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Schedule:• Review (Q & A) up to 6 PM• Midterm (about one hour)• Return graded work and

turning work in• Class (about 1¼ hour)• Lab 8 Part 1

Atoms and StarsIST 2420

Class 8, March 3Winter 2008

Instructor: David BowenCourse web site: www.is.wayne.edu/drbowen/aasw08

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Agenda• Assignments and passbacks• Contributions of major cultures• “Expanding circles” – a model of scientific

progress• Physical Science and natural disasters• Upcoming assignments• Lab 8 Part 1: Horizontal Motion

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Contributions of Major Cultures (to the rise of science) (Q21)

• Prehistoric: attention and observation, e.g. recording phases of Moon

• Early urban: primarily procedures (recipes)• Greek: theories, that is idea of theories as

natural explanationso Frank M. Snowden: role of Blacks as equals

then• Islamic: preserved Greek science, improved

observations• Renaissance: united theory and experiment

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Lab 8 Part 2

Dropping objects• Can from different heights

o Impact increases with greater height (speed), not weight

• Can and blocko Aristotle said heavier object would fall faster,

in proportion to the weight, because the force is the weight

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Expanding CirclesWhat Happens When Science Progresses?

• “Science is Progressive” (two meanings)• Science always has a boundary• Science makes progress beyond boundary

o Past discoveries become new tools (barometer)o Extend theories beyond current experiments

• Important in science, but can be misleading• Some scientists say that any religion is incompatible

with science, but actually, that is an extension (more)

• Old questions still important; new answers

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Expanding Circles

• After rise of science, most revolutionary scientific advances (late 19th and 20th centuries) extend scope, leave core valid (at least numerically – watch for Quantum Mechanics later)1. Newton (our common idea)2. Special relativity (max speed, energy = mass)3. General relativity (gravity, creation of space)4. Quantum Mechanics (uncertainty at atomic

level and smaller)

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Expanding Circles• “Expanding circles of

knowledge” (DB)o Exact shape (circle)

unimportant – “blob”o Science moves boundary

outo Progresses (expands) by

extending known into new territory• Theory and experiment

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Expanding Circles

Review:• Greek and later science developed isolated

areas of knowledgeo Air and water pressureo Speed of lighto Falling and sliding objectso Motions of the planets and stars

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Expanding Circles

• Implication #1: eventually, expanding circles must meet and overlapo Different approaches, different theories – will

not agree

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Expanding Circles

• Implication #2: circles could meet and fill the spaceo What happens then?

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Natural Disasters #1

• Hurricanes, tornadoes, earthquakes, tsunamis, mudslides

• Hurricanes best understoodo Rising air over warm ocean – spirals

counterclockwise as seen from above in Northern Hemisphere due to earth’s rotation

o Picks up water vapor, condenses out higher up

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Natural Disasters #2• Hurricanes best understood

o When water condenses, air heats again – “fuel”o Strength: indicated by low pressure in the eye

• No storm, 30” Mercury – if eye gets to 27”, get out of there! (Katrina)

o Very large size, winds to about 200 mpho Called typhoons in Asia

• Tornadoes also circular, form over land, smaller but higher winds (about 300 mph)o Less well understood than hurricanes

(“supercell”)

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Natural Disasters #3

• Earthquakeso “Plate Tectonics” gives general explanationo Earth molten when formed ~ 4.5 BYAo Cooled, surface condensed into continents (thin

“plates”) floating on molten core (“magma”)o Currents in core, like currents in boiling water,

carry plates, like the skin on cooking puddingo Plates crash into each other earthquakes

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Example: North & South America were joined to Europe and Africa, magma is boiling up at Mid-Atlantic Ridge, pushing them apart.

Geography and species from before split match across Atlantic ocean

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Natural Disasters #5

• Earthquakeso As plates crash, tension in “crust” builds up longer time between quakes larger quakeo Cannot presently tell when quake will happen

• Tsunami – wave formed from underwater earthquakeo Sensors, warning system, disaster network can

move population out – Hawaii and Alaska monitoring centers

o No such system in Asian 2004 tsunami, in place now

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Natural Disasters #6

• Mudslideso Deforestation and development mean

vegetation on hillsides being cut backo People living in these areas due to growth in

populationo Heavy rains weaken hillsideo Depth of mud can be hundreds of feet or moreo Can be foreseen, but weak societies cannot act

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Natural Disasters #7

• Natural Disasterso At present, we cannot predict or control theseo We are learning a lot about them

• Earthquake and hurricane construction codes• Modern buildings in California much better against

quakes, in Florida against hurricaneso Prediction will come first, control is a maybe

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For next class

• Next class – in two weeks, on March 17o WSU Spring Break March 10 - 15o Reader: “The Planet Mars and Kepler’s Three

Laws of Planetary Motion,” “The Crime and Punishment of Galileo Galilei”

o Read the manual, Experiment 13 (Parallax)o Turn in report on Experiment 8 Part 1

• Essay 2 discussion coming up next classo Summing up the whole semester, does this

course have a core, and if so, what is it?• Also Questions for Final, Information Sheet

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Lab 8 Part 1

• Rolling carts with good bearingso Case 1: wheels free to turno Case 2: wheels taped so they can’t turn

• Manual says to tape wheels yourself, but instead swap carts – some will do taped first

• Then wheels free, block on top of cart, crash into book

• NOT IN MANUAL: Then tape paper air barrier in back of block, crash again

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For Lab 8 Part 1

• Motion – Aristotle (terrestrial) and Newtono In many ways, Aristotle and Newton are

opposites hereo Aristotle: without a continuing force (a push),

nothing moves• Motion stops as soon as push stops• Coasting is a problem (see next slide)

o Newton: a force causes a change in motion• Force necessary to start and to stop• No force, no change – if at rest (not moving), stay at

rest, but if moving with no force, then no change in speed or direction

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Terrestrial Motion: Aristotle

• Object only moves if force appliedo Object stops immediately if force stops

• Universe is fullo Air moves out at

front, comes in at backo Explanation for coasting: air coming in from

back pushes object to keep it movingo (Today: air actually streams away, vacuum in

back, creates drag)

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…and Newton (1687 A.D.)• Newton’s Second Law: F = ma

o Force = mass × accelerationo Acceleration = rate of change in velocity (speed

and/or direction)o Constant speed in a straight line: no

acceleration, no forceo Inverse also true: no force means no

acceleration, result is no change in velocity = no change in speed and no change in direction

• “An object in motion tends to stay in motion. An object at rest tends to stay at rest.”