Atoms and Stars, IST 2420
Midterm Makeup in 122 Cohn
Monday, November 17
4:50 – 5:50 PM
Atoms and Stars
IST 2420
Class 11, November 17
Fall 2008
Instructor: David Bowen
Course web site: www.is.wayne.edu/drbowen/aasf08
Agenda
•
•
•
•
•
•
•
•
Assignments and passbacks
Upcoming assignments
Relativity
Expanding Circles – Implication #1
Update: planets and exoplanets
Readings: Atomic Nature of Matter
Converting Sixteenths to Decimal
Lab 9 Part 2 (Ellipse): Archimedes’ Exploits
11/17/08
Atoms and Stars, Class 11
3
Upcoming …
• Don’t put of Essay 1!!! See me instead.
• This week (November 17):
o Remember to initial the sign-in sheet
o Reader: The Atomic Nature of Matter
o Manual: Lab 9 – the Ellipse
• Next week (November 24):
o Reader: Chemistry
o Manual: Lab 7 – Specific Gravity
o Hand in Lab 9 as a whole
11/17/08
Atoms and Stars, Class 11
4
Upcoming …
• Two weeks, December 1: Essay 2 due via
Digital Dropbox in Blackboard
o Lab 11 – the Orbiting Bottle
o SET
• Three weeks: December 8. (last regular
class)
o Lab 4 – The Chemical Composition of Water
o Review for Final Exam
o Due: all work to count in regular grade
• Four weeks: December 15. Nothing that
night but the Final
Exam
11/17/08
Atoms and Stars, Class 11
5
Grade What-If
• Grade What-If (on course web site – see
first slide for this URL)
o Reminder: 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
o To see what happens if you miss assignments,
put in zeroes for those (this is what I will do)
11/17/08
Atoms and Stars, Class 11
6
Semester is Ending!
• If you have been relying on being able to
turn work in late, it is time to get going
o Alternatives: D, F, I, drop – see counselor!
• Getting ready for Final:
o Read Information Sheet carefully – a lot of
information there
o Look at Final Topics carefully
o Use Review Session!
11/17/08
Atoms and Stars, Class 11
7
Expanding Circles (Review)
• Implication #1: eventually, expanding
circles must meet and overlap
o Different approaches, different theories – will
not agree
11/17/08
Atoms and Stars, Class 11
8
Expanding Circles (Review)
• Implication #2: circles could meet and fill
the space
o What happens then?
o DB: what happens is what makes science
valuable
11/17/08
Atoms and Stars, Class 11
9
Expanding Circles
• Implication #1: eventually, expanding
circles must meet and overlap
• Three examples in this course:
o Isaac Newton (review, this class)
o James Clerk Maxwell (Class 9, November 3)
o Ludwig Boltzmann (later class)
11/17/08
Atoms and Stars, Class 11
10
Expanding Circles
• Implication #1: eventually, expanding
circles must meet and overlap
• Possible interactions:
o
o
o
o
o
Withdrawal
One wins out over the other
Compromise
Synthesis
???
11/17/08
Atoms and Stars, Class 11
11
Expanding Circles
First example: celestial and terrestrial mechanics
• Case of Newton uniting terrestrial and celestial
mechanics
o Newton – new theory united them
o Each is understood more accurately and causally
o A bonus – applies to all motion, calculus, applied in
technology, model for new science
o Led to understanding interactions of planets and
discovery of Neptune (a future class)
11/17/08
Atoms and Stars, Class 11
12
Expanding Circles
• Expanding Circles – my conclusion
o When two domains meet, become fused into one with a
bonus
o Not a compromise – both areas transformed
• Implications:
o This is additional evidence for science
•
If theories were imaginary, different imaginations would rule
o Hard to attack just one area of science, since they are
becoming more tightly tied together
•
11/17/08
Creationists and Intelligent Design advocates finding they have
to attack 4.5 billion year age of earth, Big Bang, etc. (readings),
radioactive dating
Atoms and Stars, Class 11
13
Limits on Space Travel
• The idea of space travel has always been
attractive.
