The Expanding Universe

1. The Expanding Universe If everything is moving away from us, then in the past everything was a lot closer. Density was greater; pressure was greater. Temperature was higher. Sometime in the past, it was very small and HOT! Conclusion: There should be residual radiation left over from this dense hot period.

2. What Should Light from This Period Look Like? Energy density per unit wave length Black-body Spectrum: Red-Shift Energy density change At detection: Temperature goes down with expansion. System stays in equilibrium

3. Cosmic Microwave Background Test of the Big Bang Model Peebles (and others): If the universe had a very hot early phase, then the radiation from the phase should still be present today. That radiation will be red shifted by the red shift factor z=Rthen/Rnow-1. Discovery: 1964 Penzias and Wilson Bell Labs Nobel Prize, 1978

4. T=2.725+/-.002o K COBE Satellite

5. COBE Fluctuations Dipole Movement – Earth through Microwave background Remnant Milky Wave light Background Fluctuations 1 part in 100000.

6. Boomerang Measurements South Pole Measurement Colors represent microwave intensity

7. Boomerang Measurements Intensity Legendre polynomial l

8. Big Bang Model Universe started as a hot dense medium in quasi-thermo equilibrium and expanded under the laws of physics to our present universe. Implications: Galaxies are receding. Microwave background -- measure of the universe at an age of 700,000 years (present age ~1/H0 ~ 14 billion years). Are there other clues?

9. Temperature as a Function of Time Example: Flat Mass Dominated Universe Energy Density: Temperature: Decrease time from big ban by a factor of 10, temperature goes up by a factor of 100.

10. Time Temperature 14 billion years 2.3o K Today 700 Million years 920o K 6.4 Red Shift Objects Atoms form Microwave Background 700,000 years 3500o K=.3 eV 200 sec 100 keV Break up Nuclei 10 sec 300 keV Electrons and Positrons Neutrinos interact with nuclei 1 sec 1 MeV 10 msec 300 MeV m, p strong interactions 100 nsec 3 GeV t, charm quark 100 psec 300 GeV Produce W, Z, t quark Timeline from Big Bang

11. Time Temperature 14 billion years 2.3o K Today 700 Million years 920o K 6.4 Red Shift Objects Atoms form Microwave Background 700,000 years 3500o K=.3 eV 200 sec 100 keV Break up Nuclei 10 sec 300 keV Electrons and Positrons Neutrinos interact with nuclei 1 sec 1 MeV 10 msec 300 MeV m, p strong interactions 100 nsec 3 GeV t, charm quark 100 psec 300 GeV Produce W, Z, t quark Timeline from Big Bang D/H ratio Light Elements

12. Big Bang Nucleosynthesis Competition: Other reaction: Exact ratios are determined by cooling rate which depends on baryon density.

13. Baryon Density Measurements All measurements consistent with one baryon density

14. Time Temperature 14 billion years 2.3o K Today 700 Million years 920o K 6.4 Red Shift Objects Atoms form Microwave Background 700,000 years 3500o K=.3 eV 200 sec 100 keV Break up Nuclei 10 sec 300 keV Electrons and Positrons Neutrinos interact with nuclei 1 sec 1 MeV 10 msec 300 MeV m, p strong interactions 100 nsec 3 GeV t, charm quark 100 psec 300 GeV Produce W, Z, t quark Timeline from Big Bang HEP predictions

15. And What Before That? ????