Download Notes for Class 7, March 2

Atoms and Stars
IST 2420
Class 7, March 2
Winter 2009
Instructor: David Bowen
Course web site: www.is.wayne.edu/drbowen/aasw09
Agenda
• Assignments and passbacks
• Reminders: Online Grade Reports,
Grade What-If, Essay grades
• Readings: “Watershed”
• Preview: Galileo
• Review: Boyle’s Law
• Upcoming assignments
• Essay 2
• Review for Midterm
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Handouts & Announcements
• Initial the sign in sheet
Due tonight
• Report for Lab 8 Part 2
3/2/09
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Coming up…
• Tonight:
o Review session for Midterm
• One hour, at the end of class (replaces lab)
• Next week: Midterm
o One hour at the start of class
o 3 to 5 questions from the list
o Regular class, with lab, after Exam
• Only assignment (except for studying): read Manual
for Experiment 13
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Information sheet for Midterm
•
•
•
•
Will get clean copy on Exam
Many basic facts
Direct answers for many questions
Must use your own words – no credit for
simply copying from the information sheet
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New 1.j after 1.i
Type
Star
Planet
Earth
3/2/09
Ancient idea
All rotate together
around stationary
earth
Wanders among
stars, has retrograde
motion
Fixed at center of
universe / solar
system
Modern idea
Shines with its own
light (a nuclear
reactor)
Orbits a star, shines
by reflection from
star
A planet circling
our sun (a star)
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New 1.j after 1.i
Type
Moon
Ancient idea
Only one known,
circles Earth
Galaxy
Not known
Comet
Surprise
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Modern idea
Anything that orbits
a planet – many
known
A large group of
stars, 10 million to
1 trillion
Orbits sun, has
coma (tail)
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New 1.j after 1.i
Type
Ancient idea
Asteroid Surprise
Modern idea
Orbits sun, has no
visible coma (tail)
Updated version on course website, still
under Class 6
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Grade What-If (repeat)
• What is your average now?
o What grade are you headed for?
o What do you have to improve to get a better
grade?
• It’s the Grade What-If (doing what-if with
your Atoms and Stars grade)
o On the course web site
o Save to a disk drive if you want to save results
o Early in semester to work on course grade
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Essays back…
• Essay 1 being returned through BlackBoard
Digital DropBox
• File with comments and grades
o AAS_W09_ESSAY_1_YTIg.doc
• “YTI” = “Your Three Initials”
• “_” if no middle initial on file with WSU
• g = “graded,” comments and grades in [ ]
• These grades, like all here, can be discussed
• This assignment, like all here, can be redone
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Problems in Essays
• Some wrote that Aristotle was a scientist:
NO.
o Generalist, not specialist
• Archimedes much more like modern scientist here
o Used logic only, not experiment
• Aristotle did not do experiments, and we
have no indication that he followed any or
all of Copi’s seven steps, although several
people wrote that he did.
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Issue With Digital DropBox
• DO NOT use # with the Digital DropBox,
either in the file name or in any other way.
• Everything will seem to work well when
you drop the file off
• BUT the Instructor will not be able to
access it anyway
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Missing a Class…
• No excuses needed
• BUT you are still responsible for the
material (standard for College level).
o Syllabus: get the notes, read them (and other
assignments), and get any questions cleared up
before the next class.
• To make up the grade, write a two-page
summary of the NOTES (see Syllabus for
details).
o Missing one or two classes lowers your grade
by only a small amount.
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The Watershed
Chapter 6. The Giving of the Laws
• 1609 The New Astronomy with first two
laws
o Precise verifiable mathematical laws, divorced
from theology and spheres
o Solar system: free-floating bodies in space
moved by forces between them
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The Watershed
• Brahe “gave” Mars to Kepler – the most
elliptical.
