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Brand die son regtig en word dit kleiner?

Brand die son regtig en word dit kleiner?


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Brand die son regtig en word dit kleiner? As dit so is, omdat daar geen lug in die ruimte is nie, wat kan dit aanhou brand en watter materiale word verbrand? As geen lug benodig word nie, wat kan die brandproses versnel of stop?


Die enigste ander detail wat ek kan byvoeg tot wat reeds hierbo gesê is, gaan oor die werklike samesmeltingsproses binne die Sun - sy enjin.

4H -> Hy + neutrino's + gammastraalfotone

Massa van 4H = 6,693e-27 kg Massa van He = 6,645e-27 kg

Massa verlore per enkele samesmeltingsreaksie = 0,048e-27 Kg

Dit genereer 4.3e-12 J

As 1Kg H in He omgeskakel word, gaan 'n massa van 0,007 kg (0,7% van die totale aanvanklike massa) tydens die proses verlore, wat 6.3e14 J. genereer. Dit is gelykstaande aan 20e6 kg steenkool.

Ons weet dat die son se helderheid 3,9e26 J / s is, wat gedeel deur die energie / kg hierbo gedefinieër die massa H omgeskakel per sekonde gee: 600e12 Kg.


Die son is nie brand, maar ondergaan kernfusie in die kern van die ster. Daar word waterstof onder groot druk en hoë temperatuur omgeskakel in Helium en energie (lig).

As u Einstein se vergelyking $ E = mc ^ 2 $ onthou, is energie gelyk aan massa, wat beteken dat 'n klein hoeveelheid massa in 'n groot hoeveelheid energie omgeskakel kan word.

Die werklike proses om die waterstof na Helium om te skakel, is ingewikkeld.


Ek sal nie die moeite doen om te antwoord hoe die son sy brandstof "verbrand" nie. Dit word reeds in hierdie vraag beantwoord. U tweede vraag is of die son al kleiner word; die antwoord hang af van wat u met "kleiner" bedoel. Ons sal dit op twee maniere ontleed:

Radius

As ons die radius van die son definieer op afstand tussen die kern en die fotosfeer, word die son nie kleiner nie. In werklikheid is dit groei met verloop van tyd, soos aangetoon in hierdie grafiek:

Beeld met dank aan Ribas (2009), gekleur deur gebruiker RJHall op Wikipedia onder die Creative Commons Erkenning-Deel gelyk 3.0 Unported-lisensie

Die hoogte van die fotosfeer neem selfs so effens toe, selfs in die hoofreeksstadium van die Son; spesifiek, Tabel 3 van Sackmann et al. (1993) verklaar dat dit by die son se nul-ouderdoms hoofreeks $ 0,9 R_ odot $ in radius was, en op sy terminale ouderdomshoofreeks $ 1,6 R_ odot $ sou wees. Dit beteken dat die radius van die son gedurende ongeveer 10,9 miljard jaar met $ 0,7R_ odot $ toegeneem het - ongeveer 70% van die huidige radius.

As ons die wiskunde $ left (0.7R_ odot over 10.9 text {Gyr} right) $ doen, kan ons vind dat die son se gemiddelde radiusverhoging (van begin tot einde hoofreeks) ongeveer 4,5 sentimeter is elke jaar (1,77 duim). Hierdie berekening moet nie te ernstig opgeneem word nie, omdat die groeikoers nie lineêr is nie, maar dit wys hoe stadig die son gegroei het.

Die son sal baie stadig groei totdat dit sy hoofreeksstadium verlaat. Sodra dit in die rooi reuse-tak kom, sal dit sy huidige grootte baie keer groei tot ongeveer 1 AU.

Massa

Die son verloor massa om twee redes: die kernfusie in sy kern omskep massa in energie, en protone en elektrone met hoë energie word voortdurend uitgestoot uit die son se korona as sonwinde. Wood et al. (2002) toon aan dat die son se massaverlieskoers $ dot {M} $ omgekeerd eweredig is aan die vierkant van sy ouderdom $ t $:

$$ dot {M} propto t ^ {- 2.00 pm 0.52} $$

Van nou af $ $ dot {M} = 10 ^ {- 14} frac {M_ odot} { mathrm {yr}} $. Nadat die son die hoofreeks verlaat het, verloor dit sy massa baie vinniger. Soos vermeld in Sackermann et al., Kan die tempo waarmee 'n ster na die hoofreeks massa verloor, veralgemeen word volgens die wet van Reimers:

$$ dot {M} = - eta (4 keer 10 ^ {- 13}) frac {LR} {M} $$

waar $ eta $ 'n waarde is afhangend van die ster (afgelei tot ~ 0,6 vir die son), $ M $, $ L $ en $ R $ in soneenhede, en $ dot {M} $ in sonkrag massas per jaar. Dit is vereenvoudig, maar gee ons 'n idee van hoe die fase van die son die massaverlies koers beïnvloed.

Teen die tyd dat die son die rooi reuse-tak binnedring, sal dit net 72,5% van sy huidige massa hê en sy helderheid en radius sal onderskeidelik $ 2300L_ odot $ en $ 170R_ odot $ bereik. As ons die waardes inprop, vind ons dat die tempo van massaverlies $ 1,3 keer 10 ^ {- 7} frac {M_ odot} { mathrm {yr}} $ sal wees. Dit sal massa vinniger verloor in die asimptotiese reuse-tak, wanneer die massa ~ 54,1% word van wat dit nou is, wat beteken dat $ dot {M} $ $ 2,5 keer 10 ^ {- 7} frac {M_ sal wees odot} { mathrm {yr}} $.


Verloor dit massa, volume of nie, of albei, terwyl die son brand?

Die antwoord is ingewikkelder as die moontlikhede wat u gebied het.

Bedoel u die son spesifiek, of sterre in die algemeen? Omdat die verandering in volume wild gaan wissel, afhangende van die tipe ster en in watter evolusiefase dit is.

Wat die son betref, die lig wat ons sien, is die gevolg van waterstoffusie. Om 'n lang verhaal kort te hou, weeg 'n Helium-atoom (die eindresultaat van die samesmeltingsproses) minder as die somtotaal van 2 protone en 2 neutrone. Die massaverskil word in die proses omskep in energie. Sommige van die energie is in die vorm van fotone. As die son dus lig uitstraal, verloor dit tegnies massa.

Boonop lewer die son eintlik 'n sonwind, waarin dit ongeveer 2-3 verdryf. 10 -14 M_☉ (sonmassas) per jaar.

Die son verloor ook massa deur sonfakkels en koronale massa-uitwerpings, wat ongeveer een orde van grootte minder is as die sonwind.

Ander sterre, soos Wolf-Rayet-sterre, sal baie meer massa verloor as gevolg van winde. 'N Vinnige google-soektog het my die artikel gegee, wat skat dat baie massiewe sterre (60 M_☉) ongeveer 10 -5 M_☉ per jaar verloor. Daar bestaan ​​nog massiewe sterre (& gt 100 M_☉), wat deur winde nog meer massa sal verloor.

Wat volume betref, moet u basies 'n hele boek oor sterre-evolusie volgens massa lees om te sien wat gebeur met watter sterre in watter fase, maar dit is voldoende om te sê dat dit ingewikkeld is. Gedurende die hoofreeks sal die meeste sterre betreklik stabiel wees, maar baie sterre ondergaan groot veranderings in volume gedurende hul leeftyd, sommige pols selfs heel uitermate (byvoorbeeld: Cepheids- en RR-Lyrae-sterre).

Die son sal vir nou relatief stabiel wees. Sodra die verbranding van waterstofkern stop, sal dit uitbrei en 'n rooi reus word. Sodra die brandstof van die waterstofdop begin, sal dit pols. Sodra die verbranding van Heliumkern begin, sal dit relatief stabiel wees totdat die AGB-fase begin, waartydens dit nog meer sal pulseer omdat daar 'n wisselaar sal wees tussen die verbranding van waterstofdop, die verbranding van heliumkern, beide en nie een nie. Sodra dit gedoen is, sal die buitenste lae verdwyn en 'n wit dwerg bly oor (wat in die grootte van die grootte van die aarde is).


Is daar enige teoretiese rede waarom die relatiewe groottes en afstande van die son / maan presies dieselfde is?

