Atoms and Stars IST 2420

1
Atoms and StarsIST 2420

• Class 12, April 7
• Winter 2008
• Instructor David Bowen
• Course web site www.is.wayne.edu/drbowen/aasw08

2
Agenda

• Assignments, passbacks, initial signin sheet
• Experiment 9, Part 1
• Miscellaneous cleaning up
• Upcoming assignments
• Experiment 7
• Essay 2
• Reading Chemistry
• Waves and the Uncertainty Principle
• Lab 9 The ellipse

3
Upcoming

• Dont put off Essay 1!!! See me instead.
• This week (April 7)
• Reader Chemistry
• Manual Lab 9 the Ellipse
• Turn in Lab 9 as a whole
• Next week (April 14)
• Essay 2 due on diskette
• Lab 7 Specific Gravity
• One of the things Archimedes did
• SET

4
Upcoming

• April 21 (last regular class)
• Lab 11 the Orbiting Bottle
• Checking up on Newton
• Review for Final Exam
• Due all work to count in regular grade
• April 28 nothing that night but the Final Exam

5
Grade What-If

• Grade What-If (on course web site see first
  slide for this URL)
• Reminder to get current course average, do NOT
  put anything in for assignments you havent been
  graded for yet
• If you put anything in, remove it using delete
  key
• To see what happens if you miss assignments, put
  in zeroes for those (this is what I will do)

6
Semester is Ending!

• If you have been relying on being able to turn
  work in late, it is time to get going
• Alternatives D, F, I, drop see counselor!
• Getting ready for Final
• Read Information Sheet carefully a lot of
  information there
• Look at Final Topics carefully
• Use Review Session!

7
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.

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Essay 2 (contd)

• 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 (thats for SET).
• The topic asks for a core concept and suggests
  a starting point for your analysis
• Due 4/14. At the end of tonights class, we will
  have covered all of the core topics.
• Review Syllabus for other requirements
• All quotes must have references

9
Effects of Newtons 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
Newtons Laws (contd)

• 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)
• Newton clockwork universe, God as clockmaker
• Role of God in celestial motion is possible but
  not required maybe hand of God as cause
• We cannot escape this change (explanation)

11
What Can We Trust as a Fact?

• As practical matters, Newton Laws, Special
  Relativity, General Relativity and Quantum
  Mechanics (all 20th 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
• Changes are very, very small

12
Fact? (contd)

• So science offers practical certainty, but not
  philosophic certainty
• Also, scientific knowledge changes
• Does religion offer certainty?
• Each claims to be certain, but they disagree
• Each 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
Readings Chemistry (Q10c2)

• Chemistry developed after Newton (physics)
• Alchemy transmutation of elements
• Medicine
• Industry much demand for chemicals 1700s
• Mechanical approach from Descartes Newton
• 1700 still the four Aristotelian elements
• Earth fixed volume shape
• Water fixed volume only

14
Chemistry

• 1700 still Aristotelian elements
• Air volume shape expanded to container
• Fire 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
• But liquids supposed to evaporate into air
• Fire combined with liquid air? Many types?
• Water could be solid, liquid, vapor differ by
  fire?

15
Chemistry

• How could big four be elements?
• 1750s Joseph Black experiments with magnesia
  alba, gave off fixed air that extinguished
  flame (CO2), denser than common air, turned
  limewater cloudy
• Use limewater test to show fixed air came from
  fermentation charcoal combustion, would not
  support life
• Fixed air became specific name for this gas
  (CO2)

16
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)
• Many 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
Chemistry

• Antoine Lavoisier (1743 1794)
• Graduated in law but continued science studies
• Accurate weighing, also many practical results
• (Calcination turn a metal to powder (calx) by
  heating in air below melting point phlogiston
  theory explained this as driving off phlogiston)
• But Lavoisiers weighing showed that weight of
  calx increased, for all metals a problem for
  phlogiston theory of combustion

18
Chemistry

• Calx of mercury (oxide of mercury) when heated
  gave off air (gas) that supported combustion and
  life
• Priestley found this air better (5) for
  combustion and life than common air (air)
  eminently respirable air
• Lavoisier had assumed it was common air
• Lavoiser confirmed this, but common air was then
  a mixture

19
Chemistry

• 1778 Lavoisier showed this air also formed acids,
  named it oxygen (acid former) (but we now know
  that hydrogen makes acid)
• 1783 Cavendishs assistant told Lavoisier about
  Cavendishs experiment of applying spark to
  inflammable air (H), finding dew which was
  identified as water
• Lavoisier water was not an element, combination
  with oxygen for all combustion

20
Chemistry

• Lavoisier named flammable air hydrogen for
  water former
• Lavoisier and others formed new chemical
  terminology speaking well was like reasoning
  well
• Oxide combination with oxygen
• Names indicated amount of oxygen (ous lt ic)
• Sulfurous acid H2SO3
• Sulfuric acid H2SO4

21
Chemistry

• Lavoisier terminology
• Gas any vapor
• Air the atmosphere, a mixture (80 N, 20 O)
• Fire was caloric (no correct theory until 19th
  century started by Count Rumford)
• John Dalton (1766 1844), meteorologist
• Converted to chemistry when he understood air was
  a mixture why didnt different gases separate
  by gravity?

