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Vital Statistics of the Universe the Big Bang So Far… Vital Statistics of the Universe Today… Observational evidence for the Big Bang Vital statistics of the Universe Hubble’s Constant (H 0) Curvature (k) Density ( Ω) How will it all end? Ho (Expand forever - or collapse?) ΛΛΛ Ω K Our Evolving Universe 1 The Big Bang so far… The universe is expanding & cooling after an initial ‘explosion’ ~14 billion years ago. T = 0 380,000 years Now The CMB… Very hot ~ 3K ‘Inflation’ Matter ‘Recombination’ Structure Particle/photon ‘Freeze-out’ formation Soup ‘Nucleosynthesis ’ Our Evolving Universe 2 PHY111 Our Evolving Universe Lecture 3: Vital Statistics of the Universe Evidence for the Big Bang 1996 type 1 SNe Hubble’s Law × V = H 0 D (H 0=Hubble’s Constant) Evidence for expanding universe (not specifically for Big Bang) The Cosmic Microwave Background Photons from ‘recombination’ at T= 380,000 yrs Evidence for a HOT beginning Our Evolving Universe 3 Evidence for the Big Bang The evolution of galaxies Distant (older) galaxies look different from those nearby. Older galaxies generally smaller, more irregular & more interacting More active galaxies Evidence for changing, non- eternal universe. Earlier lecture ‘Evolution of Galaxies’ Our Evolving Universe 4 PHY111 Our Evolving Universe Lecture 3: Vital Statistics of the Universe Evidence for the Big Bang… The abundance of elements Big Bang Nucleosynthesis predicts: p 4 Mostly Hydrogen & Helium formed - 2H with much smaller quantities of heavier n elements. p 3He n 4He Relative abundance of 4Helium to Hydrogen predicted to be 25% (by mass) of total. Dependent on ratio of proton to neutrons at the +3He (Rare) time of nucleosynthesis (~7:1) 9Be 7 2 3 7 Li Levels of H, He and Li also predicted. 6Li 4He 3He 2H 1 Theory makes clear predictions H A=8 based on ‘well understood physics A=5 Our Evolving Universe 5 Evidence for the Big Bang… The abundance of elements Observations… Observed value Predicted values (Current abundances 1 dependent on density of ~25% ordinary matter at He ‘Allowed’ nucleosynthesis - & density therefore density now). 10 -3 Observations agree VERY D WELL with predictions More STRONG evidence 10 -6 for Hot Big Bang Li -9 (Allowed ‘baryon’ density also of 10 great interest for later studies Abundance (Relative Element to Hydrogen) of ‘Dark Matter’) 0.005 0.01 0.02 ρ Baryon (normal matter) density (% of c) Our Evolving Universe 6 PHY111 Our Evolving Universe Lecture 3: Vital Statistics of the Universe Evidence for the Big Bang… Summary… Overall… Plenty of evidence FOR the Big Bang… Nothing directly AGAINST. Our Evolving Universe 7 Vital statistics of the universe Parameters needed to describe the state (& predict the fate) of The fate of the universe… the Universe : Ω=<1, k=-ve Ω=1, k=0 Hubble’s constant (H0) ?? ρ Ω Density ( or ) Ho Ω ρ ρ Now… • = density/critical density = / c Ω>1, k=+ve Curvature (k) • (For ‘flat’ universe k = 0). Einstein’s General Hubble’s Cosmological Constant Constant Relativity says how it all fits together. Density term Curvature term … Our Evolving Universe 8 PHY111 Our Evolving Universe Lecture 3: Vital Statistics of the Universe Vital statistics of the universe… Measurement of Hubble’s constant Type 1 Many ways to do this Supernovae Study redshift easy: distance challenging need long distances HST Cepheid Variable study (>300 Mlyr or so) Recent results: 73±2±4 km s -1 Mpc -1 (compilation, 2010) 69.8±1.5 km s -1 Mpc -1 (WMAP + galaxy surveys) Our Evolving Universe 9 Vital statistics of the universe… Measurements of curvature Curvature (k) Is dependent on total density Ω. Inflation predicts universe is FLAT! (i.e. k = 0). Curvature can be determined through analysis of the ripples in the CMB Position gives: k = 0 (Flat!) (Also H = 70±2 km/s/Mpc) Our Evolving Universe 10 PHY111 Our Evolving Universe Lecture 3: Vital Statistics of the Universe Vital statistics of the universe… Measurements of density (1) 1) Contribution of stars Density ( Ω) Add up the masses of all stars… Ω = density/critical density ρ ρ = / c ρ -26 -3 c ~ 10 kg.m ~ 6 H atoms per m 3! There are many different ΩΩΩ ~ 0.005 ways of determining the starsstars density of the universe… ~0.5% of what is needed to make a flat universe! Our Evolving Universe 11 Vital statistics of the universe… Measurements of density (2) 2) Contribution of galaxies Over 90% of the Dark total mass of Matter galaxies is in the form of a ‘ Dark Matter ’ Halo Luminous matter R NGC6503 Halo ΩΩΩ galaxies ~ 0.1 ‘Rotation curves’ tell us about distribution Disc < 10% of what is needed to make a & amount of mass in Gas flat universe! galaxies Our Evolving Universe 12 PHY111 Our Evolving Universe Lecture 3: Vital Statistics of the Universe Vital statistics of the universe… Measurements of density (3) 3) Contribution of clusters B) ‘Bulk flow’ study… Using redshift to look at motion A) Gravitational lensing study… of large scale structures… Images of galaxies ‘PSCz’ Infrared warped by Experiment central mass ΩΩΩ ΩΩΩ ≥≥≥ clusters ~ 0.25 Velocitybulkflow 0.25 survey MoreAt darklargest scales we see matter!~25% of what is needed to Mass make a flat universe. distribution Large scale implied by structures warping Our Evolving Universe 13 Vital statistics of the universe… ΩΩΩ - how it all adds up… Results so far… Results so far… Inflation theory and CMB Prediction of Inflation observations indicate: Flat 1 The universe is FLAT universe Ω (ie. total = 1) CMB ripples Bulk Flow Galaxy ~25% of the mass needed is Clusters seen in observations of largest 0.1 structures Galaxy: All Mass Ω Ω Ω Ω BUT - the majority (>90%) of 0.01 the mass in the universe is some form(s) of non-luminous Galaxy: Stars and unknown DARK MATTER … 0.001 Is this enough to 0.0001 0.01 1 100 10000 understand the fate of Scale (Mpc) the universe? Our Evolving Universe 14 PHY111 Our Evolving Universe Lecture 3: Vital Statistics of the Universe Vital statistics of the universe… A new twist? 1999 - Type 1a supernovae studies of Hubble’s law at large distances… Expected: The expansion rate to have decreased due Ω= 0 to pull of gravity. Ω = 1 Ω = 2 Found: The expansion rate has increased! The expansion of the Universe is accelerating! Our Evolving Universe 15 Vital statistics of the universe… A new twist? What is causing this The Cosmological Constant is back! accelerating expansion? Some kind of ‘Vacuum energy’ ΛΛΛ ΛΛΛ that OPPOSES pull of gravity? Also known as: Prediction of Inflation ‘DARK ENERGY’ 1 ΩΩΩΛΛΛ Because it is energy it also All Matter 0.1 Galaxies contributes to the universe’s Ω total mass (or density) 0.01 Stars ΩΩ = ΩΩ + ΩΩΛΛΛ totaltotal mattermatter 0.001 1 0.3 0.7 Scale (Mpc) Our Evolving Universe 16 PHY111 Our Evolving Universe Lecture 3: Vital Statistics of the Universe of which only 1/10 Recipe for the Universe stars! From WMAP data + galaxy clusters, supernovae etc. Our Evolving Universe 17 How will it all end? Λ How does ΛΛ affect the fate Ω= 1 ΛΛΛ of the universe? (Flat) With Even though universe is nearly flat - it will continue Without ΛΛΛ to EXPAND FOREVER… …at an EVER-INCREASING rate What is What is But… And… DARK ENERGY (ΛΛΛ)? DARK MATTER? Our Evolving Universe 18 PHY111 Our Evolving Universe Lecture 3: Vital Statistics of the Universe Summary Evidence for the Big Bang (as against alternative models) includes: The Cosmic Microwave Background. Recent evidence indicates: The evolution of galaxies. A positive cosmological The abundance of elements. constant ( Λ) is causing the expansion of the universe to increase. Vital statistics of the universe: The fate of the universe is to Ho = 73±5 km.s -1Mpc -1 continue to expand and cool forever…… Curvature = 0 (FLAT) × ρ Matter Density = 0.3 c ~98% of the mass of the universe is dark ~85% is exotic ‘Dark Matter’ Our Evolving Universe 19 PHY111 Our Evolving Universe Lecture 3: Vital Statistics of the Universe.
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