Dit lyk kranksinnig onwaarskynlik dat die grootte van die son en die maan in die lug amper dieselfde is. Is daar selfs 'n teoretiese rede waarom dit gebeur, of is dit werklik 'n toeval?

Nope. Dit is regtig 'n vreemde toeval en is waarskynlik uiters ongewoon. Dit gaan nie eens vir altyd so wees nie - die maan is stadig besig om af te neem en lyk asof dit kleiner word. Uiteindelik sal die maan merkbaar kleiner wees as die son in die lug, en ons sal nie meer totale verduisterings hê nie. Ons is dus dubbel gelukkig deurdat ons net regs hier is tyd asook die regte plek.

Baie ander planete het verduisterings vanaf hul mane, veral in die buitenste sonnestelsel waar die son baie klein lyk. Maar om uiters kort totale verduisterings in 'n smal strook te hê, is baie ongewoon. Dit is meer waarskynlik dat u slegs gedeeltelike (dws ringvormige) verduisterings (of selfs net deurgange) het, of dat u regtig lang verduisterings oor 'n groot deel van die planeet sal hê.

As daar in die uiterste toeval in ag geneem word, kan daar iets van die antropiese beginsel wees?

Die hoofrede waarom u spesifieke toekenning daaraan toeskryf, is slegs 'n kognitiewe vooroordeel. As die maan die helfte van die hoekgrootte van die son was, of twee keer, sou u dit ook noemenswaardig wees en verbaas wees oor hoeveel toeval dit is.

Dit word nog erger deur hierdie bietjie:

Met watter% van die verskil hou u op om identies te dink & quot; Sou u nie net so verbaas gewees het as dit & amper & quot of & quotof ongeveer & quot of net & quotsomewat & quot identies was nie?

Dit is 'n onvervulbare antwoord, maar dit is meer as gevolg van die aard van die vraag. Veral as u in ag neem dat die afstand tussen die maan en die aarde nie presies konstant is nie. Wat is die kans dat u sou lewe in 'n tyd waarin die maan is soos hy is? Verdwyn my dun. Die kans dat iemand wel is, is baie, baie hoër. Dieselfde idee tussen die kans dat u die lotto wen en iemand wat die lotto wen.

Die kans vir enige spesifieke gebeurtenis word altyd al hoe kleiner namate die spesifisiteit toeneem. En die betekenis wat aan daardie waarskynlikheid geheg word, gaan ook daarmee saam afdraande, en die rede word gewoonlik óf & toeval & quot, óf & quot weens die begintoestande van die heelal & quot, afhangende van hoe u deterministies voel.

Natuurlik argumenteer / waarneem ons van die verkeerde kant van dinge af. Ons is hier. Dit is die geval, ons kyk terug na die natuurgeskiedenis en is verbaas oor al die onwaarskynlike toevallighede wat die omstandighede tot gevolg gehad het wat tot ons bestaan ​​gelei het.

Maar gesien vanuit die oogpunt van die begin, het daar willekeurige dinge gebeur wat net lukraak / toevallig tot ons bestaan ​​gelei het.

ONS is miskien net toevallige resultate.

Vanuit die oogpunt van die RESULTATE lyk alles wat daartoe lei ongelooflik, beplan, bedoel, ontwerp en beheer. As toevallig ander wesens as ons die resultaat was, sou hulle waarskynlik ook so voel.

Ek verloën, terloops, geen geloof of geloof in 'n skepper nie, en wys net daarop dat as u vanuit die RESULTATE redeneer, dit u & # x27s perspektief kan skeefloop.

Ek stem nie saam nie, ek dink nie twee keer of die helfte sal naastenby so interessant wees nie. En dit is duidelik dat hoe minder identies dit is, hoe minder interessant dit is, maar ek dink dat ons die waarskynlikheidsverdeling vir die skynbare groottes van hierdie twee dinge kan waardeer en dat dit so naby is, baie onwaarskynlik en interessant op 'n manier dat ander uitkomste nie sou wees nie. wees.

Ek haat toeval as 'n verklaring vir enigiets, maar ek dink, dit is waarskynlik dat daar soms toevallighede gebeur. Of, soos Terry Pratchett dit gestel het, & quotWetenskaplikes het bereken dat die kans op iets so uiters absurd is [die skyfwêreld] eintlik bestaan ​​dit miljoene teen een. Maar kulkunstenaars het bereken dat miljoen-tot-een-kanse nege keer uit tien opduik. & Quot

Toeval verklaar die meeste dinge. Soortgelyke situasies gebeur oor en weer, so die kans mislei. Wat is die kans dat ek by 'n gebou gaan stap en 'n klavier op my kop sal laat val? Redelik laag. Wat is die kans dat ten minste een van die 7 500 000 000 mense 'n klavier op hul kop sal laat val? Baie baie hoër.

Toeval. Die son is ongeveer 400 keer die deursnee van die maan en is ongeveer 400 keer verder weg.

Aangesien die baan van die Maan groter word, was dit vir die grootste deel van die Aarde se geskiedenis nie waar nie, en sal dit in die toekoms nie waar wees nie. Ons leef net op 'n tyd dat die maan dieselfde grootte as die son in die lug het.

Aangesien die antropiese beginsel soveel meer oor die gemak van die heelal vir ons dek, is dit eintlik die enigste ding wat net onverwags is. Daar is geen spesifieke rede waarom ons bestaan ​​gedurende 'n tyd waarin ons elke tipe sweefverduistering kan waarneem nie. Ons is net gelukkig dat ons dit doen.

Dit is die een punt wat ek aan die godsdienstige kamp gee wat glo dat die wêreld spesiaal vir ons geskep is. Elke ander ding het 'n goeie verduideliking, maar vir hierdie een is ons net gelukkig.

Edit: om duidelik te wees, daar is redes waarom ons verwag om 'n groot maan te hê. Dit is 'n meteoriese skild en kan 'n intelligente lewe baie meer waarskynlik maak deur massa-uitsterwingsgebeurtenisse te verminder. Maar dit gee nog steeds 'n goeie reeks waardes wat slegs ringvormige of slegs gedeeltelike / totale verduisterings moontlik maak.

Die toeval beteken dat die antikiterameganisme deur Archimedes gebou is om verduisterings te bereken (wat 'n groot saak vir hulle was) - wat uiteindelik gelei het tot moderne rekenaars

Miskien is daar 'n verklaring soos 'n groot maan wat groter getye veroorsaak, wat beter is om chemikalieë te meng om lewe te vorm, ens. Maar sonder 'n groter steekproefgrootte van planete met die lewe, dink ek dit sal baie moeilik wees om te bepaal. Daar kan vreemdelinge wees wat vra waarom hulle die enigste planeet is sonder 'n groot maan en met ewe oortuigende redenasies vorendag kom.

Hoe dit ook al sy, ek dink mense oorskat massief hoe toevallig die ooreenkoms in die oënskynlike hoeke is. Op die naaste van die maan kan die maan 'n totale verduistering veroorsaak, en op sy verste punt is dit net 'n ringverduistering. As u die gasreuse beskou as 'n & oppervlakte & quot, dan is ons nie die enigste planeet wat 'n maan met hierdie eienskappe het nie. Op grond van hierdie weliswaar klein monster is die kans dat 'n maan hierdie eiendom het, ongeveer 1%, wat skaars 'n gedagtes toevallig is.

U kan ook verskillende soorte verduisterings hê as u op een van die mane van 'n gasreus woon, en ek het gedink dat totale verduisterings waarskynliker sou wees, aangesien daar meer drastiese veranderinge sou wees in die skynbare deursnee van ander mane, alhoewel ek dit nie doen nie. weet van iemand wat dit getoets het. As ons rondom 'n binêre ster woon, kan dieselfde ook geld.


Ons is dalk alleen hier buite. - Wat is die kans regtig?

Ek het lukraak gedink en begin wonder hoe klein die kans is dat ons ooit 'n ander vreemde beskawing sou teëkom, en of ons die kleiner kans sou kry dat ons een sou ontmoet met 'n tegnologiese vlak gelykstaande aan ons eie.

My denkproses was dit. Die heelal is amper 14 miljard jaar oud. Ons ster is 4,5 miljard jaar oud. Homo Sapiens is ongeveer 400 duisend jaar oud. Die mensdom kan ons planeet al 60 jaar verlaat.

