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Vital Statistics of the

Today…

 Observational evidence for the  Vital statistics of the Universe  Hubble’s Constant (H 0)  (k)  ( 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 ago.

T = 0 380,000 years Now

The CMB…

Very hot ~ 3K

‘’ ‘Recombination’ Structure Particle/ ‘Freeze-out’ formation Soup ‘ ’

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 Background  from ‘recombination’ at T= 380,000 yrs  Evidence for a HOT beginning

Our Evolving Universe 3

Evidence for the Big Bang

 The of

 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 & 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 to at the +3He (Rare) of nucleosynthesis (~7:1) 9Be 7  2 3 7 Li Levels of H, He and Li also predicted. 6Li 4He 3He 2H 1 makes clear predictions H A=8 based on ‘well understood 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 ‘’ density also of 10

great interest for later studies Abundance (Relative Element to Hydrogen) of ‘’) 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 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  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 + 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 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 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 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’ 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 . Ω = 1 Ω = 2 Found: The expansion rate has increased!

The expansion of the Universe is accelerating!

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Vital statistics of the universe… A new twist?

 What is causing this The Cosmological Constant is back! accelerating expansion?  Some kind of ‘Vacuum ’ ΛΛΛ ΛΛΛ that OPPOSES pull of gravity?

 Also known as: Prediction of Inflation ‘’ 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