Ch. 14 Cosmology (or “The Whole Enchilada”)

The Universe on the Largest Scale A. No evidence for structure B. Somewhat Homogeneous 1. Strands & voids 2. Similar anywhere, though C. Isotropic: Same # of galaxies in every direction

NRAO - void found in 2007

II. The Big Bang A. Olber’s Paradox - why isn’t the sky bright? B. Early 1900’s discoveries 1. Vesto Slipher found most galaxies were red-shifted 2. Edwin Hubble (1923) - distance to galaxies (Andro.)

C. Hubble’s Law (1929) 1. Hubble compared his distances to Slipher’s velocities: v = Hod 2. Galaxy 2x farther/2x faster 3. Hubble “time”: 1/Ho ~ 15 billion yrs. (assumes constant velocity)

D. The Big Bang All matter & radiation were confined to a single point –the “singularity”, or “primeval atom”. The point expanded rapidly The location & velocity of galaxies today is a result of this “explosion” of space

The Big Bang

4.Hubble’s Law holds as viewed from anywhere Ex/ Coins on a balloon 5. There is no center of the universe- space itself expanded! Ex/ Raisin bread

E. Cosmological Redshift: A photon’s wavelength is stretched as the universe expands Ex/ Wave on a balloon

III. Cosmic Microwave Background A. Penzias & Wilson Bell Labs (1964) B. Radio hiss was the leftover radiation of the Big Bang C. Universe at 380,000 yrs. old

D. Severe redshift of orig. radiation E. Current blackbody temp: 2.7 K F. Seemed to be smooth, though G.Proven by COBE (1989) -not smooth

COBE

WMAP

F. Relativity 1. “Space tells matter how to move.. ..& matter tells space how to curve” 2. Einstein’s cosmological constant was meant to halt the universe

IV. Dark Energy & the Accelerating Universe Fate of the universe 1. Bound or unbound? 2. Critical density: Mass/gravity needed to halt expansion 3. Big Crunch 4. Big Chill: Expansion forever

B. Critical density measurements The ratio of the actual density to the critical density is Ωo. Ωo < 1 Expansion Ωo > 1 Contraction Galaxy counts : Ωo = .01 Ωo = .2 - .3 including dark matter (up to 95% MCluster is dark)

1st Direct “Map” of Dark matter

C. Acceleration 2 groups in the ‘90s compared nearby & distant Type I supernovae Distant galaxies receding less rapidly than Hubble’s Law predicts Universe is accelerating!!

D. DARK ENERGY ?? 1. “Vacuum pressure”- force exerted on empty space 2. Only noticeable on very large scales 3. As space expands, greater effect 4. Not matter or radiation. #1 influence on universe - a new cosmological constant?

E. What We Know 1. Composition a. 65% Dark energy b. 31% Dark matter c. 4% Regular matter 2. The universe is 13.8 billion yrs. old a. Consistent with globular clusters (oldest are ~ 12 billion yrs. old) b. Consistent w/ dark energy

3. Evidence for Inflation! a. Universe experienced faster- than-light expansion early on (Alan Guth, 1980) b. Gravity waves expanded during this “inflation” c. Imprint of gravitational waves detected in the CMB (2014)

V. M-theory & Before the Bang A. “M” for membrane? B. In 1995, Edward Witten united the 5 versions of string theory C. Had to include an 11th dimension (!) D. Do membrane collisions create new universes? (i.e. the Big Bang) E. Do we actually live in a “Multiverse”??? V. M-theory & Before the Bang

F. Penrose / Hawking and the Singularity 1. Hot, dense point 2. How does one escape a black hole? 3. What is inside a black hole?

Deep Field 2014