22
Chemistry

• John Dalton (1766 1844), meteorologist
• Also gases dissolved in water proportional to
  pressure why?
• Hypothesized gases composed of atoms, each gas
  interacted with itself (see later slide)
• Law of definite proportions chemicals
  combined by weight in simple ratios
• Dalton proposed formulae based on these
  chemical atomism

23
Chemistry

• John Dalton (1766 1844), meteorologist
• Dalton proposed formulae based on these
• Many of his formulae were wrong
• Example he said water is HO
• More were right, enough to straighten out the
  errors over time
• (DB) Physicists did not accept chemical atomism
  until they accepted Maxwell and Boltzmann at the
  end of 19th century
• (DB) Direct observations of atoms in 20th century

24
Chemistry (DB)

• John Dalton (1766 1844), meteorologist
• What led Dalton to hypothesize atoms?
• Characteristics of matter
• Solids cannot occupy the same space
• Some liquids can
• All gases can
• Why didnt 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
Experiment IV (not done) (Q11)

• Chemical composition of water
• Electrical current decomposes water H2O ? 2H O

Lab ManualPg 13
26
Atomic Nature of Matter (Review)

• First direct evidence 1827 Robert Brown (10c2)
• Noticed spores jiggling under microscope
• Brownian motion bombarded by molecules
• Robert Brown, 1827
• See next slides, orhttp//www.is.wayne.edu/drbowe
  n/Class-Room_Models/Welcome.htm
  http//www.colorado.edu/physics/phet/web-pages/si
  mulations-base.html
• Now we have more direct evidence

27
Brownian Motion (Review)
Jagged tracks of pollen particles. Gas molecules mode visible. Jagged tracks explained as due to collisions with gas molecules.
28
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?
• My answer science drives technology (C11S15-19)

29
Expanding Circles

• Implication 1 What happens when two expanding
  circles meet? I promised three examples (Q15)
• Example 1 Newton uniting celestial (stars) and
  terrestrial (on land) already done (C10S32-33)
• Examples 2 and 3 now.

30
Expanding Circles (Q15)

• Example 2 Statistical Mechanics
• Ludwig Boltzmann, end of 19th century
• Physicists had never accepted idea of atoms
• Boltzmann (Austrian physicist) one of first
• Worked out Newtonian mechanics for a gas of
  colliding atoms and molecules - Statistical
  Mechanics
• With J. Willard Gibbs now his own stamp
• DB Atomic Theory meets Isaac Newton
• Same results as Thermodynamics (accepted)
• Also explained how those results came about
  (explanatory)
• Other physicists still sharply rejected these
  ideas
• May have contributed to Boltzmann's 1906 suicide

31
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
Expanding Circles

• Now Boltzmann honored as pioneer
• Statistical Mechanics very important
• Significantly modified by Quantum Mechanics.
• Second Law of Thermodynamics
• If 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
A Taste of Statistical Mechanics

• See next slide, but here is the explanation
• Gas with spaces for 4 atoms
• Gas divided into left right halves
• Two green atoms, two blue
• In each half, the 4 atoms arrange randomly
• Atoms too small to see, we see the average color
  in each half
• One chance for left being green, right blue
• Another chance for the opposite
• 4 chances for mixed turquoise
• Chances get more lopsided with more atoms

34
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
Expanding Circles

• Example 3 Electromagnetism
• Greeks Electricity and magnetism separate
• Electricity static electricity
• Magnetism compasses
• 1775 1890 they became practical
• Electric (E) and Magnetic (B) fields
• Generators, motors, some E-B interaction
• Volta, Ampere, Ohm, Joule, Hertz (and our own
  Benjamin Franklin)

36
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

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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
Expanding Circles

• Maxwell confirmed in all respects
• In other words, we now know that light is
  electromagnetic waves
• Thomas Young had shown light to be waves in 1801,
  not particles as Newton had said
• Speed known since Roemer in 1676
• Maxwell (a) hypothesized complete laws for
  electricity and magnetism, and (b) showed what
  light was (bonus)

