Astronomy

Chat times for 2012/2013
Weds 8pm ET/5pm PT
Dr. Christe Ann McMenomy

Student Guide:
How to survive a science course, with special attention to the problems of studying astronomy

Why Study Science?

At the heart of all science is something called the scientific method. The simple version of the scientific method is based on the idea that the objective reality of the universe can be determined by carefully observing phenomena, recording appropriate measurements, then studying the data from these observations for patterns that can be used to describe the general behavior of classes of natural objects. When we can control the circumstances of the observations, we are performing experiments, but often we cannot control all the factors before we make observations. There are scientists who believe that the only valid scientific data is that which comes from controlled experiments; in their view, most of astronomy, meteorology, geology, and many parts of biology are not rigorously scientific. For the purposes of this course, we will use a somewhat looser definition of valid scientific observation that accepts carefully recorded, repeated observations of natural phenomena.

Man's search for patterns led him to keep track of many astronomical phenomena from very early in recorded history. Many astronomical events are periodic, that is, they happen over and over with much the same frequency, in much the same way. When scientists find periodic phenomena that occur in the same order and at the same rate, they want to study them to see if there is some kind of cause-and-effect relationship between them. When the scientist finds a reasonable explanation, he or she proposes a hypothesis, a testable statement about the phenomena. Hypotheses that stand up over many repeated observations are combined to make theories; distillations of theories that have no known exceptions may be called natural laws. In astronomy, we are particularly concerned with theories of space, time, and relativity; and with the natural laws of motion, gravity, light propagation, and thermodynamics.

The Science Course Online

Science classes are frightening for many students. They anticipate difficulties with the concepts, with the details, and especially with the math. But science is just one way of thinking about the natural world around us, and anyone can learn to think like a scientist. Don't waste energy worrying about your ability to learn the material; use your energy to learn it! Once you get the hang of it, you'll be able to discover, understand, and appreciate the complexity of God's creation better. You will also be better prepared to take your place as a steward of that creation.

Review the prerequisites for the course. These are the concepts and math skills that you should have mastered in order to succeed in learning the material. The math prerequisites for this course are described in the course overview page. If you have any questions about your readiness for the course, be sure to ask for help during our first session. I will arrange to work with you so that you can gain the required skills quickly.

Every science course has as its main components lectures, reading assignments, labs, and lots of homework to prepare you for taking quizzes and exams. In addition to these, our online course has this website, the Moodle class site, and e-mail to provide the functions that would normally exist in talking to your teacher face-to-face, or looking at a bulletin board or whiteboard. Keeping track of all the components can be a daunting task, especially at first, so plan to spend some time becoming familiar with the course website, your text and CD, and the Moodle class site. Once you have mastered the mechanics of using these tools, you can concentrate on learning the material that they contain.

Why are there so many parts to the course? Well, part of the reason is that you learn in many ways. You memorize facts, you comprehend relationships, and eventually, you understand concepts. You learn by reading, by analyzing pictures and graphs, by watching demonstrations of processes, by participating in discussions, and by applying what you are learning to specific situations in the homework and labs. You "cement" what you've learned by teaching others. The organization and materials of the course require that you take all these approaches.

Managing Your Time

Make the commitment now to spend adequate time on coursework. While this astronomy course is not as demanding as some of the others offered at Scholars Online, you cannot do all the work for a given unit on one day ... and you shouldn't do it just before chat session! The table below is a rough guide and a suggested pace for this course. The amount of time you spend on each part of the assigned work will vary greatly from student to student, and from chapter to chapter, and your schedule will of course depend on your other commitments. Determine what is a reasonable work load and stick to it!

Try to do your reading as early as possible. This allows you to think about the questions and material, review it in your mind, and absorb it more critically.

