The Sun--Introduction

A word of caution

    The sections of "Stargazers" covering the Sun started as an afterthought. Other sections were mostly complete when a teacher of astronomy, viewing the material for his own course, pointed out the omission. "How can I give them astronomy and not discuss the electromagnetic spectrum?" All our information about stars, he noted, is carried by light and in other electromagnetic radiations.

    Yes, indeed--and therefore this part was added. If you, dear reader, are engaged in a personal voyage of discovery, dig right in. It contains many interesting subjects, and your only limitations will be your own time and your own patience. As in preceding sections, no calculus is used.

    However, if you are a teacher presenting a class in astronomy, your time is severely limited. Even without optional sections, "Stargazers" contains much more than can be presented in a single school year. You are therefore advised to select your material either from the sections on Newtonian mechanics or the ones the Sun that follow here, but perhaps not both.

    A class stressing astronomy may skip mechanics. Newton's law of gravitation will then be missed, as will be some interesting applications such as weightlessness in space. However, almost all the material on the Sun fits seamlessly into the sections that precede it or follow it, and lesson plans have been provided for sections #S-1 to #S-7 as well. If your class stresses physics, you might prefer to cover mechanics and omit (or skim) the parts on the Sun, which are less mathematical, although they also cover interesting areas of physics.

What is covered here ?     (mainly for teachers)

    This part of "Stargazers" uses the Sun as the key to the astronomical universe, a key that opens many other doors as well: to weather and the atmosphere (section #S-1), to magnetism (#S-3), to the study of spectra (#S-4), to the notions of electromagnetic waves and photons (#S-5), to X-rays (#S-6) and to the atomic nucleus (#S-7). This part may therefore is studied not just for what it tells about the Sun, but also as an introduction to subjects of modern physics.     Brief optional sections were added during the writing of the lesson plans: on the three-color theory of vision (#S-4A; an alternative approach is also cited), on the interplanetary magnetic field (#S-6A) and on the history of atomic and nuclear theory (#S-7A). The first two contain hands-on exercises.

    In compiling educational material, it is all too easy to get carried away and add interesting but optional material. And this particular writer is so easily tempted! Section #1 was therefore extended to a 3-section discussion covering aspects of the processes driving weather and climate. Section #S-7 also contains ideas on the evolution of stars, e.g. supernovas and their remnants, including black holes. Later, when evidence emerged about the black hole at the center of our galaxy, a section on that exotic object was also added. Also, the subject of dark matter in space fits naturally with observed violations of Kepler's 3rd law in galaxies.

    A study of the Sun also involves nuclear physics and the beginning of quantum physics. A regular high-school course can hardly accommodate these, but (mainly for independent students) two mini-courses are added here, on quantum phenomena and on nuclear energy. Use of calculus is still avoided, so the presentation rather elementary.

    The 8 sections on quantum physics follow naturally section S-5 on waves and photons.
    Nuclear energy was originally covered in sect. S-8 on Nuclear Power, but this was expanded to the 6 sections #S-8A on nuclear power generation, a mini-course developed for the state of Virginia. Still later a section on nuclear weapons was added, a reluctant concession to reality.

    Enough introduction. Go to it and discover!