The History and Philosophy of Astronomy Lecture 23: Steady State vs Big Bang. Presentation

Astronomy 350L (Fall 2006)

The History and Philosophy of Astronomy (Lecture (Lect ure 23: 23: Steady Steady Stat State e vs Big Bang) Bang)

Instructor: Volker Bromm TA: Jarrett Johnson The University of Texas at Austin

Stead St eady y State State vs Big Ban Bang g Uni Univer verse se Perm Pe rman anen ence ce vs ch chan ange ge!! Parmenides

• ch chan ange ge is is illu illusi sion on!! • ti time me has has no no begi beginni nning ng • “Wh “What at is, is, cann cannot ot not not be! be!””

Heraclitus

• eve everyth rything ing is in perpe perpetual tual flux flux!! • bas basic ic el eleme ement nt:: fir fire e • “Panta Rhei!”

Origin of the Big Bang Theory • 19 1922 22:: an expan expandin ding g univer universe se (solving Einstein’s equations of General Relativity without cosmological cosmological constant)

Alexander Friedmann (1888-1925)

Origin of the Big Bang Model • 19 1927 27:: Le Lema mait itre re ind indepe epende ndent ntly ly (re (re-) -) dis disco cover vers s the the expanding-universe solutions of GR

Abbe Abb e Geo Georges rges Lema Lemaitr itre e (1894-1966)

Lemait Lem aitre re mee meets ts Eins Einstei tein n (Pasadena, 1933)

Origin of the Big Bang Model • Lem Lemaitr aitre: e: Imagi Imagine ne that that you you run expa expansi nsion on of universe backwards in time!

observer

Cosmic time

• in dis distant tant pas past: t: uni univer verse se was much denser and hotter!

Origin of the Big Bang Model • 19 1931 31:: Le Lema mait itre re’s ’s “P “Pri rime meva vall At Atom om”: ”:

• Pri Primev meval al atom: atom: super-hea super-heavy, vy, radio radioact active ive!! • Radi Radioact oactive ive decay decay somehow somehow trigg triggers ers expansi expansion! on! Lemaitre: “Father of the Big Bang”

Origin of the Big Bang Model • Geo eorg rge e Gam amow ow 1904 190 4 (Odess (Odessa) a) – 196 1968 8 (Bould (Boulder) er) • distinguished career in nuclear physics (“tunnel effect”) • 1948: theory of Big Bang nucleosynthesis (with R. Alpher)

• fa famo mous us po popu pula lari rize zerr of sc scie ienc nce e (“Mr. Tompkins in Wonderland”)

The Riddle of the Chemical Elements Abund Ab undanc ance e vs at atomi omic c numbe numberr

• Hydrogen and helium by far the most abundant cosmic elements • Why: 1 He atom per 10 H atoms? • Why are all the other elements so very rare?

Big Bang Nucleosynthesis

“Hot Big Bang”

ylem

• Bi Big g ide idea a (Al (Alph pher er an and d Gam Gamow ow 19 1948 48): ): Sy Synt nthe hesi size ze all elements during earliest, hot and dense, phase • Raw materi material al = “Ylem”: “Ylem”: primord primordial ial soup soup of proton protons, s, neutrons, electrons, and photons

Big Bang Nucleosynthesis

• Gr Grea eatt suc succe cess ss:: Big Big Ba Bang ng nuc nucleo leosy synyh nyhes esis is ca can n successfully explain Helium abundance (1 He atom per 10 H atoms) • pub publis lished hed (April (April 1, 1948) 1948) as Alpher Alpher,, Bethe, Bethe, & Gamow Gamow (the “alphabetical paper”: alpha, beta, gamma…)

Big Bang Nucleosynthesis Robert Herman

Ralph Alpher

Big Bang Nucleosynthesis

• Big problem: theory doesn’t work for heavier heavier element elements: s: - He He+n +neu eutr tron on,, He He+p +pro roto ton n un unst stab able le!! - He + He ( Be) unstable!

