it was as young as a few hundred thousand years old. And by examining the spread of CMB radiation, scientists can find out how the universe has developed since the Big Bang and how it will continue to develop -- or even end.
Until the giant galactic void was further studied by the University of Minnesota researchers, it was known as the "WMAP Cold Spot" because NASA scientists measured colder temperatures in the region than in surrounding areas. The temperature difference only amounted to a few millionths of a degree, but that was enough to indicate something was much different about that section of space.
In order to understand why galactic voids show up as cooler, it's important to consider the role of dark energy. Like donker materie, dark energy is prevalent throughout the known universe. But in an area lacking dark energy, photons (originating from the Big Bang) pick up energy from objects as they approach them. As they move away, the gravitational force of those objects takes that energy back. The result is no net change in energy.
An area where dark energy is present works differently. When photons pass through space containing dark energy, the dark energy gives the photons energy. Consequently areas with a lot of photons and dark energy show up on scans as more energetic and hotter. Photons lose some of their energy if they pass through a galactic void lacking in dark energy. Those areas in turn emit cooler radiation. A giant void where little matter or dark energy is present, like the WMAP Cold Spot, causes significant drops in radiation temperature.
Both dark matter and dark energy remain rather mysterious to scientists. Much scientific research is underway to examine these substances and their roles in various cosmic processes. Dark energy may be even less understood than dark matter, but scientists do know that dark energy serves an important role in accelerating the universe's growth, especially in recent cosmological history. We also know that photons passing through dark energy allow for the kind of energy changes that produce varying temperatures that are in turn represented in the CMB map. Examining these temperature fluctuations allows scientists to learn how the universe is growing and developing. And considering that dark energy is the most common type of energy in the universe, it should continue to occupy a prominent role in cosmological research for years to come.
For more information about voids, dark energy and related topics, please check out the links on the next page.
Mushballs and a Great Blue Spot: What Lies Beneath Jupiter’s Pretty Clouds
NASA’s Juno probe is beginning an extended mission that may not have been possible if it hadn’t experienced engine trouble when it first arrived at the giant planet.
Jupiter and its southern hemisphere, captured by NASA’s Juno spacecraft in February 2019. Credit. NASA/JPL-Caltech/SwRI/MSSS/Kevin M. Gill
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For something that was to have been done and thrown away three years ago, NASA’s Juno spacecraft has a busy schedule ahead exploring Jupiter and its big moons.
The spacecraft entered orbit around Jupiter on July 4, 2016, and has survived bombardment from intense radiation at the largest of the solar system’s planets. It is now finishing its primary mission, but NASA has granted it a four-year extension and 42 more orbits. Last week, it zipped past Ganymede, Jupiter’s largest moon.
“Basically, we designed and built an armored tank,” said Scott J. Bolton of the Southwest Research Institute in San Antonio, who is the mission’s principal investigator. “And it’s worked.”
Jupiter is essentially a big ball of mostly hydrogen, but it has turned out to be a pretty complicated ball. The mission’s discoveries include lightning higher up than thought possible, rings of stable storms at the north and south poles, and winds extending so deep into the interior that they might push around the planet’s magnetic fields.
“I think this has been a revelation,” said David J. Stevenson, a professor of planetary science at the California Institute of Technology and a co-investigator on the mission.
Juno’s highly elliptical path, pitched up at almost a 90-degree angle to the orbits of Jupiter’s moons, passes over the planet’s north and south poles. On each orbit, Juno swoops in, reaching a top speed of 130,000 miles per hour as it passes within a few thousand miles of Jupiter’s clouds.
An early problem with the propulsion system led mission managers to forego an engine firing that would have shortened the orbit to 14 days from 53 days. The mission’s scientists had to be more patient but that has become a blessing.
In the original timeline, Juno would have completed its work by early 2018. With the spacecraft’s more languid trajectories, researchers will get to watch changes in and around Jupiter that they might have missed had the mission wrapped up sooner.
The additional orbits of the extended mission will also enable further investigations of the mysteries that Juno has revealed, like the rings of storms at the north and south poles — eight storms around the north pole, five around the south pole.
At one point, it looked as if a sixth storm was entering the group at the south pole, but then it was pushed away.
“It’s like five bullies on the playground, right?” said Candice J. Hansen-Koharcheck, a scientist at the Planetary Science Institute in Tucson, Ariz., who is responsible for the operation of the spacecraft’s primary camera, JunoCam. “Oh, no, you cannot join our game.”
Why do the storms, which last for years and are all about 2,500 miles in diameter, appear to remain constant in number?
Two storms would easily fit in a polar region without disrupting each other, said Yohai Kaspi, a professor of earth and planetary sciences at the Weizmann Institute of Science in Israel and a co-investigator on the mission. “But if you had 100, then that would be too close, and they wouldn’t be stable,” he said. “There is this magic number that can make them fit.”
The atmospheric patterns in the top half of Jupiter differ from those of the bottom half. “We tested a little bit with different dynamics of the north and the south,” he said, in order to understand why the two poles have different numbers of storms.
