GEOG303I - THE EARTH'S BIOPHYSICAL ENVIRONMENTS EXERCISE NO. 2 - EARTHVIEW AND EARTHWALK

PRINCIPLE

As you learned in Unit 5 of the textbook, the earth's orbit around the sun, its diurnal rotation on its axis, and the tilt of that axis lead to the periods of daylight and nighttime that are experienced at any point on earth, and to the patterns of daytime and nighttime on the globe. For places in the midlatitudes of the northern hemisphere such as Carbondale, we know that daylength varies from about 15 hours in late June to about 9 hours in December. The seasonal difference in daylength from shortest day to longest day throughout the year increases toward the North Pole, and decreases toward the tropics. Places at the Equator have 12-hour days year-round. Places in the southern hemisphere have the same pattern for their latitude, but offset by six months compared to what we experience.

This cycle of daylength sets in motion a seasonal variation in virtually all the environmental processes we can think of. Air temperatures, which respond to the cycle of energy provided by the sun called insolation, are the most apparent to us. But a year in Carbondale, will also tell you that the type of storms we experience vary as well, from spring and summer thunderstorms to the drizzle and occasional snowstorm of winter. Ice cream sells better in some months than others; so do snow shovels. Each place on the earth has its cycle of environmental events that are driven by changes in daylength, either at that place or at some other place. Understanding the patterns of day and night and how they change throughout the year to create seasons is fundamental to understanding how environments function. No matter what your major, at least some of the things that relate to your professional life will be driven by the seasons.

But we have a problem. The earth-sun relationships that create day and night and the seasons are hard to visualize because we are "stuck' here on the earth's surface. We see only the results, and have to keep track of them for a long time to get an overview. If we could only get a global perspective on these processes and speed them up they would make more sense. And if we can then transfer this information back to a more hands-on view, then we can create the set of understandings and mental images that will help us to understand earth-sun relationships, and how the environment works. The purpose of Exercise 2 is to syncopate betwen the information a computer can give us about earth-sun relationships with a more hands-on perspective.

OBJECTIVES

  1. Visualize the pattern of day and night on the earth, and how this changes through a 24-hour period, and over months and seasons.
  2. Visualize how the earth-moon system revolve around the sun and how this leads to the lunar cycle, from new moon to full moon, and back again.
  3. Understand the relation between the pattern of day and night and its seasonal change and the tilt of the earth's axis relative to the plane of the ecliptic.
  4. Anticipate how these relationships affect other environmental processes.
PREPARATION FOR THIS EXERCISE

  1. Concepts - Read the following pages in the textbook before coming to your laboratory session so that you will be able to understand the exercise and work efficiently. Read Unit 5 "Earth-Sun Relationships", pp. 50-59. Pay special attention to the section "Earth's Planetary Motions" (pp. 50-52), and Seasonality" (pp. 52-56).
  2. Resources - The things you will need to work on this exercise are:

    1. A computer with Home Planet installed, the ability to install it on your own computer, or a series of printouts that show a sequence of images and maps.

    2. A globe or ball, e.g., a beachball or a basketball with the continents printed on it, to serve as the earth.

    3. Another ball to serve as a moon, preferably smaller than the globe.

    4. A third ball, or some handy object to remind you of the sun.

    5. Some open space, a classroom or your living room floor, where you can ceate a mini solar system.

    6. The computer simulations you will use are part of public domain software called "Home Planet" that is on Internet. While you can run it over Internet, there is too much waiting time. We downloaded the program and have installed it on several computers in a computer lab on campus. You may be able to view it over Internet, FTP the files to your computer, or borrow a cdrom that is available through the Reserve Room in Morris Library. Here are three ways to use Home Planet.

    7. View Home Planet over the Internet. Its URL is: http://www.fourmilab.ch/earthview/vplanet.html Select map of the Earth to view a map of the portion of the earth in daylight and in night at the time you go to Earth Viewer. Remember that the line that separates the areas in sunlight and those having nighttime is called the "circle of illumination." Alternatively, you can view the earth with its circle of illumination as if you were on the sun (seeing only the sunlit half of the earth), or the moon, or from the night side of the earth, or any selected place on the earth. There are other options that you will discover when you go to Earth Viewer.

    8. Download this software to your computer by anonomous FTP, so that you can use it more efficiently. Instructions for doing this are given at the bottom of the Earth Viewer home page. We have downloaded the software and installed it on the computers you will use. You will need Windows 3.1 or Windows 95, and your hard drive must have at least 30 megabytes of available space.

    9. The easiest way to use this on your own computer is to check out the cdrom disk from the Reserve Room in Morris Library and install Home Planet on your own computer. The steps for doing this are:
      1. The name of the cd is "Home Planet."
      2. Open the Install directory, or folder.
      3. Execute "Setup" by double clicking on it. Setup will automatically install 'Hplanet" on your C drive, or other drive you select. You will need to answer some questions, but the installation is simple.

      4. After Hplanet is installed, transfer two more files from the cdrom in your D drive to ther Hplanet subdirectory on your C drive. The two files are XXXXXXXXXXX
      5. Add a line in your Autoexec file that specifies your time zone. A window appears when you are installing Hplanet that shows the format. For the Central Time Zone, write

      "SET TZ=CST6CDT".
    10. Use Hplanet on one of the computers in the CAIRL computer lab in 3206 Faner Hall. It is open from 8:30 - 5:00 every day.

    PROCEDURES

      Menus in Home Planet - You will become comfortable with using the menus in Home Planet very quickly. Here are the main and secondary menus in the order you will probably use them. You see the main menus on the menu bar at the top of the screen. Pull down the main menu to see the submenus by clicking on the main menu.

