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Wednesday, Nov. 28

Wednesday, Nov. 28. Part III Beginning of Movie. Agenda. Announce: Finish book next week Projects in two weeks…any special needs? “We leave that to you” Vacuum Energy Anthropic Principle. We leave that to you. Dilemma: World is very complicated, can’t master it all

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Wednesday, Nov. 28

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  1. Wednesday, Nov. 28 Part III Beginning of Movie

  2. Agenda • Announce: • Finish book next week • Projects in two weeks…any special needs? • “We leave that to you” • Vacuum Energy • Anthropic Principle

  3. We leave that to you • Dilemma: • World is very complicated, can’t master it all • Many purported experts with different opinions • Whom to believe/accept?

  4. Example: Global Warming • Should the USA adopt potentially costly policies to address global warming?

  5. Example: Global Warming • Should the USA adopt potentially costly policies to address global warming? • Is Earth heating up? • Is it caused by humankind? • Is it worth doing something? • What can be done and at what cost?

  6. Other issues you can’t leave to others? • Should schools teach Creationism/ID in science class? • Is an antimissile system feasible and should it continue receiving funding? • Should NASA’s unmanned science program be shortchanged to fund manned exploration? • Is genetically modified food safe? • Etc (UFOs, astrology/tarot)

  7. Problems w/ the Cosmological Constant

  8. Picturing Vacuum Energy • In a region of space take everything out of it…vacuum • Probe for magnetic fields: • A big, slow probe will find no (average) field • A fast, small probe finds large, random fields • On average, energy doesn’t average out…energy of vacuum *is* the cosmological constant

  9. Predictions for Cosmological Constant • Continue at smaller and smaller length/time scales, random fields get bigger • Keeps increasing till one gets to the Planck length • Expected cosmological constant huge: ~10^120

  10. The Problem • Theory predicts a huge constant • Experiment/observation shows a small one • Difference of about 10^120% error!!!!!! • Perhaps a symmetry causes cancellation • But then would expect a zero constant not small!

  11. Introducing the Anthropic Principle • What kind of universe do you expect • Specific values of fundamental constants as “predicted” by physics theories? • Arbitrary values that happen to have formed the Universe as we find it today? • “Designed” values (e.g. God, higher beings, etc)? • Multitude of universes…and we, by necessity, find ourselves in one suitable for intelligent life?

  12. The Argument • If fundamental values were changed, intelligent life would be impossible • Example: change mass of neutron • Smaller and proton would decay resulting in a neutron universe • Larger and only hydrogen found in Universe • Example from Weinberg: different values of cosm. Constant • Negative: collapse of universe • Large positive: no galaxy formation

  13. Is it Science? • Can it be tested? • Is it giving up?

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