Cosmology -- the Origin and Structure of the Universe Cosmological Principle the Universe appears the same from all directions. There is no preferred location. (The physical laws apply to the whole Universe). Is there a preferred time ? The Distance Redshift Relation (Hubble Law) The Distribution of Matter Large Scale Structure Implications of the finite velocity of light Consequences of star birth and death Cosmological models -- world views How we perceive our Universe and our relation to it Historical models -- geocentric heliocentric galactocentric By mid 20 th century -- 3 models or theories Big Bang -- Father LeMaitre, George Gamow Oscillating Universe Steady State -- Fred Hoyle Early 21 st century Big Bang cosmology firmly established Four Fundamental Forces Gravity ~ m1m2/r 2 Large scale structure and motions Electromagnetic ~ 1/r 2 attraction and repulsion Strong (nuclear) -- nuclear binding force Weak (nuclear) force -- nuclear reactions Grand Unified Theory -- GUT Limit to observable Universe Set by c and age of Universe -- 1/H = 4400 Mpc Hubble radius Standard Big Bang model extrapolating backwards Universe began in a superdense state of matter and energy Time T = 0 ? From t = 0 to sec Planck time -- GUT Gravity separates At t = sec cooled to K Strong nuclear force separates INFLATION occurs At sec K EM force separates At sec K, gm/cm3, proton, neutrons exist Like neutron star At 1 sec (IMPORTANT) + >< e + + e - (E = mc 2 ) Density 10 5/ cm 3, K This reaction ceases, anti-matter no longer created At 3 minutes fusion occurs from p + and n fusion H He4 traces of Li, Be, B At 300, 000 yrs temp cooled to 3000 K Recombination occurs p + + e - atoms Up until this time, Universe was filled with hot, ionized gas a plasma, the photons and electrons interacted Opaque -- the primordial fireball Now transparent to radiation Photons the original BB photons are now fee Predicted by theory to exist but because of expansion cooled or redshifted to 3 K 3 degree background radiation or cosmic microwave background radiation (CMB) Nobel Prize 1978 Subsequent work -- numerous measurements, balloon, satellites COBE WMAP The Big Bang -- the standard model -- ~14 x 10 9 yrs The Early Universe the Hubble Deep Field (HDF) Deepest exposure with HST 10 consecutive days, 342 exposures, Reaching > 30 th mag Small irregular galaxies - among first objects Glow from first stars ? Other considerations -- the critical density of matter, finite or infinite ? and the shape of space Critical Density of the Universe the required density for a flat Universe not contracting due to gravity Need mass and radiation densities radiation from photons (most from BB but redshifted) 4.6 x kg/m 3 matter or mass --- luminous matter 3.6 x kg/m 3 but mass from rotation curves of galaxies and mass required to bind clusters of galaxies -- 2 kg/ m3 (dark matter) Luminous matter ~ 10 % of all matter Today matter dominates over radiation Combined mass density (matter + energy) Critical density c = 3 H 2 / 8 G = 9.2 x kg/ m 3 Density parameter 0 = 0 / c Space Curvature Type Density ( 0 ) Spherical positive Closed > 1 Flat flat Flat = 1 Hyperbolic negative Open < 1 Numerous studies + CMB flat or nearly so +/- 10% But density due to matter m / c = So m < 0 So missing density ! propose missing density (dark energy) Einsteins cosmological constant Type Ia supernovae, the accelerating Universe and dark energy Nobel Prize 2011 Saul Perlmutter Brian Schmidt Adam Reiss So there are three numbers m = 0.2 0.4 (matter, mostly dark) = ? 0 ~ 1.0 +/- 10 % At the beginning of the 21st century: The Universe began in a superdense state; it is flat, expanding, the expansion is accelerating, it is dominated by dark energy, and will expand forever. What about the future ?