• Einstein’s Special Theory of Relativity
(1905) set limitations on space travel.
o Maximum possible speed is speed of light – one
year to travel one light year (but today we
cannot reach even a small fraction of this)
o Nearest star is 4 light years away
o Galaxy ~100,000 light years across
11/17/08
Atoms and Stars, Class 11
14
Background
• Before 1905, we could not see expected
changes in the speed of light when the
direction of the earth changed as it orbited
the sun.
• Tried to explain this by saying that distancemeasuring devices got shorter in direction
of motion.
• Didn’t work.
11/17/08
Atoms and Stars, Class 11
15
Relative Motion
• Newton said that speeds in the same
direction should add, nothing special about
light.
• Simulation – car traveling on top of a
railroad car:
http://www.is.wayne.edu/drbowen/Class-Room_Models/Welcome.htm
• Speed of car with respect to station = speed
of railroad car + speed of car on railroad car
• Speed of light could be exceeded – no issue
for Newtonian view
11/17/08
Atoms and Stars, Class 11
16
Relative Motion
Relative motion of rr-car and car on top. car speed
wrt station = rr-car speed + car speed on top of rr-car
11/17/08
Atoms and Stars, Class 11
17
Special Relativity
• Newtonian Relativity simple, correct at normal
speeds, but wrong for very high speeds (light).
• Einstein’s Theory of Special Relativity (1905)
said constant measured speed of light is a
property of space and time themselves. No
explanation – that’s the way things are, a
fundamental condition.
• Space and time went from the passive stage for
the universe to active players in the drama.
• Revolutionary, but it works.
11/17/08
Atoms and Stars, Class 11
18
Reading: What is Gravity?
• Newton: we do not know what gravity is
• DB: After 20th century, two explanations
o These don’t agree, so that is a problem, but a
possible unification
• Explanation #1: 1915: Einstein’s General
Theory of Relativity
o Gravity is due to the bending of space by
masses
o Analogy of a ball rolling on a sheet of rubber
around a heavy object
11/17/08
Atoms and Stars, Class 10
11
19
What is Gravity? (cont’d)
• Explanation #2: Quantum Mechanics (applies
to very small objects) about 1925:
o All forces, including gravity, are due to the
exchange of (very small) particles between
objects
o Particles observed for weak, strong (nuclear) and
electromagnetic forces (photon for e-m)
o Not yet observed for gravitational force
o Difficult to find, but would be serious if not found
11/17/08
Atoms and Stars, Class 10
11
20
What is Gravity? (cont’d)
• Both General Relativity and Quantum Mechanics
are well-established science
• Explanations for gravity from General Relativity
and Quantum Mechanics have not yet been
reconciled (two theories explaining same thing)
o Would be called Quantum Theory of Gravity
o Does not yet exist
o Are reconciled in latest theories, e.g. String Theory, but
this does not yet have experimental verification – we do
not yet even know what experiments to do or how to do
them
• String Theory may turn out to explain itself
11/17/08
Atoms and Stars, Class 10
11
21
Status of Newton’s Laws
• Are scientific theories reliable? Many hedges
in this course, for example:
o
o
o
o
o
o
Scientific knowledge is provisional
Experiments do not prove theories
One experiment can overturn a theory
Science has a limited scope – a boundary
Science is not an adequate basis for living
Scientists often do not follow scientific method
• Maybe only foolish people use science? Not!