Modern View of Nucleosynthesis 1. Hydrogen, helium: Big Bang 2. All oth ther er el elem emen ents ts:: In Inte teri rio or of of sta stars rs

• Bri Bridgi dging ng the the “Hel “Helium ium-ca -carbon rbon gap” gap”:: Triple-alpha process (Edwin Salpeter, 1952)

Modern View of Nucleosynthesis

• Succe Successful ssful theory of creating creating the elements elements in stars: stars: - Burb Burbidg idge, e, Burbi Burbidge, dge, Fowl Fowler, er, & Hoyle Hoyle (B2FH 1957)

Predicting Cosmic Background Radiation

photons

• Bi Big g ide idea a (Alp (Alphe herr an and d Herm Herman an 19 1948 48): ): Ou Outt of of primordial fireball in early universe an intense sea of photons that is still around us today

Predicting Cosmic Background Radiation • Exp Expans ansion ion of Unive Universe rse stretc stretches hes light light toward towards s longer wavelength (i.e., redder and less energetic)

• Cos Cosmi mic c ba back ckgro ground und to today day:: red redsh shif ifte ted d in into to microwave region of electromagnetic spectrum!

Predicting Cosmic Background Radiation • Pre Predic diction tion (1948): (1948): Cosmic Cosmic microwa microwave ve backgro background und at a (radiation) temperature of ~ 5 Kelvin

(CMB)

• Why was CMB not dis discov covered ered then then??? ??? (

CMB was eventually discovered in 1965 by serendipity)

- fail failure ure to explain explain creati creation on of elements elements beyond beyond Helium Helium!! - brea breakdown kdown of comm communica unication tion between between theoris theorists ts and experimentalists experime ntalists (radio astronome astronomers) rs) - gene general ral disregard disregard for anythin anything g related related to “Early Unive Universe” rse”

Vatican endorses the Big Bang • Pop ope e Piu ius s XI XIII (1939 – 58) - Eugenio Pacelli • 1951: official endorsement

- sp spee eech ch `T `The he Pro Proof ofs s for for the Existence of God in the Light of Modern Natural Science’ • Big Bang =

moment of Creation

Soviet Union bans the Big Bang • Ma Marx rxis ismm-Le Leni nini nism sm • philo los sop oph hy: dialectical materialism • materi ria alis ism m no creation of matter out of nothing (matter, and therefore the universe, must have existed forever!) • Soviet scientists scientists endorsing Big Bang were sent to `Gulag’!

Cosmic Age Problem

• rec recess ession ion speed speed = (Hubble) (Hubble) cons constant tant x dist distanc ance e • v = H0 x d • (H0=500 km s-1 Mpc-1) - Hu Hubb bble le’s ’s ori origi gina nall value 500

2

• Age of of the univ universe erse (in (in Big Big Bang model model)) shorter shorter than estimated age of the Earth (~ 4 billion years)!!!

History of H0 1200

Compilation by John Huchra

1000

   )    c 800    p    M    /    s    / 600    m    k    (

Baade Baade ident identifi ifies es Pop. Pop. I and II Cepheids

   0

“Brightest “Brightest stars” identified identified as H II regions

   H 400 200

Jan Oort 0 1920

1930

1940

195 0

1 960

Date

1 970

1980

1990

200 0

The Steady State Alternative (1948)

Fred Hoyle (1915-2001)

Hermann Bondi (1919-2005) Thomas Gold (1920-2004)

• work worked ed out at at Cambridg Cambridge e Univers University, ity, Engl England and

Hoyle coins the term “Big Bang” • 19 1950 50:: BBC BBC radio radio in inte terv rview iew • de derog rogat ativ ive e term term for for riv rival al theory to his own steady-state • be befo fore re th that at,, “B “Biig Ba Bang ng”” wa was s called “dynamic evolving model”

Fred Hoyle

• Bo Both th Ho Hoyl yle e and and Gam Gamow ow fo foug ught ht a PR PR bat battl tle! e!

Steady State Alternative Evolving universe (“Big Bang”) • den densit sity y chang changes es with with tim time e • pas pastt diffe differen rentt from from presen presentt • be begi ginni nning ng of ti time me (“Big Bang”) Steady state universe • den densit sity y consta constant nt over over time time • uni univer verse se ne never ver cha change nges s • no beg begin inni ning ng of of tim time e

Steady State Alternative • How does dens density ity cha change nge over over time time? ?

Steady state universe Evolving universe (“Big Bang”)

Steady State Alternative • How can densi density ty be con consta stant nt despi despite te cosmic expansion?

• con contin tinuous uous crea creation tion of of matter matter (“C-fi (“C-field eld”) ”) • Nee Need: d: 1 atom atom per per liter liter per per billio billion n years years

Steady State Alternative • Ho How w and when when is is matt matter er cre creat ated? ed? Evolving universe (“Big Bang”)

Steady state universe

time time

• al alll of of mat matte terr at at beginning of time

• sm smal alll amou amount nts s of of mat matte terr all the time

• For both models: matter is created out of nothing!