Scientists will get a closer look at the eight storms at the top of Jupiter in the coming years. Jupiter’s immense gravity is tugging on Juno’s orbit so that the spacecraft’s closest approaches — what the scientists call perijoves — no longer occur over the equator but are migrating northward. By the end of the extended mission, the perijove of the orbit will occur at a latitude that is the equivalent of where St. Petersburg, Russia, lies on Earth.
Those orbits will also provide closer observations of the perplexing lightning high in the atmosphere.
The colorful, swirling stripes of Jupiter are just the tops of the highest clouds, which are made of frozen ammonia crystals coated with soot. But Jupiter’s water clouds — where lightning observed by earlier spacecraft appeared to originate — are 30 to 40 miles deeper than the cloud tops. Within the water clouds, lightning probably occurs much as in thunderstorms on Earth, fueled by the collision of water droplets with ice crystals that build up electrical charge.
But the dim, never-before-detected flashes that Juno spotted were higher up in the atmosphere, where temperatures, about minus-125 degrees Fahrenheit, are far too cold for water to remain a liquid.
When she first saw the flashes, the reaction of Heidi N. Becker, a scientist at NASA’s Jet Propulsion Laboratory in California who is the lead for Juno’s radiation monitoring research, was “Uh oh, what’s wrong?”
The key to unraveling this mystery was ammonia in the atmosphere, which acted as an antifreeze.
“Jupiter has incredibly violent storms that can fling up water ice particles from below at 100, 200 miles per hour and get to these very high altitudes,” Dr. Becker said.
High up, the water ice crystals mix with the ammonia vapors and melt. The water-ammonia droplets then collide with additional ice crystals flung up from below, building electrical charge to generate lightning.
Seemingly paradoxically, the ammonia is also key to explaining why there is so little ammonia in the same swaths of the atmosphere where the lightning occurs. Scientists had expected that beneath the ammonia ice clouds, the churning winds of Jupiter would mix the ammonia gas evenly throughout the atmosphere.
“But this is not what’s happening,” said Tristan Guillot, director of research at the Côte d’Azur Observatory in France and a co-investigator on the mission. “We have regions down to 200 kilometers below or perhaps more, that contain much less ammonia than other regions.”
That appears to be caused by downpours of mushballs — viscous, sticky conglomerations the size of baseballs.
Scientists realized that the ammonia-water droplets do not remain as small droplets. Instead, they continue to grow until they are too heavy to remain suspended in the air. “Like big hailstones on Earth,” Dr. Stevenson said.
The raining mushballs, scientists believe, carry much of the ammonia to the deeper reaches of Jupiter’s atmosphere.
The mission has furthered understanding of the Great Red Spot, showing that the iconic giant storm, which has persisted for centuries, extends more than 200 miles deep into Jupiter’s atmosphere, and it has led to the discovery of a new region scientists call the Great Blue Spot.
It is not actually blue the name is an artifact of the color scheme used in mapping Jupiter’s magnetic field. Indeed, photographs yield no visible hints of the Great Blue Spot. The dark blue region in the magnetic map just indicates a confluence of invisible magnetic field lines entering Jupiter at that point — almost a second south pole sticking out near the equator.
Kimberly M. Moore, a postdoctoral researcher at Caltech, compared Juno’s magnetic measurements with observations by earlier spacecraft to see how magnetic fields in the Great Blue Spot have changed over the decades.
It appears that the center of the Great Blue Spot is being blown to the west by one jet of winds while eastward winds are shearing the top and bottom sections of the spot in the opposite direction.
That would suggest that the winds of Jupiter extend far below the cloud tops, down to regions where pressures and temperatures are high enough to turn hydrogen into an electrical conductor. Electrical currents generate magnetic fields.
The strength of the magnetic fields within the Great Blue Spot is changing by as much as one percent per year — growing stronger in some places, weakening in others. By the end of the extended mission in 2025, Dr. Moore will have almost a decade of data to test her hypothesis, which foresees changes of up to 10 percent during that time. “That’s what our model predicts, and we want to test it,” she said.
The scientists are likely to come across new mysteries too. The Great Blue Spot is at about the same latitude as the Great Red Spot. Are the two related or separate phenomena?
“The fact that they travel at different speeds suggests that maybe they’re unlikely to be related,” Dr. Moore said. “But maybe there is some sort of causal mechanism. It is all just one fluid planet, after all.”
During the extended mission, Juno will also fly by three of Jupiter’s large moons.
Last week, Juno provided scientists with the first close-up look in more than 20 years of Ganymede, the largest of Jupiter’s moons. At more than 3,200 miles wide, Ganymede is larger than the planet Mercury, and it is the only moon known to generate its own magnetic field.
Dr. Hansen-Koharcheck will be comparing pictures of Ganymede taken by Juno with older images. Parts of the surface are marked by grooves often seen on icy moons. Although there is still an ocean of liquid water beneath the moon’s icy crust, the ice is thought to be more than 60 miles thick, and Ganymede’s grooves most likely formed a few billion years ago when the surface was warmer and more bendable, Dr. Hansen-Koharcheck said.
“It’s highly unlikely that the groove terrain now is in communication with that water mantle,” she said. “However, if we were to find it, I would also be jumping up and down screaming.”
