2/2/05Atoms and Stars, Class 41 Atoms and Stars IST 2420 and IST 1990 Class 4: February 2 Fall 2005...

2/2/05 Atoms and Stars, Class 4 1

Atoms and StarsIST 2420

and IST 1990http://www.is.wayne.edu/drbowen/aasW05

Class 4: February 2

Fall 2005

David Bowen


Handouts• PowerPoint notes• Re-revised assignment schedule (experiment

numbering same as lab manual)• Passbacks

Names• Initial by your name on signin list

• Go through class names again


Due this week

• Report for Lab 7 (Density)o Assignments go in the “IN” folder

For next week…• Reader Pp 23 – 29

• Manual Pp 35 – 41, Experiment 8

• Turn in Report for today’s Lab 3

• Essay 1 due next week


Review of Essay Assignment

• Due February 9• Topic: We have studied the process by which

Aristotle's view that nature abhors a vacuum was replaced by the sea of air hypothesis. Following Copi's seven step account of the scientific method, explain how this transition took place. Draw on material from the reading, class discussion, and the laboratory experiments. Also write about what this tells us about the scientific method.


Essay Assignment (cont’d)

• 3 to 4 pages, 12-point Times Roman, double-spaced, 1” margins top and bottom, 1½” left and right.

• Content: 40%. Reading and understanding course materials, applying them to topic, consistent point of view



• Form: 40%. Title page, Introduction (roadmap), Body (organized, transitions between topics, detail to support general points), Conclusion (review content, draws to an end)

• Mechanics: 20%. Spelling, grammar, punctuation. Use spell-check and grammar-check (note on passive) or dictionary.



• Sequenceo Aristotle: universe is full, nature abhors a

vacuumo Critical experimentso Sea of Air


Readings“Greeks Bearing Gifts,” Chapter 4 in Section 1 (“From Ape to Alexander”) in Science and Technology in World History: An Introduction, by James E. McClellan and Harold Dorn• Hellenic Period 600 – 300 BC (BCE)

o “natural philosophy” – scientific theory without regard to practical applications, for its own sake

o Freestanding, independent “schools”


Readings (cont’d)

• Hellenic Period 600 – 300 BCo Built on Egyptian and Mesopotamian cultures

but Greece decentralized, dependant on trade, loved arguing about politics

o Actually originated on western shore of Turkey (see next slide)

o pre-Socratic


Readings (cont’d)

Ionia

Greece


Readings (cont’d)

• Hellenic Period 600 – 300 BCo Thales (~625 - ~545 BC) was pivotal

• Theories became identified with a person, previously scientists were anonymous

• Natural explanations, not attributed to Gods

• Not, however, atheistic

• Water as fundamental element, first instance of theory about what things are made of

o Other Greeks had other theories


Readings (cont’d)

• Hellenic Period 600 – 300 BCo Empedocles (~545 BC): earth, air, fire, water

• Also two forces, Love and Strife

o Pythagoreans followed Pythagoras (~525 BC)• Introduced math, focus on number (hidden reality)

• Pythagoras – right triangle a2 + b2 = c2

• Implied irrational numbers, didn’t like this

• Plane geometry (Elements), mathematical proofs


Readings (cont’d)

• Hellenic Period 600 – 300 BCo Atomists (Leucippus and Democritus) ~420 BC

• Atoms - indivisible, elementary• Not much influence at the time

o “Philosophers of Change”• Heraclitus ~500 BC, change is constantly happening• Parmenides ~480 BC, change is an illusion• Reliability of senses, possibility of knowledge


Readings (cont’d)

• Hellenic Period 600 – 300 BCo Unlike other fields, medicine held to usefulness

• Hippocrates ~425 BC – observation• Four humors, health is a balance between them

o No unity, common method, or sustained research

o Changed with unifications of Plato and Aristotle


Readings (cont’d)• Hellenic Period 600 – 300 BC

o Plato 428 – 347 BC• Student of Socrates - abandoned uncertain natural

philosophy, studied good life, put to death 399 BC• Plato’s Academy at Athens – survived 800 years• Geometry important – four elements + aether,

corresponded to five regular solids• Astronomy, based on first principles (ideal form):

earth central, mechanically linked to spheres that carry heavenly bodies. Heavens alive, divine, perfect, in uniform motion (“save the phenomena”)



o Plato• Others inserted additional spheres to account for

retrograde motion and other effects, simplicity lost– Spheres intersection

– Scientific community, shared model

o Aristotle 384 – 322 BC• Studied under Plato

• 343 Phillip II of Macedon made him tutor to Alexander (Alexander the Great)



o Aristotle• First technology supplied needs, then we can study

philosophy, motivated by curiosity

• Sensation & observation the only road to knowledge– Against transcendentalism of Plato

