1. 4/7/08Atoms and Stars, Class 121 Atoms and Stars IST 2420 Class 12, April 7 Winter 2008 Instructor: David Bowen Course web site: www.is.wayne.edu/drbowen/aasw08

2. 4/7/08Atoms and Stars, Class 122 Agenda Assignments, passbacks, initial signin sheet Experiment 9, Part 1 Miscellaneous cleaning up Upcoming assignments oExperiment 7 Essay 2 Reading: Chemistry Waves and the Uncertainty Principle Lab 9: The ellipse

3. 4/7/08Atoms and Stars, Class 123 Upcoming … Don’t put off Essay 1!!! See me instead. This week (April 7): oReader: Chemistry oManual: Lab 9 – the Ellipse Turn in Lab 9 as a whole Next week (April 14:) oEssay 2 due on diskette oLab 7 – Specific Gravity One of the things Archimedes did oSET

4. 4/7/08Atoms and Stars, Class 124 Upcoming … April 21 (last regular class) oLab 11 – the Orbiting Bottle Checking up on Newton oReview for Final Exam oDue: all work to count in regular grade April 28: nothing that night but the Final Exam

5. 4/7/08Atoms and Stars, Class 125 Grade What-If Grade What-If (on course web site – see first slide for this URL) oReminder: to get current course average, do NOT put anything in for assignments you haven’t been graded for yet If you put anything in, remove it using “delete” key oTo see what happens if you miss assignments, put in zeroes for those (this is what I will do)

6. 4/7/08Atoms and Stars, Class 126 Semester is Ending! If you have been relying on being able to turn work in late, it is time to get going oAlternatives: D, F, I, drop – see counselor! Getting ready for Final: oRead Information Sheet carefully – a lot of information there oLook at Final Topics carefully oUse Review Session!

7. 4/7/08Atoms and Stars, Class 127 Essay 2 Review) TOPIC: What has this course been about? You should answer this question with a core concept or idea, perhaps with dependent parts, and illustrated by referring to course experiences, such as labs and discussions, and materials, such as readings, notes, lab materials, and so on. A starting point is the “Course Description” section in the Syllabus. You can agree with, make changes to, or disagree with this description, but if you disagree, include an equivalent description – that is, one that covers the course as a whole.

8. 4/7/08Atoms and Stars, Class 128 Essay 2 (cont’d) This topic does NOT ask for a simple listing of all of the topics and activities (“laundry list”), and does not ask for an evaluation of me or the course (that’s for SET). The topic asks for “a” core concept and suggests a starting point for your analysis Due 4/14. At the end of tonight’s class, we will have covered all of the core topics. Review Syllabus for other requirements oAll quotes must have references

9. 4/7/08Atoms and Stars, Class 129 Effects of Newton’s Laws Changed view completely from planets locked on spheres with earth fixed at center (Aristotle) to bodies mutually acting on each other through known laws, with nothing fixed Each (Copernicus to Newton) saw themselves as making marginal changes to improve model supported by religion

10. 4/7/08Atoms and Stars, Class 1210 Newton’s Laws (cont’d) However, looking back from where we are, Newton made it possible to see a universe without a God (except for setting up universe and starting it off) oNewton: “clockwork universe,” God as clockmaker oRole of God in celestial motion is possible but not required – maybe “hand of God” as cause oWe cannot escape this change (explanation)

11. 4/7/08Atoms and Stars, Class 1211 What Can We Trust as a Fact? As practical matters, Newton Laws, Special Relativity, General Relativity and Quantum Mechanics (all 20 th Century) are extremely accurate, within their range of authority. Philosophically, each of the more recent ones undermines the earlier ones, even within their range of authority oChanges are very, very small

12. 4/7/08Atoms and Stars, Class 1212 Fact? (cont’d) So science offers practical certainty, but not philosophic certainty oAlso, scientific knowledge changes Does religion offer certainty? oEach claims to be certain, but they disagree oEach claims to be eternal and unchanging, but they have changed My conclusion: humans cannot have universal, eternal truth, but we can do well enough for any practical purpose

