Chapter 17 The Beginning of Time Copyright 2009 Pearson Education Inc Do you believe that science will ever understand the beginning of the Universe A Yes B No Copyright 2009 Pearson Education Inc Flip a coin A Heads B Tails Copyright 2009 Pearson Education Inc Give your clicker to someone else Flip a coin A Heads B Tails Copyright 2009 Pearson Education Inc Flip again Now answer the question Do you share your clicker or click for someone else If Heads tell the truth If tails lie A I have only used my clicker B I have clicked for a friend Copyright 2009 Pearson Education Inc Copyright 2009 Pearson Education Inc 17 1 The Big Bang Our goals for learning What were conditions like in the early universe What is the history of the universe according to the Big Bang theory Copyright 2009 Pearson Education Inc What were conditions like in the early universe Copyright 2009 Pearson Education Inc The universe must have been much hotter and denser early in time Estimating the Age of the Universe Copyright 2009 Pearson Education Inc The early universe must have been extremely hot and dense Copyright 2009 Pearson Education Inc Photons converted into particle antiparticle pairs and vice versa E mc2 The early universe was full of particles and radiation because of its high temperature Copyright 2009 Pearson Education Inc What is the history of the universe according to the Big Bang theory Copyright 2009 Pearson Education Inc Defining Eras of the Universe The earliest eras are defined by the kinds of forces present in the universe Later eras are defined by the kinds of particles present in the universe Copyright 2009 Pearson Education Inc Four known forces in universe Strong Force Electromagnetism Weak Force Gravity Copyright 2009 Pearson Education Inc Thought Question Which of the four forces keeps you from sinking to the center of Earth A B C D Copyright 2009 Pearson Education Inc Gravity Electromagnetism Strong Force Weak Force Thought Question Which of the four forces keeps you from sinking to the center of Earth A B C D Copyright 2009 Pearson Education Inc Gravity Electromagnetism Strong Force Weak Force Do forces unify at high temperatures Four known forces in universe Strong Force Electromagnetism Weak Force Gravity Copyright 2009 Pearson Education Inc Do forces unify at high temperatures Four known forces in universe Strong Force Electromagnetism Weak Force Gravity Yes Electroweak Copyright 2009 Pearson Education Inc Do forces unify at high temperatures Four known forces in universe Strong Force Electromagnetism Weak Force Gravity Yes Electroweak Copyright 2009 Pearson Education Inc Maybe GUT Do forces unify at high temperatures Four known forces in universe Strong Force Electromagnetism Weak Force Gravity Yes Electroweak Copyright 2009 Pearson Education Inc Maybe Who knows GUT String Theory Planck Era Time 10 43 s Temp 1032 K No theory of quantum gravity All forces may have been unified Copyright 2009 Pearson Education Inc GUT Era Time 10 43 10 38 s Temp 1032 1029 K GUT era began when gravity became distinct from other forces GUT era ended when strong force became distinct from electroweak force Copyright 2009 Pearson Education Inc Electroweak Era Time 10 10 10 10 s Temp 1029 1015 K Gravity became distinct from other forces Strong weak and electromagnetic forces may have been unified into GUT force Copyright 2009 Pearson Education Inc Particle Era Time 10 10 0 001 s Temp 1015 1012 K Amounts of matter and antimatter are nearly equal Roughly one extra proton for every 109 proton antiproton pairs Copyright 2009 Pearson Education Inc Era of Nucleosynthesis Time 0 001 s 5 min Temp 1012 109 K Began when matter annihilates remaining antimatter at 0 001 s Nuclei began to fuse Copyright 2009 Pearson Education Inc Era of Nuclei Time 5 min 380 000 yrs Temp 109 3000 K Helium nuclei formed at age 3 minutes The universe became too cool to blast helium apart Copyright 2009 Pearson Education Inc Era of Atoms Time 380 000 years 1 billion years Temp 3000 20 K Atoms formed at age 380 000 years Background radiation is released Copyright 2009 Pearson Education Inc Era of Galaxies Time 1 billion years present Temp 20 3 K The first stars and galaxies formed by 1 billion years after the Big Bang Copyright 2009 Pearson Education Inc Primary Evidence for the Big Bang 1 We have detected the leftover radiation from the Big Bang 2 The Big Bang theory correctly predicts the abundance of helium and other light elements in the universe Copyright 2009 Pearson Education Inc What have we learned What were conditions like in the early universe The early universe was so hot and so dense that radiation was constantly producing particle antiparticle pairs and vice versa What is the history of the universe according to the Big Bang theory As the universe cooled particle production stopped leaving matter instead of antimatter Fusion turned the remaining neutrons into helium Radiation traveled freely after the formation of atoms Copyright 2009 Pearson Education Inc 17 2 Evidence for the Big Bang Our goals for learning How do we observe the radiation left over from the Big Bang How do the abundances of elements support the Big Bang theory Copyright 2009 Pearson Education Inc How do we observe the radiation left over from the Big Bang Copyright 2009 Pearson Education Inc The cosmic microwave background the radiation left over from the Big Bang was detected by Penzias and Wilson in 1965 Copyright 2009 Pearson Education Inc Background radiation from the Big Bang has been freely streaming across the universe since atoms formed at temperature 3000 K visible IR Creation of the Cosmic Microwave Background Copyright 2009 Pearson Education Inc Background has perfect thermal radiation spectrum at temperature 2 73 K Expansion of the universe has redshifted thermal radiation from that time to 1000 times longer wavelength microwaves Copyright 2009 Pearson Education Inc
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