• Four elements composed of primal matter with qualities hot-cold, wet-dry superimposed

– A rational basis for alchemy

• Earth at center of universe due to gravity



o Aristotle• Spherical earth – based on shadow on moon

• Motionless – object thrown straight up returns

• Everything up to the moon is natural, heavens are aether (incorruptible, unlike elements)

• Natural motion in straight lines on earth, circles in heavens, all else requires outside impetus

– Problems with arrow

• Heavier objects have greater force, fall faster



o Aristotle• Motion must occur in a material medium, not a

vacuum (would have infinite speed, logically impossible)

• Atomism implies vacuum between atoms, impossible, rejected

• Also close biological observer, hierarchical taxonomy

• Basis for higher learning in other cultures, religions


Readings (cont’d)• Hellenistic Period after Alexander (323 BC)

o Empire split into three partso Social support for research

• Museum and Library at Alexandria 280 BC– 500,000 scrolls, 100+ scientists and scholars

– Abstract, formal mathematics

• Other libraries also – Pergamum, Plato’s Academy

• Had legal status

• Useful results emphasized but fame of sponsor also


Readings (cont’d)• Hellenistic Period (after 323 BC)

o Eratosthenes, head of Library at Alexandria• Famous calculation of circumference of earth

• Also geography and cartography

o Aristarchus• Heliocentric, earth turns on axis, rotates sun

• Held implausible because things would fall off

• No parallax of stars observed (accuracy too poor) unless universe much larger than thought



o Ptolemy (2nd cent AD) used new tools to simplify geocentric model of heavens• Epicycle (small circle rotated on sphere, plant on

larger circle)

• Eccentrics (circle displaced from earth)

• Equant – point from which planet appeared to move at constant speed

• Almagest – manual of Astronomy



o Alchemy – transmutation of base elements into gold after Platonic forms• Often mystical and secret

o Archimedes• Simple machines – level, wedge, screw, pulley,

windlass

• Balance led to theory of weight

o Many small incremental practical improvements



o Roman engineering important but little Roman science, little translation of Greeks into Latin

o Roman navy, roads, aqueducts basis of empire o Invention of cemento Greek physician Galen (130 – 200 AD) became

known in Empire• Some advances, but thought veins and arteries

separate, so blood not able to circulate



o Decline and fall of Roman Empire – causes much debated

o Decline in science also• No desire even to preserve existing knowledge• Skepticism about possibility of secure knowledge• Several theories

– No clear social role or support– Availability of slaves meant little incentive for improvement– Other-worldly orientation of new religions, especially

Christianity



o Tolerance of Christianity 313 AD, became state religion of Roman Empire in 391 AD• Hostility towards earlier civilizations included science

o Alexandria damaged when retaken 270-275 after Syrian and Arab invasion• Christian fanatics murdered Hypatia, first female

mathematician, last scholar at Library in 415

o Empire split, Western attacked by barbarians



o Eastern part lasted longer but conquered by Islam in 7th cent

o Last Western Roman noble, Boethius, executed by Ostrogoth king Theodoric in 524

o Literacy declined, knowledge of Greek disappeared


Temperamental CanAll connected by pressure, some by *

1. Imploding upside-down can

Analogy – pulling the paper gently Vs yanking


Lab Reports

1. Cover Sheeto Your nameo Experiment, number and titleo Lab date and date that report turned ino Names of group


Lab Reports (cont’d)

2. Data sheeto Procedure – what you dido Observations and measurementso If you copy it over or type it, include the original also

• (I may go to initialing them during lab)


Lab Reports (cont’d)

3. Answers to questions, explanations, hypotheses, theories, tables, calculations

Main ideas:

• Keep data separate from the resto What you dido What you saw and/or measured

• Good detail in procedure and observations


Observations and Explanations

• Procedure and Observation: I did “A” (procedure) and then I saw and/or measured “B” (observation)o Be specific. Object is to let someone else do

exactly the same thing.o Sketches are goodo Keep on a separate sheet of paper

• Explanations – hypotheses, theories


Observations and Explanations(cont’d)

• Explanations can be wrong but observations still valido Keep them clearly separatedo Write details of observations – may be other

aspects importanto Louis Agassiz – observation of a fish


Lab 2 - Density

Additional point:• Displaced water

has same volumeas object thatdisplaced it(Archimedes in bath – “Eureka”)


Lab 2 – Density (cont’d)

Question asked – what is the density of air?