13. 4/7/08Atoms and Stars, Class 1213 Readings – Chemistry (Q10c#2) Chemistry developed after Newton (physics) oAlchemy – transmutation of elements oMedicine oIndustry – much demand for chemicals 1700s oMechanical approach from Descartes & Newton 1700 still the four Aristotelian elements oEarth – fixed volume & shape oWater – fixed volume only

14. 4/7/08Atoms and Stars, Class 1214 Chemistry 1700 still Aristotelian elements oAir – volume & shape expanded to container oFire passed through container walls 1727 – Stephen Hale: released “fixed” air (put out flames) from solids, much interest 1749 Jean-Jacques DeMairan evaporated liquids (e.g. ether) in a vacuum, froze water oBut liquids supposed to evaporate into air oFire combined with liquid = air? Many types? Water could be solid, liquid, vapor –differ by fire?

15. 4/7/08Atoms and Stars, Class 1215 Chemistry How could “big four” be elements? 1750s Joseph Black experiments with “magnesia alba,” gave off “fixed air” that extinguished flame (CO 2 ), denser than “common air,” turned limewater cloudy oUse limewater test to show fixed air came from fermentation & charcoal combustion, would not support life “Fixed air” became specific name for this gas (CO 2 )

16. 4/7/08Atoms and Stars, Class 1216 Chemistry 1766 Henry Cavendish: “inflammable air” H 1772 Joseph Priestley obtained “fixed air” in other ways, demonstrated solubility in water (& taste – birth of carbonated beverage industry) oMany other types of air – “dephlogisticated air” O Phlogiston theory of combustion – burning releases phlogiston – from Germany, industrially useful –Phlogiston theory before Caloric and Kinetic theories of heat When air is saturated with phlogiston, combustion and life cease

17. 4/7/08Atoms and Stars, Class 1217 Chemistry Antoine Lavoisier (1743 – 1794) oGraduated in law but continued science studies oAccurate weighing, also many practical results o(Calcination – turn a metal to powder (“calx”) by heating in air below melting point – phlogiston theory explained this as driving off phlogiston) oBut Lavoisier’s weighing showed that weight of calx increased, for all metals – a problem for phlogiston theory of combustion

18. 4/7/08Atoms and Stars, Class 1218 Chemistry Calx of mercury (oxide of mercury) when heated gave off air (gas) that supported combustion and life oPriestley found this air better (5×) for combustion and life than “common air” (air) – “eminently respirable air” Lavoisier had assumed it was common air oLavoiser confirmed this, but common air was then a mixture

19. 4/7/08Atoms and Stars, Class 1219 Chemistry 1778 Lavoisier showed this air also formed acids, named it oxygen (“acid former”) (but we now know that hydrogen makes acid) 1783 Cavendish’s assistant told Lavoisier about Cavendish’s experiment of applying spark to inflammable air (H), finding dew which was identified as water oLavoisier – water was not an element, combination with oxygen for all combustion

20. 4/7/08Atoms and Stars, Class 1220 Chemistry Lavoisier named flammable air “hydrogen” for “water former” Lavoisier and others formed new chemical terminology – speaking well was like reasoning well oOxide – combination with oxygen oNames indicated amount of oxygen (ous < ic) Sulfurous acid H 2 SO 3 Sulfuric acid H 2 SO 4

21. 4/7/08Atoms and Stars, Class 1221 Chemistry Lavoisier terminology oGas – any vapor oAir – the atmosphere, a mixture (80% N, 20% O) oFire was caloric (no correct theory until 19 th century – started by Count Rumford) John Dalton (1766 – 1844), meteorologist oConverted to chemistry when he understood air was a mixture – why didn’t different gases separate by gravity?

