A Historical Journey of Astronomy

Tools of Astronomy

Synopsis: The following lessons are a subunit of the Astronomy unit, introducing the solar system through a historical and technological perspective.  Activities include regular class instruction, independent or group research & discussions, constructing a simple telescope, demonstration of concepts,
and  student observations of celestial bodies with and without instruments.

Grade level: grade 8 & 9

Time required: Approx. 9 - 10 (45 min.) class periods (does not include Night Sky Watch)

Class format: varies with the lesson

Standard M: Students will understand the historical, social, economic, environmental, and ethical implications of science and technology.
Indicator: MG 2. Describe the historical and cultural conditions at the time of an invention
or discovery, and analyze the societal impacts of that invention. Synopsis: Introduce the following homework assignment at least one month prior to the unit. Students are to sky gaze nightly , observe and record movement of star(s), planet, and moon.  Students should have a minimum of one month observations at start of
the unit which will serve as the basis for discussion.  The lesson will address the Ptolemy    and Copernican system models to the invention of the telescope.

Time required:  15 min.  for explanation of assignment & star/planet/moon gazing chart
 approx. 4 - 5 (45 min.) class periods for the lesson

Homework Activity: Celestial Observations (introduce at least one month prior to unit)
Format:  Divide the class into groups of 3.
Each student within the group is responsible for either the star, planet or moon observations.

Procedure: Star /Planet/Moon Observations
1. Pick out a bright star or constellation and stand somewhere so it lines up with an     immobile landmark, such as a tree.
2. Note the time and return to the same spot an hour later; note its position...record day,     time and draw your observations using the Observation sheet on page 11 and example on page 3.  Do #2 for five consecutive days, then
3. Look out for the same star/constellation over the next month at the same time and from     the same spot; record and draw your observations.  If you skip a night, leave the     frame on your observation sheet empty.
4. Use angular measurements (see example on  page 3) to indicate distance the object shifted  from fixed point.
5.  Do # 1 -4  for planet observations...pick one planet and observe nightly.
6.  Do # 1-4 for moon observations...drawing should also indicate phase of moon.
 
 

Observation chart:  Examples of how to record observations

Homework Activity:  continued...
7. Discussion questions  based on observations.  Students answer the following questions in their notebooks:
  . How can you tell the object is a star or planet?
  . What movement did you observe, if any?  What direction?
  . Draw a diagram of where the object will be in several days/a month.  How did you
   determine that?
  . What motion does the hour difference in time represent?
  . What motion explains the daily drifting?
 **8. Class follow-up (What do the clues tell you?)  Discuss studentsí answers.  Terms    such as rotation, revolution and direction of each should be addressed.   Stars do not    have a well defined edge (they appear to twinkle), planets have a more defined shape in    the night sky.
*Resources  for location of planets and stars in the night sky are,  Astronomy,
 and Science And Children magazines.

Introduction/background information
Teacher instruction:
For as loing as people have walked the Earth, they have looked to the stars.  The stars have
provided guidance of many of the advances of civilization.  Farmers have sown and harvested
crops according to the phases of the moon and positions of other heavenly bodies.  Explorers
and sailors have charted their courses across deserts, forests, and open seas with the aid of
the stars.  Cultures have studied the sky.  The Babylonians first grouped the stars into con-
stellations, the Chaldeans and Egyptians used astronomical observations to calculate the
length of the year as 365-1/4 days; the Greeks determined the circumference of Earth and
catalogued 1,080 stars, grouping them by their brightness.
* Break for the following exercise.

Activity: What do the clues tell you? (**8 of homework assignment)
1. In groups of three (if homework assignment was distributed in groups, have the same
 groups convene) have students discuss their observations ...use the following
 prompt questions.
 . What happened to the star/planet/moonone hour later?  Was there any shift in
 position?  If so, in what direction?  How much?
 . What was your observation the following day?  any changes?
 . What discoveries did you make?  Your group?
 . What generalization(s) can you make from your observations?  From your groupsí?
2. Groups share their generalizations/ideas.
3. Students should save their observations for a later lesson on the motions of celestial bodies.