Checklist

Completed? Task Approximate Time Scheduled for...
1 _____ Check Website for instructions 15 minutes Immediately after class session
2 _____ Read Web Lecture 1/2-1 hour Fridays
3 _____ Read Text Assignment 1-2 hours Friday/weekend
4 _____ Review animations at Companion Website 1 hour Monday
5 _____ Work through Starry Night exercises 1 hour Tuesday
6 _____ Verbalize answers to assigned questions 1 hour Wednesday
7 _____ Complete Homework 1-2 hours Weds/Thursday before class
8 _____ Take Companion Website quiz 15 minutes Before class
9 _____ Post assignment to class forum 1/2 hour Thursday before class
10 _____ Make observations for lab 2-3 hours
11 _____ Perform calculations/reduce data 1 hour
12 _____ Write lab report 1 hour
13 _____ Take online quiz 20-30 minutes Before next class

Web Lectures

Rather than take our precious chat time by lecturing to you, all unit lectures are posted to the site. You need to read these as well as the text. Most of the Web Lectures have a

  • study guide section on the reading assignment
  • main lecture with further detail on some area of the text presentation or on topics the textmaterials don't cover
  • practice with concepts (checkpoints for your understanding)
  • list of discussion questions to prepare for chat
  • optional website readings for your copious free time.

The "checkpoint" exercises ask you to figure something out, then offer you the opportunity to check your answer. Try to figure things out before hitting the "answer" button! If you were correct, and your reasoning was correct, congratulations! You are ready to continue with the next concept. If you missed the answer, but understand the correction, make a note to review the concept later. If you don't understand the explanation, ask me during class, or send e-mail requesting further help.

As you read the web lecture, make notes on anything that puzzles you, and be sure to raise your questions in class.

Using the Textbook

Astronomy has long been considered the queen of the sciences, the one in which the basic concepts of math, physics, chemistry and now even biology come together. Although there is not a lot of "heavy math" in this text, certainly not in comparison to the Scholars Online chemistry or physics courses, there are still a lot of concepts to master and integrate. As you plan your workload, be sure that you give yourself enough time to

TAKE NOTES! Outline the chapter, even if the text supplies you with an outline. After each section, write down the important points it makes, any items of particular interest, and any questions that you have.

Using the Companion Website

A real asset to learning planetary astronomy is a good planetary motion demonstrator. The textbook is supported by animations and interactive exercises at the (free) companion website. Take the time to work look at them as you read the associated chapters.

You should also have received the Backyard Version of Starry Night, a planetarium program that will simulate the appearance of the sky for a given date and time. Become familiar with the program and use it to create star maps for your observing sessions, and simulate the apparent motion of the stars and planets over time.

As with the text, take notes on anything that puzzles you. If you don't understand how the examples work, e-mail me or ask during chat, or compare the problem to another homework practice problem solution that you do understand.

Doing Homework

Homework is not merely useful, it is essential for mastering the concepts of a science course. You will know whether you understand a concept if you can use it to solve a "real-world" problem, and when you can teach it to someone else. We use both techniques in this course. You will be assigned both word-essay questions and calculation problems for each unit. You should work all of these. You will also be asked to post the answer to at least one question and one calculation problem to the class forum. This is your opportunity to explain to your fellow students what you know.

NB: mycroft, the original bot for my science classes, has long since been freed to do other things, like attend class, make obnoxious remarks, and aid stumped students. If you really get stuck figuring out the problem you've been asked to post, mycroft has been known to accept bribes in the form of virtual Oreo cookies to finish your problem for you.

Essay questions

Essay questions ask you to explain a concept in words. As you answer a science essay question, be prepare to cite calculation information as well as concepts, or give examples.

For example: Why can't you see any surface features on Mercury when it is closest to the Earth?

A good answer will be grammatically and syntactically correct, using proper English, as well as contain the correct information. It will cover more than one point in supporting its argument.

You cannot see any surface features on Mercury because it is always very close to the sun. Much of the time, it's reflected light (which is low because it's abledo is only .12, meaning that it reflects only 12% of the light falling on it) is lost in the sun's glare. When it is furthest from the sun, it still can only be seen just after sunset or just before sunrise, when it is near the horizon. Its image is distorted since it is seen through the maximum amount of Earth's atmosphere.

Math Questions

Most astronomy concepts are based on simple physics principles. Newton's form of Kepler's law (which we discuss in chapter 4) is

which is relatively simple math. Our problem is in the application of such concepts to real situations.

So here is a "general problem solving" approach.

