The Most Incomprehensible Thing About the Universe Is That It Is Comprehensible

The most incomprehensible thing about the Universe is that it is comprehensible. (Albert Einstein)

Living on the Earth may be expensive, but it includes an annual free trip around the Sun. (Anonymous)

Physics is not a religion. It it were, we’d have a much easier time raising money. (Leon Lederman)

January 6, 11 AY13 Astro 13 Galaxies & Cosmology LECTURE 2 Thur 6 Jan 2011 P. Madau

• 15m II Finish Scale of the Universe • 5m III Cosmic Calendar • 15m IV Great Moments in the Universe • 5m V Great Moments in Human History • 10m Break • 15m VI Great Moments in Ancient Cosmology • 15m VII Great Moments in Pre-Modern Cosmology • 15m VIII Great Moments in Modern Cosmology

January 6, 11 AY13 The Astronomical Distance Scale cm OBJECT Light-year 10+18 ONE LIGHT YEAR 1 10+19 Nearest Stars 10 10+20 Thickness of Milky Way 100 10+21 Nearest Globular Clusters 1000 (1K) 10+22 Sun to Milky Way center 10K 10+23 Sun to Large Magellic Cloud 100K 10+24 Sun to Andromeda Galaxy 1000K (1M) 10+25 Virgo Supercluster of Galaxies 10M 10+26 Rich Clusters of Galaxies 100M 10+27 Supercluster of Clusters 1000M (1G) 10+28 Visible Universe 10 G 10+29 ?? Unobserved Universe 100 G

January 6, 11 AY13 Microwave Map of Sky

Temperature Fluctuation Map WMAP Team

Angular Power Spectrum (Caldwell et al 2003)

+SN & +HST ==>

January 6, 11 AY13 From NASA WMAP Homepage Nearby Galaxies (250 Million Ly )

January 6, 11 AY13 January 6, 11 AY13 Abell 2218 Cluster - 2 Billion Light Years Away

January 6, 11 AY13 January 6, 11 AY13 MOON vs Hubble Ultra Deep Field -- 1 Ms Exposure HUDF

January 6, 11 AY13 January 6, 11 AY13 Blowup of Tiny Part of HUDF

January 6, 11 AY13 January 6, 11 AY13 January 6, 11 AY13 January 6, 11 AY13 Massive Black Holes in Quasars (1 Billion Suns)

Sun - Earth = 1 AU 1.5x1013cm = 500 light-s

Sun - Pluto = 40 AU 6x1014cm= 5.5 light-Hours

January 6, 11 AY13 Great Moments in Modern Cosmology

DATE NAME CONTRIBUTION 1916 A. Einstein General Relativity 1929 E. Hubble Expanding Universe 1948 R. Alpher, Predict Cosmic Radiation G. Gamow from Big Bang 19481948 H.H. Bondi Bondi,, T. Gold Propose Proposed Steady Steady State T. Gold,F. Hoyle Theory State Theory 1965 A.F. Penzias Hoyle Discovered Cosmic Radiation 1965 R.A. Wilson Penzias, Discoversupporting CosmicBig Bang model 1981 R.A. GuthWilson etc InﬂationaryRadiation Universesupporting Big Bang 2000 SN teams “Concordance Model” of Univ: 1981 A. Guth etc. Inflationary Universe 2009 WMAP team Flat, open, age=13.7Gyr, 4% 1992Baryons, 73%G. Smoot Dark Energy, etc Fluctuations 23% Dark Matter in Cosmic January 6, 11 AY13 Cosmic Calendar

January 6, 11 AY13 Great Moments in the Universe

After Big Before Red- Epoch Event Bang Today shift 0 ~20 By Singularity Big Bang 10-43 sec “ 10+32 Planck Particle Creation 10-6 sec “ 10+13 Hadronic Proton-Anti-Proton Annihilation 1 sec “ 10+10 Leptonic Electon-Positron Annihilation 1 min “ 10+9 Radiation Helium & Deuterium Creation 10,000 y “ 10+4 Matter Matter Energy Dominates 300,000 y “ 10+3 Decoupling Transparent U. ~1-2 By 18-19 ~20 Structure Galaxy Birth? By Formation 3 By 17 By 6 “ Quasar Birth? 15.4 By 4.6By 0.4 “ Earth is Born 17 By 3 By 0.2 Life Begins 19.8 By 200My 0.01 Mesozoic First Mammals

