GST 2420: Atoms and Stars:
An Historical Introduction to Astronomy, Physics, and Scientific Discovery.
Fall 2002, Section 983, Call Number 16050
Agenda 8 for 10/23

1. Announcements:
   1. Midterm tonight. Report on last week'ss Experiment IXa is due next week on 10/30.
   2. Course web site: http://www.cll.wayne.edu/isp/drbowen/aasf02 (also links from Pipeline).
   3. Online Life at WSU updated and with live links at http://www.cll.wayne.edu/isp/drbowen/OnlineLife. New: How to forward your WSU Email after you have activated your AccessID and Password.
2. Midterm
3. Science in the news
   1. The anthrax attacks happened about one year ago. At the time, there was little scientific knowledge about how anthrax spread, and virtually no doctor had seen or even read a medical account of anthrax. Anthrax had been virtually eliminated for decades. While other private and government offices were shut down and decontaminated when anthrax was discovered, post office buildings were not. It was not understood that pores in envelopes were large enough to allow "weaponized" anthrax spores through, and that modern automated letter-handling equipment squeezed letters quickly enough that a puff of air could force spores out through the pores. Postal workers were assured that they were safe, but in fact several were killed by anthrax (some survived an anthrax infection), as were several seemingly unconnected civilians. Postal workers say that they were lied to, and put in danger while office workers were treated with greater care. What do we know, and when do we know it - questions of epistemology again.
   2. I am concerned that I may have left the impression that statistical knowledge, common in medical studies, is less useful than theoretical knowledge. This is not the case, especially if the theories do not exist! Statistical knowledge is like Brahe's measurements or Kepler's three laws (First two published in 1609), in the time before Newton's Principia (1687). Statistical knowledge, while less certain, can still provide crucial guidance in managing personal and societal health. For example, for managing my diabetes, I rely on well-established and consensus guidelines that keeping carbohydrate intake low (but above 80 mg/dL) is a good thing, while not following newer, less-well established results concerning a "Glycemic Index" that advocates say shows that some carbohydrates can safely be eaten at higher levels; I treat all carbohydrates as equally bad, at least above recommended levels. (Glycemic Index studies do include some clinical studies as well, involving blood sugar levels.) At present, such choices are personal ones, hopefully made after gathering expert advice. Also, if you are basing personal health decisions "the latest" studies, you need to monitor the field and expect changes, sometimes substantial changes.
   3. Jane Brody New York Times 10/22/02 Pg D7, "Separating Gold From Junk In Medical Studies," a guide to reliability of medical studies. The press often does not understand subtleties of different types of studies, and often announce "facts" before really warranted. So, it is increasingly up to public to judge the quality of medical studies. In order of increasing certainty:
      1. Animal studies - results often do not translate to humans
      2. Epidemiological studies following a given population - relationships may be true or tied to some other variable
      3. Case-control studies - patients with and without condition are paired and followed - can suggest but not prove
      4. Meta-analyses - combining several existing studies - no better than underlying studies (?)
      5. Placebo-controlled, randomized, double-blind clinical trial is best but still may give errors - who volunteers for study may bias results - those volunteering may be more health-conscious.

      Secondary outcomes incidental to the main focus of a study have less value - example of study to find relationship between pancreatic cancer and smoking found effect due to coffee, which eventually proved to be untrue. Size of population and time span also a factor, with different effects for different types of studies. You might also want to consider who paid for study, did the experimenters or sponsors have control, were there conflicts of interest, was there independent evaluation? A related indicator of quality is independent confirmation. Finally, one study bringing about a major change in treatment or prevention is rare.

   4. The termination of the large double-blind hormone replacement therapy experiment has further resulted in the termination of a related study on a specific population, and researchers are considering terminating a third.