39
Visible Electro-Magnetic Spectrum
40
Electromagnetic Radiation
Radio Radio Microwave Infrared Visible
Light
Ultraviolet Light X-Rays Gamma Rays
Modified from Physical Science Today, CRM Books,
1973

• Spectrum of Electromagnetic Radiation
• Numbers power of ten in frequency (Hertz, Hz)
• Examples 6 means MHz 106 Hz, 9 means GHz 109
  Hz
• WDET 101.9 MHz, wireless phones 5.8 GHz

41
Back to Expanding Circles

• Expanding Circles Implication 1, three examples
• When two domains meet, become fused into one with
  a bonus
• Not a compromise both areas transformed,
  improved
• Implications
• This is additional evidence for science
• If theories were imaginary, different
  imaginations would rule
• Hard 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
Expanding Circles (Review)

• Implication 2 circles could meet and fill the
  space
• What happens then?
• DB what happens is what makes science valuable

43
Expanding Circles

• Implication 2
• Joined 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 Newtons time (1687
  Principia, 1704 Opticks)
• In 19th century, influence became mutual
• Example contribution of Thermodynamics (movement
  of heat) to steam engine efficiency

44
Expanding Circles

• Implication 2 (Q16, Q17)
• In 20th century, science began to drive
  technology. These 20th-century technologies were
  predicted by science well ahead of time
• Atomic / nuclear energy (didnt understand until
  later that E mc2 made this prediction)
• Laser
• Computer, transistor, microchip, Internet
• Radio, TV, telephone, cell phone
• Jet and rocket engines

45
Expanding Circles

• Implication 2 (Q16, Q17)
• Science driving technology (contd)
• 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
Expanding Circles

• Implication 2
• Science driving technology (contd)
• 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
Two different types of things

• Particle (thing, object)
• Examples baseball, soup can, projectile, star
• One location (or center)
• Newtons three laws govern motion
• Wave
• Examples waves in water, sound waves, radio
  waves
• Spread out, exists in many places
• Wave Equations governed motion (not Newton)

48
Two different types of things
Particle Wave
Position Definite one position (center) Spread out, no one place
Try to catch it result is Get all or none Only get part, if that
Collision with another Ricochet, bounce, shatter Pass through each other
Existence All by itself In something the medium (before Maxwell)
49
Demonstrations

• PhET (Physics Education Technology)http//www.col
  orado.edu/physics/phet/web-pages/simulations-base.
  html
• Particles Gas Properties they bounce
• Waves Sound gtgt Interference by Reflection
• Interference light ? peak, dark ? trough
• http//www.colorado.edu/physics/2000/schroedinger/
  big_interference.html some areas gray (unlit)
• Light early 1800s, Thomas Young proved light is
  a wave double slit experiment
• http//www.colorado.edu/physics/2000/schroedinger/
  two-slit2.html
• Confine a wave it spreads out

50
Particles collide
Particles of gas mix together, collide
51
but waves pass through each other
Sound wave and its reflection(type sound - is
unimportant here)
52
Waves interfering
Confine a wave and it spreads out
53
Waves

• Wavelength distance between peaks (or troughs)
• Fixed speed
• Until 20th century, Wave / Particle we thought
  everything was one or the other

Wavelength
54
Wave-Particle Duality

• In 20th century, with rise of Quantum Mechanics,
  we understood that everything was both.
• For a wave, x (position) and v (velocity)
  connected
• Momentum p m v (m mass, amount of matter)
• Led to Uncertainty Principle
• Irreducible uncertainty in our knowledge

55
Uncertainty Principle

• 1795 Carl Friedrich Gauss (college student)
• Also Uncertainty Principal 1927 Werner Heisenberg
  cannot locate particle exactly

56
Uncertainty Principle

• No practicaleffect atmacroscopic level
• A philosophical problem with The Mechanical
  Universe and with The Gods eye view or The
  Clockwork Universe over age of universe
• Important at atomic and molecular level
• Uncertainties are large on atomic scale
• What underlies our reality is strange

57
Experiment 9 last week

• Converting 16ths to decimal the check
• The Goal is the tenths!!!

58
Experiment 9, Part 1

• Method measuring circumference using pins and
  string
• Circle agrees with C ?d, ? 3.14
• Can be proven in Plane Geometry (Euclid)
• Requires careful technique, but most groups agree
  within 0.2 inches
• Group with disagreement of 0.4 inches should
  repeat
• Tonight, extend this to circumference of an
  ellipse

59
Experiment 9 overall

• Important conclusions from last week
• The formula is almost certainly correct
• Value of ? almost certainly correct
• The 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?