Nou het ons 'n paar onbekendes. Gaan interstellêre reise ooit moontlik wees in enige metode buite ruimteskepe van generasie, sal ons onsself vernietig of onsself ten minste terugstoot in ons tegnologiese evolusie, ens.

My punt is dat die tydsraamwerke al hoe kleiner word. As ons aanvaar dat ons niks spesiaals is nie, het ons nie baie vinniger of baie stadiger ontwikkel as wat normaal is nie, dan is die kans dat daar 'n ander soort soortgelyke ras in die tegnologieboom is. Ons sal heel waarskynlik 'n spesie in die grot-man-stadium van hul ontwikkeling vind (dit vorm 99,9% van ons spesietyd op die planeet) of as ons in ag neem hoe vinnig ons tegnologiese vooruitgang sien (meer vooruitgang in die afgelope 100 jaar as die vorige 4000 deur 'n groot marge) 'n spesie wat eeue of millennia gevorderd is of moontlik selfs meer waarskynlik is, al lankal dood weens hul eie foute of natuurrampe.

Om 'n intelligente, vreemde lewe teë te kom, sal ons hulle dus moet ontmoet binne dieselfde tegnologiese ontwikkeling van ongeveer 100 jaar (as ons aanvaar dat dit soortgelyk aan ons eie is en as ons aanvaar dat die vooruitgang nie binnekort 'n belangrike wet van die fisiese muur is nie), is dit baie klein as dit gemeet word aan die ouderdom en tydsduur van die heelal. Dit sal onwaarskynlik wees dat 'n geskikte ster wat slegs 10 000 jaar voor of na die vorming van ons Sol gevorm het, die lewe sou hê wat bestaan ​​het in 'n hedendaagse, eie tyd.

Behalwe vir die GROOT aanname dat ons die mensdom en ons eie geskiedenis as 'n betreklik ordentlike skaal kan gebruik (basies nie veel vinniger of veel stadiger as die gemiddelde ontwikkeling nie), sien iemand 'n groot gat in my logika?

Weet iemand ook hoe gou na die oerknal toe die eerste G-tipe sterre met sonnestelsels begin vorm? Hulle leef ongeveer 10 miljard jaar, so as hulle kort na die oerknal sou kon ontstaan, sou daar 'n hele geslag van hulle wat gevorm het, nou geleef en gesterf het.

Net om te verduidelik: dit verdwyn onwaarskynlik dat ons eintlik alleen in die heelal is, maar dit is ook uiters onwaarskynlik dat ons ooit kontak sal maak met 'n buiteaardse volk, of dat enige twee buiteaardse beskawings met mekaar kontak sal maak, gegewe galaktiese tydskale.

Wat vroeëre sonne betref, is my begrip dat die eerste generasie sterre ná die oerknal nie planete gevorm het nie, ten minste nie aardse nie. Die elementêre verspreiding was nie reg nie. Eers nadat die eerste stel sterre supernova geword het en nuwe sterre uit die oorblyfsels gevorm het, het ons sterrestelsels gekry.

Ons het in 150 jaar van stoomtreine na die nabyheid gekom om beskawingsbesoedeling in eksoplaneetatmosfere op te spoor, en dit & # x27s sonder om ernstig te probeer, as u die begrotings vir astrofisika oorweeg.

Die versending van inligting tussen sterre met die gebruik van presies gerigte laser is glad nie onuitvoerbaar nie. Die & quotchat & quot kan eeue se agterstand hê, maar dit pla ons net omdat ons dom ongeduldig is, dit is alles.

of dat enige twee buiteaardse beskawings met mekaar kontak sal maak, gegewe galaktiese tydskale.

Ek is nie seker of dit waar is nie. Die sterrestelsel is 10 miljard jaar oud, maar tog sal dit net 'n miljoen jaar neem voordat die intelligente lewe deur die hele sterrestelsel versprei sodra hulle oor die nodige tegnologie beskik. En dit sal net een keer moet gebeur vir die sterrestelsel om vol intelligente lewe te wees.

Ek stem saam. As ek alleen in die heelal sê, bedoel ek alleen dat die kans om 'n ander te ontmoet op 'n vlak wat gelyk is aan onsself om nuttig te wees, so klein is.

Stel jou voor dat jy ligsnelheidsreis ontwikkel wat jou toelaat om by 10C te reis. U gaan uit, u vind die regte sterre, vind die planete in die regte sone, en die beste ding wat u vind, is waarskynlik die vreemde ekwivalent aan Australopithecus Africanus.

Ja, ek het gelees van vroeë sterre en hoe dit massief was, vinnig gebrand het en nie lank geleef het nie. Ek het gewonder hoe lank na die oerknal voordat G-Type sterre soos ons Sol begin vorm het. Sol het 'n BB + 10b gevorm (oerknal plus 10 miljard), is dit vroeg of vorm G-tipes by BB + 1b? Ek het nie genoeg gegrawe om uit te vind dat sterrekundiges selfs 'n rowwe antwoord het nie. As 'n G-Type-ster geen invloed op buite gehad het nie, sou dit teen BB + 3.5b of vroeër moes vorm om nou te sterf.

U kry al die verkeerde antwoorde, en u gevolgtrekkings is ook af. Daar is 'n paar dinge wat u MOET weet om wiskundige gevolgtrekkings te maak.

Die kans dat dit begin.

Hoe vinnig intelligensie buite die aarde kan ontwikkel.

As u dit nie kan beantwoord nie, kan u geen waarskynlike gevolgtrekkings maak oor die bestaan ​​van ander lewens nie.

En aangesien ons geen idee het van watter proses die lewe begin of wat die kans is nie, kan ons geen gevolgtrekkings maak nie. Vir alles wat ons weet, kan die lewe in die lugruim begin en is dit glad nie planete of atmosfeer nodig nie. Ons weet die belangrikste lewensvorms in die heelal het NUL ooreenkomste met die lewe op aarde nie. Vir alles wat ons weet, is die begin van die lewe so ongelooflik skaars dat ons die enigste is. Vir almal weet ons dat die lewe so maklik is om te begin, en so baie dat die sterrestelsel daarmee gevul is.

Wiskundig is die kans dat ons uniek is baie laag. Dit beteken nie dat ons nie is nie, maar in terme van suiwer statistieke. Die aantal sterre wat bestaan ​​en die aantal planete en die aantal sterre in die Gouelokkiesone, wat al dan nie relevant is vir ander lewensvorme nie.

Oorweeg ook die feit dat as u noem dat soveel van ons geskiedenis as 'n kaviaar & quot tye bestee is, dat dit ook sterk beïnvloed word deur die tipe dier waaruit ons ontwikkel het en die aard daarvan. Sê nou ons het altyd ontwikkel uit miere wat altyd saamwerk om 'n kookdoel te bereik. Of luiaards, wat nie aggressief is nie. Sonder oorloë het ons baie vinniger gevorder.

Sou ons vinniger vorder sonder oorlog? Homo Sapiens is tussen 300 000 en 500 000 jaar oud. Maar sover ons kan sien, het al die vooruitgang van belang (buite die skepping van gesproke taal) die afgelope 10 000 jaar plaasgevind. Dit lyk onwaarskynlik dat oorlog met stokke en klippe ons vertraag om meer as 300 000 jaar tegnologies vooruit te gaan. Ek dink dit kan meer in die lyn van sekere aspekte van tegnologiese evolusie wees, kan net so lank duur. Tegniese evolusie kan 'n sneeubaleffek wees, dit is net dat die sneeubal atoomgrootte begin.

Ontwikkeling soos miere kan die wetenskap nog meer vertraag. 'N Ultra-doeltreffende samelewing hoef dalk nie vooruit te gaan nie; almal sal hul rol ken en daarin bly.

Dit kan ook nie help om soos luiaards te ontwikkel nie, waarom meer maak, beter doen, meer uitvind as daar geen druk is om dit te doen nie. Ook as luiaards die oorheersende spesie was, kan 'n mens nie sê dat hulle sou bly soos hulle is nie en dat die skaarsheid van hulpbronne konflik veroorsaak het tussen verskillende groepe wat kultureel in isolasie ontwikkel het en dus hul eie tale, sosiale houdings, ideologieë, ens.

Ek gaan 'n bietjie terugdruk, nie omdat ek nie saamstem nie, maar omdat ek sommige van u aannames wil bevraagteken en alternatiewe weë vir 'n teoretiese buiteaardse lewe wil beskryf.

