The Uniqueness of our Universe A Physicist’s Point of View Dr. Paul Ohmann University of St. Thomas November 30, 2012

What can Science tell us? Experiments and Observations: We discover facts. Facts are interpreted through our senses. Facts should be testable and reproducible. Theory: We build models to understand facts. Models explain how facts are related  leads to understanding Models are tested by further experiments  subject to change Scientific Process

Anthropic Coincidences Observation: Universe is amazingly conducive to life Anthropic Coincidences  ways in which Universe characteristics are tuned to support life Questions: Are these “coincidences” really “coincidences”  or must Nature evolve with these characteristics? What role might random chance play in the characteristics of the Universe? Would life arise in many types of Universes? Do the Anthropic Coincidences suggest a Creator?

Anthropic Coincidences 1. Strengths of the Fundamental Forces Strong Nuclear Force ~ 10 2 EM Force ~ 10 5 Weak Nuclear Force ~ Gravity Interplay between Strong Nuclear and EM Force: Consider Helium  protons try to break nucleus apart Weaker strong force or stronger EM force  less stability Heavier atoms are particularly susceptible: Our Universe: Heaviest (relatively) stable element  U (92 protons) If EM force were 10 times stronger  Heaviest element: Ne (10 protons) No Ca, no Fe…. life would be drastically different!

Anthropic Coincidences, cont. Stellar Formation: proton – proton cycle: 1 H + 1 H  2 H + e H + 1 H  3 He +  3 He + 3 He  4 He H Then 3 He, 4 He, and H make Li, Be, B Suppose the strong force… Net reaction: 4 1 H  1 4 He MeV …were 10% weaker: 2 H unstable  no elements heavier than H !!  no sunlight !! …were 4% stronger  additional reactions: 1 H + 1 H  2 He n + n  2 n

Anthropic Coincidences, cont. Why is a stronger Strong Force bad? 1 H + 1 H  2 H + e + + Current Universe: is a weak nuclear interaction proceeds slowly: stars live a long time Alternate Universe: 1 H + 1 H  2 Heis a strong nuclear interaction proceeds quickly: stars rapidly burn out The weak nuclear interaction is needed to give life time to develop!

Anthropic Coincidences, cont. 2. Flatness of Space/Cosmological Constant Key Idea: Big Bang expansion must not be too fast or too slow Too fast: Stars/galaxies wouldn’t form  no life! Too slow: Universe would gravitationally collapse Current Age of Universe: billion years…and still expanding “Fine tuning” needed to account for Universe age/content: Expansion rate (Cosmological constant): 1 part in Curvature of Space (Flatness): 1 part in

3. Proton stability Anthropic Coincidences, cont. Unstable proton  no stable Hydrogen  Stellar Formation? Water? Question: Why are protons stable? (Neutrons are unstable!) allowed:  ~ 15 minutes disallowed  Why? Answer: neutrons are a bit heavier than protons! m n = MeV/c 2 m p = MeV/c 2 Question: Why does m n > m p ? No one knows….

Anthropic Coincidences, cont. 4. Matter/Antimatter Asymmetry Early Universe  Highly symmetric (we think) But perfect symmetry: matter + antimatter  light Current Universe: # matter > # antimatter by 1 in 10 9  necessary for life! Science: Matter/Antimatter Asymmetry  “CP Violation” e.g. K 0 decay:  ~ 5.2 x s  ~ 0.9 x s slightly favored

Anthropic Coincidences: Summary 1.Strong Force must be between 0.90 and 1.04 of current value 2.EM Force cannot be much stronger than its present value 3.Expansion must allow for galaxies/stars without Universe collapsing 4.Proton stability 5.Matter/Antimatter Asymmetry For life to exist in the Universe: Question: Did we just get lucky???

Evidence for God? Anthropic Coincidences Wouldn’t a Creator want life to arise? (Strong Anthropic Principle) First Cause of Universe (Aquinas) Big Bang Natural Laws Question: Are there scientific alternatives?

Scientific Explanations: Anthropic Coincidences 1. Lucky Hypothesis. Universe evolved by chance into a form conducive for life 2. Necessary Hypothesis. Universe was required to evolve into its present form 3. Many Universes Hypothesis. Many Universes (or domains) exist, with varying laws and initial conditions. Weak Anthropic Principle: Obviously we’re in a Universe conducive to life!

Final Thoughts Many Universe Hypothesis: untestable? Observable Universe: Natural laws seem consistent Other Domains: Inherently unobservable? (Conjecture: Interference Ripples in CMB) Creator Hypothesis: untestable? God works through Natural Laws with few exceptions (none that seem scientifically testable) Philosophical evidence: Consciousness/Free Will/Rational Thought (Can these arise from purely material entities?) Personal evidence: Untestable  no control group Science: Gives an appreciation for the special nature of the Universe

ExtraSlides

Symmetries Noether’s Theorem: Symmetries = Conservation Laws Action Principle (Phys 331): External Symmetries: related to particle motion (any type of particle) L = T - V conservation translation invariance symmetry x 0 arbitrary conservation rotation invariance symmetry θ 0 arbitrary E conservation time invariance symmetry Invariance of L under appropriate symmetry  something is conserved

Symmetries, continued Internal Symmetries: related to particle intrinsic nature (particle-dependent) Electric Charge (QED) conservation  U(1) symmetry Weak Charge conservation  SU(2) L symmetry Strong Charge (QCD) conservation  SU(3) symmetry Baryon # conservation (e.g. p, n) Lepton # conservation (e.g. e, ) SU(3) x SU(2) L x U(1) symmetry Note: U(1), SU(2) L, and SU(3) are groups (Math 301-2) Quantum Field Theory  particle = field   relate particles to forces Symmetry of L under group transformation    e i  (x)Q yields conservation laws (Q = generator of appropriate group)

Higher Symmetry? Grand Unified Theories: Incorporate lower symmetries into one larger symmetry e.g. SU(3) x SU(2) L x U(1)  SU(5) Fundamental Assumption: Universe is simple But: Universe of today  many distinct symmetries Guess: Early Universe has one large symmetry Original symmetry “broken” as universe cooled Suppose this is true. Question: Why must there be this original symmetry? Science: This is a tough question! Aquinas: First Cause  God

Anthropic Coincidences, cont. 5. The 3-  process: Production of 12 C Life Cycle of a Star: Hydrogen phase  proton-proton cycle: 1 H + 1 H  2 H + e H + 1 H  3 He +  3 He + 3 He  4 He H Helium phase  3-  process: hydrogen depleted  gravitational collapse  core heating [Note:  = 4 He] 4 He + 4 He + 4 He  12 C MeV Problem: Negligible probability of 3 nuclei simultaneously colliding! Consider 2-step process: 4 He + 4 He  8 Be 8 Be + 4 He  12 C Problem: 8 Be highly unstable:  ~ s Question: How can we produce 12 C?

Anthropic Coincidences, cont. Resonance  12 C happens to have a resonance at 7.7 MeV…and 8 Be + 4 He reaction is just energetic enough (with thermal energy) to hit resonance! 4 He + 4 He  8 Be 8 Be + 4 He  12 C*(7.7 MeV) Equilibrium condition: But also: 12 C*  12 C MeV  leakage from system Conclusion: Without 7.7MeV (± 0.3 MeV) resonance  No 12 C !! Resonance = big increase in production rate! Further reaction: 12 C + 4 He  16 O just 0.04 MeV above resonance! Enough 12 C for carbon-based life!