  1. Visualize the situation described.
  2. Identify and list all the knowns given in the problem and the unknown to be found.
  3. Set up a notation system for the knowns and unknowns, so that you can use the symbols in math relationships.
  4. Check for any hidden information — values that you know because of the situation, but which may not be explicitly given in the description.
  5. List everything you know and the unknowns.
  6. Look for a relationship that relates what you know to what you don't know. You need one equation per unknown value.
  7. Solve the formula for the unknown. Don't substitute values in prematurely: you'll only wind up doing more math.
  8. Once you have the final version of the formula in place, substitute the known values into place.
  9. Do the arithmetic.
  10. Check your answer for reasonableness, direction, and proper units.

Let's look at an example:

  1. Visualize the situation described. Be sure that you understand the concepts involved before you think about how they relate to a mathematical description. Here, visualize what is happening: Io orbits Jupiter under the influence of their mutual gravitational attraction, according to the law of gravity.
  2. Identify and list all the "knowns" and the "unknowns". We know Io's distance from Jupiter and Io's period.; these were given in the problem statement. If they had not been, we could refer to the appendix to determine them. We need to find the combined mass of Io and Jupiter.
  3. Set up a notation system for the knowns and unknowns, so that you can use the symbols in math relationships. Distance between two orbiting bodies is usually designated with r, so r = 421600km. Period is p = 1.77 days; mass will be mJ + mI.
  4. Check for any hidden information — values that you know because of the situation, but which may not be explicitly given in the description. There are no unknowns to worry about; but we may need to change units, depending on the relationship we use.
  5. List everything you know and the unknowns, in Standard units (meters, seconds, grams)

    r = 421600km = 4.216 * 108m
    p = 1.77 days = 1.529 * 105s
    mI + mJ = X gr
  6. Look for a relationship that relates what you know to what you don't know. You need one equation per unknown value. In this case the relationship we need is the law cited above:
    p2 = [ 4 pi2/G(m1 + m2)] a3
  7. Solve the formula for the unknown. Don't substitute values in prematurely: you'll only wind up doing more math. We need the sum of the masses, m1 + m2, which in this case are mI + mJ. Solving gives us
    m1 + m2 = 4 pi2a3 / Gp2
  8. Once you have the final version of the formula in place, substitute the known values into place.
    m1 + m2 = 4 pi2(4.216*108)3 / (6.67 * 10-11)(1.529*105)2
  9. Do the arithmetic.
    If you work out the numbers above, m1 + m2 = 1.9 * 1027kg
  10. Check your answer for reasonableness, direction, and proper units.
    Comparing this number with value for Jupiter in the appendix shows that we are at the right order of magnitude.

You are done!

Getting the Most from Chat

Chat sessions are 90 minutes. Plan accordingly, and take a break just before class starts. Do some stretching, go to the bathroom, eat or get your drinks before you enter the classroom. Be sure to try to connect to your ISP and check mail 10 minutes before class if possible, in case any late notices have been sent by the teacher. Give yourself the extra time. High traffic on your ISP or the school server can slow you down and force you to miss the first 5 to 10 minutes of class.

If you have not already done so, post your assigned questions and answers to the class forum before the start of class.

Bring your textbook, notes, homework calculations, calculator, and paper and pencil to class. If you are comfortable using a desktop calculator and taking notes in a text utility like Notepad (available as different applications on both Windows and Macintosh), you can use those. Take notes during class. If you are logging, you do not need to document things the teacher or other students say, but it is useful to note your own questions and observations as they occur, so that you can study them later.

Take part in the discussion. Ask questions as they occur to you (or note them and ask them at the end of class).

Chat sessions in astronomy often involve discussion of mathematical calculations. Because of the limitations of chat entry, we cannot use super and subscript notations. The convention we use is underscore (_) for subscript and up-arrow (^) for superscript. The term x_1 ^2 means "take the value x-sub-1 and square it". You may be more used to seeing this written as x12, but we can't do that in chat.

Print the log out. As soon as possible after class, review the log and make notes on it about any points that bother you, and be sure to ask about these in our next session. Mark important points for review later. Save the log to review before the next session and before semester examinations.

Quizzes

There are two sets of quizzes for each unit of the course. The first is the one on the CD-ROM. You should take this quiz as a review after we discuss in class the material it covers. You do not need to record your score or send it to me. You may take the quiz as many times as you like. Study any questions that you miss, and e-mail your teacher if there is still a problem.

Then take the online quiz. This quiz may be taken only once. It is timed. Your score for the quiz will be recorded. You will receive an explanation of the answers once you have submitted the quiz for a grade. You should note the questions that you miss, and be sure to study the correct answers and the concepts behind them before the semester examination on the unit.

