DevineASTR 100 Coastline Community College

Lesson 1:Rising,Setting of theSun, Moon and Planets; The Seasons

(Sections 1-3 through 1-6 of your text)

“One must learn by doing the thing; for though you think you know it, you have no certainty until you try.” Sophocles (496-406 BC)

Introduction:Humans have been looking up at the heavens since time immemorial and pondering the beauty of the Sun, Moon and stars. It wasn’t long before they noticed patterns in the appearance of these heavenly objects, and that some of those “stars” wandered about in the sky relative to the other points of light. Those wanderers were given the name “planets” (Greek for wanderers), and were associated with gods who were trying to communicate with us mortals. This led to the creation of Astrology, and for thousands of years folks have been referring to the heavens for guidance in the form of horoscopes and such.

You can still see traces of this history in the names of the days of the week. There are seven heavenly objects that are easily visible to the human eye: The Sun, Moon, Mercury, Venus, Mars, Jupiter and Saturn. This is why we have seven days in a week, and if you look up the names in different languages you will probably see their connection to gods and various religions (see HW question 1).

Astronomy and Astrology are very different from each other, and should not be confused. Astrology is more closely related to religion. It is not science. The main ingredients of Science are that observations should be reproducible, regardless of who is doing the observing, and Astrology is anything but reproducible (if you go to different websites to read your horoscope you will rarely find the same results). We will not be concerned with Astrology in this class.

Astronomy, like Physics, is an attempt to understand Nature. I don’t know why Nature is so fascinating to some of us, she just is, and the value of understanding her (or at least trying) is unquestionable for some folks. Based on your responses to the Discussion Forum, you folks share that wonder and curiosity about the heavens, so let’s get started.

The first rule is this: ANASTRONOMY TEXTBOOK IS NOT A NOVEL. It is a reference, and should be used as such. In other words, if you are stuck or don’t know the meaning of something (like a HW question) then go to the section associated with the question and read what you need to in order to get started. Use the Homeworkand Reading Quizzes as your guide for what parts to read, don’t just start on page 1 and try to plow through the book. Better yet, if you are curious about something or you have a question related to Astronomy that you have always wondered about, go to that chapter or section and see what you find. You will always learn better if you are curious and interested. One of my goals for this class is for you to develop a lifelong habit of generating questions, seeking answers, and evaluating the reliability of your sources.

The ancients depended on the heavens to track the days, months and years, to signal when to plant or harvest, or even when to declare war or get rid of a king. We don’t need the heavens to tell us these things today, and as a result we have lost touch with the rhythms of Nature. Therefore my first goal is to plug you into Nature so that you can start to see the patterns and cycles that were familiar to the ancients. In order to begin, do the following exercise.

Exercise 1: Sun, Moon and Planets. Go to the following:

You should be able to see a Sunrise and Moonrise window, and at the bottom you should see an option for Rise & Set (Planets, Sun and Moon). Follow that link, select your viewing location for Friday August 31, and something like the followingtable should eventually appear: (Note: you will also see Day Length and information for Uranus, Neptune and Pluto, but I am leaving that stuff out).

Friday, August 31, 2012

Rises / Sets
Sun / 6:24 A.M. / 7:17 P.M.
Moon / 7:10 P.M. / 6:32 A.M.
Mercury / 5:38 A.M. / 6:57 P.M.
Venus / 2:53 A.M. / 4:47 P.M.
Mars / 10:55 A.M. / 9:45 P.M.
Jupiter / 12:00 A.M. / 2:07 P.M.
Saturn / 10:09 A.M. / 9:30 P.M.

This table has all the information you need in order to figure out where the moon and planets are located in the sky. For example, Mercury rises about 45 minutes before the Sun, so it is visible just before dawn. Since it has just risen, it must be in the East (heavenly objects rise in the East and set in the West). So Mercury is visible in the East before sunrise. Note that Mercury sets before the Sun, so Mercury is not visible just after sunset. You will soon see that this is not always the case, and that planets (and stars) are visible in different directions and times throughout the year.

  1. What planets (including the Moon) are visible just before sunrise (just before = within an hour of), and are they in the Eastern sky or the Western sky?
  2. Repeat Q1 “just after sunset”.
  3. Make a note of the Day Length and change the date to September 5. Are the days getting longer or shorter?
  4. Change the date to Halloween (October 31). Repeat Question 1. See the differences? Now you should have an idea of why the planets are called “wanderers”.
  5. Return to August 31 and your viewing location (which I assume is in California). Change the location to New York, NY. Do your answers to question 1 change? If you have done things correctly, you should see some small differences in the rise and set times, but on the whole the patterns have not changed.
  6. Now let’s switch hemispheres and check sunrise and sunset for Australia. Go to the following website: Compare the sunrise and sunset times and the day length. Check out Figure 1-15, you should be able to see what is going on.
  7. Special Dates: Look up the definitions of the Equinoxes and Solstices in your textbook. Go to the following: This is related to Figure 1-15 and the cause of the seasons on Earth. If you click on the bottom link (Guide to Arctic Sunrise and Sunset) you will see that the sun does not always rise and set for all locations on Earth. Astronomers are taking advantage of this by putting telescopes at the South Pole, however the extreme cold makes this a very difficult job.

Returnhome and play. (How about the day you were born?).

Get started on HW1! (Posted on Seaport).