BIG BANG: beginning of Time Early times in the Universe were really - PowerPoint PPT Presentation

ASTR 1120 OUR Universe: General Astronomy: Accelerating Universe REVIEW Stars & Galaxies • Dark Energy is causing the • FINAL: Saturday, Dec 12th, 7:30pm, HERE expansion of • ALTERNATE FINAL : Monday, Dec 7th, 5:30pm the universe to in Muenzinger E131 speed up over time! • Last OBSERVING session, Tue, Dec.8th, 7pm • Please check your grade on clickers, midterms, • Scientists don’t HWs on CU learn - e-mail Thomas if you see know what this discrepancies/missing grades dark energy might be. • Homework #9 due TODAY, by 5pm Chapter 23: In the VERY Beginning BIG BANG: beginning of Time Early times in the Universe were really Hot Stuff!! • If the universe is cooling and expanding now… – The Universe was hotter at earlier times • The temperature at the earliest times was more than the energy we create in even our largest particle accelerators • Cosmology at the earliest times is explored via particle physics

Matter, Antimatter, and Energy Planck Era Photons converted into 0 - 10 -43 sec particle-antiparticle pairs and vice-versa Before (Matter and Energy are Planck time the same!!) =??? E = mc 2 •Things were so small and Early universe was full so dense… modern of particles and physics fails radiation because of its –No theory high temperature of quantum gravity Do forces unify at The Four Known high temperatures? Forces in the Universe Four known forces in the universe: • Gravity • Gravity • Electromagnetism • Electromagnetism • Strong Force • Strong Force • Weak Force • Weak Force

Do forces unify at Do forces unify at high temperatures? high temperatures? Four known forces Four known forces in the universe: in the universe: • Gravity • Gravity • Electromagnetism • Electromagnetism • Strong Force • Strong Force • Weak Force • Weak Force Yes! Yes! Maybe (Electroweak) (Electroweak) (Grand Unified Theories) Do forces unify at high temperatures? Four known forces GUT Era in the universe: ~10 -43 -10 -38 sec • Gravity Lasts from Planck time to • Electromagnetism end of GUT force • Strong Force • Weak Force Yes! Maybe Who knows? (Electroweak) (GUT) (String Theory)

Inflation of the Universe Electroweak Era • As strong force ~10 -38 -10 -10 sec becomes distinct (end of GUT era), a huge Lasts from end of GUT force to end amount of energy is of electroweak released force •Universe still • Universe INFLATES: made up of – Universe of atomic elementary nucleus size becomes particles (quarks) solar system size in 10 -36 sec The Particle Era Particle Era • Universe still hot: 10 15 to (10 -10 -.001 sec) 10 12 K Finally temperatures low • Particles now exist: enough that electrons, protons, anti- quarks can protons, anti-electrons, combine to form neutrinos etc. subatomic particles (protons, • Particle soup! Particles antiprotons, and photons/energy neutrons, created and annihilated antineutrons, etc…)

Clicker Question Clicker Question At the end of the particle era, temperatures are low At the end of the particle era, temperatures are low enough that photons cannot collide to create enough that photons cannot collide to create matter/anti-matter anymore. Nearly all the matter and matter/anti-matter anymore. Nearly all the matter and antimatter that is in the universe at that time collides antimatter that is in the universe at that time collides and forms photons. But a little bit of some type of and forms photons. But a little bit of some type of matter remains… which type is it? matter remains… which type is it? A. Regular matter A. Regular matter B. Anti-matter B. Anti-matter C. There’s no way we C. There’s no way we can tell! can tell! Matter and Anti-matter Era of Nucleo- synthesis • At end of particle era, 0.001 sec-3 min universe contains matter! Begins when • Protons must have matter annihilates slightly outnumbered anti- remaining protons antimatter • Universe ratio today: – 1 billion photons (light) for every 1 proton (matter) • Universe ratio then: – 1 billion and 1 protons for every 1 billion anti-protons

Nucleosynthesis stops after Era of Nucleosynthesis about 3 minutes (Fusion) • Fusion ends because density drops • Matter particles are “frozen out” – remember the universe has been expanding this – no longer whole time spontaneously – Matter left as ~75% hydrogen, ~25% helium, with generated to/from photons trace amounts of lithium, deuterium • Temperatures hot • Amounts seen throughout the universe today enough to fuse (with slight enhancements of heavy elements protons (hydrogen nuclei) into helium from fusion in stars) nuclei The era of nuclei created a lot of Era of Nuclei 3 min - light but it couldn’t get anywhere!! 380,000 yrs •Most matter was in the shape of • Density was so hydrogen/helium high, photons nuclei, electrons would hit an •Universe has electron or nuclei become too cool before getting to blast helium anywhere apart but too hot to allow electrons – Just like the to combine with random walk nuclei to make inside the Sun! atoms

Era of Atoms Era of Atoms • Finally cool enough 380,000 years (3000 K) for electrons to 1 billion combine with nuclei years to form atoms (380,000 yrs) •Finally, the temperature • Photons now “decoupled” = free drops to about to fly away 3000 K and electrons all • Universe becomes combine with transparent to light nuclei to form the first atoms Era of Galaxies Era of Galaxies 1 billion years - now • About 1 billion years after Big Bang, first stars and galaxies start to form • We live in the Era of Galaxies now.

Big Bang evidence Spectrum of Cosmic Microwave Background (CMB) Penzias & Wilson in 1965 discovered Cosmic Microwave Background (CMB) radiation --> 2.73 K “black body” 2.73 K `black body’ Photons created when hot universe was only 380,000 yrs old – as first atoms formed 1978 Nobel Prize Very uniform radiation from everywhere – 1 part in 100,000 severely redshifted by WMAP expansion of universe Light from beginning of time • This faint light looks light a solid glowing wall • Thermal spectrum at 3000 K, if redshifted by factor ~1000 � microwaves! • Helps measure degree of isotropy in early Universe

Chemical abundances also Clicker Question confirm the Big Bang model Which of these abundance patterns (by mass) is an • Big Bang Theory prediction: 7-1 unrealistic chemical composition proton-to-neutron for a star? ratio – Should lead to 75% H, 25% He A. 70% H, 28% He, 2% other (by mass) B. 95% H, 5% He, less than 0.02% other • Matches C. 75% H, 25% He, less than 0.02% other observations of D. 72% H, 27% He, 1% other nearly primordial gas Clicker Question Clicker Question Which of these abundance Which of the following is not an patterns (by mass) is an evidence supporting the Big Bang unrealistic chemical composition theory? for a star? A. Cosmic microwave radiation A. 70% H, 28% He, 2% other B. The Hubble expansion of the universe B. 95% H, 5% He, less than 0.02% other C. Helium is 25% of all matter C. 75% H, 25% He, less than 0.02% other D. Gamma ray bursts D. 72% H, 27% He, 1% other

Clicker Question Which of the following is not an evidence supporting the Big Bang theory? A. Cosmic microwave radiation B. The Hubble expansion of the universe C. Helium is 25% of all matter D. Gamma ray bursts