January 6, 11 AY13 Great Moments in Human History Years Ago Event 70 M Pre-Primates Evolve 20 M Apes Separate from Monkeys 5 M Apeman “ Chimps 2 M Homo Erectus - 600,000 Homo Sapiens 360,000 Use of Fire 40,000 Complex Language ~20,000 Agriculture Invented 13,000 Ceramic Pottery 6,700 Babylonian Calendar 5,500 Writing Developed 3,500BC January 6, 11 AY13 Great Moments in Ancient Cosmology

DATE NAME CONTRIBUTION 2,500 BC Stonehenge Built 2,200 BC ------Astronomy in Egypt, Babylonia, India, China 1,500 BC ------Sundial in Egypt 500 BC Pythagoras Spherical, Rotating Earth Revolving a Central Fire 370 BC Plato Stationary Earth, Planets in Circular Orbits 360 BC Eudoxus 33 Concentric spheres around a Still Earth 330 BC Aristotle 55 Concentric spheres; immutable Heaven 280 BC Aristarchus Heliocentric system !! 140 AD Ptolemy Geocentric system; good epicycle theory

January 6, 11 AY13 Great Moments in Pre-Modern Cosmology

DATE NAME CONTRIBUTION 600-1500 Very Dark Negative BCAD Ages 1543 AD Nicholas Heliocentric model revived Copernicus 1572 Tycho Brahe Sees Nova --> Aristotle wrong ~1600 Johan. Kepler Laws of planetary orbits ~1600 Galileo Galilei Uses telescope: sees moons of Jupiter, sunspots, phases of Venus 1666 Isaac Newton Universal law of gravity ~1750 I. Kant, First concepts of Milky H. J. Lambert, Ways and Galaxies T. Wright ~1800 W. Herschel Observes nebulae; Uranus discovery confirms Newton January 6, 11 AY13 Nicolaus Copernicus devised the ﬁrst comprehensive heliocentric model • Heliocentric (Sun-centered) theory simpliﬁes the explanation of planetary motions • In a heliocentric system, the Earth is one of the planets orbiting the Sun

January 6, 11 AY13 Stars Saturn Jupiter Mars

EARTH Venus Mercury

Heliocentric Model of SUN Copernicus January 6, 11 AY13 A planet undergoes retrograde motion as seen from Earth when the Earth and the planet pass each other

January 6, 11 AY13 January 6, 11 AY13 January 6, 11 AY13 Tycho Brahe’s astronomical observations disproved ancient ideas about the heavens

January 6, 11 AY13 Johannes Kepler proposed elliptical paths for the planets about the Sun

• Tycho Brahe’s data enabled Kepler to deduce his famous laws of planetary motion:

January 6, 11 AY13 Galileo’s discoveries with a telescope strongly supported a heliocentric model

• The invention of the telescope led Galileo to new discoveries that supported a heliocentric model • These included his observations of the phases of Venus and of the motions of four moons around Jupiter

January 6, 11 AY13 • One of Galileo’s most important discoveries with the telescope was that Venus exhibits phases like those of the Moon • Galileo also noticed that the apparent size of Venus as seen through his telescope was related to the planet’s phase • Venus appears small at gibbous phase and largest at crescent phase

January 6, 11 AY13 Phases of Venus are related to the planet’s angular distance from the Sun

January 6, 11 AY13 Geocentric - Epicyclic Models do not explain Galileo’s Venus data

• To explain why Venus is close to the Sun, Ptolemy’s epicycle model never allowed Venus to be on the opposite side of the Sun from the Earth. Thus Venus could never show the phases and sizes seen by Galileo.

January 6, 11 AY13 • In 1610 Galileo discovered four moons, now called the Galilean satellites, orbiting Jupiter. This established that not everything revolved around only Earth.

January 6, 11 AY13