My punt is dat die tydsraamwerke al hoe kleiner word. As ons aanvaar dat ons niks spesiaals is nie, het ons nie veel vinniger of stadiger ontwikkel as wat normaal kan wees nie.

Dit is 'n redelike aanname, maar daar is data wat alternatiewe voorstel, waarvan sommige meer oortuigend is. Byvoorbeeld, 'n bekende drywer van evolusionêre divergensie is katastrofes, soos 'n massiewe vulkaanuitbarsting of asteroïde-impak. Daar is vermoedelik 'n verskeidenheid vulkaniese en asteroïde aktiwiteite wat 'n biosfeer kan weerstaan, met die minimum vulkanisme van 'n tektonies-aktiewe planeet met 'n funksionerende magnetosfeer, en die maksimum frekwensie van sulke rampe dat die lewe daarby kan aanpas sonder om permanent te wees verminder of heeltemal uitgewis word. Met geen ander voorbeelde van bewoonbare planete waarmee ons kan vergelyk nie, kan ons die aarde nie akkuraat in hierdie reeks plaas nie. Maar dit is redelik om te dink dat die aarde glad nie uiterste is nie. Om dit terug te bring na die tempo van evolusie, is dit moontlik dat die totale evolusietempo met 'n hoër frekwensie van katastrofes versnel kan word, maar miskien is daar 'n drempel waar 'n te hoë frekwensie diversifikasie vertraag. U kan u dan voorstel dat uitheemse biosfere vinniger en stadiger ontwikkel, met implikasies vir die evolusie van sapience en tegnologiese beskawings.

Ander hipoteses sluit in: Groter suurstofkonsentrasie wat vinniger ontwikkeling van oksidatiewe fosforileringstegnieke aanmoedig om chemiese energie op te wek, wat lei tot vinniger opkoms van meerselligheid Groter waterkonsentrasie van biobeskikbare stikstof, wat proteïenmetabolisme, aktiwiteit en diversifikasie in die mariene mikrobioom aanmoedig, wat kompleksiteit stimuleer. die vermindering van die metaboliese vraag na temperatuurreguleringsmeganismes by makroskopiese diere, die vrystelling van energie- en voedingsbronne vir ander take, die stimulering van diversifikasie, ens.

. dan is die kans om 'n ander soort soortgelyk aan onsself op die tegnologiese boom te vind, baie laag.

In plaas van die potensieel onbeperkte tegnologiese vooruitgang wat eksponensieel vorder, wat as daar 'n boonste horisontale asimptoot is, soos hier uitgebeeld? 'N Mens kan verwag dat gevorderde uitheemse beskawings verby die infleksiepunt en & quot; Die vraag word dan waar die mensdom op hierdie dubbelasimptootgrafiek is.

Om 'n intelligente, vreemde lewe teë te kom, sal ons hulle dus moet ontmoet binne dieselfde tegnologiese ontwikkeling van ongeveer 100 jaar (as ons aanvaar dat dit soortgelyk aan ons eie is en as ons aanvaar dat die vooruitgang nie binnekort 'n belangrike wet van die fisiese muur is nie), is dit baie klein as dit gemeet word aan die ouderdom en tydsduur van die heelal. Dit sal onwaarskynlik wees dat 'n geskikte ster wat slegs 10 000 jaar voor of na die vorming van ons Sol gevorm het, die lewe sou hê wat bestaan ​​het in 'n hedendaagse, eie tyd.

Dit is akkuraat. As teoreties tussen die sterre kan reis en vrylik kan verken en al die wêrelde wat ons lewenslank teëkom, kan steek, is die meeste van die komplekse lewensvorme wat ons sien, soos plante en wilde diere, miskien met sosiale spesies en komplekse gedrag, maar die sapente lewe is onwaarskynlik, en tegnologiese beskawings is minder so. As die leeftyd van die heelal soos 'n 1-triljoen tweede film is (amper 32 000 jaar!), Bestaan ​​ons sonnestelsel al die laaste 4,5 miljard sekondes, en die lewe bestaan ​​al die afgelope 3,9 miljard sekondes, maar ons tegnologiese moderne beskawing het net vir die laaste bestaan

150 sekondes, as dit. Ons het mense 'n minuut gelede die ruimte in gestuur. As ons karakters na enige ander lewensdraende wêreld gaan, is die kans dat ons 'n soortgelyke tegnologiese beskawing vind, baie laag. Ons deel dieselfde 150-500 sekondes van die triljoen sekondes (of hoe lank dit ook al duur voordat ons onsself ineenstort / vernietig), wat statisties redelik onwaarskynlik is. Maar nie onmoontlik nie. Dinge raak interessant as u besef dat daar in die skynbaar oneindige ruimte 'n virtuele statistiese sekerheid is dat 'n soortgelyke beskawing êrens bestaan. Miskien nie in hierdie sterrestelsel nie, maar êrens in die letterlike honderde miljarde ander sterrestelsels. En ons het selfs nie al die super gevorderde beskawings bereik wat rondom die boonste asimptoot rondhang wat hul eie sake doen nie.

Behalwe vir die GROOT aanname dat ons die mensdom en ons eie geskiedenis as 'n betreklik ordentlike skaal kan gebruik (basies nie veel vinniger of veel stadiger as die gemiddelde ontwikkeling nie), sien iemand 'n groot gat in my logika?

Hier is 'n oortuigende argument waarom die mensdom as standaard prakties gebruik kan word, selfs met 'n steekproefgrootte van een: ons is deel van die heelal en ons bestaan ​​toon dat lewe moontlik is. As lewe hier moontlik is, is dit teoreties êrens anders moontlik met soortgelyke toestande. Dit kan die geval wees dat lewe ontstaan ​​waar toestande aanvaarbaar is, en in die regte evolusionêre konteks, kan die regte druk een of meer spesies tot 'n sapensie laat beweeg. As hierdie toestande herskep kan word, kan ons eksperimenteer (waarskynlik oneties) en toetsmense skep wat hul eie uitheemse beskawings sal skep. Wat as dit 6 miljoen jaar gelede met sjimpanseevoorouers gebeur het en dat dit ons gemaak het?

Om op meer gegronde verklarings te fokus, is ons (en die hele aarde) van koolstof, omdat koolstof 'n vrugbare chemikalie is wat vier kovalente bindings kan vorm, en anders as silikon, die volgende vrugbaarste, het koolstof 'n tussentydse stabiliteit wat dit maak. ideaal vir die dinamika biochemie. Silikon vorm baie sterk kovalente bindings, wat dit moeilik en energie-duur maak om te gebruik in 'n proses wat analoog is aan koolstof-transformerende prosesse soos fotosintese of die Krebbs-siklus. In die konteks van 'n tegnologiese beskawing sou enige uitheemse spesies voldoende persepsie (oë, ore, ens.) En liggaamsdele (teenoorgestelde duime, vingers) benodig om die omgewing hipereffektief te manipuleer om gereedskap, skuiling, ens. Te skep. nog nooit bestaan ​​het nie, het vreemdelinge wat hierheen gekom het, tot die gevolgtrekking gekom dat olifante en walvisse intelligent is, maar nie die vermoë het om tegnologiese beskawing te beoefen nie. Dit is 'n paar voorbeelde van fundamentele eienskappe wat ons kan verwag om te sien in die vreemdelinge van die een of ander xenos-beskawing.


The Moon is Wrong: Astronomy 101 & # 124 Bookmans

As u soos 'n tipiese Bookmans-werknemer is, staan ​​u om 03:00 in u tuin uit en wonder wat is fout met die maan. Hierdie gedrag kan ook gekoppel word aan die grootword in Tucson. Klein woestynkinders bestee baie tyd om op te kyk of op die grond te lê en na die naghemel te staar, moontlik omdat daar soveel is om na te kyk. Arizona is al lank 'n middelpunt vir astronomiese navorsing met die Flandrau Planetarium en Kitt Peak van die Universiteit van Arizona. In plaas van dieper sielkundige verkenning wat ons potensieel verleentheid kan betoon om laat in die nag in ons erwe te staan, sal ons net sê dat dit tipies is vir Tucsonans. Ons doen sulke dinge.

