Lecture17OriginsofElements_001 - Lecture 17 Origin of the...

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Lecture 17 Origin of the Elements MODEL : Origin of the Elements or Nucleosynthesis Fundamental Particles quarks, gluons, leptons, photons, neutrinos + Basic Forces gravity, electromagnetic, nuclear OUTLINE: Primary Sources of the Elements (1) Big Bang – Creation (2) Stellar Nucleosynthesis (3) Cosmic-Ray Interactions I. Cosmological Nucleosynthesis: The Big Bang (Gamow) A. Evidence 1. Red Shift: Doppler Effect Light from all distant galaxies is shifted to the RED  is proportional to distance (Hubble) Implication: Everything is moving away from us ; a. Universe is EXPANDING b. Matter has a COMMON ORIGIN Age = 13 ± 2 × 10 9 years 2. Universal Black-Body Radiation – Remnant of primordial Explosion T present = 2.7 K 10 31 g/cm 2 (Penzias & Wilson) This radiation is isotropic in space ; i.e., it's not from our galaxy U n i v e r s e : Interactions Elemental Abundances Conservation Sea of Stability Laws Evolution
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3. Abundances of the Light Elements – esp. in old halo stars 1 H dominates the universe ; 2 H, 3 He, 4 He (little variation) ; 7 Li Conclusion: Universe must have formed from the simplest particles. 4. STANDARD MODEL: Universe originated in a hot, dense explosion involving the simplest particles: T H E B I G B A N G B. Basic Assumptions of Standard Model (small subset) 1. Only the known particles and forces are allowed GUTS = Grand Unification Theories – Origin of Forces 2. Matter vs. Energy Dominance: E = Mc 2 Energy drives expansion; gravity (mass) constrains expansion 3. T = f (density) Universe cools as it expands: <E> = (3/2) kT ; k = 0.86 10 10 MeV/K C. Chronology of the Big Bang 1. Elementary Particle Phase: [time < 10 6 s; T > 10 13 K > M n ] a. Most of mass-energy of the Universe in the form of ENERGY.
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Lecture17OriginsofElements_001 - Lecture 17 Origin of the...

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