The Big Bang Fact or fiction? The Big Bang: Fact or Fiction? Dr Cormac O’Raifeartaigh.
Download ReportTranscript The Big Bang Fact or fiction? The Big Bang: Fact or Fiction? Dr Cormac O’Raifeartaigh.
The Big Bang Fact or fiction? The Big Bang: Fact or Fiction? Dr Cormac O’Raifeartaigh The expanding universe (1929) many galaxies moving apart The origin of the universe rewind graph: universe converges infinite density, temp beginning of time: Big Bang? t~ 14 billion yr Expanding and cooling ever since Georges Lemaitre Newton’s gravity • planet orbits due to gravity • gravity caused by sun’s mass Mm F G 2 r What is pushing out? Newton Modern theory of gravity General theory of relativity • space + time = space-time • space-time not fixed • affected by mass gravity = curvature of space-time Einstein Relativity and the expanding U Apply Einstein’s gravity to Universe Alexander Friedmann dynamic U expand or contract depends on mass Evidence II: Composition of the elements BB Prediction U = 75% H, 25% He Georges Gamow Observed Heavier elements: 0.1% Formed in stars Evidence III: Cosmic background radiation BB prediction radiation leftover from BB Alpher, Gamow and Herman low temperature low frequency Cosmic microwave background (1965) Observed Penzias and Wilson radio interference low frequency temperature 3 K Echo of Big Bang Modern measurements • accurate CMB spectrum • homogeneous? • how do galaxies form? COBE satellite (1992) WMAP satellite • highly homogeneous • flat universe • ev idence for inflation WMAP satellite (2002) Inflation Alan Guth Hyper- expansion immediately after BB explains galaxy formation explains flatness of U solves horizon problem New surprises U speeding up Supernova U flat Dark energy Outstanding puzzles Nature of inflation? Nature of dark energy ? Singularity at time zero? Further reading: ANTIMATTER Summary The Big Bang model 14 billion years ago, universe concentrated at a point Primordial explosion of matter, energy, space and time Universe expanding and cooling ever since Misnomer: singularity problem Cosmological model Flat universe Known matter: 4% Dark matter: 23% Dark energy: 73% Evidence for general relativity • bending of light by gravity • time stretching by gravity • black holes