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 !

Case II: If clustered matter does not dominate: Case I: Flat, matter dominated Universe

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 !

Mass density/critical density 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 Background Anisotropy 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 have negative pressure

Positive pressure time energy density

Negative pressure Matter dominates time energy density

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?

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

Case II: If clustered matter does not dominate: Case I: Flat, matter dominated Universe

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?