11/17/08
Atoms and Stars, Class 10
11
22
Status of Newton’s Laws
• Range of authority for Newton’s Laws:
o Objects moving slower than about three million
miles per hour
o Objects weighing more than about
0.000,000,000,000,000,000,01 pounds (19 zeroes)
o Objects weighing less than about (31 zeroes)
40,000,000,000,000,000,000,000,000,000,000 lb
• Within this range of authority, Newton’s Laws
are extremely reliable and precise
11/17/08
Atoms and Stars, Class 10
11
23
Status of Newton’s Laws
• Newton’s Laws have passed stringent tests
o Control of spacecraft
o Use in design and control of countless machines
o 1846 predicted mass and orbit of Neptune from
its effect on the orbit of Uranus (productive)
• For very small masses (molecular), Quantum
Mechanics is needed instead
• For very fast objects, Special Relativity
• For very massive objects, General Relativity
11/17/08
Atoms and Stars, Class 10
11
24
“Stars” Summary
• Long human interest in astronomy
• Greeks (Aristotle and Ptolemy) geocentric
• Catholic Church gave this additional
importance
• Copernicus – first modern heliocentric
theory – simpler, more accurate
• Brahe – accurate continuing measurements
11/17/08
Atoms and Stars, Class 11
25
“Stars”Summary
• Kepler – Three Laws, orbits are ellipses – a
descriptive theory – what the patterns are
• Galileo – observations calling aspects of
Aristotle’s and Church’s astronomy into
doubt
• Newton – explanatory theory – why the
orbits are ellipses, etc. (because of the
force)
11/17/08
Atoms and Stars, Class 11
26
Update: What is a planet?
• 1846 Neptune discovered from changes to orbit of
Uranus, using Newton’s Laws
o Predicted position and mass
o Productivity
• Pluto discovered 1930, orbit radius ~30 AU
• 2002 – 2006 other solar system objects found by
looking for motion between exposures
o Quaoar, 2003 VB12 (“Sedna”), 2004 DW, Xena
• Xena larger than Pluto – is it a planet?
• 39 to 97 AU (very flattened ellipse)
• Plane ~ 43° to ecliptic
11/17/08
Atoms and Stars, Class 11
27
New “planets”
(cont’d)
• Neptune outermost
“real” planet
• New ones near
Kuiper belt
(asteroids)
• “Reals” formed
from dust cloud,
forced orbits to
circular
11/17/08
Atoms and Stars, Class 11
28
New “planets” (cont’d)
• “Classification” - what is a planet?
o Follows “description” in development of
science
o What are the real differences?
11/17/08
Atoms and Stars, Class 11
29
2007 Change
• New planets are not planets, neither is Pluto
(“planetoid”)
o Now, eight planets
• New characteristic of planet: has cleared its
orbit of other bodies
11/17/08
Atoms and Stars, Class 11
30
What are these things??
Category
Star
Greek
“Fixed” – travel
together
Modern
Shines with own
light
Planet
“Wanderer” –
does not travel
with stars, Earth
not a planet
Only one, like
planet
Circles a star,
shines by reflected
light (New: clears
out orbit)
Circles a planet,
reflected light
Moon
11/17/08
Atoms and Stars, Class 11
31
Exoplanets
• Exoplanet – outside our solar system
o Circle other stars, shine by reflected light
o Can they support life?
• Methods:
o Star wobbles (Newton’s Third Law)
o Dip in brightness of star as planet passes over
o Just this week: direct observation
• Count: 327 around 278 stars
o None earthlike yet
11/17/08
Atoms and Stars, Class 11
32
Exoplanets
11/17/08
Atoms and Stars, Class 11
33
Three waves of science?
1. Physical science – the subject of this course –
mature, quantitative (95%)
•
Very controversial when it was new
• 1400 – 1800 AD, although very long roots & still developing
•
Now pretty much settled for everyday objects
2. Biological or life science – qualitative (30%?)
•
Much newer, evolution is the basis, still controversial
publicly, but for scientists it is settled
• 1800 – 1935 AD
•
•
11/17/08
Coming into general use in society & economy
Will qualitative change to quantitative?
Atoms and Stars, Class 11
34
Three waves of science?
3.Cognitive science – how emotions and the
mind work – just starting (5%)
o Will be as controversial, if not more
o Potential for controversy: Science of Desire :
The Gay Gene and the Biology of Behavior &
The God Gene (spirituality) / Dean Hamer
• Spirituality predestined for some, denied to others?
