Salient Features of the Universe• Homogeneity and isotropy for 6000 Mpc > x > 100 Mpc

• Universe expanding uniformly

• ordinary matter is more abundant than ordinary antimatter

• chemical composition is roughly 75% H, 25% He, + trace

• thermal background of radiation with T~3K

• nearly scale invariant, adiabatic CMB fluctuations

• hierarchy of lumpy structure from 1 kpc to 100 Mpc scales

• matter is a minority (1/4x) of all energy

• ordinary matter is a minority (1/6x) of all matter

• universe is spatially flat

• expansion rate is accelerating

Best evidence: we exist !

0)(

v

t

0)( 1

pt

vvv

G42

130

a

1vrv

a

a

13

4

rG

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v

t

0)( 1

pt

vvv

G42

130

a

1vrv

a

a

13

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rG

ksclustkk kcHH )(2 22232

atk ~~ 3/2

ta

aH

3

2~

Case II: If clustered matter does not dominate:

6.0~~ clustk wherea

kclustkk HH 2322

Case I: Flat, matter dominated Universe 1clust

a ~ 1/1000

a ~ 1/5

~ a(t) grows by only 200

Salient Features of the Universe• Homogeneity and isotropy for 6000 Mpc > x > 100 Mpc

• Universe expanding uniformly

• ordinary matter is more abundant than ordinary antimatter

• chemical composition is roughly 75% H, 25% He, + trace

• thermal background of radiation with T~3K

• nearly scale invariant, adiabatic CMB fluctuations

• hierarchy of lumpy structure from 1 kpc to 100 Mpc scales

• matter is a minority (1/4x) of all energy

• ordinary matter is a minority (1/6x) of all matter

• universe is spatially flat

• expansion rate is accelerating

Best evidence: we exist !

Ma

ss d

ensi

ty/c

ritic

al d

ensi

ty

Hubble constant (x 100 km/s/Mpc)

J. Ostriker & PJS, Nature (1995):

Compelling evidence for Low Matter Density

J. Ostriker & PJS, Nature (1995):

Compelling evidence for Low Matter Density

Fluctuations in the Cosmic Microwave BackgroundAnisotropy

Compelling case for a Flat Universe

J. Ostriker & PJS, Nature (1995):

Compelling evidence for Low Matter Density

Compelling case for a Flat Universe

Only possible if there is Dark Energy

J. Ostriker & PJS, Nature (1995):

Compelling evidence for Low Matter Density

Compelling case for a Flat Universe

Only possible if there is Dark Energy

… but, then, the dark energy better havenegative pressure

Positive pressure

time

ener

gy d

ensi

ty

Negative pressure

Matter dominates

time

ener

gy d

ensi

ty

J. Ostriker & PJS, Nature (1995):

Compelling evidence for Low Matter Density

Compelling case for a Flat Universe

Only possible if there is Dark Energy

… but, then, the dark energy better havenegative pressure

… but, then, the universe must be accelerating

Type IA Supernovae

CosmologicalConstant

orQuintessence?

V

V

V

V

p

p

pT

221

221

221

221

V

Vpw

221

221

w < -1/3 means KE < V/2

scalar fields

atk ~~ 3/2

ta

aH

3

2~

Case II: If clustered matter does not dominate:

6.0~~ clustk wherea

kclustkk HH 2322

Case I: Flat, matter dominated Universe 1clust

Steady expansion

Observed Features of the Universe• Universe is homogeneous and isotropic on lengths > 100 Mpc

• Universe expanding uniformly

• ordinary matter is more abundant than ordinary antimatter

• chemical composition is roughly 75% H, 25% He, + trace

• thermal background of radiation with T~3K

• nearly scale invariant spectrum of CMB fluctuations

• hierarchy of structure from 1 kpc to 1 Mpc scales

• matter is a minority (1/4x) of all energy

• ordinary matter is a minority (1/6x) of all matter

• universe is spatially flat

• expansion rate accelerating

Observed Features of the Universe• Universe is homogeneous and isotropic on lengths > 100 Mpc

• Universe expanding uniformly

• ordinary matter is more abundant than ordinary antimatter

• chemical composition is roughly 75% H, 25% He, + trace

• thermal background of radiation with T~3K

• nearly scale invariant spectrum of CMB fluctuations

• hierarchy of structure from 1 kpc to 1 Mpc scales

• matter is a minority (1/4x) of all energy

• ordinary matter is a minority (1/6x) of all matter

• universe is spatially flat

• expansion rate accelerating

Observed Features of the Universe• Universe is homogeneous and isotropic on lengths > 100 Mpc

• Universe expanding uniformly

• ordinary matter is more abundant than ordinary antimatter

• chemical composition is roughly 75% H, 25% He, + trace

• thermal background of radiation with T~3K

• nearly scale invariant spectrum of CMB fluctuations

• hierarchy of structure from 1 kpc to 1 Mpc scales

• matter is a minority (1/4x) of all energy

• ordinary matter is a minority (1/6x) of all matter

• universe is spatially flat

• expansion rate accelerating

Observed Features of the Universe• Universe is homogeneous and isotropic on lengths > 100 Mpc

• Universe expanding uniformly

• ordinary matter is more abundant than ordinary antimatter

• chemical composition is roughly 75% H, 25% He, + trace

• thermal background of radiation with T~3K

• nearly scale invariant spectrum of CMB fluctuations

• hierarchy of structure from 1 kpc to 1 Mpc scales

• matter is a minority (1/4x) of all energy

• ordinary matter is a minority (1/6x) of all matter

• universe is spatially flat

• expansion rate accelerating

Looking for some problems?

• What is the nature of dark matter?

• What is the nature of dark energy?

• What is origin of supermassive black holes?

• What role does dark energy and cosmic acceleration play?

• Why is the cosmological constant so small?

• What is the origin of matter-antimatter asymmetry?

• Is the inflationary theory correct? (or the cyclic?)

• What is the inflaton or cyclic field responsible?

• How far does space extend?

• Is the Big Bang a beginning of space and time?

• Why are there three large spatial dimensions?