THE BIG BANG HOW CLOSE CAN WE COME Michael Dine May 2003 New York Times April 2003 Reports a debate among cosmologists about the Big Bang lll1 html Dr Tyson who introduced himself as the Frederick P Rose director of the Hayden Planetarium had invited five distinguished cosmologists into his lair for a roasting disguised as a debate about the Big Bang It was part of series in honor of the late and prolific author Isaac Asimov 540 books written or edited What turned out to be at issue was less the Big Bang than cosmologists pretensions that they now know something about the universe a subject about which the public feels some sense of ownership Dr Tyson said Imagine you re in a living room he told the audience You re eavesdropping on scientists as they argue about things for which there is very little data Dr James Peebles recently retired from Princeton whom he called the godfather Dr Alan Guth from the Massachusetts Institute of Technology author of the leading theory of the Big Bang known as inflation which posits a spurt of a kind of anti gravity at the beginning of time and Dr Paul Steinhardt also of Princeton who has recently been pushing an alternative genesis involving colliding universes Rounding out the field were Dr Lee Smolin a gravitational theorist at the Perimeter Institute for Theoretical Physics in Waterloo Ontario whom Dr Tyson described as always good for an idea completely out of left field he s here to stir the pot and Dr David Spergel a Princeton astrophysicist But Dr Smolin said the 20th century revolution was not complete His work involves trying to reconcile Einstein s general relativity which explains gravity as the curvature of space time with quantum mechanics the strange laws that describe the behavior of atoms Quantum mechanics and gravity don t talk to each other he said and until they do in a theory of so called quantum gravity science lacks a fundamental theory of the world The modern analog of Newton s Principia which codified the previous view of physics in 1687 is still ahead of us not behind us he said Although he is not a cosmologist it was fitting for him to be there he said because all the problems those guys don t solve wind up with us Today you are listening to someone seemingly more out in left field a particle physicist Particle physics seeks to determine the laws of nature at a microscopic really submicroscopic level What does this have to do with the Big Bang EVERYTHING With due respect to the New York Times articles like this give a very misleading impression We know There was a Big Bang This even occurred about 13 Billion Years Ago We can describe the history of the universe starting at t 3minutes There is now a huge amount of data and a picture with great detail There are lots of things we don t know With due respect to Lee Smolin the correct address for these questions is Particle Physics We can t answer any of these questions without resolving mysteries of particle physics These will be the subject of this talk What is the dark matter Why does the universe contain matter at all What is the dark energy What is responsible for inflation What happened at t 0 Physical Law and the Universe Newton F ma FG M1M1 R2 Motion of Planets Laws of electricity and magnetism nuclear physics Understanding of Stars Einstein General Relativity Expansion of the Universe EINSTEIN 1905 special relativity photoelectric effect Brownian Motion 1916 General Relativity Culmination of a 9 year struggle to understand Newton s Gravity starting with equivalence principle Tests Precession of Mercury s Orbit Bending of Light Implications for the universe COSMOLOGY Einstein Copernicus Assume the universe is homogeneous and isotropic no special place or direction Einstein s equations have no Static solutions The universe expands Einstein was very troubled remember that at that time c 1920 Astronomers didn t know about galaxies Edwin Hubble who started out as a lazy rich kid became one of the most important of all astronomers HUBBLE 1921 Galaxies move away from us at a speed proportional to their distance The Cosmic Microwave Background Still limited evidence for a Big Bang Gamow Peebles if true there should be a glow left over from this Huge explosion but of microwave radiation not light Objects give off a characteristic spectrum of electromagnetic radiation depending on their temperature blackbody The temperature then was 20 000 degrees today it would be About 6 degrees Discovered by Penzias and Wilson 1969 Today thanks to COBE satellite best measured black body spectrum in nature Artist s Rendering of COBE COBE measured the temperature of the universe 3 minutes Synthesis of the Light Elements CMBR A fossil from t 100 000 years He Li De Produced at t 3 minutes p e Neutrino reactions stop neutrons decay n Results of Detailed Nucleosynthesis Calculations The fraction of the universe made of baryons protons neutrons During last two years an independent measurement from studies of CMBR Very impressive agreement The CMBR and the Copernican Principle Just how homogeneous and isotropic is the universe Reasonably so for galaxies on scales of 100 s of millions of light years What about the CMBR the temperature is the same to a part in 10 000 in every direction in the sky Small variations only observed in 1993 Now studied with great precision MAP OF THE SKY Is this reasonable Remember the CMBR is light from the time that the universe was 100 000 years old At that time 1 000 times smaller than it is today When we look at photons separated by 3 o in the sky those photons came from points that were separated by far greater distance than light any signal could have traveled between at that time in the history of the universe they are causally disconnected So it s not reasonable The solution Inflation the universe underwent a period of very rapid expansion probably at about t 10 24 seconds Is there evidence for this Yes The very rapid expansion of the universe produces small variations in the energy density energy in different places which lead eventually to the formation of galaxies and stars The same small variations appear in the temperature of the CMBR Observational Confirmation From satellites and earth based balloon experiments Most recently the WMAP satellite WMAP ORBIT Detailed information about the universe COMPOSITION OF THE UNIVERSE If 5 of the Universe is Baryons What is the Rest From studies of CMBR of distant Supernova explosions and from Hubble and GroundBased