Teacher instruction continued...introduce the Ptolemaic & Copernican model

 If we see the sun, the moon, and the stars rise in the east each day, cross the sky, set in
 the west, and come up again the following day, it is only natural to assume that that is what
 is actually happening.  Our senses give us no clue that the Earth is in motion.  Therefore, the   earliest models of the heavens placed the Earth at the center of the world.
  About 2,000 years ago, the Greeek astronomer Ptolemy developed a detailed model of the   universe based on the idea of revolving spheres.  In this model the Earth is stationary.
 The moon, the sun, and the fixed stars revolve about the Earth in circular orbits
 at different distances and speeds.  Each planet revolves in a small circle called an epicycle,
 while the center of its epicycle moves around the Earth from above the North Pole.  From this
 position the celestial objects revolve about the Earth in a clockwise (or westward)section.  Thus
 the model explains, in a general way, the features of the apparent motion of the celestial objects.
 The chief problem of the Ptolemaic model was that it did not show uniform circular motion and
 match the observed positions of the planets.  With minor modifications the system remained
 in use for nearly 1500 years and no one seriously questioned the epicyclic model for more
 than 1000 years.
 After the time of Ptolemy, western civilization suffered a long decline.  The knowledge of the
 ancient astronomers might have been lost had it not been for Arabic astronomers, who
 preserved ancient writings and translated them into Arabic.
 By the 15th century, the astronomy of the ancients had been rediscovered by Europeans.
 Astronomers had begun to observe again and to test hypotheses against observations.
 The geocentric model of Ptolemy was accepted by nearly all astronomers.  Some astronomers,
 however, had growing doubts about Aristotleís theory of motion and his arguments that the
 Earth must be motionless.
 Nicolaus Copernicus,  Polish astronomer , was the first to disagre publicly with the accepted
 belief that the Earth stood still and everything else revolved about the Earth.  In the heliocentric
 model, Copernicus set up a general picture of the universe with the sun at the center and the
 Earth revolving , as a planet, about the sun.  The eastward rotation of the Earth produces the
 apparent westward diurnal motion of the celestial sphere.  The annual motion of the Sun against
 the background of the stars is caused by the Earthís annual orbit around the Sun.  Finally, the
 retrograde motions of the planets can be explained without the use of epicycles.  Retrograde
 motion occurs whenever one planet catches up with and passes another as they both orbit
 the Sun.  This system also made it possible to use geometry and observations to determine
 all the planetary distances in terms of the Earthís orbital distance which is called as an
 astronomical unit (AU).

Demonstration:  Use the ** Copernican system model  and the diagram of the retrograde motion of Mars
 (pg. 14,make overhead copy) to demonstrate how retrograde motion occurs whenever one   planet catches up with and passes another planet.
Teacher instruction continued...
The triumph of the heliocentric model was also aided by a series of observations made by
Galileo Galilei shortley after the telescope was invented.  Galileoís observations were totally
different from any made before.  With his telescope he could observe remarkable phenomena
that no astronomer could have seen w ith the unaided eye.
*Stop here...start Activity:  Scientists who...next class period.

**Homework assignment:  In each class have students track the visible planets in the night sky nightly, and      show their orbital location using the Copernican system model. Rotate the observation responsibility  from one student to  another on a weekly basis in each class.

Activity:  Scientists who have made a difference!
Time required:  2 -3 class periods (90 - 120 min.)
Format: Groups
1. Divide class into groups (number of students in each group depends on the number
  of scientists that need to be addressed (possibilities are:  Aristotle, Ptolemy, Copernicus,
  Brahe, Galilei, Keppler, Wilhelm Herschel).
 2. Each member of the group is responsible for researching  a scientist from the list.
 3. Students are to research:
  . name, date of birth
  . historical background (social, economic, environmental, and ethical)
  . personal background
  . significant achievements in the field of astronomy
  . factors that encouraged and/or interfered with the achievement
  . interesting facts
 4. Convene as a group; group reaches a consensus in regards to the following questions
  (groups must be able to support their answers with examples; choose one member
  as the recorder to record anwers, and another as the spokesperson who will present the
  answers to the class); write all answers on the board to make a composite list.

. How does society/culture influene the discoveries that are made and who makes them?
. How does the period in history influence the discoveries that are made and who makes     them?(example - would rockets have been invented if WW II had not taken place?)
. How do the economic and environmental conditions influence the discoveries that are made and who makes them?

Standard G, indicators MG 1, 5, and SG 1 (same as lesson 1)
Synopsis: This lesson focuses on how the telescope works and its use.  Methods of instruction    include class instruction, demonstration, the construction of a simple telescope, and observations.