22. 4/7/08Atoms and Stars, Class 1222 Chemistry John Dalton (1766 – 1844), meteorologist oAlso gases dissolved in water proportional to pressure – why? oHypothesized gases composed of atoms, each gas interacted with itself (see later slide) o“Law of definite proportions” – chemicals combined by weight in simple ratios oDalton proposed formulae based on these – chemical atomism

23. 4/7/08Atoms and Stars, Class 1223 Chemistry John Dalton (1766 – 1844), meteorologist oDalton proposed formulae based on these oMany of his formulae were wrong Example: he said water is HO More were right, enough to straighten out the errors over time o(DB) Physicists did not accept chemical atomism until they accepted Maxwell and Boltzmann at the end of 19 th century o(DB) Direct observations of atoms in 20 th century

24. 4/7/08Atoms and Stars, Class 1224 Chemistry (DB) John Dalton (1766 – 1844), meteorologist oWhat led Dalton to hypothesize atoms? Characteristics of matter –Solids cannot occupy the same space –Some liquids can –All gases can Why didn’t lighter gas rise, heavier sink –Composition of atmosphere the same to 15,000’ –Fog Gases could interpenetrate if it was atoms with lots of empty space in between Water could be gas, liquid, solid, these must have atoms Extended to all liquids and solids

25. 4/7/08Atoms and Stars, Class 1225 Experiment IV (not done) (Q11) Chemical composition of water Electrical current decomposes water: H 2 O  2H + O Lab Manual Pg 13

26. 4/7/08Atoms and Stars, Class 1226 Atomic Nature of Matter (Review) First direct evidence 1827 Robert Brown (10c#2) oNoticed spores jiggling under microscope o“Brownian motion” – bombarded by molecules Robert Brown, 1827 oSee next slides, or http://www.is.wayne.edu/drbowen/Class-Room_Models/Welcome.htm http://www.colorado.edu/physics/phet/web-pages/simulations-base.html http://www.is.wayne.edu/drbowen/Class-Room_Models/Welcome.htm http://www.colorado.edu/physics/phet/web-pages/simulations-base.html oNow we have more direct evidence

27. 4/7/08Atoms and Stars, Class 1227 Brownian Motion (Review) Jagged tracks of pollen particles. Gas molecules mode visible. Jagged tracks explained as due to collisions with gas molecules.

28. 4/7/08Atoms and Stars, Class 1228 Expanding Circles Review: science started out as isolated areas Then areas expand – science always pushing its boundaries Implication #1: What happens when two expanding circles meet? Implication #2: What happens when circles fill the space? oMy answer: science drives technology (C11S15-19)

29. 4/7/08Atoms and Stars, Class 1229 Expanding Circles Implication #1: What happens when two expanding circles meet? I promised three examples (Q15) oExample 1: Newton uniting celestial (stars) and terrestrial (on land) – already done (C10S32-33) oExamples 2 and 3 now.

30. 4/7/08Atoms and Stars, Class 1230 Expanding Circles (Q15) Example 2: Statistical Mechanics Ludwig Boltzmann, end of 19th century oPhysicists had never accepted idea of atoms oBoltzmann (Austrian physicist) one of first oWorked out Newtonian mechanics for a gas of colliding atoms and molecules - Statistical Mechanics With J. Willard Gibbs – now his own stamp oDB: “Atomic Theory meets Isaac Newton” oSame results as Thermodynamics (accepted) Also explained how those results came about (explanatory) Other physicists still sharply rejected these ideas oMay have contributed to Boltzmann's 1906 suicide

31. 4/7/08Atoms and Stars, Class 1231 Expanding Circles Statistical Mechanics Theory: molecules in a gas move and collide randomly, governed by laws of statistics Once particles mix, essentially no chance of their separating again Computer simulation

32. 4/7/08Atoms and Stars, Class 1232 Expanding Circles Now Boltzmann honored as pioneer oStatistical Mechanics very important Significantly modified by Quantum Mechanics. Second Law of Thermodynamics oIf a hot object and a cold one are in contact, energy always goes from hot to cold Atoms in hot object more energetic (Rumford), travel more Slowed down by collisions with slower atoms from cold object, but these are sped up Statistical Mechanics explains why this happens Demonstration – diffusion – atoms of dye

33. 4/7/08Atoms and Stars, Class 1233 A Taste of Statistical Mechanics See next slide, but here is the explanation o“Gas” with spaces for 4 atoms oGas divided into left & right halves oTwo green atoms, two blue oIn each half, the 4 atoms arrange randomly oAtoms too small to see, we see the average color in each half oOne chance for left being green, right blue oAnother chance for the opposite o4 chances for mixed – turquoise Chances get more lopsided with more atoms