Mense van Michigan gaan visvang, ons staan ​​en kry 'n knik in die nek. Ons sien dus dinge raak, dinge wat nie reg is nie en soos die maan. Net voor die nuwe jaar, ongeveer 18 Desember, het sommige van u dalk ook in u tuin gestaan ​​en opgemerk dat die maan verkeerd was. Heeltemal verkeerd. Dit het soos gewoonlik kleiner geword, maar dit het van bo af na onder verdwyn. Aanvanklik het dit gelyk of wolkbedekking die boonste kwart van die Maan maar NOPE verduister. Dit het aand na aand hierdie vreemde ding bly doen. Dit was eintlik besig om te kwyn (jou eerste tegniese term beteken dat dit kleiner word, ja, ek moes dit opsoek om seker te wees) vanuit 'n horisontale posisie. Verkeerde. Nee, nee, die maan word veronderstel om van links na regs of regs na links kleiner te word & # 8211 of groter, afhangend van die fase en waar u op die planeet is. Ons sal probeer om dit alles te dek, maar dit word morsig.
Die punt is dat ons almal bekend is met die sekelmaan. Dit is 'n gerusstellende beeld, ons verstaan ​​dit (soort). Ons het dit ten minste al gesien, maar hierdie maan wat van onder af verdwyn, is 'n probleem. Dit is 'n goeie ding dat ons 'n boekwinkel soos Bookmans het om dit te help verduidelik. Hier is die saak, dit gebeur. Ons is nie mal nie, ten minste nie as gevolg van die maan nie, en ander het dit ook gesien.
Dit word die sywaartse maan genoem (2de tegniese term). Hier is u groot tegniese verduideliking: & # 8220die ekliptika is gekantel, maar dit draai nooit oor homself nie, dus die enigste keer dat die son en die maan dieselfde asmut is, is tydens 'n nuwe maan. 6 uur weg beteken net dat hulle 90 grade van mekaar af in azmut is, en dit is net losweg gekoppel aan wanneer dit sal styg of sak. Wat dit wel beteken, is dat as die son nou reg wes is, is die maan nou suid en 6 uur van nou af sal die son reg noord wees en die maan reg wes. Afhangend van die skuins van die ekliptika vir u seisoen en ligging, kan die son, die maan, albei of nie een van die twee tye opstaan ​​nie. & # 8221 Verwysing https://www.physicsforums.com/threads/sideways -maan.203670 /.
Skokkend genoeg is dit vir ons ook sinvol. Dan weet ons weer baie oor hierdie dinge, want ons woon in Arizona en kyk na die lug. Dit is 'n geweldige verligting om te weet dat die aarde nie van sy as afgeglip het nie, of dat die maan wild buite beheer draai om reg in die son te val of iets. Dit was egter 'n oproep en 'n waarskuwing vir ons almal; ons moet beter by Bookmans kom en boeke oor sterrekunde opneem. Dit lyk asof dit nie altyd genoeg is om die naghemel in te staar nie. Ons het ons eie advies gekry en 'n paar boeke gevind wat ons veiliger en slimmer laat voel!
40 nagte om die lug te ken deur Fred Schaaf is ondertitels A Night by Night Skywatching Primer. Hierdie werk is perfek, dit bevat kaarte, grafieke, foto's en duidelike verduidelikings waarom ons nie moet paniekerig raak as ons 'n sywaartse maan sien nie. It also includes information about astrology, the brightest stars, the ecliptic and the zodiac, and how to NOT observe a solar eclipse. That last bit is probably especially important for us, just saying. Next is Spring Forward, the Annual Madness of Daylight Saving Time by Michael Downing. We really love this book because we don’t do Daylight Savings Time so we can sit back and laugh while the rest of the country tries to figure out their clocks and watches. Yeah, who’s crazy now? Last is Astronomy for Dummies by Stephen P. Maran, 2nd ed. The best part of this work are the color photos included. We also appreciate how straightforward it is and easy to follow. So don’t worry, don’t panic, we can explain everything to you. We have a large Astronomy section that will plainly cover all these strange things you seen in our desert sky. We can even explain those aliens, yes we saw them too, they are out there. That is a different section though, just ask us, we’ll talk.


what do you think ?
have you googled something like .
1) the surface temperature of the Sun or
2) the core temperature of the Sun ?

there's 2 things for you to do an report back with your findings

Red dwarf stars are main sequence stars but they have such low mass that they’re much ' cooler' than stars like our Sun.

Then Simple question here : Sun is cool or hot??

The sun has coronal holes which are not convective. The corona further complicates the hot vs cool question.

The temperature of a star is a real number. There is no obvious gap in the hertzsprung-Russell diagram. The transition from not having a core to having a tiny core is very difficult to see. Somewhere in the M3 to M4 range. CNO burning of hydrogen is taking place in the Sun but at a rate too slow to cause core convection. You could find an overlap where a star has some core convection and some surface convection.

Are they divided by star types or by telescope/detector type? It would also be reasonable for Astronomers to group by the age of the stars they are studying. It is hard to see M-dwarfs that are far away.

Would a study of the Orion Nebula go to the "hot star" conference or the fit in with the "cool" astronomers?

A paper link. Also a video from NASA.

They also found the temperatures reversed. The more massive brown dwarf is cooler. This could be caused by spots.

If you are interested in cold spots on hot stars do you go to the cool conference or the hot conference?

I assume you are referring to the hottest part of the sun, which lies above the surface of the sun. As we get to the surface, temperatures drop significantly. Observations suggest that below the surface temperatures drop even more. Indeed, looking into holes indicates lower temperatures.

According to emmited heat, the consensus seems to be that our sun may be average or slightly below. It is about at the median. This is also complicated by the definition of a star.

There appears to be no consistent temperature throughout the sun and it is very difficult to get emissions deep in the sun. So, the answer is difficult. For most other stars I think we only measure emission temperatures.


Tiny Planet Mercury Is Shrinking Fast

The surface of Mercury is shrinking faster than previously thought, photos from a NASA spacecraft orbiting the tiny planet reveal.

The first comprehensive survey of the surface of Mercury by NASA's MESSENGER spacecraft shows that planet's crust has contracted as it cooled by as much as 4.4 miles (7 kilometers), significantly more than previous estimates. The findings clear up a long-standing clash between scientists' understanding of the heat production and loss and the contraction of Mercury.

"These new results resolved a decades-long paradox between thermal history models and estimates of Mercury's contractions," said study lead author Paul Byrne of the Carnegie Institution for Science in a statement. [Latest Photos of Mercury from NASA's MESSENGER Probe]

The incredible shrinking planet

The surface of Mercury is made up of just one continental plate covering the entire planet. Its enormous iron core, estimated to be about 2,500 miles (4,040 km) across, leaves only 260 miles (420 km) for a mantle and crust — an extremely thin skin for the solar system's smallest planet. The Earth's mantle, for comparison, is about 1,800 miles (2,900 km) thick, while the crust above it averages 25 miles (40 km) in thickness.

And as if that weren't enough for little Mercury, the tiny planet is shrinking.

Over the billions of years since its formation at the birth of the solar system, the planet has slowly cooled, a process all planets suffer if they lack an internal source of heat renewal. As the liquid iron core solidifies, it cools, and the overall volume of Mercury shrinks.

When NASA's Mariner 10 mission circled the planet in the 1970s, it captured images of surface features created by the shrinkage. The contracting planet pushed the crust up and over itself, forming scarps that can extend miles below the planet's surface. At the same time, the shrinking surface caused the crust to wrinkle up on itself, forming so-called "wrinkle ridges."

Byrne and his team used NASA's MESSENGER spacecraft to identify 5,934 ridges and scarps created by the contracting planet, ranging from 5 to 560 miles (9 to 900 km) in length. This created a substantially larger sample than those collected Mariner 10, which only imaged 45 percent of the surface. MESSENGER was able to map the entire surface.

NASA's MESSENGER probe (the name is short for MErcury Surface, Space ENvironment, GEochemistry, and Ranging) launched in 2004 and is currently in the middle of an extended mission around Mercury.

From Mariner 10 to MESSENGER

The scarps and wrinkle ridges identified by Mariner 10 allowed scientists to estimate that the planet had lost approximately 1 to 2 km, in global radius, a finding that contrasted with their understanding of the heat loss the planet suffered over time. Byrne's findings of a contraction of up to 4.4 miles (7 km) fits far more cleanly with present models.

"The discrepancy between theory and observation, a major puzzle for four decades, has finally been resolved," MESSENGER principle investigator Sean Solomon said in the same statement.