Exams

Start your review two weeks prior to the scheduled examination.

Go through the Key Words listed at the end of each chapter. Are there any that you still don't understand? Note them down, and look them up. If you still have trouble remembering the meaning of the term, make a flash card for it and drill yourself.

Read the Key Ideas sections at the end of the chapter. These list the main points of the chapter. You should have any information in these points memorized, and you should be able to explain and use this information to solve problems.

Review the chat logs, and go over your notes.

Review your performance on quizzes, and make a list of the concepts with which you are still unfamiliar or which still puzzle you.

Look these up in the index or table of contents, and review the textbook discussion. If the idea still confuses you, write up a question for the review session, or e-mail the teacher.

Study Groups

Yes, of course you may study together — remember that explaining or teaching what you just learned to someone else is one of the important techniques of learning! You may also work together to solve the homework problems ... but be sure that you can solve them on your own afterwards, since you cannot work as a study group on quizzes or examinations. I encourage you to set up a regular meeting time outside our class discussion session for your study group.

Post the study time to the class forum. You may use the course classroom any time it is not already in use.

Doing Labs

Lab Techniques

The Scientific Experience

One of the basic methods of science is to secure documented observations of periodic or common events in order to make some general summary about the behavior of natural objects. We can do this in several ways.

Special concerns for Astronomy Labs

Determining Observing Times

Universal Time: The occurance of most events is listed in the literature as though you lived in Greenwich, England, on the Prime Meridian (0 degrees longituded), in hours and minutes of Universal Time, using a 24-hour clock. If you use a program such as Starry Night or Voyager III (there are about a dozen good ones), you can set the local time display for your location. Then when you look up an event such as a lunar eclipse in Sky and Telescope, you can easily "process" to the proper Universal Time listed, and see your local time displayed as well. But it is theoretically possible that you may be without this software from time to time.

Correcting for clock time. Universal Time is 5 hours earlier than Eastern Standard Time (8 hours earlier than Pacific Standard Time.) To determine when an event scheduled for 23:15 UT will occur in your local time zone, subtract the number of hours different. UT 23:15 is 15:15 PST.

Remember that if your local time is currently using Daylight Savings Time, your clock has "sprung forward" one hour: 15:15PST is 14:15 PDT. So an event at 23:15 UT on August 15 will occur when it is 14:15 in Seattle, or in the middle of the Seattle day (and probably be unobservable).

Sidereal Time: Long-duration phenomena are not listed as occuring at any given moment; rather, the location of the phenomena is listed in terms of celestial coordinates. Suppose a comet makes an appearance, and, moving slowly, will be at 6 hours Right Ascension, -18 degrees (south) declination. You want to know when it will be visible.

Aligning a Telescope

Using Binoculars

Binoculars are very useful instruments for viewing large areas of the sky. Even low-power binoculars (8X) can show you the craters of the moon, the phases of Venus, the rich starfields of the Milky Way, the hazy disc of Andromeda, and the 4 large moons of Jupiter, and give you a sense of position in space that is difficulat to achieve with a more powerful telescope.

The major problem with binoculars is that they are usually hand-held, causeing the image to jump around. When using binoculars to view astronomical objects, try to brace your arms or the binoculars against a stable object (the side of the house, a fence post, the hood of your car). If possible, mount the binoculars on a camera tripod or telescope tripod.

Writing Lab Reports

Your lab report is the evidence of your observations of a particular phenomena. Your observations should be presented in such a way that the data is easy to understand and supports your conclusions, but also with enough detail on how you obtained them that any peer with similar equipment could repeat your experience and confirm your results (or challenge them, as the case may be).