Steady State Alternative • ste steady ady-sta -state te equilib equilibrium rium:: Patterns Patterns remain, remain, but matter mat ter flows flows con constan stantly tly `th `throug rough’ h’ them

• A: st stea eady dy st stat ate: e: pattern (here: volume) doesn’t change • B: st stat atic ic ca case se:: nothing changes (e.g., Einstein’s Universe)

Einstein’s Eternal (and static) Universe • 191 1917: 7: Einstei Einstein n construc constructs ts model model of the univers universe e that is eternal and static • ba bala lanc nce e be betw twee een n attractive gravity and repulsive cosmological constant (“anti-gravity”)

• fin finite ite but but without without boundary boundary (spat (spatiall ially y closed) closed)

Steady State Alternative • st stea eady dy-st -stat ate e theory theory obey obeys s perfect cosmological principle 

• cos cosmol mologic ogical al princi principle ple : unive universe rse looks looks everywhere  the same (on average) isotropy and homogeneity • perfec perfectt cosmologic cosmological al princip principle le (PCP): (PCP): univers universe e looks looks everywhere and everywhen the same (homogeneity in space and time)

• aesthe aesthetic tic appeal of PCP PCP because because of higher higher symmet symmetry ry

Stea St eady dy St State ate vs Bi Big g Ban Bang g • Dec Decisi ision on has to come come from from observa observatio tions! ns! 1. Ra Rad dio Ga Gallaxi xies es and Qu Quasa sars rs

Martin Ryle (1918-84)

Cambridge (England) radiotelescope

Stea St eady dy St State ate vs Bi Big g Ban Bang g • Dec Decisi ision on has to come come from from observa observatio tions! ns! 1. Ra Radi dio o Gal Galax axie ies s (RG (RGs) s) an and d Qu Quas asar ars s

Density of RGs vs time Radio emission

N

Ryle Ry le’s ’s ob obse serva rvati tion on

Steady-state

• radio galaxies (discovered in 1950s)

Time

today

Stea St eady dy St State ate vs Bi Big g Ban Bang g • Dec Decisi ision on has to come come from from observa observatio tions! ns! 1. Ra Radi dio o Gal Galax axie ies s (RG (RGs) s) an and d Qu Quas asar ars s

• RGs and qu quas asa ars were mo morre numerous in the past! • Ry Ryle le’s ’s ob obse serv rvat atio ions ns co cont ntra radi dict ct steady-state model, but are in accordance with Big Bang

Martin Ryle (1918-84)

• Ry Rylle wi wins ns 19 1974 74 No Nobe bell Pr Priize in Physics

Stea St eady dy St State ate vs Bi Big g Ban Bang g • Dec Decisi ision on has to come come from from observa observatio tions! ns! 2. Discovery of Cosmic Microwave Background 1965: Bell Labs Holmdel (NJ) horn antenna

• Se Seren rendi dipi pito tous us disco discove very ry:: There is unaccounted `nois `no ise’ e’ in mi micro crowa wave ve band band!! • Wh What at is it? t??? ?? Robert Wilson

Arno Ar no Pe Penz nzia ias s

Stea St eady dy St State ate vs Bi Big g Ban Bang g • Dec Decisi ision on has to come come from from observa observatio tions! ns! 2. Discovery of Cosmic Microwave Background

• Gamow’s old Big Bang fireball prediction!

• a per perfe fect ct th ther erma mall (`blackbody’) spectrum!

Stead Ste ady y Stat State e vs vs Big Ban Bang g

• In 19 1940s 40s an and d 50s, 50s, tw two o riv rival al mod models els of co cosm smol ology ogy:: - “B “Big ig Ban Bang” g” (G (Gam amow ow,, Alph Alpher er,, and Her Herma man) n):: - univ universe erse starte started d out in exceeding exceedingly ly dense and and hot state state - Hyd Hydrogen rogen and and Helium Helium are created created in first first few minute minutes s - univ universe erse is stro strongly ngly evol evolving ving - Stea Steady dy State State (Hoyl (Hoyle, e, Bondi, Bondi, and and Gold): Gold): - un unive iverse rse had no begi beginni nning ng - cont continuou inuous s creat creation ion of matt matter er

• Dec Decisi ision on by observ observati ations ons in favo favorr of Big Bang Bang - Red Redshi shift ft dis distri tribut bution ion of radi radio o galaxie galaxies s and quasa quasars rs (Ryle) (Ryle) - discove discovery ry of cosmic microwave background (Penzias/Wilso (Penzias/Wilson) n)