"It is wonderfully affirming to see that our theoretical understanding is at last matched by geological evidence."

Byrne's paper was published online today (Mar 16) in the journal Nature Geoscience.


Gedeelde flitskaartstel

Which of the following practices is not considered to be plagiarism?

A. Copying the answer from your neighbor during an exam

B. Combining Wikipedia answers with APOD descriptions

C. Formulating the answer in your own words

D. Selecting answers from a web source and giving the reference to that source

Approximately, how many astronomical units (AU) are there in one light year (ly)?

The number 7.14 x 10^6 is equivalent to:

Why does the Moon appear to move relative to the stars as observed from Earth?

A. It is due to Moon rotating on its axis

B. It is due to the Earth rotating on its axis

C. It is due to Moon revolving around the Earth

D. It is due to the Earth rotating around the Sun

What types of distances are typically listed in parsec?

B. The length of speed-skating races

C. Distances in the solar system

D. The diameter of the universe

Which is Kepler&rsquos first Law

A. The orbits of planets are ellipses with the Sun at one focus

B. Force equals mass times acceleration

C. The orbits of planets are circles with the Sun at the center

D. What goes up has to come down

What does Kepler&rsquos second law indicate about the orbital speed of a planet?

A. The orbital speed of each planet is constant

B. The orbital speed of a planet varies in no predictable way

C. A planet moves at its slowest when it is closest to the sun

D. A planet moves at its fastest when it is closest to the sun

On Earth, if we drop a feather and a hammer at the same moment from the same height, we see the hammer hit the ground first. On the moon both strike the ground at the same time. Hoekom?

A. The surface gravity of Earth is stronger than the gravity of the moon

B. There is no air resistance effect on the moon

C. In strong gravity fields, heavier objects fall faster

If the semi-major axis of a planet is 4 AU, what is its orbital period?

The mass of &alpha Cen A is about 8 times larger than the mass of it&rsquos distant, faint binary companion,

Proxima Centauri. Which describes best the location of the center-of-mass of the &alpha-Proxima system?

A. Half-way between the two stars

B. 8 times closer to &alpha Cen than to the Proxima

C. Because &alpha Cen A has an almost equaly massive, close-in companion &alpha Cen B, there is no such thing as a center of mass in this system

D. 8 times closer to the Proxima than to &alpha Cen

Consider the energy output of the Sun. How is this energy produced, year after year after year?

A. The Sun is made up of coal, that slowly burns up to emit the energy we observe today

B. Inside the Sun, a process called nuclear fusion occurs that powers the Sun

C. The Sun is slowly getting smaller and is converting its gravitational potential energy into light

D. Because the Sun is very hot and ionized, there is a semi-continuous electric discharge happening

(a.k.a., lightning) that generates the light that we see

A spy satellite orbiting Earth that is designed to &ldquoresolve&rdquo objects the size of people needs to have a

A. that fully reflects X-rays so as to be able to penetrate the Earth&rsquos atmosphere

B. as large as 10 meters because it is a really difficult job to see a person at such a large distance

C. of medium size, say one foot, because this task is neither very difficult nor very easy

D. that needs not be very big, say three inches, since the spy satellite is orbiting so close to the Earth

According to Newton&rsquos laws, how does the amount of gravitational force exerted on Earth by the Sun

compare to the amount of gravitational force exerted on the Sun by Earth?

A. The amount of force exerted on Earth by the Sun is greater by the ratio of the Sun&rsquos mass to

B. The amount of force exerted on the Sun by Earth is negligible

C. The amount of force exerted on the Sun by Earth is greater by the ratio of the Sun&rsquos mass to

D. The amount of force exerted on the Sun by Earth is the same as the amount of force

exerted on Earth by the Sun

Suppose that Planet Q exists such that it is an identical planet to Earth in mass and size, yet orbits

the Sun at a distance of 3 AU. How does the amount of gravitational force exerted on Planet Q by the

Sun compare to the amount of gravitational force exerted on Earth by the Sun?

A. The amount of force on Planet Q is 1/3 the force on Earth

B. The amount of force on Planet Q is 3 times the force on Earth

C. The amount of force on Planet Q is 1/9 the force on Earth

D. The amount of force on Planet Q is 9 times the force on Earth

Which of the following would cause the gravitational force between the Moon and the Earth to decrease

A. Double mass of the Earth

B. Halve the mass of the Earth

C. Quadruple the mass of the Moon

D. Halve the radius of the Moon

The visible part of the electromagnetic spectrum can be divided into seven color bands: red, orange,

yellow, green, blue, indigo, and violet (from long to short wavelength). A single photon of which of

these colors has the greatest amount of energy?

The entire electromagnetic spectrum can be divided into seven bands: radio, microwave, infrared,

visible, ultraviolet, X ray, and gamma ray (from longest to shortest wavelength). To which of these

two bands is Earth&rsquos atmosphere the transparent?

B. ultraviolet and infrared

C. visible and ultraviolet

Which power of a telescope might be expressed as &rdquo0.5 seconds of arc&rdquo?

Which power of a telescope is the most important?

What advantage do the builders of large telescopes today have over the previous generation of telescope

A. Large mirrors can now be made thinner and lighter than before

B. Tracking celestial objects today is computer controlled and can take advantage of simple/cheap

C. High-speed computing today can be used to reduce the effect of Earth&rsquos atmosphere

The primary mirror of telescope A has a diameter of 20 cm, and telescope B has a diameter of 100 cm.

How do the light gathering powers of these two telescopes compare?

A. Telescope A has 5 times the light gathering power of telescope B

B. Telescope B has 5 times the light gathering power of telescope A

C. Telescope A has 25 times the light gathering power of telescope B

D. Telescope B has 25 times the light gathering power of telescope A

An astronomer proposes to install an adaptive optics system on the successor to the Hubble Space

Telescope, the &ldquoJames Web Space Telescope.&rdquo This idea is:

A. Wonderful because it compensates the blurring due to the atmosphere

B. Wonderful: it compensates the thermal stresses due to the enormous heat load from the Sun

C. Nonsense!, it is a space telescope above the atmosphere

D. Nonsense!, the JWST is so large that is does not need any adaptive optics

What do the newer light-sensitive electronic CCD chips do better than the older photographic plates

coated with light-sensitive chemicals?

A. They have a greater sensitivity to light

B. They can detect both bright and dim objects in single exposure

C. The CCD images are easier to manipulate

Why must far-infrared telescopes be cooled to a low temperature?

A. To reduce interfering heat radiation emitted by the telescope

B. To protect the sensitive electronic amplifiers from overheating by sunlight

C. To improve their poor resolving power

D. To improve their poor magnifying power

If the temperature of star B is twice the temperature of star A, what can we say about the energy

emitted by the surface of star B compared to the energy emitted by star A?

A. Each square meter of B emits 2x as much energy per second as A

B. Each square meter of B emits 4x as much energy per second as A

C. Each square meter of B emits 8x as much energy per second as A

D. Each square meter of B emits 16x as much energy per second as A

Which subatomic particle(s) ha(s)(ve) no charge?

The amount of electromagnetic energy radiated from every square meter of the surface of a black body

A. proportional to temperature

B. inversely proportional to temperature

C. proportional to temperature to the fourth power

D. inversely proportional to temperature to the fourth power

The wavelength of maximum intensity that is emitted by a black body is:

A. proportional to temperature.

B. inversely proportional to the temperature

C. proportional to temperature to the fourth power

D. inversely proportional to temperature to the fourth power.

. Of the following, which color represents the lowest surface temperature for a star?

What conditions produce a bright (emission line) spectrum?

A. a hot solid, liquid, or high-density gas

C. light from a continuous spectrum source passing through a cooler low-density gas

Which of the following is true of an atomic nucleus?

A. It contains all of an atom&rsquos positive charge

B. It contains no electrons

C. It contains more than 99% of an atom&rsquos mass

What is the acceleration of gravity of Earth?

B. about 10 m^2/s^2 downwards

If your mass is 60 kg on Earth, what would be your mass on the Moon?

Suppose an object is moving in a straight line at 50 km/hr. According to Newton&rsquos first law of motion, the object will

A. continue to move in the same way forever, no matter what happens

B. continue to move in the same way until it is acted upon by a force

C. eventually slow down and come to a stop

D. continue to move in a straight line forever if it is in space, but eventually come to a halt if it is on Earth

Gasoline is useful in cars because it has

A. gravitational potential energy

B. chemical potential energy

C. electrical potential energy

Which of the following statements correctly describes the law of conservation of energy?