o Brahe and others could not make it fit
• Copernican orbits centered on earth’s orbit,
not sun, but sun supposed to cause orbits
• K saw balance between a force in sun
(today, gravity) and a force in the planet
(today, inertia or resistance to motion)
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Ellipse
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Drawing an Ellipse
• Two pins, a loop and a pen
to draw an ellipse
• Distance from yellow pin
(focus) to ellipse + distance
from blue pin (the other
focus) = a constant
• From Wikipedia
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The Watershed
• Plane of Mars orbit passed through sun,
angle between Mars plane and earth’s fixed
• Initially kept circular orbits but threw out
constant speed
o reasoned that force varied with distance from
sun, so speed could also
• Verified hypothesis with four of Brahe’s
positions, but added two – did not work
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The Watershed
• Insisted on both the facts and the theory
o A break with previous civilizations – Alfred
North Whitehead
o Even a break with K’s Mysterium
Cosmographicum
o Koestler: Made necessary by change from
fitting to geometrical theories towards physical
causes
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The Watershed
• Started over, threw out circular motion as
well
• Did not assume shapes of orbits as his
predecessors did
o Only three points determine a circle
o Calculated enough points to show the shape,
had to start with earth since Mars seen from
earth
o Work on Second Law had many errors but he
found and corrected them, theory worked in the
end
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The Watershed
• Developed new methods, refined his skills,
became familiar with numbers
• Returned to shapes of orbits, showed Mars
orbit not a circle
• Frightened by abandoning circular orbits
• Convinced himself by combining force of
sun and force of planet that orbit was eggshaped (bigger at one end)
o (Ellipse has both ends the same)
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The Watershed
• Used ellipse as an aid to calculations for
years while insisting orbit was egg-shaped
• Calculations were laying the foundation for
calculus (invented by Newton later) –
theory of area of irregular shapes
• Clued in by numerical relationship which
seemed at first like a coincidence
• K: “The roads that lead man to knowledge
are a wondrous as that knowledge itself.”
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The Watershed
• Rejected an orbit because he had made a
mistake in calculations and also didn’t
realize it was an ellipse, tried an ellipse and
came back to that equation
o
 = “eccentricity”
o “Ah what a foolish bird I have been”
• But rest was mopping up
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The Watershed
• Kepler saw no particular reason for these
laws, or egg, did not make sense until
Newton
o Ashamed of abandoning circular orbits
• Prouder of orbits based on five regular
solids
• Unique in devotion to both theory and
observation, even switching back and forth
• Also deep immersion, knowing the numbers
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The Watershed
• Removed astronomy from geometry to
physics – motion and its causes – looked at
it in a new frame
o Koestler: essence of creativity
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The Watershed
Chapter 7. Kepler Depressed
• Publishing difficulties, difficulties getting
Brahe’s data, getting paid, etc. (Tengnagle)
• Broke with King, didn’t give edition to
King but sold it to publishers in lieu of
salary
• Not a friendly reception: friends but no
colleagues
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The Watershed
• Germans did not recognize significance, but
English did, most importantly, Newton
• Kepler getting known, somewhat happier
but always complaining about health,
money
• King Rudolph (patron) getting eccentric,
isolated, brother grabbing kingdom
• Kepler saw a second exile coming
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The Watershed
Chapter 9: Chaos and Harmony
• Galileo invented telescope, but Kepler
explained how it worked – 1610: Dioptrice
o Very straightforward and plain
• 1611 King Rudolph abdicated (died a year
later), wife and child dead (K still kept title)
• Modest provincial mathematicus post in
Linz, upper Austria, but he got the salary
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The Watershed
• Religious problems – disagreed with
doctrines the Lutherans later abandoned
o Mother accused of witchcraft in Leonburg,
threatened with burning at the stake 1615 –
1621
o Accused of the evil eye, entering houses
through locked doors and more
o K shot back as Imperial Mathematicus,
demanded he receive all documents, etc.
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The Watershed
o Mother transferred to Wuerttemburg, led to
torture chamber, refused to confess, failed
“weeping test,” was released (Pg 220) a year
later
o Could not return to Leonburg – threatened with
lynching
• 1618 Kepler discovered 3rd law (t2  r3)
more straightforwardly, with only one
backtrack
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The Watershed
• Contribution of Kepler was methods; did
not abandon mysticism
• Without calculus, Kepler could not see the
connections between his three laws
• Koestler: “…Kepler set out to discover
India and found America.”
