Transcript Big Bng
The Big Bang by Robert Nemiroff Michigan Tech Physics X: About This Course • Officially "Extraordinary Concepts in Physics" • Being taught for credit at Michigan Tech o Light on math, heavy on concepts o Anyone anywhere is welcome • No textbook required o Wikipedia, web links, and lectures only o Find all the lectures with Google at: "Starship Asterisk" then "Physics X" o http://bb.nightskylive.net/asterisk/viewforum.php?f=39 Universe Beginning: Steady State of Big Bang? • Steady State Universe o Perfect cosmological Principle: universe does not evolve with time • Big Bang Universe o o Universe evolves in time Cosmological Principle: universe looks the same from every location The Big Bang • t < 10-43 seconds • Planck epoch • Before Planck epoch, the general relativity description of spacetime breaks down. • No one knows what happens before 1043 seconds The Big Bang: Energy Everywhere • 10-43 < t < 10-35 seconds • Universe expands and cools • Radiation epoch o All particles have speed near light • Nuclei not stable o Broken apart soon after forming The Big Bang: Energy Everywhere • 10-35 < t < 10-32 seconds • Inflationary epoch • Repulsive gravity dominates • Universe expands exponentially The Big Bang: Energy Everywhere • 10-32 < t < 10-6 seconds • Universe expands and cools o T drops to 1013 K • (Another) Radiation epoch o All particles have speed near light • Nuclei still not stable o Broken apart soon after forming The Big Bang: Particles Freeze Out • • • • 10-6 < t < 1 second Universe expands and cools 1013 < T < 1010 Kelvin Protons, neutrons, electrons, positrons now frozen in o All particles have speed near light • Nuclei not stable o Broken apart soon after forming The Big Bang: Nuclei Freeze Out • • • • • 1 < t < 100 seconds Universe expands and cools 1010 < T < 1013 Kelvin Nuclei become stable Primordial nucleosynthesis Determines what nuclei remain in the universe o Universe mostly hydrogen & helium o The Big Bang: Nuclei Become Atoms • • • • t = 400,000 years Universe expands and cools T = 3000 Kelvin Recombination o o Atoms become stable Nuclei able to retain electrons • Photons fly free for first time o Still flying – form microwave background radiation today The Big Bang: Formation of Stars and Galaxies • 400,000 < t < 4,000,000 years • Dark Ages • Stars not yet formed • 4 million years < t < 13.7 billion years • Stars form, galaxies form • Universe cools to 3.7 Kelvin Light from the First Stars Credit: NASA/JPL-Caltech/A. Kashlinsky (GSFC) et al. APOD: 2007 January 2 Zooming in on the First Stars Credit & Copyright: Visualization: Ralf Kaehler (ZIB) & Tom Abel (Penn. State) Simulation: Tom Abel (Penn. State), Greg Bryan (Oxford) & Mike Norman (UCSD) APOD: 2003 June 10 Building Galaxies in the Early Universe Credit: NASA, ESA, and N. Pirzkal (STScI/ESA) et al. APOD: 2007 September 10 http://en.wikipedia.org/wiki/Image:Universe_expansion.png Inflating the Universe Credit: WMAP Science Team, NASA APOD: 2006 March 23 http://en.wikipedia.org/ wiki/Image: Cosmological_composition.jpg The Big Bang: Epochs • Radiation dominated o o Photon-like energy most abundant t < 300,000 years Except for brief inflationary epoch • Matter dominated o o Atoms, molecules, dark matter most abundant 300,000 < t < 5 billion years • Dark energy dominated o o Inflationary epoch Now (barely) The Hubble Deep Field Credit: R. Williams, The HDF Team (STScI), NASA APOD: 2002 September 1 HUDF: Dawn of the Galaxies Credit: R. Windhorst (ASU), H. Yan (SSC, Caltech), et al., ESA, NASA APOD: 2004 September 29