A. An object always has the same amount of energy

B. Energy can change between many different forms, such as potential, kinetic, and thermal

C. The fact that you can fuse hydrogen into helium to produce energy means that helium can be turned into hydrogen to produce energy

D. It is not really possible for an object to gain or lose potential energy, because energy cannot be destroyed

The wavelength of a wave is

B. the distance between two adjacent peaks of the wave

C. the distance between a peak of the wave and the next trough

D. the distance between where the wave is emitted and where it is absorbed

Which of the following statements about electrical charge is true?

A. Two negative charges will attract each other

B. Two positive charges will attract each other

C. A positive charge and a negative charge will repel each other

D. positive charge and a negative charge will attract each other

Which of the following statements about electrons is not true?

A. Electrons orbit the nucleus somewhat like planets orbiting the Sun

B. Within an atom, an electron can have only particular energies

C. An electron has a negative electrical charge

D. Electrons have a lot of mass compared to protons or neutrons

Observations of radio waves from astronomical objects suffer from poorer resolution than visible observations because

A. the signals are so weak in the radio region.

B. the wavelength of radio waves is much longer than the wavelengths of visible light.

C. radio telescopes are generally much smaller in diameter than optical telescopes.

D. it is very difficult to detect radio waves.

You are in a space ship heading directly towards 3 stars. The stars are the same distance away from

you. One star is red, one star is yellow, and one stars is blue. Which star has a blueshifted spectrum?

Dubhe, in Ursa Major, is a spectroscopic binary star 2 stars each have more mass than the Sun, but

separated by 23 AU. They orbit every 44 yr. Why aren&rsquot these stars a visual binary?

A. One is always in front of the other

B. They are too far away to resolve

C. They are too faint to see

D. They both emit mostly non-visible light

Imagine that the Sun&rsquos core was somewhat cooler than it is today. What would that change about fusion

A. Fusion could not happen

B. Fusion reactions would be less frequent

C. Fusion reactions would happen at a higher rate

D. H would not fuse, but He would

Imagine you blow up a balloon and knot it. Then you take the balloon into the freezer department at

Costco. What will happen to the balloon?

A. The balloon will expand

B. The balloon will shrink

C. The balloon will start leaking

Two stars have same Temperature (T), but 1 has 2x bigger radius (R) How do their Luminosities (L)

A. Bigger star has 4x bigger L

B. Bigger star has 2x bigger L

C. Bigger star has 2x smaller L

D. Bigger star has 8x bigger L

Two stars have same T, but one star has 4x bigger Luminosity. How do their Radii compare?

A. Brighter star has 16x smaller R

B. Brighter star has 4x smaller R

C. Brighter star has square root of 8x smaller R

D. Brighter star has 2x larger R

Two stars have the same apparent brightness (b), but one is further away than the other one. Which

has the larger luminosity?

A. They have the same luminosity

B. Can&rsquot tell with the provided info

C. The more distant one has higher luminosity

D. The more distant one has lower luminosity

The stars Antares and Mimosa have the same luminosity Antares is spectral type M and Mimosa is

spectral type B. Which star is larger in radius?

D. Insufficient information to determine

A. a numerical scale that measures stellar brightness

B. a measure of the distance of a star

C. the location of a star in the HR diagram

D. a numerical scale that measures stellar faintness

The apparent magnitudes of the Sun, Proxima Centauri and Sirius are approximately -26, +11 and

-1.5, respectively. Rank these three objects from brightest to faintest (to the human eye).

A. a numerical scale that measures the intrinsic power of stars

B. a measure of the distance of a star

C. the apparent brightness of a star if it were at a distance of 10 pc

D. a measure of the temperature of a star

A Hertzsprung-Russel diagram is a plot of the following stellar properties:

B. color versus apparent brightness

D. temperature versus luminosity

The spectral sequence (OBAFGKM) sorts stars according to

On a Hertzsprung-Russell diagram, where would we find stars that are cool and dim?

On a Hertzsprung-Russell diagram, where on the main sequence would we find stars that have the

On a Hertzsprung-Russell diagram, where would we find white dwarfs?

The mass-luminosity relation is valid for:

The stellar main-sequence is determined by:

A. hydrogen burning in the stellar core

B. helium burning in the stellar core

C. deuterium burning in a shell around the core

What would the HR diagram look like if we plotted brightness (b) on the y-axis instead of luminosity

A. About the same as if we plotted using L

B. A complete jumble, with no patterns

C. The main sequence would still be obvious, but the white dwarfs and giants/supergiants would be

D. The patterns would be reversed, like a mirror image

Considering supergiants (SG), white dwarfs (WD), main-sequence stars (MS) and giants (G), which

ordering in absolute luminosity is most correct? (from bright to faint)

What type of spectrum (in visible light) would you see from a reflection nebula?

A. Emission, because the dust is heated by starlight

B. Absorption, because the dust is reflecting starlight

C. Absorption, because the dust is scattered thinly in space

D. Continuous, because the dust is solid

Interstellar dust is made up of

D. silicon, carbon, oxygen & iron

A dark cloud is characterized by

A. the absence of stars in certain regions when taking optical images of the sky, while infrared images do show the stars

B. the absence of stars in certain regions when taking optical images of the sky

C. the absence of stars in certain regions when taking x-ray images of the sky

D. the absence of stars in certain regions when taking infrared images of the sky, while optical images do show the stars

When you see a reflection nebula, what else might you see nearby

Which of the following is the most common type of main-sequence star?

If the temperature of star B is twice the temperature of star A, what can we say about the energy emitted

by the surface of star B compared to the energy emitted by star A?

A. Each square meter of B emits 2x as much energy per second as A

B. Each square meter of B emits 4x as much energy per second as A

C. Each square meter of B emits 8x as much energy per second as A

D. Each square meter of B emits 16x as much energy per second as A

Which of the following is not known to be a component of the interstellar medium?

A giant molecular cloud typically needs an external triger to start collapings to start forming stars.

A. Galaxy-scale spiral shock waves

B. Colliding molecular clouds

During a star&rsquos formation, the protostar shrinks from gravity. How does its rotation change?

A. Its rotation will slow down.

B. Its rotation will stay the same

C. Its rotation will speed up

D. Its random, so we can&rsquot tell

Consider the formation of stars form the interstellar medium, which of the following phases do they

The temperature of a gas is a measure of the:

B. amount of heat that flows out of the gas

C. total number of atoms in the gas

D. average motion of its atoms

If a star has weak Balmer lines in its spectrum, what are possible reasons?

A. The star is much cooler than 10,000 K.

B. The star is much warmer than 10,000 K.

C. The star contains no hydrogen

D. either the star is much cooler than 10,000 K or the star is much warmer than 10,000 K

The luminosity (total energy emitted per second) of a star is an excellent measure of:

B. the mass lost from the Sun due to magnetic reconnection (per second)

C. the temperature of the star

D. the amount of hydrogen converted into helium (per second)

Which is closest to the temperature of the core of the Sun?

How does the Sun generate energy today?

D. gravitational contraction

The light radiated from the Sun&rsquos surface reaches Earth in about 8 minutes, but the energy of that light

was released by fusion in the solar core about

C. about a hundred years ago

D. about one hundred thousand years ago

Since all stars begin their lives with the same basic composition, what characteristic most determines


Ask a NASA astronomer! Is there proof that the Earth is round?

Dr. Michelle Thaller is an astronomer who studies binary stars and the life cycles of stars. She is Assistant Director of Science Communication at NASA. She went to college at Harvard University, completed a post-doctoral research fellowship at the California Institute of Technology (Caltech) in Pasadena, Calif. then started working for the Jet Propulsion Laboratory's (JPL) Spitzer Space Telescope. After a hugely successful mission, she moved on to NASA's Goddard Space Flight Center (GSFC), in the Washington D.C. area. In her off-hours often puts on about 30lbs of Elizabethan garb and performs intricate Renaissance dances. For more information, visit NASA.

Michelle Thaller: So, Oscar, you asked the question, &ldquoWhat are some of the easiest ways that you can prove that the Earth is round?&rdquo Because apparently, this is something that we&rsquore debating&mdashI have no idea why.