• 0.00129 gm / cm3

(grams per cubic centimeter)o Compare to water, 1 gm / cm3

(by definition of the gram)

• Or 0.0805 lb / ft3 or ~1¼ oz / ft3

o Compared to water at 62.4 lb / ft3


Sea of Air

• Many people said they could hear air rushing out of the spheres when valve opened. Positive pressure inside would push spheres apart. Must have heard air rushing in. (gauge pressure)

• When thick bottles did not implode, someone said to listen when top opened. Good! What was the hypothesis?


Measurements

• Physical Science (Physics, Chemistry, Astronomy) now has mathematical theories that make numerical predictions that are checked against measurementso Exception is Geologyo Earlier, mostly qualitative theories checked

against observations (some mathematical)

• Life sciences currently mostly qualitative


Measurements (cont’d)• Measurements have accuracy, must check

how accurately your measurements areo Repetition is a good methodo Agreement with theory within measurement

accuracy

• Why are Life Sciences not mathematical?o Started later?o More difficult, takes longer?o A different type of science?


Lab

• Timing with stop watcho Push “MODE” switch

until top row of dots shows, not just one

o Then red Start/Stop starts timing and second time stops it, Reset to start over


Lab

• Timing with stop watcho Practice technique firsto Accuracy – repeat four times (four values), at

least two people compare four timings onceo For multiple measurements, average is best

valueo Accuracy is spread – within one person’s

measurements, between people


Lab

• Inclined track (Part I)o Ignore directions, roll ball down tracko Prop one end of track up with blocks,

clayo Ball should roll smoothly without

hops or jump• If necessary, try smoothing track where

ball jumps

• Steeper track will make jumps matter less, but makes times shorter, harder to measure


Lab (cont’d)• Inclined track (Part I)

o Measure and record height of track in case you need to rebuild it, make a sketch

o Timing – all times from beginning to mark• For example, A0 to D9

o Analysis: tabulate and compare time to B1 ÷ 1, time to C4 ÷ 2, time to D9 ÷ 3, time to E16 ÷ 4.

o Longer time intervals will be more accurately measured

o Consider null hypothesis – no difference


Lab (cont’d)

• Projectiles (Part II)o Follow directions hereo Accept level start only - reject trials in which

projectile starts out angling upwardso Consider null hypothesis – no difference


Density as Demo• Bigger objects – one sinking, one floating• Volume of displaced water = volume of

object• Different method for measuring weight of

displaced water• Accuracy of measurement – estimate by

repeating measurements• Null hypothesis – if difference is within

accuracy, cannot say it is different than zero


Density as Demo (cont’d)• Specific gravity – weight of object ÷ weight

of equal volume of water. Also = ratio of densities

• Null hypothesis: if two quantities are equal within their accuracies, they are effectively equal


Density as Demo (cont’d)ObservationsDumbbell• Object weight in air: __________• Object weight in water:

__________• Weight of displaced water: __________Wood• Object weight in air: __________• Weight of displaced water: __________


Density as Demo (cont’d)

AnalysisDumbbell

• Specific gravity: __________

• Weight change, air / water: __________

• Weight of displaced water: __________

Wood

• Specific gravity: __________


Density as Demo (cont’d)

TheoryWeight difference(air to water) isweight of displacedwater, and is due towater pressure.(This theory has explanatory power.)


ISP 3360 – break time

ISP 3340 starts


ISP 3340

• Pictures for Moodle?

• Essay 3 topics on course web site

• Other articles on course web site – password needed

• Essay 1 on Rocks of Ages and other articleso Due February 23o Title page must list topic and descriptive title


End for ISP 3340

Lab

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2/2/05Atoms and Stars, Class 41 Atoms and Stars IST 2420 and IST 1990 Class 4: February 2 Fall 2005...

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