• A single gene is unlikely to be the sole cause
o Will call into question how we view ourselves
11/17/08
Atoms and Stars, Class 11
35
Summary, Once More…
• Strong dose of the value of science here
• One more time, about science:
o Two pillars – repeatable experiment (what makes it
reliable) and explanatory theory (what makes it valuable)
• Developed 1400 – 1800 AD: Copernicus to Dalton
o Developing hypotheses and theories is creative
o Has a boundary but expands aggressively
 not a complete basis for living
o Now drives technology (coming up)
o We all use the technology
o Conflicts with some, but not all, religious beliefs
• People do not agree on what “Christian” is, let alone other
religions
o People of all ethnicities have been able to contribute
11/17/08
Atoms and Stars, Class 11
36
Two parts
• Newton ended the “Stars” part of this course
• This week starts the “Atoms” part
• “Element” – Greeks understood this to be
something fundamental, without parts, not made
from other things, could not be broken down
o Aristotle: air, earth, fire & water are elements
o First discoverers of atoms disproved Aristotle, thought
atoms were the Greek elements
o Today we still call atoms “elements,” but not in the
same sense – they are made of other things
o Still have question of what (if anything) is elemental
11/17/08
Atoms and Stars, Class 11
37
And now…
• “Atoms”
• Before Einstein & E = mc2, matter and
energy separate
• Atomic Theory – all matter is made up of
atoms
• Start by looking at our knowledge of atoms
• Then, how did this knowledge come about?
11/17/08
Atoms and Stars, Class 11
38
Readings
“Atomic Nature of Matter”, Hewitt
• All matter is atoms (“Atomic Theory”)
o Atoms are elements – “indivisible” – mostly
empty (10c#1)
o 109 types total, 90 are natural, rest radioactive
• Each type has its own properties, e.g. weight,
reactions
o Hydrogen most common atom in universe
• Rare by itself on earth
o Life primarily C, H, O, N
• Atoms small enough to be invisible - waves
11/17/08
Atoms and Stars, Class 11
39
Atomic Nature of Matter
• First direct evidence 1827 Robert Brown (10c#2)
o Noticed spores jiggling under microscope
o “Brownian motion” – bombarded by molecules
• Robert Brown, 1827
o See 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
o Now we have more direct evidence
• Atoms bond into molecules – many types (10c#1)
o Molecules - compounds
o Molecules have separate properties from atoms
o Burning is combination with O
• New - modern automobiles very little CO
11/17/08
Atoms and Stars, Class 11
40
Brownian Motion
Jagged tracks of pollen
particles.
11/17/08
Gas molecules mode visible.
Jagged tracks explained as
due to collisions with gas
molecules.
Atoms and Stars, Class 11
41
Brownian Motion
Imagine the red molecules were so small that we couldn’t see
them – blue ones would “jostle” for no apparent reason.
11/17/08
Atoms and Stars, Class 11
42
Atomic Nature of Matter
• 1811 (Amedeo) Avogadro’s hypothesis
(now Law)
o At same T & P, equal Vs of gas have equal #s
o Each atom, molecule heavier  gas heavier
• Amu = atomic mass unit
• C 12 amu, H  1 amu, O  16 amu, U  238 amu,
H2O  18 amu – also combine in gm, lb etc.