That&rsquos a hard thing for me to even start talking about because there are so many proofs that the Earth is round, it&rsquos difficult to know where to start. And it&rsquos not okay to think that the Earth is flat. This is not a viable argument.

I have friends who have been on the International Space Station, they have orbited the Earth once every 90 minutes I've had personal experience with people who have been up in space and can see with their own eyes that the Earth is round. And of course, we&lsquove taken all of these amazing pictures from space they&rsquore so beautiful, all those pictures of the Earth.

So I don&rsquot really know what&rsquos going on right now with this 'Earth is flat' thing, but I will tell you that this is one of the things I really enjoyed teaching my own astronomy class about because there are proofs all around you. It is not difficult to know that the Earth is round. In fact, people have known of this for way more than 2,000 years. The ancient Greeks actually had a number of really elegant, wonderful proofs that the earth was a sphere.

So let&rsquos start from the simple to the slightly more complicated. One of the things you can see yourself, with a pair of binoculars, is if you actually go out to a lake and there are boats on that lake, the farther away a boat is the more the bottom of the boat will disappear, and you&rsquoll basically just see the mast of the boat. And as a boat goes farther and farther away the last thing you will see is the very top of the mast of that boat, and that&rsquos because the boat is actually going over the horizon that&rsquos curved&mdashand that means that as it goes farther and farther away you see less and less of the bottom of it, and more of the top of that. You can see that with binoculars by an ocean, by a lake, it&rsquos really easy. That wouldn&rsquot happen if the Earth were flat&mdashyou would simply see the boat getting smaller and smaller and smaller as it went farther away, but you&rsquod be able to see the whole thing with the same proportions.

Now, another way that you can tell that we&rsquore on a sphere is to think about how there&rsquos something called the tropics on the Earth, and the tropics are places near the equator of the earth were sometimes the sun is overhead in the sky. This was actually something that the Greeks used, not only to prove that the Earth was round about 2000 years ago, but they actually measured the circumference of the Earth, accurate to within just a couple percent. 2,000 years ago we&rsquove known that the Earth was round.

There was a really brilliant Greek scientist called Eratosthenes, and Eratosthenes noticed that there was a town called Syene, and on a certain date the sun would actually shine straight down to the bottom of a well. That meant the sun was directly overhead you could look down a well and see the sun shining back at you.

And on the very same date, farther away in the city of Alexandria, that didn&rsquot happen. The sun was not directly overhead, it was a slight angle, and all that Eratosthenes did was he measured the difference in the angle of the sun. It was straight overhead in Syene in Alexandria it was a little bit less than overhead, and he rationed that that change in angle from one city to another was probably indicative of us being on a curved surface, and you could make all kinds of measurements even between those two cities and see that the angles were different&mdashthe sun was at a different place in the sky. Using this, he actually measured the circumference of the Earth, and he got it right 2,000 years ago.

So another really simple proof is that on any given date, at different cities and different places around the world, the sun is at different angles in the sky. That wouldn&rsquot happen if the Earth wasn&rsquot round.

Then there are some other proofs that are a little more obscure, but they&rsquore actually really lovely. One is to observe what happens during a lunar eclipse. Now, a lunar eclipse happens when the Earth casts a shadow on the moon. The moon actually goes dark, in fact, if you&rsquove seen one you can actually see the Earth&rsquos shadow go across the moon, and when the moon is entirely in the Earth&rsquos shadow the moon looks kind of dark and even kind of red-colored it&rsquos really, really beautiful.

What&rsquos happening, in that case, is that the sun is on one side of the Earth&mdashthe Earth is in the middle&mdashand the Earth is casting a shadow on the moon, and as the shadow moves across the moon you&rsquoll notice that the shadow is curved, it&rsquos round.

And so something like the sun that&rsquos bigger than the Earth and is able to cast a shadow of the Earth on the moon can actually show you the shape of the Earth. &ldquoAh-ha!&rdquo you might say, &ldquobut could the Earth to be a disk? Could it be flat but it&rsquos actually still shaped like a disk, not like a sphere?&rdquo

There was a Greek scientist called Aristarchus and what he noticed was that you can get a lunar eclipse at many different angles where the sun is sometimes the shadow goes straight across the moon, sometimes it just kind of glances the moon&mdashjust a little bit is in shadow just on the top or on the bottom. From every different vantage point, every different angle the sun is casting a shadow, you always get a perfectly curved shadow. The only shape that can cast a shadow that&rsquos curved from any direction you put the light is a sphere.

So people have known that the Earth is spherical for thousands of years. It&rsquos not okay to say that the Earth is flat. This is some sort of strange denial, I don&rsquot know where it comes from, and it&rsquos something where I keep getting this question. We really need to put this question to bed because we&rsquove known the Earth is a sphere for a long time.

There&rsquos even some well-meaning people who say, &ldquoI don&rsquot really believe the Earth is flat, but I&rsquom not really sure what to think about it.&rdquo And they&rsquove asked me some interesting questions, like they&rsquove heard that space is a very hot, that when you go up above the atmosphere the temperature of space is millions of degrees, which is true. The problem is there&rsquos basically no air at all. So the gas right around the Earth is actually millions of degrees hot. That&rsquos actually true, but there&rsquos almost none of it, there&rsquos almost nothing. Like one single proton whizzes by you at a temperature of a million degrees, it&rsquos not the same as temperature in the air, it&rsquos not the same thing at all. So that's one that I get sometimes.

And the other one is&mdashI actually said this to somebody, and I couldn&rsquot believe they had never thought of it&mdashthat with binoculars you can see planets, you can see Saturn and Jupiter, you can see Mars with a telescope, the sun and the moon, everything else you see in the solar system is a sphere. So we&rsquore the one thing that is different? And that actually made somebody who was more interested in actually hearing information, that actually got them to think. They were like, &ldquoYou&rsquore right&hellip everything else we take a picture of is a sphere!&rdquo

Hey flat Earthers, it's time to put your theory to bed once and for all! A curious stargazer by the name of Oscar has submitted a question to Big Think's 'Ask an astronomer' series with NASA's Michelle Thaller. Oscar wants to know: "What would be the easiest proof that the Earth isn’t flat, that I could come back with whenever I get challenged on this issue?" Thaller sets the record straight. "There are so many proofs that the Earth is round, it’s difficult to know where to start. And it’s not okay to think that the Earth is flat this is not a viable argument," she says. The ancient Greeks figured out we were living on a sphere over 2,000 years ago, and there are things you can do to prove that the Earth is indeed round—just go to a body of water and look at ships or boats on the horizon with binoculars. Thaller explains three observable proofs that instantly debunk flat-Earth theory with irrefutable evidence of the Earth's round, curvaceous, gloriously spherical shape. You can follow Michelle Thaller on Twitter at @mlthaller.


Curious Kids: Why don’t the planets closest to the Sun melt or burn up?

Chris Tinney is an employee of UNSW Sydney, a Fellow of the Astronomical Society of Australia, a member of the Australian Academy of Science's National Committee for Astronomy, and a Non-Executive Director of Astronomy Australia Limited.

Vennote

UNSW provides funding as a member of The Conversation AU.

Die Conversation UK ontvang befondsing van hierdie organisasies

This is an article from Curious Kids, a series for children. The Conversation is asking kids to send in questions they’d like an expert to answer. All questions are welcome – serious, weird or wacky!

Can you tell me why the planets closest to the sun don’t melt or burn up, please? – Sophie, aged 6, Brisbane.

Hi Sophie. That’s a good question.

The planets closer to the Sun than the Earth are indeed hotter than the Earth is. But that still doesn’t make them hot enough to melt the rocks that they are made from!

Mercury is the small, rocky planet nearest the Sun. The side that faces the Sun has a temperature of around 430℃. Remembering that 100℃ is the temperature at which water boils, that make 430℃ very hot indeed. In fact, it’s hot enough to melt some types of metal, like lead.

However, Mercury is not made of lead. It is made of rocky materials that have melting points above about 600℃.

So while Mercury is indeed very hot, it is not hot enough to melt. And certainly not hot enough to boil or turn into gas.

Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to us. They can:

* Email your question to [email protected]
* Tell us on Twitter by tagging @ConversationEDU with the hashtag #curiouskids, or
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Please tell us your name, age, and which city you live in. You can send an audio recording of your question too, if you want. Send as many questions as you like! We won’t be able to answer every question but we will do our best.