• Quote from Heinrich Herz (discovered radio
waves) Pg 225
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The Watershed
• King Wallenstein wanted Kepler for
astrological advice, but Kepler felt this was
unethical, avoided it.
o King got planetary positions from Kepler, gave
them to his other astrologers
o Kepler dismissed
• Wandered, looking for a position, trying to
get money owed him
• Died in Ratisbon, Germany 1630
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Readings – Galileo and Later
The Rise of Science
(the core of this course)
Copernicus
Brahe
Kepler
Galileo
Descartes
The Greeks
Bacon
Newton
1450
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1500
1550
1600
1650
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1700
1750
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Galileo: Preview (Q25)
• Astronomical observations with telescope
o Mountains on moon (not perfect)
o Discovered Moons of Jupiter (Earth not unique)
o Saw phases of Venus, argued (falsely) these
were incompatible with geocentrism (Q26)
• Argued (falsely) that tides on Earth
incompatible with geocentrism (Q26)
• Sensational book brought attention
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Galileo (continued) (Q25)
• Publicly supported Copernicus, Church said
he had to be evenhanded with Ptolemy
o Put Pope’s words in mouth of “Simplicius”
• Church (Inquisition) put him on trial, forced
him to stop saying the Earth moved, put him
under house arrest
o He transformed his career
o Apparently disagreed, privately
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Boyle’s Law (cont’d)
• Boyle’s Law is an example of “the new
Physics” Q12
o Makes specific testable mathematical
predictions
o Exhibits mathematical regularities in nature
• (Modern changes:
o
o
3/2/09
Correct when atoms in gas are far apart
Pressures higher than this when atoms close)
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Boyle’s Law (cont’d)
• Mathematically: P1 × V1 = P2 × V2 Q13
o P: Pressure
o V: Volume
o 1: “sub 1” means time 1 - before (a change – any
change)
o 2: “sub 2” means time 2 - after (the same change)
• Assumes temperature the same at time 1 and time 2
• Will always be the case in problems for this course
• A more general law if temperature changes
o Ignore the pressure and volume units (no unit
conversions here)
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Boyle’s Law (cont’d)
• Mathematically: P1 × V1 = P2 × V2
• Problem: given numbers for any three of P1,
V1, P2, V2, find the fourth number
• Method Q13c:
1.Identify what each of the three given numbers is
2.Substitute numbers into Boyle’s Law
3.Multiply two numbers on same side
4.Divide to yield answer (get unknown by itself)
• Check: multiply both sides afterwards
o Optional but know you are right
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Boyle’s Law Examples
• Example 6: A gas with a volume of 20
quarts and a pressure of 1.5 atmospheres is
compressed to a pressure of 6 atmospheres.
Find its new volume.
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Boyle’s Law Examples (cont’d)
• Example 7: A gas with a volume of 3 quarts
and a pressure of 4 atmospheres beforehand
is expanded to a volume of 6 quarts. Find its
pressure after the expansion.
• Example 8: A gas with an earlier pressure
of 2 inches of Mercury and a volume of 6
cubic feet is compressed to a pressure of 3
inches of Mercury. Find its volume after the
compression.
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Life on Other Planets?
• Life like us?
o May be alternate forms, but we haven’t come
up with any
• Deep space empty, cold, dark.
o Life would need self-contained energy, light,
materials
• Stars have energy, but temperatures are
millions of degrees, much too hot
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Life on Other Planets?
• So focus on planets
• In our solar system, no good candidates
except Earth
o Closer ones too hot
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Life on Other Planets?
• So focus on planets
• In our solar system, no good candidates
except Earth
o Further ones too cold
o Mars the best other possibility
• Current search is for water on Mars
• We may find microscopic life, or its remains
o Moons too small to have atmospheres
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Life on Other Planets?
Mars picture: a dust-covered frozen sea?
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Life on Other Planets?
• Planets around other stars?
• We are finding other stars with planets
o Present techniques best for planets close to star
o So far, too close to star, too hot
o If planets around other stars are common,
maybe there will be some planets with the right
conditions, and maybe some of them will have
life
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Life on Other Planets?
• Our other approach is to look for radio
signals
o SETI: Search for Extraterrestrial Intelligence
o Distances mean powerful signals, imply a much
more advanced civilization than ours
o Long distances imply radio waves started long
ago if they reach us now, would be even more
advanced
• Aliens visiting earth not supported in
mainstream science
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For next week
• Midterm, first hour in class
• Read the manual, Experiment 13
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Essay 2
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 (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) or you.
• The topic asks for “a” core concept and
suggests a starting point for your analysis
• Due 4/20. Note that we have not covered all
of the core topics yet.
• Review Syllabus for other requirements
o All quotes must have references
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Review Session
Question and Answer