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Cosmology and the Big Bang

Cosmology and the Big Bang. The expansion of the Universe implies a finite age to the Universe Speed = Distance/Time or v= d/Time => Time = d/v If v = H o d, then Age of the Universe = 1/H o. If H o = 23 km/s/Mly (71 km/s/Mpc), then Age of the Universe = 13,700,000,000 years

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Cosmology and the Big Bang

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  1. Cosmology and the Big Bang

  2. The expansion of the Universe implies a finite age to the Universe Speed = Distance/Time or v= d/Time => Time = d/v If v = Hod, then Age of the Universe = 1/Ho

  3. IfHo = 23 km/s/Mly (71 km/s/Mpc), then Age of the Universe = 13,700,000,000 years Note: This assumes Ho is constant. Is it?

  4. Recent observations of Type I supernovae in distant galaxies show that the expansion may be accelerating!

  5. Recent observations of Type I supernovae in distant galaxies show that the expansion may be accelerating! This is still controversial among astronomers. WMAP data suggests that a Dark Energy component may be a contributor

  6. The Future of the Universe There are three possible fates: 1. The Universe expands forever (Open) 2. The Universe stops expanding and eventually collapses (Closed) or

  7. 3. The Universe stops expanding only after an infinite amount of time passes (Critical/Flat)

  8. An Open Universe: - The gravity of mass in the Universe cannot overcome the energy in the expansion => expands forever The Big Chill How much mass is needed? 10-29 g/cm3 the critical density

  9. A Closed Universe: - The gravity of mass in the Universe overcomes the energy in the expansion =>expansion stops, universe collapses The Big Crunch density of Universe > 10-29 g/cm3

  10. A Flat Universe: - The gravity of mass in the Universe exactly balances the energy in the expansion => expansion stops after an infinite amount of time density of Universe = 10-29 g/cm3

  11. Which Universe do we live in? Open Universe - Age 13 -18 Billion yrs Closed Universe - Age < 13 Billion yrs Flat Universe - Age = 13 Billion yrs Current Universe Density = close to critical (including Dark Energy) => appears to be OPEN, or close to FLAT

  12. The Big Bang How do we know it happened?

  13. Evidence for the Big Bang: 1. The Hubble law 2. The Cosmic Background Radiation (CBR)

  14. Penzias and Wilson and the “horn” antenna

  15. John Bahcall, Institute for Advanced Studies, Princeton

  16. Data from WMAP

  17. Evidence for the Big Bang: 1. The Hubble law 2. The Cosmic Background Radiation (CBR) 3. The abundance of H and He

  18. The Early Universe Time PeriodEraTemp 0 - 10-43 sec Planck Era > 1032 K

  19. The Early Universe Time PeriodEraTemp 0 - 10-43 sec Planck Era > 1032 K 10-43 - 10-35 sec GUT Era 1032 - 1027 K

  20. Gravity

  21. Time PeriodEraTemp 10-35 - 10-10 sec Electroweak 1027 - 1015K Era The Inflationary Epoch occurs near 10-35 sec : Universe expands by a factor of 1050 as strong nuclear force freezes out

  22. Problems: 1. The Horizon Problem How do the far ends of the observable Universe know to look similar?

  23. 2. The Flatness Problem The Universe must have been very close to critical immediately after the Big Bang -> “flat” Solution: the inflationary epoch

  24. Time PeriodEraTemp 10-10 sec - 0.001sec Particle Era 1015 - 1010K The Universe is now cool enough to make particles: Neutrons first, then Protons, and finally electrons

  25. Time PeriodEraTemp 0.001sec - 3 min Nucleosynthesis 1010 -107K Era The Universe is now cool enough for Nucleosynthesis of He from H to occur

  26. Time PeriodEraTemp 3 min - 300,000 yrs Era of Nuclei 107 - 3000K The Universe is a plasma - no photons can travel farther than ~ 1 cm

  27. Time PeriodEraTemp 300,000- 109 yrs Era of Atoms 3000K- 10K Stars begin to form

  28. Time PeriodEraTemp 109 yrs - present Era of Galaxies <10K Galaxies form at 1 -2 Billion yrs after the Big Bang

  29. We now live in a Matter-dominated Universe The Early Universe was Radiation-dominated

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