      Animate - These menu items control the animation parameters
      Animate - click to animate at a given time step, direction and speed
      Stop/Run - this stops the animation, or runs it
      Time Step - select a time step from a second to a millenium, and more
      Direction - make the earth spin from west to east, or backwards
      Speed - change speed of animation, from slow, medium or fast

      Display - These menu items give you extra information views
      Sun/Moon Information - Shows a table with information
      Show Moon - Displays moon with its quarter
      Planetary Positions - Relative position of planets from a point on earth
      Orrery - Current position of planets in solar system
      Sky - Location of major stars above a designated observatory
      Object Catalog - Information on celestial objects, including images
      View Earth From - Alternative places to view earth from; Sun, Moon and Observatory are most useful (see Edit menu)
      Map Window - Change coloring of map - choose Full Color
      Icon - Change icon used to show satellites, including a flying pig
      Map Image - Select map being used for display

      Edit -
      Copy - I don't know what this does
      Set Universal Time - Specify the time for the simulation
      Set Julian Dates - Similar to above.

      File -
      Exit - Leave Home Planet - An easy way to get back to the current time and date is to exit and then reopen.

      Save Settings - If you have selected new settings, e.g., an observatory location, you may save it before leaving Home Planet
      Default Settings - Return to original settings
      Satellite - Add a satellite to the image to see its orbital path
      Track Satellite - Lists satellites
      Satellite Database - Select satellites by category
      Change Satellite Icon - Same as Icon in the Display menu

      This exercise is a combination of "high tech" and "low tech" ways to explore earth-sun relationships and how they affect daylength and seasons. As a bonus, you will see how the moon enters into the picture to give you a new perspective on phases of the moon. This is an unstructured exercise, and its main purpose is to give you a chance to explore earth-sun relationships. There are some questions that are asked later in the procedures in order to guide your exploration and thinking about what is happening in the simulations. I hope you enjoy using Home Planet.

      1. Set the circle of illumination on the map into motion using Animate. Try different time steps, up to an hour for the diurnal cycle, and a week or month for the annual cycle. Interpret what ylu are looking at.

      2. Add View Earth From the Sun (Display menu). Note that the Earth-Sun distance is shown, as are the latitude and longitude of the "sub-solar" position (or viewed from Earth, the place where the sun is at the zenith).

      3. Display the Sun/Moon Information, and compare the information for the sun with what you saw in the previous view.

      4. Change to View Earth from the Moon, which is the astronauts' view of Earth.

      5. Change "View Earth From" to "Observatory. Change the location of the observatory to Carbondale, whose latitude is 37deg 42 min N and whos elongitude is 89 deg 12 min W.

        Answer Sheet Page 1

        EXERCISE NO. 2 - EARTHVIEW AND EARTHWALK

        E-Mail Address Name
        ID Number Section Date
        Photograph No. 1. Aerial View of SIUC: Photo on the Undergraduate Catalog Cover

          1a. You are looking south over the "old campus" part of SIUC. Can you identify some of the buildings? Write the building names on the black and white photograph on Answer Sheet Page 2.

          1b. If you are facing toward the south in this photograph and you can see the north and east walls of some of the buildings, which wall(s) are in the direct sunlight?

          1c. Which way are the shadows of the trees facing (if you were at the bottom of a tree and looking along its shadow, which way would you be facing)?

          1d. Approximately what time of day is it?

          1e. If this is a work/school day, what is the evidence that this photograph was taken before or after classes began for the day?

          2. Photograph No. 2. Overview of SIUC Campus and Countryside to the South 2a. What is the evidence that this photograph was taken earlier/later in the growing season than the previous photograph? Hint: compare how dense the leaves on some of the trees are. 2b. What direction was the wind blowing? Hint: find a flag and see which way it is pointing. 2c. What time of day was this photograph taken? Was it still part of the work/school day? How do you know? Answer Sheet Page 2 2d. What is the evidence in this photograph that Carbondale, Illinois is in a humid region? Briefly describe how you are deriving your answer. 3. Photograph No. 3. Aerial Photograph of the SIUC Campus and Surrounding Area 3a. Calculation of the scale of the aerial Photograph: The length of the football field on the photograph is (include your unit of measure) _____ The actual length of the football field (in the same units of measure) is ___________ The scale of this aerial photograph is 1 : ______________. 3b. Briefly characterize the unique aspects of the pattern for each land use as you see it on the photograph. Residential land Use Agricultural Land Use Forest Water Body Answer Sheet Page 3 Answer Sheet Page 4 4. Satellite Image Map of Illinois 4a. The SIUC football field would be _________ on this map (include unit of measure). The smallest object you can see on this satellite image map is about: 4b. Features represented by the colors red, gray and black are: 4c. Evidence that agriculture is important in Illinois: 4d. Reason why agricultural land is shown in gray tones: 4e. Evidence for Shawnee National Forest 4f. Evidence that river bottoms are productive agricultural land. 4g. Five other features on the map. Feature 1 - Feature 2 - Answer Sheet Page 5 Feature 3 - Feature 4 - Feature 5 - 5. Earth from Apollo 12 5a. The scale of this photograph is approximately 1: _________________. 5b. Light feature in northern Africa and how you can identify it. 5c. Is this a June or December photo, and how do you know? 5d. Five other features on the Apollo photograph of Earth. Feature 1 - Feature 2 - Feature 3 - Feature 4 - Feature 5 -