34. 4/7/08Atoms and Stars, Class 1234 A Taste of Statistical Mechanics Start with gas (4 slots) and atoms We see average of color in each half Most common is mixed Odds more lopsided with more atoms

35. 4/7/08Atoms and Stars, Class 1235 Expanding Circles Example 3: Electromagnetism: Greeks : Electricity and magnetism separate oElectricity: static electricity oMagnetism: compasses 1775 – 1890 they became practical oElectric (E) and Magnetic (B) fields oGenerators, motors, some E-B interaction oVolta, Ampere, Ohm, Joule, Hertz (and our own Benjamin Franklin)

36. 4/7/08Atoms and Stars, Class 1236 Expanding Circles 1865 James Clerk Maxwell wrote equations for electricity and magnetism Noticing that the laws as known then said that a changing B could produce an E but not the reverse, Maxwell boldly added a term so that a changing E could produce a B Then a changing E could produce a changing B which produced an E again

37. 4/7/08Atoms and Stars, Class 1237 Expanding Circles (  0 &  0 previously known) But the equation of a wave was known to be: So electricity and magnetism must coexist in waves with speed = 186,000 miles per second

38. 4/7/08Atoms and Stars, Class 1238 Expanding Circles Maxwell confirmed in all respects In other words, we now know that light is electromagnetic waves oThomas Young had shown light to be waves in 1801, not particles as Newton had said oSpeed known since Roemer in 1676 Maxwell (a) hypothesized complete laws for electricity and magnetism, and (b) showed what light was (bonus)

39. 4/7/08Atoms and Stars, Class 1239 Visible Electro-Magnetic Spectrum

40. 4/7/08Atoms and Stars, Class 1240 Electromagnetic Radiation… Spectrum of Electromagnetic Radiation oNumbers = power of ten in frequency (Hertz, Hz) oExamples: 6 means MHz = 10 6 Hz, 9 means GHz = 10 9 Hz WDET: 101.9 MHz, wireless phones: 5.8 GHz Radio Microwave Infrared Visible Light Ultraviolet Light X-Rays Gamma Rays Modified from Physical Science Today, CRM Books, 1973

41. 4/7/08Atoms and Stars, Class 1241 Back to: Expanding Circles Expanding Circles – Implication 1, three examples oWhen two domains meet, become fused into one with a bonus oNot a compromise – both areas transformed, improved Implications: oThis is additional evidence for science If theories were imaginary, different imaginations would rule oHard to attack just one area of science, since they are becoming more tightly tied together Creationists and Intelligent Design advocates finding they have to attack 4.5 billion year age of earth, Big Bang, etc. (readings)

42. 4/7/08Atoms and Stars, Class 1242 Expanding Circles (Review) Implication #2: circles could meet and fill the space oWhat happens then? oDB: what happens is what makes science valuable

43. 4/7/08Atoms and Stars, Class 1243 Expanding Circles Implication #2: oJoined circles expand to fill plane of knowledge (Q17) In earlier times, science and technology developed independently –When there were interactions, technology drove science –Some improvement of scientific instruments resulting from theory in Newton’s time (1687 Principia, 1704 Opticks) In 19 th century, influence became mutual –Example: contribution of Thermodynamics (movement of heat) to steam engine efficiency

44. 4/7/08Atoms and Stars, Class 1244 Expanding Circles Implication #2: (Q16, Q17) oIn 20 th century, science began to drive technology. These 20 th -century technologies were predicted by science well ahead of time: Atomic / nuclear energy (didn’t understand until later that E = mc 2 made this prediction) Laser Computer, transistor, microchip, Internet Radio, TV, telephone, cell phone Jet and rocket engines

45. 4/7/08Atoms and Stars, Class 1245 Expanding Circles Implication #2: (Q16, Q17) oScience driving technology (cont’d): Industry uses science to develop products better- faster-cheaper Designs are science-based, often simulated on computers before prototyping Theory – what makes science valuable, not only for scientists, but for society WMU study: Michigan has to do better at this to be competitive –Manufacturing –Life sciences

46. 4/7/08Atoms and Stars, Class 1246 Expanding Circles Implication #2: oScience driving technology (cont’d): Many scientists believe that US lead in science and technology is disappearing –Degrees granted –Science prizes e.g. Nobel –Scientific articles published –Patents granted, etc. … and that this threatens our technology and economy Probably need at least a core of people who understand “big picture” for innovation