• Atom has electrons orbiting nucleus
o Electrons – volume but very little mass
o Nucleus – mass but very little volume
11/17/08
Atoms and Stars, Class 11
43
Atomic Nature of Matter
• Electron, e – negative charge, flow of
electrons is electrical current
• Nucleus has neutrons, n (no charge) and
protons, p (positive charge)
o Cube 3/8” would weigh 133,000,000 tons
• Like charges repel, unlike charges attract
o Nucleii positive, repel each other
o Atoms neutral; number of e = number of p
• (not = under special circumstances)
11/17/08
Atoms and Stars, Class 11
44
Atomic Nature of Matter (end)
• Electrons in shells (2, 8, 18, …)
o If shells filled, element is inert
o Unfilled shells determine activity
o #p = atomic number, chemical characteristics
• Same element even if atom loses or gains electrons
• Antimatter – anti-electron (1932), antineutron, anti-proton
o Annihilate  100% energy (light)
• Nuclear reactions normally 1%
• End of article…
11/17/08
Atoms and Stars, Class 11
45
Element, Compound, Mixture
(Q10 a-b)
• Element: matter with all atoms the same
o Examples: C, S, H, O
• Compound: made up of the same molecules
o Examples: H2O, CO2
o Matter with all molecules the same
o Atoms bond together into chemical
combination
o Always the same composition
11/17/08
Atoms and Stars, Class 11
46
Element, Compound, Mixture
(end)
• Mixture (Q10a-b)
o Atoms and molecules not close enough to bond
o Composition varies
o Examples:
• Air (mostly N and O) but variable
– Amount of greenhouse gases an issue – CO2
• Earth – composition extremely variable
– Add various fertilizers
• Dough – vary composition for different breads
• Cinnamon and sugar
o Constituents could in principle be separated
11/17/08
Atoms and Stars, Class 11
47
Epistemology
• Several times you have asked me “Is this
absolutely true?” I tend to hesitate with
questions like this – here is why.
• Epistemology – the study of knowledge –
why do we accept things as true?
• Two properties we would like for truth:
o Eternal – unchanging
o Universal – the same everywhere
11/17/08
Atoms and Stars, Class 11
48
Epistemology (end)
• Science doesn’t do “eternal”
o Scientific truth is provisional – subject to change
o We keep learning new things and improving
theories
• Religions have problems with “universal”
o Each religion claims universality but how can
different religions differ, if there is one truth?
o For science and religion, Galileo agreed with
modern Catholic doctrine – there is one truth
• Reinterpret Bible if it disagrees with accepted science
11/17/08
Atoms and Stars, Class 11
49
Converting Sixteenths to Decimal
(Q1)
• Converting inches and sixteenths to decimal
inches, and pounds and ounces to decimal
pounds:
o How many sixteenths of an inch are there in
one inch?
o How many eighths of an inch are there in one
inch?
o On exams, will be given ounces in a pound (16)
if needed, but not sixteenths of an inch in an
inch
11/17/08
Atoms and Stars, Class 11
50
Converting Sixteenths to Decimal
(Q1)
• Converting inches and sixteenths to decimal
inches, and pounds and ounces to decimal
pounds:
1. Divide # sixteenths by 16 (result between 0 and
1), call this “X” (make it a whole number)
2. Check: multiply X by 16, get about the original
number of sixteenths – SHOW THIS CHECK
ON DATA SHEET !!!
3. Add X to # whole inches to get decimal inches
11/17/08
Atoms and Stars, Class 11
51
Experiment 9
• Good technique (both parts):
o When you stick pins in, leave some of metal
shaft exposed – string goes around this part
o Do not stretch string (thread doesn’t stretch
much at all, thicker twine can stretch)
o Use a pen to make marks on the string, measure
between the marks
11/17/08
Atoms and Stars, Class 11
52
Experiment 9
• Measure length of curved lines by winding
string around line, measuring string
• Possible sources of error: (a) stretching, (b)
thickness (middle of string along the curve)
o Protect against these!!!
• To multiply by , calculate length
differences etc.: convert lengths from inches
and sixteenths to decimal inches
INCLUDING CHECK !!!
11/17/08
Atoms and Stars, Class 11
53
Experiment 9
• Part 1: Circle
o Data Sheet: Assignments 1 – 15
o Analysis: Assignments 16 – 24
o If Assignment 16 discrepancy > .2 inches, show me
how you did it
• Part 2: Ellipse
o Data Sheet: Assignments 25 – 32 & 36
o Analysis: Assignment 33
• In Addition (overall, not in manual):
o Are measurement errors for circle and ellipse the same,
or different?
o If they are different, how can this be the case?
11/17/08
Atoms and Stars, Class 11
54