The Search for the Complete History of the Cosmos Neil Turok * The Big Bang * Dark Matter and Energy * Precision Tests * A Cyclic Universe? * Future Probes
BIG Questions * What are the Laws of Nature? * What is the Universe made of? * How big/curved is the Universe? * How fast is it expanding? * How did galaxies, stars and planets form? * How did the Universe begin? * How will it end?
Unreasonable effectiveness Of Theory
Big Bang Cosmology Assume: Hot, uniform, expanding initial state + laws of gravity, thermal, nuclear + particle physics Evidence: Uniform Expansion Hot Radiation filling space Light Element Abundances
Uniform Expansion:......... Speed oc distance (Hubble, 1930)
Uniform Expansion Velocity (km/sec) 40000 30000 20000 10000 (Supernovae, Reiss et al. 1997) V/D~ 65 5 km s -1 Mpc -1 + - 0 0 100 200 300 400 500 600 700 Distance (Mpc)
COBE Maps the Sky (1992) Near-perfect black-body spectrum Intensity Error Bars (X 400) Planck (1905) : origin of quantum mechanics
Primordial Abundances e.g. Deuterium QSO (black hole) Intensity gas cloud (12.5 billion yrs ago) - D fits big bang prediction Wavelength
Seeing the Dark Matter gravitational lensing
Empty space: Dark Energy (Λ) * Only visible to gravity * Energy doesn t grow with speed (Lor.Inv.) * Negative pressure: gravity is repulsive! Simplest way to look for it: acceleration of cosmic expansion Supernovae surveys (1999): Λ> 0!
Cosmic Concordance (late 90s) Einstein: Best Fit: Expansion Rate = Density + Curvature Flat Universe, fractional densities Ω DE ~.7, Ω DM ~.25, Ω ord ~.05, Ω ν ~.003, Ω rad ~.0003 + small, growing mode, scale-invariant, density variations Fits a wide array of observations: many alternative models ruled out
Looking Back to the Beginning 13.6 billion lt yrs 300,000 lt yrs
The Wilkinson-MAP Satellite (2003)
The Wilkinson-MAP Satellite
The Cosmic Microwave Sky (~20 resolution)
Comparison with COBE (7 o resolution) (1/3 o resolution)
Theory versus Reality Fluctuation Level: Temperature Polarisation <TE> predicted by Coulson et al 1994 100 10 1.1 (l = 2π/θ) Angle on Sky (Degrees)
Polarisation of the Cosmic Radiation
CMB Polarisation Observed Kovac et al. 2002 Sum Difference 100 Declination (arcmin) 50 0 50 100 5 uk 100 50 0 50 Right Ascension (arcmin) 100 100 50 0 50 Right Ascension (arcmin) 100
TQ correlation T Q θ Coulson, Crittenden, NT 1994
Forward with Newton 3.10 5 yrs 2.10 6 1.10 9 today
Galaxy Clustering Real Simulated
Back to the BIG Puzzles Why is the Universe so big, flat and smooth? What produced the density variations? Conventional answer (since 1981): INFLATION -a temporary phase of dark energy domination in the early Universe
Inflation Go! V(φ)=Λ Stop! φ Most remarkable side effect: Quantum fluctuations in φ lead to Hawking 1982 small, growing, near-scale invariant density variations (form anticipated by Harrison,Peebles,Z eldovich, 70s)
Inflation de Sitter: Vacuum energy =dynamite! Lorentz invariance implies P=-ρ Scale factor Density.. a = - a (4π G/3) (ρ + 3P).. ρ = - 3 (a/a) (ρ + P) ρ=const, a ~ Exp(Ht) Explains flatness, homogeneity, expansion Vacuum energy ρ=λ produces `free lunch
Doubts about Inflation Start the Universe `by hand Initial singularity? not removed What is φ? Mystery of Λ doubled -> Λ today ~ 10-100 Λ inflation -> perhaps we need a new approach
Brane Worlds String theory -> Extra Dimensions Old idea: Kaluza-Klein `hose-pipe Brane string New idea: we live on a `brane embedded in higher dimensions: - Bulk + Brane
Brane Collision = Big Bang? Khoury et al. (2001)
The Cyclic Universe Steinhardt, NT 2002 branes V d Field-theory d M-theory
The Cyclic Universe Beginning at the present epoch V d dark energy dominates, branes stretch &.
The Cyclic Universe V d Matter diluted away homogeneity & isotropy established (low energy inflating phase)
The Cyclic Universe V d Vacuum energy decays away, branes pulled towards each other
The Cyclic Universe Quantum ripples on branes amplified ->Scale invariant variations! V d
The Cyclic Universe BIG CRUNCH V d collision! but only the extra dimension collapses
The Cyclic Universe Brane ripples Density perturbations in ensuing hot big bang V d
contraction expansion (of extra dimension) The Cyclic Universe BIG CRUNCH BIG BOUNCE V d
The Cyclic Universe V d New era of expanding and cooling
Conventional???? inflation Cyclic bang radiation cold future???? Λ uninvited guest matter dark energy contraction crunch Λ is key player big bounce
Key Observational Test Inflation -> long wavelength gravitational waves. Cyclic model -> none... falsifiable
Gravity Waves from Inflation φ 2 inflation dust Lewis et al 2001
Walking the Planck -ESA 2007
-> will distinguish cyclic model from inflation (bet with Hawking) Polarisation Windows -sensitive only to component of polarisation produced by gravitational waves but not by density variations
Conclusions * We live in a golden age for cosmology * Standard theory works but isn t complete * Potential connections to superstring theory * From philosophy to physics