The Life of the Universe

1. The Life of the Universe From Beginning to End

3. Early Universe is extremely hot and dense All 4 forces were merged As Universe cooled, forces became unique Energy of photons high enough to create matter and vice versa • GUT – strong and electroweak forces united • SuSy – GUT and Gravity united

5. The Big Bang Theory • The early Universe was exceedingly hot and dense • Big Bang theory explains how the early Universe cooled and evolved into the Universe we observe today • Relies on Theoretical and Observational data

6. Planck Era • t < 10-43 s • T > 1032 K • Current physics is unable to understand times before the Planck era • Need to unite physics of large scales (general relativity) with physics of small scales (quantum mechanics)

7. GUT Era • 10-43 s < t < 10-38 s • 1029 K < T < 1032 K • Supersymmetry force splits into GUT force and gravity

8. Electroweak Era • 10-38 s < t < 10-10 s • 1015 K < T < 1029 K • GUT force splits into strong and electroweak forces • Huge release of energy  Inflation • Inflation expands Universe at exponential rate

9. Particle Era • 10-10 s < t < 10-3 s • 1012 K < T < 1015 K • Electroweak splits into weak force and electromagnetism • All four forces distinct • T too low for spontaneous conversion of photons to particles • Photons became quarks, which merge into protons and neutrons

10. Era of Nucleosynthesis • 0.001 s < t < 5 min • 109 K < T < 1012 K • Fusion begins • T still so high that most He nuclei will break apart again • Expansion reduces density so fusion ceases despite T being so high • 75% H, 25% He, trace others

11. Era of Nuclei • 5 min < t < 380,000 years • 3000K < T < 109 K • Photons still hot enough to ionize, so electrons and nuclei stay separated • Photons cannot travel far because they are scattered by electrons

12. Era of Atoms • 380,000 yrs < t < ~109 yrs • T < 3,000 K • T drops low enough for atoms to form • With electrons bound to nuclei, photons can travel long distances • Cosmic Microwave Background

13. Era of Galaxies • t > 109 years • Universe filled with nearly homogeneous distribution of matter and dark matter after era of atoms • Slightly overdense regions collapse to form first stars and galaxies • Gravity dominates on large scales

16. A Few Questions • Where did the large scale structure come from? • Why is the Universe so uniform? • Why is the density of the Universe so close to the critical density?

17. Inflation • Separation of strong force from GUT force would release enormous amount of energy • Energy would cause the Universe to expand by factor of 1030 in 10-36 sec

18. Huge expansion would make tiny quantum fluctuations in density large ripples A ripple the size of a nucleus would become the size of our solar system Creates density enhancements that give rise to the structure we observe today Inflation and Structure

19. Inflation and Uniformity • No reason why things so far away should be similar • Things close by should be • Inflation takes things that were very close together and spreads them out a lot • Universe was all close together, so everything was uniform, then inflation spread it out

20. Density implies curvature of spacetime Think general relativity Critical density has flat geometry If Universe started somewhat curved, inflation would make it seem much flatter Inflation and Density

21. Evidence for the Big Bang

22. The Cosmic Microwave Background

23. Line – a theoretically calculated thermal radiation spectrum based on the Big Bang Theory Dots – Observed data They match! The CMB

24. The Fate of the Universe

25. Two Things to Consider • Expansion of the Universe • Gravity – makes things collapse

26. Critical density – the density required to balance gravitational attraction and expansion • Dark energy – a repulsive force  opposite of gravity

27. An Accelerating Universe • SN Ia data show that we most likely live in an accelerating universe • Acceleration is driven by some force that is not well-understood • Dark energy

28. The Big Rip The End