47. 4/7/08Atoms and Stars, Class 1247 Two different types of things Particle (“thing,” “object”) oExamples: baseball, soup can, projectile, star oOne location (or center) oNewton’s three laws govern motion Wave oExamples: waves in water, sound waves, radio waves oSpread out, exists in many places o“Wave Equations” governed motion (not Newton)

48. 4/7/08Atoms and Stars, Class 1248 Two different types of things ParticleWave Position:Definite – one position (center) Spread out, no one place Try to catch it – result is: Get all or noneOnly get part, if that Collision with another: Ricochet, bounce, shatter Pass through each other Existence:All by itselfIn something – the “medium” (before Maxwell)

49. 4/7/08Atoms and Stars, Class 1249 Demonstrations PhET (Physics Education Technology) http://www.colorado.edu/physics/phet/web-pages/simulations-base.html http://www.colorado.edu/physics/phet/web-pages/simulations-base.html oParticles: Gas Properties – they bounce oWaves: Sound >> Interference by Reflection Interference: light  peak, dark  trough ohttp://www.colorado.edu/physics/2000/schroedinger/big_interference.html – some areas gray (unlit)http://www.colorado.edu/physics/2000/schroedinger/big_interference.html Light: early 1800s, Thomas Young proved light is a wave – “double slit experiment” ohttp://www.colorado.edu/physics/2000/schroedinger/two-slit2.htmlhttp://www.colorado.edu/physics/2000/schroedinger/two-slit2.html oConfine a wave – it spreads out

50. 4/7/08Atoms and Stars, Class 1250 Particles collide… Particles of gas mix together, collide

51. 4/7/08Atoms and Stars, Class 1251 but waves pass through each other Sound wave and its reflection (type – sound - is unimportant here)

52. 4/7/08Atoms and Stars, Class 1252 Waves “interfering” Confine a wave and it spreads out

53. 4/7/08Atoms and Stars, Class 1253 Waves Wavelength – distance between peaks (or troughs) Fixed speed Until 20 th century, Wave / Particle – we thought everything was one or the other Wavelength

54. 4/7/08Atoms and Stars, Class 1254 Wave-Particle Duality In 20 th century, with rise of Quantum Mechanics, we understood that everything was both. oFor a wave, x (position) and v (velocity) connected Momentum p = m × v (m = mass, amount of matter) oLed to “Uncertainty Principle” Irreducible uncertainty in our knowledge

55. 4/7/08Atoms and Stars, Class 1255 Uncertainty Principle 1795 Carl Friedrich Gauss (college student) Also Uncertainty Principal 1927 Werner Heisenberg – cannot locate particle exactly

56. 4/7/08Atoms and Stars, Class 1256 Uncertainty Principle No practical effect at macroscopic level oA philosophical problem with The Mechanical Universe and with “The God’s eye view” or The Clockwork Universe over age of universe Important at atomic and molecular level oUncertainties are large on atomic scale oWhat underlies our reality is strange

57. 4/7/08Atoms and Stars, Class 1257 Experiment 9: last week Converting 16ths to decimal & the check: The Goal is the tenths!!! Start: 16ths Goal: decimal Check: 16ths Step 1: divide by 16 Step 2: multiply by 16 Step 3: Equal?

58. 4/7/08Atoms and Stars, Class 1258 Experiment 9, Part 1 Method: measuring circumference using pins and string Circle: agrees with C =  d,  = 3.14… oCan be proven in Plane Geometry (Euclid) Requires careful technique, but most groups agree within 0.2 inches oGroup with disagreement of 0.4 inches should repeat Tonight, extend this to circumference of an ellipse:

59. 4/7/08Atoms and Stars, Class 1259 Experiment 9: overall Important conclusions from last week: oThe formula is almost certainly correct oValue of  almost certainly correct oThe method for measuring C is valid within.1” or.2” Method: putting pins along path, looping string along pins, removing string and measuring its length Circle part and ellipse part are connected. DO NOT treat them as separate. Should measurement errors be the same, or different? If they are different, how can this happen?