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30/04/2012 COSMOLOGY Study of the structure, history, and fate of the Universe THE ANCIENT UNIVERSE THE MODERN UNIVERSE In 1054, a star in the Taurus constellation underwent a supernova. Centuries later, astronomers can observe the Crab Nebula, the glowing remnant of the dead star. A FLAT EARTH GEOCENTRIC MODEL or the importance of men Aristotle (384 BC – 322 BC) Ptolemy (c. AD 90 – c. AD168) (300 years after Aristotle) SKY OBSERVATION HELIOCENTRIC MODEL REVISITED HELIOCENTRIC MODEL Copernicus (1473 – 1543) Tycho Brahe (1546-1601) Astronomical Sextant Armillary Sphere 1 30/04/2012 Tycho Brahe’s Observatory Tycho Brahe’s Instruments THE TELESCOPE SKY OBSERVATION HELIOCENTRIC MODEL REVISITED Kepler (1571 –1630) Galileo (1564–1642) Galileo’s first telescope World’s Largest Telescope Canary Islands LAW OF GRAVITATION GENERAL RELATIVITY F = G M1 M2 / r2 G = 6.673 X 1011 N m2 /kg2 Newton (1643 –1727) mass attracts mass Einstein (1879–1955) Nobel Prize 1921 2D representation of a 4D concept Black Hole: infinite curvature of space-time, attracts all surrounding material Gravity's effect is apparent even at the largest scales: just as gravity keeps the Earth orbiting the sun, it holds these two irregular galaxies M32 and M110 in orbit around the larger Andromeda galaxy. 2 30/04/2012 1919 SOLAR ECLIPSE: PROVING GENERAL RELATIVITY EINSTEIN’S STATIC UNIVERSE Eddington 1882 - 1944 Light bent by the curvature of Space-Time BIG BANG THEORY COMPILING THE EVIDENCE EXPANSION OF THE UNIVERSE: HUBBLE’S LAW v = H0 d General Relativity Cosmological Principle CMB Nucleosynthesis Expansion of Universe Edwin Hubble (1889 –1953) Evolution of Stars and Galaxies EXPANSION OF THE UNIVERSE: REDSHIFT EXPANSION OF THE UNIVERSE Redshift Absorption lines in the optical spectrum of a supercluster of distant galaxies (right), as compared to absorption lines in the optical spectrum of the Sun (left). Arrows indicate redshift. Wavelength increases up towards the red and beyond (frequency decreases). Causes galaxies to appear to be moving apart. The size of the cube will change. The galaxies inside the cube stay the same size. The Big Bang is not an explosion IN space, it is an explosion OF space! 3 30/04/2012 NUCLEOSYNTHESIS OF ELEMENTS EVOLUTION OF GALAXIES The shape of galaxies 14 billion years, 9 billion years, 5 billion years, and 2 billion years (from left to right) after the Big Bang. Notice how galaxies dating from 2 billion years are irregular and blob-like, while those from 9 billion years and onward are more regular spirals. COSMOLOGICAL PRINCIPLE NUCLEOSYNTHESIS OF ELEMENTS The structure and chemical content of astronomical objects provides valuable information about what the universe's conditions must have been like long ago in order to account for currently observed elemental ratios. isotropic homogeneous The universe has no center and expands in nothing! An accretion disk forms during the birth of a star. A forming galaxy COSMIC MICROWAVE BACKGROUND OBSERVATION OF THE UNIVERSE Penzias and Wilson first detected CMB in 1965 at Bell Laboratories in New Jersey. Penzias and Wilson Nobel Prize 1968 Looking farther out in space is looking back in time! COBE (launched in 1989): Cosmic Background Explorer Mather and Smoot Nobel Prize 2006 WMAP: Wilkinson Microwave Anisotropy Probe (launched in 2001) (childhood of universe at 380 000 years) (shows germs of stars and galaxies, gives information about age, composition and form of universe) 4 30/04/2012 ORIGINS OF THE CMB CMB AND REDSHIFT During the first 380,000 years after the Big Bang, the universe was opaque. As the universe expanded and cooled, light and matter decoupled and the universe became transparent. The CMB is a perfect example of redshift. The light first radiated from this process is the CMB. UNDERSTANDING THE CMB MAP THE PREDICTIVE POWER OF THE CMB The CMB is one of the strongest pieces of evidence for the Big Bang model. The Big Bang theory makes highly accurate predictions about the size and types of anisotropies in the CMB as well as its nearly perfect blackbody spectrum, all of which have been verified by experiment and observations. The spherical map of the CMB translates to an oval in the same way a globe translates to a familiar oval map when flattened. THE AGE OF THE UNIVERSE CONSEQUENCES OF THE BIG BANG From redshift data from distant galaxies and supernovae: 13.7 billion years old. 5 30/04/2012 THE VISIBLE UNIVERSE INFLATION, EXPANSION, AND OUR GROWING VISIBLE UNIVERSE The timeline of the Universe is not straight but curved like a bell, reflecting alternating periods of acceleration and deceleration. HISTORY OF UNIVERSE FROM t=0 TO TODAY 6 30/04/2012 INFLATION DARK MATTER: MISSING MASS IN THE UNIVERSE THE FATE OF THE UNIVERSE Hot Dark Matter (HDM) • Low mass fundamental particles which can travel at relativistic velocities: neutrino. • Current theories about structure formation ruled out HDM candidates. Cold Dark Matter (CDM) • heavier fundamental particles, brown dwarf stars and primordial black holes. • WIMPS (Weakly Interacting Massive Particles) are high mass particles which only interact via gravity and the weak force. • Extensions to the Standard Model incorporating supersymmetry predict the existence of WIMPs, requiring that each known fundamental particle have a heavier supersymmetric partner. • WIMPs are the leading CDM candidates. CURRENT RESEARCH DARK ENERGY HUBBLE 1990 (Discovery) Images of the Universe WMAP (2001) Cosmic baby picture Compton (1991-2000) Gamma-Ray Observatory CHANDRA 1999 (Columbia) Oldest quasars SPITZER 2003 Origins and processes of galactic, stellar and planetary evolution 7 30/04/2012 FUTURE RESEARCH UNANSWERED QUESTIONS • Are there undiscovered laws of nature? • Is there a Grand Unified Theory (GUT)? • What is Dark Energy? • What is Dark Matter? • What happened before 10-44 seconds? • Why are there so many different kinds of particles? • Why did antimatter vanish? When launched, the Supernova Acceleration Probe (SNAP) will study the effects of dark energy by surveying distant type Ia supernovae and making detailed measurements of weak gravitational lensing. 8