Salient Features of the Universe
• Homogeneity and isotropy for 6000 Mpc > x > 100 Mpc
• Universe expanding uniformly
• thermal background of radiation with T~3K
• chemical composition is roughly 75% H, 25% He, + trace
• ordinary matter is more abundant than ordinary antimatter
• nearly scale invariant, adiabatic CMB fluctuations
• universe is spatially flat
• hierarchy of lumpy structure from 1 kpc to 100 Mpc scales
• ordinary matter is a minority (1/6x) of all matter
• matter is a minority (1/4x) of all energy
• expansion rate is accelerating
Best evidence: we exist !



  (  v )  0
t


  
v
 (v   ) v 
t

a 
v  r  v1
a
   4G
2


p    0

1
0
a
3
 1

4G  
 
r  1
3



  (  v )  0
t


  
v
 (v   ) v 
t

a 
v  r  v1
a
   4G
2


p    0

1
0
a
3
 1

4G  
 
r  1
3
2
2 2
2



 k  2 H  k  ( 3 H  clust  cs k )  k
2
2



 k  2 H  k  3 H  clust  k
Case I: Flat, matter dominated Universe
clust  1
a 2
H ~
a 3t
k ~ t
2/3
~ a
Case II: If clustered matter does not dominate:
k ~ a

where  ~
0.6
 clust
a ~ 1/1000
~ a(t)
 grows by only 200
a ~ 1/5
Salient Features of the Universe
• Homogeneity and isotropy for 6000 Mpc > x > 100 Mpc
• Universe expanding uniformly
• thermal background of radiation with T~3K
• chemical composition is roughly 75% H, 25% He, + trace
• ordinary matter is more abundant than ordinary antimatter
• nearly scale invariant, adiabatic CMB fluctuations
• universe is spatially flat
• hierarchy of lumpy structure from 1 kpc to 100 Mpc scales
• ordinary matter is a minority (1/6x) of all matter
• matter is a minority (1/4x) of all energy
• expansion rate is accelerating
Best evidence: we exist !
J. Ostriker & PJS, Nature (1995):
Mass density/critical density
Compelling evidence for Low Matter Density
Hubble constant (x 100 km/s/Mpc)
J. Ostriker & PJS, Nature (1995):
Compelling evidence for Low Matter Density
Compelling case for a Flat Universe
Fluctuations in the Cosmic Microwave Background
Anisotropy
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 have
negative pressure
energy density
Positive
pressure
time
energy density
Matter
dominates
Negative
pressure
time
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 have
negative pressure
… but, then, the universe must be
accelerating
Type IA Supernovae
Cosmological
Constant
or
Quintessence?
scalar fields
T








  12  2  V

 
p

 
p
 
 
 p 
w 
p


 12  2  V
 12  2  V
1  2
2
1  2
2
V
V
w < -1/3 means KE < V/2







1 2
 2   V 
2
2



 k  2 H  k  3 H  clust  k
Case I: Flat, matter dominated Universe
clust  1
a 2
H ~
a 3t
k ~ t
2/3
~ a
Case II: If clustered matter does not dominate:
k ~ a

where  ~
0.6
 clust
Steady expansion
Observed Features of the Universe
• Universe is homogeneous and isotropic on lengths > 100 Mpc
• Universe expanding uniformly
• thermal background of radiation with T~3K
• chemical composition is roughly 75% H, 25% He, + trace
• ordinary matter is more abundant than ordinary antimatter
• nearly scale invariant spectrum of CMB fluctuations
• hierarchy of structure from 1 kpc to 1 Mpc scales
• universe is spatially flat
• ordinary matter is a minority (1/6x) of all matter
• matter is a minority (1/4x) of all energy
• expansion rate accelerating
Observed Features of the Universe
• Universe is homogeneous and isotropic on lengths > 100 Mpc
• Universe expanding uniformly
• thermal background of radiation with T~3K
• chemical composition is roughly 75% H, 25% He, + trace
• ordinary matter is more abundant than ordinary antimatter
• nearly scale invariant spectrum of CMB fluctuations
• hierarchy of structure from 1 kpc to 1 Mpc scales
• universe is spatially flat
• ordinary matter is a minority (1/6x) of all matter
• matter is a minority (1/4x) of all energy
• expansion rate accelerating
Observed Features of the Universe
• Universe is homogeneous and isotropic on lengths > 100 Mpc
• Universe expanding uniformly
• thermal background of radiation with T~3K
• chemical composition is roughly 75% H, 25% He, + trace
• ordinary matter is more abundant than ordinary antimatter
• nearly scale invariant spectrum of CMB fluctuations
• hierarchy of structure from 1 kpc to 1 Mpc scales
• universe is spatially flat
• ordinary matter is a minority (1/6x) of all matter
• matter is a minority (1/4x) of all energy
• expansion rate accelerating
Observed Features of the Universe
• Universe is homogeneous and isotropic on lengths > 100 Mpc
• Universe expanding uniformly
• thermal background of radiation with T~3K
• chemical composition is roughly 75% H, 25% He, + trace
• ordinary matter is more abundant than ordinary antimatter
• nearly scale invariant spectrum of CMB fluctuations
• hierarchy of structure from 1 kpc to 1 Mpc scales
• universe is spatially flat
• ordinary matter is a minority (1/6x) of all matter
• matter is a minority (1/4x) of all energy
• 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?