GST 2420: Atoms and Stars:
An Historical Introduction to Astronomy, Physics, and Scientific Discovery.
Fall 2002, Section 983, Call Number 16050
Agenda 6 for 10/9

  1. Announcements:
    1. Due: Report on Experiment III and (for GST 1990) Essay 1. Due next week: Report on tonight's Experiment 8. Midterm coming up on 10/23.
    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
  2. Science in the news
    1. PPA Vs Ephedra - is there any basis for saying "natural is better"? Medicines, food additives and dietary supplements
    2. New mini-planet, "ball of ice and rock" in Kuiper Belt (asteroid belt), 800 miles in diameter, orbit about 4 billion miles in radius, named Quaoar (KWAH-o-ar), creator god of an Indian tribe from the Los Angeles area
    3. Jospeh LeDoux, cognitive scientist - the importance of formulating a question so that it can be investigated by science
    4. Hurricanes and the ocean of air. In-seat experiment. Blow on your hand with your mouth wide open. Repeat with your lips pursed (forming a small hole, as if you were whistling). Try to get roughly same strength or amount of airflow under the two circumstances. What difference do you feel on your hand? Hurricanes (but not tornadoes) gather energy from warm air rising over the ocean, then forming a whirlpool (an effect of the earth's rotation) that confines the flow, then gaining even more energy as the humidity condenses. The effect is like sucking really hard on a straw. What is the storm surge, and what does it come from?
    5. Experiment 7.
      1. Write-up was confusing. Reports reflected this, but:
        1. Some people's notes confused even them. Do not just write numbers down, but describe what each one is. Be oprderly. Write down what you were doing as well as the results. Some drew pictures to illustrate the situation. This is VERY GOOD.
        2. Some got the units of weight wrong. The scales read, not pounds and tenths but pounds and ounces (sixteenths). This makes a big difference in subtracting weights. For example, subtracting 9 ounces from 1 pound 3 ounces is not 1.3 - 0.9 = 0.4 or 4 ounces, but the one pound is 16 ounces, so 1 pound 3 ounces is 19 ounces, to the difference is 19 - 9 = 10 ounces.
        3. In order to find the weight of displaced water for a floating object, you must push the object under water.
      2. Generally accepted results:
        1. Objects which sink in water (marbles, chain, nails) have a higher density than water, objects which float in water (wood) have a lower density than water. Someone guessed that how low the density is for a floating object determines how high it floats out of the water. This is correct; the density is the fraction of volume that is under water while floating.
        2. A floating object displaces its own weight in water, but this cannot be used to find its density. Push the object under water as in 1.c above.
        3. The weight of an object in air (but see below) = weight in water + weight of displaced water.
      3. Are there objects or things that float in air?
    6. Essays. Generally good, obviously did the reading, paid attention to discussion, "got it." However many did not include any results from the labs, even though this was part of the topic. Some did not mention the later steps in the scientific method, even though these are very important for credibility.
    7. Essay 2 topic (due December 4). How do scientists find out about the world? Describe the process of science, using examples from the course.  Should science be a model for other activities (politics, religion, art, etc.)?  What are the limitations of science (what can’t it do?)?  Use the articles by Bronowski and Nissani to spur your thinking, but be sure to make your own argument and defend it.
  3. Motions in the Solar System (reading). These observations were known to many, if not all, societies. They form the basic facts that astronomy needs to explain.
    1. Generally, all objects in the sky rise (appear) in the east and set (disappear) in the west.
    2. Night sky revolves around earth. The axis of rotation is Polaris, the North Star. The patterns of the stars are fixed ("the fixed stars"). (There is some change but it takes more than a human lifetime to perceive it with the naked eye). Some stars form known patterns, the constellations. The rotation is once per 24 hours, or 360º / 24 hours = 15º per hour. (We can almost see the motion.)
    3. We can see the planets Mercury, Venus, Mars, Jupiter and Saturn with the naked eye. Planets are larger and sometimes brighter than the stars, vary in brightness unlike the stars, and also move generally eastward with respect to the fixed stars, like the sun and moon. However, planets also regularly have retrograde or west-to-east motion with respect to the stars. Mercury and Venus stay close to the sun, while Mars, Jupiter and Saturn move throughout the whole sky. Planets are at their brightest during their retrograde motion.
    4. The sun rotates around the earth once per day, like the stars. It also moves north and south in the sky, pausing briefly at each extreme (the winter / summer solstice) and moving its fastest in between (the vernal / autumnal equinox). The sun's motion determines plane of the ecliptic.
    5. The moon also rises in the east and sets in the west. In addition, it moves west to east with respect to the fixed stars, completing the path once every 27 days (½º per hour). The moon's motion is titled slightly with respect to the ecliptic.
    6. Solar eclipses occur when the moon intercepts the light from the sun, but the sun never intercepts the moon. From this we can infer that the moon is smaller than the sun, and closer to earth. Lunar eclipses occur when the earth blocks the sun's light from falling on the moon.
  4. Conceptual Exercise 3.
  5. Review of midterm questions, continued
  6. Video - Inertia / the Law of Falling Bodies
  7. Lab III.
    1. Background - Aristotle and Newton's ideas of motion
      1. Aristotle wrote that motion (on earth) must have a continuing cause. If a body is not pushed, it stops immediately. If a body falls, it falls to its "natural" location (earth at the core, with the layer of water, then the layer of air, then the layer of fire.)
      2. Isaac Newton developed modern mechanics in Principia Mathematica Pholosphia Naturalis (Mathematical Principles of Natural Philosophy) pub 1687, wrote that (first two of his three laws of motion)
        1. A body at rest tends to stay at rest while a body in motion tends to stay in motion, all unless acted upon by an external force
        2. A body acted on by a retarding force slows down, while a body acted on by an accelerating force speeds up (F = ma)
    2. Do the Lab as described in the Lab Manual. For pushing the sliding and rolling objects, the main point is the comparison between the two, not either one by itself.
  8. GST 1990 Directed Study only
    1. Using the CD-ROM. The trick here is generally avoiding "autoplay," which automatically starts a program on a CD disk when you insert it, on many (but not all) computers. You will know that autoplay is working if a new window pops up shortly after you insert a CD-ROM into the drive. Instead, use ""My Computer" to open files for reading.
    2. Here is what to do:
      1. If anything starts automatically, click its "Cancel" or "Close" button.
      2. Start "My Computer" by double-clicking on its desktop icon (may be different than the one shown below)
      3. When My Computer starts, in the left-hand pane, double-click on the CD-ROM icon to see the list of files on the disk
      4. Select the file you want, and double-click on it's icon. If this does not start the file (password first), contact me, or make sure that you have Adobe Acrobat Reader installed, although this is very standard for computers that are newer than about five years old.