Time required: Approx.  3-4 (45 min.) class periods

Introduction /Teacher instruction:
 Demonstrate the difficulty of viewing distant objects.  Hold up a book while standing at the
 front of the room.  Ask a student in the rear of the room to try to read what is written on a page.
 Establish the fact that stars and planets are difficult to study because they are so far away.
 Elicit that astronomers use various kinds of telescopes to measure the electromagnetic radiation
 from distant objects.
 Conduct this lesson as an introduction to telescopes, instruments used by astronomers.
 Develop the fact that there are different types of telescopes.  On the board list the three main
 types of telescopes:  refracting, reflecting, and radio.  Go over the terms refracting and reflecting.
 Establish the idea that refracting means the bending of light as it passes through different   material; reflecting means the light bounces from a surface.  Display  and show a diagram  of the
 refracting and reflecting telescope and identify their parts.  Point out that the refracting telescope
 uses lenses while the reflector uses mirrors and emphasize that these are optical telescopes...
 they collect light from distant objects.
 Show a diagram  and explain the operation of the radio telescope.  Elicit from the students
 that astronomers do not look through radio telescopes but that radio signals are picked up
 by the antenna and are analyzed.  Radio telescopes can be used any time, no matter what
 the weather or time of day.

Activity:  How does a refracting telescope work?
Format: Groups (size of groupdepends on equipment available).
Procedure: Students learn how a refracting telescope works by constructing a simple
telescope...use one of two methods.
Type A

Materials needed:
Each group should have - 2 convex  lenses, 1 meter stick, and a blank index card
 1. Mount the lens on a meter stick, as shown in the diagram; aim the lens at some
   distant object.
  2. Place the screen on the meter stick and focus the image formed by the object
   on the screen (allow students to focus on their own).  What does the lens
   do to the object ?
   Point out that the distance from the lens to the screen is the focal length of
   the lens. Depending on lenses available, find the focal length of
   several different lenses (highly curved lens produces a short focal length,
   slightly curved lens produces a long focal length).
   Use the lens with the longest focal length as the object lens and one with a
   shorter focal length as the eyepiece lens.
  3. Place the eyepiece lens on the meter stick at the proper focal distance from it.
   Remove the screen and view the object through both lenses.
   Have students describe the image formed.
  4. Have students go outside with their telescopes and view the moon; then view the
   moon through a regular telescope.  Compare the results of the two telescopes.
  6. In their notebooks, have students describe and explain how the refracting telescope
   works.  Review their work and check for accuracy.

  Type B
  Materials needed:  Each group should have - 2 cardboard mailing tubes, 9cm
  and 18cm (9cm one should be slightly smaller in dia-
  meter); 2 convex lenses (eyepiece, short focal length;
  objective, long focal length); and masking tape.

  1. Tape the objective lens to one end of the larger, longer tube.
  2. Tape the eyepiece lens to one end of the smallr, shorter tube.
  3. Slide the small tube inside the larger tube.
  4. View an object through the telescope,  focus.  Have students describe the image
  formed.
 5. Have students go outside and view the moon, then view the moon through a regular telescope.  Compare the    results of the two telescopes.
  6. Same as in "A".
 

Activity:   How do relfecting telescopes work?
Demonstration
Materials needed:  1 concave shaving mirror, a candle , 1 magnifying glass.
Procedure:
  1. Review the difference between refracting and reflection, a convex  lens and concave
   lens.
  2. Put a lighted candle at the end of a table and a concave shaving mirror at the other
   end.
  3. Tilt the mirror toward the wall and project the image of the flame onto the wall.
  4. Move the mirror toward or away from the candle until there is a sharp image on the
   wall.
  5. Have students look at the image with a magnifying glass; have students describe
   the image.
  6.  Have students describe and explain how a reflecting telescope works (may use
   diagram with captions).
  7. Review  their work for accuracy.

 Discussion/Summary
  1. Compare the features of the reflecting telescope with those of the refracting      telescope.
  2. Discuss the advantages of both types of telescopes.  Point out that the lens for a
   refracting telescope must be made of high-quality glass with no internal imper-
   fections.  Both the front and back surface must be ground and polished.  In a
   reflector, on the other hand, light doesní t pass through the mirror, thus the
   mirror can be made of practically anything.  Only one surface must be ground
   and polished, which makes it easier and much less expensive to produce large
   mirrors than it is to produce large lenses.  An additional problem is the weight of
   a large lens.  It is difficult to make and support large lenses.
  3. Briefly discuss brightness of the image; elicit from the student that brightness depends
   both on the amount of light collected by the objetive (either lens or mirror) of the
   telescope and on the area of the image in the focal plane (the surface where the
   objective  lens or mirror of a telescope forms the image of an extended object).
   The more light that can be collected, the brighter the image.
  4. Briefly discuss the difference between binoculars and a telescope.

Activity:  Night Sky Watch
Format:  Students (one class or two classes at a time) are requested to attend a Night Sky Watch.  This should take place during or after students have studied planets and stars.  Simple and regular telescopes will be used for      observations.  Binoculars are also recommended.

