The Origin of the Universe Massimiliano Galeazzi Miami, 20 November 2002MALS 601

Summary The Scientific method The view of the Universe before 1900: The Greeks The Heliocentric system The view of the Universe after 1900: Einstein Theory of relativity Beyond the solar system Hubble law The Big Bang theory

The Scientific Method Observations Theory Predictions Experimental verification Philosophy

Observations Theory Predictions Experimental verification Sun

Observations Theory Predictions Experimental verification Sun Moon

Observations Theory Predictions Experimental verification Sun Moon Stars

Observations Theory Predictions Experimental verification Sun Moon Stars

Theory Observations Theory Predictions Experimental verification Theory 1Theory 2 Philosophy

Geocentric theory Observations Theory Predictions Experimental verification Movement is not so simple Philosophy The movement is not perfectly periodic There are monthly, annual, and longer term changes

Geocentric theory Observations Theory Predictions Experimental verification Movement is no so simple Planets Mars Philosophy

Geocentric theory Observations Theory Predictions Experimental verification Movement is no so simple Planets Distance to the objects Philosophy

Geocentric theory Observations Theory Predictions Experimental verification Philosophy Ptolemy, The Almagest, A.D. c.100-c.178

Geocentric theory Observations Theory Predictions Experimental verification Philosophy

Geocentric theory Observations Theory Predictions Experimental verification Philosophy EARTH SUN Mercury Venus

Geocentric theory Observations Theory Predictions Experimental verification Philosophy EARTH SUN Mercury Venus Simplicity

“Simpler” theories Observations Theory Predictions Experimental verification Heliocentric system: the planets (including Earth) rotate around the Sun, and the Earth is also spinning around its axis Pythagoreans, Aristarchus of Samos, Plato (?), Copernicus “Hybrid” geocentric system: the Earth is not moving, the planets rotate around the Sun that rotates around the Earth Heraclides of Pontus, Tycho Brahe

Heliocentric theory Observations Theory Predictions Experimental verification Nicolaus Copernicus, On the Revolutions of the Heavenly Spheres, Johannes Kepler, Epitome of Copernican Astronomy, The Harmonies of the World, Galileo Galilei, Sidereus Nuncius,

Heliocentric theory Observations Theory Predictions Experimental verification

The phase of Venus Observations Theory Predictions Experimental verification

The phase of Venus Observations Theory Predictions Experimental verification Galileo Galilei, c1610

Parallax Observations Theory Predictions Experimental verification

Parallax winter Observations Theory Predictions Experimental verification

Parallax summer Observations Theory Predictions Experimental verification

Parallax summer Observations Theory Predictions Experimental verification 1832 Alpha Centauri (nearest star), Henderson Vega, Friedrich von Struve 61 Cygni, Friedrich Bessel

Beyond the solar system 1) High concentration of stars along the milky way  The stars are distributed more in a disk than in as sphere

Beyond the solar system 2) The star distribution in the milky way is asymmetric, with respect to the Earth, but is rather symmetric with respect to a point in the constellation of Sagittarius (Shapley, 1915)  The Sun is not at the center of the Galaxy

Beyond the solar system 3) There are other galaxies in the Universe in addition to ours (Hubble)

Beyond the solar system 4) There are billions of galaxies in the Universe  Solar System  Galaxy  Universe  COSMOLOGY

Doppler effect

Doppler Effect in Galaxies Earth Movement Fast toward us Slow toward us Not moving Slow away from us Fast away from us

Hubble law (redshift)  Speed = H · distance (H = Hubble constant) Edwin Hubble 1929 Observations Theory Predictions Experimental verification ALL DISTANT GALAXIES ARE RECEDING FROM US

Consequences of Hubble Law If all the galaxies move away from us, does it mean that we are at the center of the Universe? What happens if we rewind the tape of the Universe? How old is the Universe?

Expansion of the Universe If all the galaxies move away from us, does it mean that we are at the center of the Universe? Raisin Cake Balloon

Expansion of the Universe What happens if we rewind the tape of the Universe? REWIND

Age of the Universe  speed = H · distance AGE OF THE UNIVERSE IS APRROXIMATELY THE INVERSE OF THE HUBBLE CONSTANT: T ~ 1/H T ~ years = 20,000,000,000 years

Evolution of the Universe What happened at the beginning? What will happen in the future? COLD BIG BANG HOT BIG BANG Observations Theory Predictions Experimental verification

The Big Bang Theory Observations Theory Predictions Experimental verification

The Big Bang Theory Observations Theory Predictions Experimental verification

The Big Bang Theory Can we try to “see” the explosion? YES!!! Speed of light: 300,000 Km/s ~ 675,000,000 Miles/h distance = 20,000,000,000 light years ~100,000,000,000,000,000,000,000 Miles Observations Theory Predictions Experimental verification

The cosmic microwave background Observations Theory Predictions Experimental verification Arno Penzias and Robert Wilson, 1965 (Nobel Prize in 1978)

What will happed in the future?

What happened before the Big Bang? ? Philosophy