Organization: A good science lab report has at least seven sections:

  1. The abstract: a short paragraph explaining the goal of the lab, the overall purpose or hypothesis, the type of data gathered, and the conclusions.
  2. Materials and equipment: a description of the consumable materials and the observing equipment, instruments used to collect data. For standard equipment, references to the make and model are generally sufficient, along with verification that the equipment was tested for proper calibration.. If the equipment was modified, or specially configured, describe the new settings. If the equipment was specially built, either summarize the intent and purpose of the equipment and methods of calibration, or refer to other documents which provide this information.
  3. Procedure: a list of steps taken to secure the data. This should be detailed enough to allow peers in the field to repeat the measurements you made under simillar circumstances. Any choices you made that might affect results should be stated, along with the reasons you made them.
  4. Raw Data: the numbers you copied from instruments, descriptions of what you saw with your own eys, notes to yourself about odd things that happened, and rough sketches made during the observation. They might also include photographs, data collected by computer, and so forth. In many cases, the amount of data collected this way exceeds the space available in a formal report, so you do not need to include all of it. You should select representative samples of this data, and retain your notebooks with the actual raw data for reference if anyone questions your results.
  5. Sample Calculations: at least one each of any calculations you did to determine reliability (statistical analyses) or to figure out derived data (e.g., density from volume and mass measurements). This allows a reviewer (such as your teacher) to determine whether you used the proper technique of data reduction in this situation.
  6. Processed Data: all the processed data on which you base your results in the most useful forms. Frequently this involves creating a table, and may additionally involve preparing graphs to show trends.
  7. Conclusions: your assessment of whether your originaly hypothesis or assumptions are supported by actual phenomena. If your results did not bear out your assumptions, but you still feel the assumption is correct, you should explain the source of the problem (errors in measurement, calculations, equipment), and outline a plane for redoing the observations. When your experiment bears out your hypothesis, your conclusion should place these results in the context of the large field, and could include suggestions for further research.Astronomy Lab Reports

Because of the nature of astronomical observations, there are some kinds of data that you should always include for any observing session.

Term Papers (Research Reports)

Part of each semester's assignments is a research paper of 4-7 pages (1000 - 1500 words), written as a research proposal on some specific area of astronomy, and due at the same time as your semester examination.

You may use any and all resources at your command, including websites, text, other books, magazine articles, etc. You may spend any amount of time on the report that you wish, and you can work on it before and finish it after the exam if you so choose, but it is usually due at the same time as the semester exam.

TOPIC: You may choose a topic from the current semester's astronomy materials, where you can discuss how it is an example of a class of solar system objects (fall) or stellar or galactic objects (spring); what makes the particular object interesting, and how it might be studied. For example, you could choose planetary atmosphers, a particular moon like Io, or a particular application Roche limit theory (formation of planetary rings around Uranus). You must submit your proposed topic to the teacher and have it approved before continuing your research.

REPORT FORMAT: The report should include the following sections:

From a grading standpoint, I would like you to show me that you understand something about the general characteristics of one of these areas:

You will upload your paper as to the Moodle assignment location by its due date. It must be in acceptable format (Word DOC (not DOCX), RTF, Ascii text (TXT), PDF, or Mac Pages format). If you use another word processor, please check with me before uploading the file; I may not be able to read it.

Mycroft's Sample Research Proposal: Is the Moon made of cheese? (a PDF file)

Resources

Obviously...

The Links option is a good source for current areas of astronomical interest on the Web.

Planning Observations....

Starry Night will show you the positions of the stars and planets, the sun, the moon and its phases, for a given observing time.

Sky and Telescope and Astronomy Magazine both contain articles on observing techniques for amateur astronomers, general articles on recent discoveries, and monthly star charts with planet locations, lunar phases, meteor showers, comets, and other information. Both magazines maintain webpages as well.

The local newspaper may carry similar information on its weather page.

Current events....

NASA's website carries important information about current manned missions (mostly to the International Space Station) and unmanned missions (Cassini to Saturn, Galileo in orbit around Jupiter, various Mars missions).

The Hubble Telescope site carries the best of the Hubble's pictures, plus extensive information about the latest pictures and their implications.

Course wares...

Astronomy is the most popular of the sciences from the public's point of view: who can resist the pretty pictures? There are more books available on astronomical topics than almost any other science (counting computers and programming as something else entirely!). Consequently, there are many textbooks which range from simpler than the one we are using to much more firmly based in physics and mathematics. When looking at texts, try to find more recent editions, since information and theories in astronomy change rapidly, even at the fundamental level!

© 2012,2013 This course is offered through Scholars Online, a non-profit organization supporting classical Christian education through Internet-based courses. Permission to copy course content (lessons and labs) for personal study is granted to students currently or formerly enrolled in the course through Scholars Online. Reproduction for any other purpose, without the express written consent of the author, is prohibited.