GST 2420: Atoms and Stars:
An Historical Introduction to Astronomy, Physics, and Scientific Discovery.
Fall 2002, Section 983, Call Number 16050
Agenda 10 for 11/6

  1. Announcements:
    1. Day scheduled as a Friday (noAtoms and Stars class) - November 27
    2. Course web site: http://www.cll.wayne.edu/isp/drbowen/aasf02 (also links from Pipeline). New today: supplementary information for GST 1990 (now vocabulary for Chapter 7 of God and Nature).
    3. Online Life at WSU updated and with live links at http://www.cll.wayne.edu/isp/drbowen/OnlineLife.
    4. Fliers for GIS 3991
    5. ISP 5660 / GIS 3340 (Creativity: Building the New) online. To see the course the last time it was taught (when it was AGS 3360) go to http://www.cll.wayne.edu/isp/drbowen/crtvyw02. Flier next week. How do online courses work? For a general description, see Online Live at WSU, above.
  2. Science in the news.
    1. HRT
  3. Telescope
  4. Readings: Isaac Newton (1642-1727)
    1. Descartes (1596 - 1650) mechanical theory, contact forces, planets pulled along in vortices in the aether
    2. Isaac Newton developed modern mechanics in Principia Mathematica Pholosphia Naturalis (Mathematical Principles of Natural Philosophy) - also invented calculus and did important work in optics
      1. Three laws of motion
        1. A body (object) at rest tends to stay at rest, a body in motion tends to stay in motion (same speed and direction), unless forces act on it
        2. Force = mass × acceleration (both the size and direction are equal)
        3. For every action (force) there is an equal (in size) but opposite (in direction) action. If object A exerts a force on object B, then object B exerts an equal but opposite force on object A.
      2. Then showed that Johannes Kepler's empirical (experimental, no explanatory theory) laws of planetary motion followed from these and an attractive gravitational force between each pair of masses, proportional to the product of the masses and inversely proportional to the square of the distance between them (F = G m1 m2 / r2)
        1. Planets orbit sun in elliptical orbits with the Sun at one focus
        2. Orbits of each planet sweep out equal areas in equal times (showed that meant that the gravitational forced was attractive and central)
        3. Period or length of year, squared proportional to radius of orbit, cubed (T2 µ r3)
      3. Also applied to Moon's orbit around Earth
        1. "weighed" the earth. Actually required laboratory experiments measuring gravitational force between two known masses
        2. Using inverse square law of gravity, projected the force on moon to the surface of the earth, it agreed with the acceleration of gravity on earth (laws of the heavens the same as terrestrial laws
      4. Progression from Tycho Brahe (accurate measurements of planetary positions to Johannes Kepler's empirical theories based on Brahe's measurements, and then Newton's mechanics. This made it unnecessary for Newton to actually compare his predictions to Brahe's data, or to take his own measurements, since they were summarized in Kepler's laws. Newton may have used his own or other measurements of the Moon's position. But this progression has shown up later in other areas science.
    3. A clockwork universe. Gave support to ideas of predetermination, fatalism. Today we know that complete predetermination does not work, combination of quantum mechanics and chaos theory.
    4. As the Reader notes (Pg 164), Newton's laws do not explain themselves. In fairness, this may be an unrealistic standard. But why does inertia exist, and what causes gravitation? In my view, as the circles of knowledge expand, we should expect explanations at some later point. And in fact, we do have the beginnings of explanations. Inertia is closely tied to the effect that other masses have on the curvature of space, in Einsteinian Relativity. And the electrical force, which is mathematically very similar to gravitation (inverse square law), is known conclusively to be caused by the exchange of photons (wave packets of electromagnetic radiation) between the two charged particles. These exchanged photons are generally not observable (they are virtual, in the language of quantum mechanics). Similarly, it is strongly believed that the gravitational force is cause ("mediated") by gravitons. The problem is that gravitons have not yet been observed, but intensive work is continuing. So Descartes, in a way, was right.
    5. Some people view Newton as the last of the old school - ranged very broadly, tried for comprehensive explanations
    6. All of these people were motivated by showing how God worked in the world. Natural explanations for mechanics and astronomy were not yet extensive enough to support a 100% natural approach to the world.
    7. Conditions for scientific progress, significance of scientific progress
  5. Video - Newton's Laws; The Apple and the Moon.
  6. Finish Lab X on lenses. Lab Manual, Pages 60 - 63. For "Writing Assignment," do not worry about the length.
    1. How to hold lenses in place here.
    2. About lenses. Converging lenses Vs diffusing lenses.