Suggested activities:
  1. Locate and identify several constellations and map their location in the celestial
   sphere. This activity can be done again at a later date (second Night Sky Watch)
   to demonstrate motion of the stars and planet.
  2. Identify at least one star that is red, one that is blue, and one that is yellow.
   Explain the meaning of these colors.
  3. Sketch the position of the Big Dipper in relationship to the North Star and the
   horizon at various times during the evening.  Record date and time of night.
  4. Locate a planet(s) and find out some differences between stars and the planets.
   Include ways to tell the difference between a star and a planet in the night
   sky.  Make a visual display to illustrate your findings.
  5. Locate several planets if possible.  How do they differ?  Which one appears larger?
  Why?  using your starviewer (directions for constructing starviewer on page13),     find  the brightness  (apparent magnitude) of each?  What determines a planetís brightness?
  6. Using a star viewer and star map, measure the brightness of several stars (have a list
  of stars available with their distances from the Earth ).  Are the brightest stars the     closest?  Why or why not?
  Possible list:
 

Star	Brightness  (apparent mag.)	Distance (L.Y)
Deneb	+1.26	650
Formalhaut	+1.15	23
Sirius	-1.46	9
Betelgeuse	+0.4	520
Antares	+1	391

7. Exploring the Moon.  Locate and identify several of the Moonís craters (light areas)
 and mare (dark flat areas) and draw a map of the Moon .
*See pages 15 & 16 for examples of some of the above-mentioned suggestions.
 

Follow-up classroom activity:
Discussion:
1. Have students make a list of things (celestial bodies and or phenomena) in the night
   sky  that could not be not be made with the naked eye.
2. Discuss with the students how the telescope has increased our knowledge
   of celestial objects.
3. Discuss with students what happens when we place telescopes above our atmo-
   sphere? Elicit from students the discoveries made with the Hubble telescope.

Directions to making a STARVIEWER:
Materials needed: scissor or exacto knife
   shoe box
   masking tape
   metric ruler
   pencil
   a quarter coin
   plastic food wrap

Directions:
1. Cut the two long sides off the shoe box.
2. Put them back to back.
3. Now tape the front and back together along one long edge (to make a hinge).
4. With your ruler & pencil, divide one side of the viewer into 5 equal sections
   then use your coin to trace a circle in the middle of each section.
5. Carefully cut out the 5 circles, make sure you cut through both front and back
   of viewer.
6. Cut a strip of plastic food wrap as long as the viewer but a little wider.  Tape the plastic
over one side of the viewer (inside).  Cut a second plastic strip that is long enough    to cover only  4 holes  but  again wider than the viewer; tape it inside the viewer
   eaving one hole with only one layer of plastic.
7. Mke a third strip long enough to cover 3 holes but wider than the previous one.  Tape
this one over the other one, leaving 2 holes uncoered.  Then make  2 more strips
each a little wider and a little shorter than the one before it.  The last strip should
cover only one hole.
8. On both sides of the viewer, write the # 1 under the hole with the five layers, 2 under
the hole with four layers, and so on, down to the last one with just one layer,
marked 5.
9. Close the sides of the viewer and tape them together on all sides.

How to use the viewer:
Looke at the same star through each of the holes.  The lowest numbered
hole  you can see the star through is the starís apparent magnitude.
Example:  Pick a star and look through the fifth magnitude hole (hole #5)
If it is visible, slide the viewer to hole #4, if you cannot see it, then
it is a fifth-magnitude star.
Faint stars will be visible through  #5
Medium stars will be visible through #5, 4 and 3
Bright stars will be visible through #5 - 1

References:
1. Engelbrektson, Sune, and Peter Greenleaf.  Letís Explore Outer Space.
  New York:  Sentinel Books Publishers, Inc. , 1969
2. Fix, John D.  Astronomy:  Journey To The Cosmic Frontier.  St. Louis:
  Mosby-Year Book, Inc., 1995
3. Macaulay, David.  The Way Things Work.  Boston:  houghtonh Mifflin Company, 1988
4. Winkler, Alan, and Leonard Bernstein, Martin Schacter, Stanley Wolfe. Concepts
  and Challenges in Science.   Newton:  Cebco, 1984
5. The World of Science.  Edinburgh:  Southside, 1989
Excellent Resources:
Magazines: Astronomy, Sky & Telescope, Child and Science
Books:  Letís Explore Outer Space (see #1 of reference list)
The World of Science Series (#5 of reference list)
Computer: The following provide daily up-to-date information on space discoveries, events, etc.:
    BAALKE@KELVIN.JPL.NASA.GOV
    TIE-L@LIST.UVM.EDU