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Tuesday, week 8

Tuesday, week 8. Arney on The Force of Truth Zita on Uncertainty Measurements Pictures Quantum mechanics Discussion Looking ahead. Break time. Zita on Uncertainty. Measurements Pictures Quantum mechanics

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Tuesday, week 8

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  1. Tuesday, week 8 • Arney on The Force of Truth • Zita on Uncertainty • Measurements • Pictures • Quantum mechanics • Discussion • Looking ahead

  2. Break time

  3. Zita on Uncertainty • Measurements • Pictures • Quantum mechanics “We may never [hit] the truth target. So what is the point of worrying about whether our beliefs are true?” (Lynch, True to Life, p.27)

  4. Measurements http://dbhs.wvusd.k12.ca.us/webdocs/GasLaw/Lab-MolarVolume/Mg-and-ruler.JPG

  5. Uncertainties in Measurements Accuracy? (dx=2mm) Precision? (x=1mm?) Reproducibility? Who decided this was a good question? Correlation vs. cause? What does it mean? (Why) does it matter? “Month of birth is important for adult stature”

  6. Picture problems http://www.sbi-online.org/sbi_home/case_of_the_month/2005_january_sbi_case_of_the_month

  7. Uncertainties in Mammograms Shadowing by/in dense tissue False positives, false negatives Structure → function? Motivations: radiologists vs HMOs Follow-up: ultrasound, surgical biopsy Diagnosis: malignant phyllodes tumor

  8. Is too much faith put in pictures? “The picture promises certainty, and it cannot deliver on that promise.” However: “Mammograms do not have to be infallible to save lives … reduces the risk of dying from breast cancer by about 10% … amounts to thousands of lives saved every year…” (Gladwell, p.7/8)

  9. Pictures of WMDs? http://www.globalsecurity.org/wmd/library/news/iraq/2003/iraq-030205-powell-un-17300pf.htm

  10. Uncertainties in WMD photos Resolution, interpretation Structure → function? Who decided this was a telling photo? Which is the fire truck? Motivations? “Leaving Saddam Hussein in possession of weapons of mass destruction for a few more months or years is not an option, not in a post-September 11 world.”

  11. Maps and models … as representations of reality… What is reality? Reality can surprise you. Predictions can be wrong.

  12. Pictures of particles? http://www.windows.ucar.edu/tour/link=/physical_science/physics/atom_particle/electron.html http://www.iun.edu/~cpanhd/C101webnotes/modern-atomic-theory/images/orbitals.jpg

  13. Uncertainties in positions There is a finite probability that “once in a very great while, your car will spontaneously ooze through the brick wall of your garage and be found the next morning on the street” (Sagan, Ch.17, Marriage of Skepticism & Wonder, Demon-Haunted World, 304)

  14. Quantum mechanical uncertainty What is the chance that an electron with energy E2 will be found in orbit r1?

  15. Quantum mechanical uncertainty Beyond theory-laden facts: Observations can change measurement outcomes. Old paradigm: Who decides position is a good thing to measure?

  16. How can QM be “true”, given all this uncertainty? • Statistical predictions are highly uncertain for a few particles, and very accurate & precise for systems of many particles: • modern electronics (e.g. semiconductors) • diagnostics (scanning tunnelling microscope, SEM, atomic force microscope) • lasers • quantum computing

  17. How to make decisions, in the face of uncertainty? “The idea that the value of pursuing the truth rests on the possibility of certainty is a myth.” (Lynch, 27)

  18. Looking ahead

  19. EVERYONE: remember to • Give feedback to your study group members on their Research Progress reports – THIS WEEK • Take the online Plagiarism quiz from week 6 if you have not already done so – THIS WEEK Correction: “Common knowledge” means whatever your peers can be sure to know without looking it up. CITE SOURCE for everything else.

  20. Research Progress reports • Get specific • What is the strongest evidence AGAINST? • What is the strongest evidence FOR? • What have you learned?

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