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

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_scie nce/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 E 2 will be found in orbit r 1 ?

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?