4. Class length
5. Tycho Brahe; pronunciation
6. Lab 8 review
   1. Block Vs cart - Aristotelian and Newtonian explanations. Using two of Newton's three laws of motion:
      1. The Aristotelian explanation for the cart's coasting for awhile after the shove is that air fills the vacuum behind it and pushes. As we discussed, this explanation would have a hard time with the cart with ball bearings. But, in order to be decisive, the block and the cart should be more closely matched (area of back, weight). Maybe the cart moved further because it had a bigger area for the air to push against. But I don't think anyone doubts what the outcome would be.
      2. Law of inertia. In the absence of an external force, a mass (body) keeps moving at the same speed in the same direction.
      3. F = ma. An external force acts to change the acceleration of a mass, matching size and direction. (If there is more than one force acting, the mass responds to the sum or net force, taking directions into account.)
   2. Falling bodies - Galileo. Falling body accelerates, speed of fall does not depend on mass (neglecting air resistance).
7. Readings: Nicholas Copernicus (1473 - 1543), Tycho Brahe (1546 - 1601) and Johannes Kepler (1571 - 1630)
   1. Kepler is known for his models that summarized Brahe's observations - his three laws. Finding these laws, which he apparently did not think were very important, took him years of mathematical and geometrical calculations, with many errors and blind alleys. His relationship with Brahe is also bizarre; Brahe essentially sponsored and hired Kepler, expressly to find a model using Brahe's data, but was very reluctant to actually share the data with Kepler. In working with Brahe's data, Kepler made several departures from accepted astronomy; he adopted a heliocentric model, and abandoned the idea of spheres for ellipses. He also completely trusted Brahe's measurements, abandoning his theories at one point when they disagreed by 8 seconds of arc, where Brahe claimed an accuracy of 4 seconds of arc. Kepler's three laws:
      1. Planets move in ellipses, with the sun at one focus. (An ellipse is a kind of flattened circle, with the single center split into to foci. Light from one focus will be focused at the second focus, and vice versa.)
      2. Planetary orbits sweep out equal areas in equal times, as measured from the sun
      3. For a planet, the period t and orbital radius r are related by t² ~ r³. Planets  For example, if two planets are in orbits with the second 8 times larger than the first, the period of the one with the larger orbit will be 4 times the period of the one with the smaller orbit (cube root of 8 is 2, then square the 2 to get 4).
   2. Biography of Kepler related to his achievements. Kepler was in poor health for much of his life, had few close friends, and seemingly with reason. He was used to persevering in poor circumstances - "soldiering on." Thus he may have been prepared by this earlier life to persevere throughout his later life in working on Brahe's data for Mars. In addition to his extraordinary perseverance, there is also the issue of his insights. The one given the most detail in the readings is the one that "hit" him during class, regarding the regular solids. But there must have been others; we can tell that there must have been others, because of the sudden shifts in his direction of work. Such flashes of insight (true or false) usually occur after a period of intense concentrated work on the topic, followed by a period of turning away from the topic (then "boom" and it hits you). In this regard, Kepler seems like many other creative giants.
   3. The transition in mechanics (terrestrial) and astronomy (celestial) from their separation with Aristotle to their unification with Newton is more complex and gradual than the transition from "abhors a vacuum" to "sea of air," in which we can identify only one or two steps from Aristotle to Torricelli, depending on whether or not we count Galileo's noting without further comment that workmen knew that suction pumps wouldn't word for heights greater than 34 feet. First, it took longer - roughly one hundred years Vs ten or so. Second, there are clearly two tracks of change involving many more people - Copernicus to Brahe to Kepler to Newton in the case of astronomy, and running through Galileo in the case of mechanics. The state of English society, and the emerging existence of a scientific community including Newton, and increasing specialization, are also important. Third, the change involved is much larger in intellectual terms. It is quite possible that all three of these differences are related; that is, that any individual, no matter how brilliant, can travel only a certain "intellectual distance." Isaac Newton said, "If I have seen further than others, it is because I stood on the shoulders of giants."
   4. "... planets behave like cars on the race track." Reader, Pg 160. True, the speed of a planet varies as it moves around its orbit, but it does not go faster on the strighter sections and slower on the curves, as with a car on a race track. Rather, the planet moves faster when it is close to the central mass (the sun, for a planet) and slower when it is further away.
8. Lab IXb. Lab Manual, Pages 53 - 59; "The Ellipse". You will make ellipses the same way you drew circles with the loop of string last week. One thing that this should demonstrate is that a circle is an ellipse in which the two foci have merged together at the same place.