K-8 Astronomy and Physics course

Transcription

1 Heavens above! K-8 Astronomy and Physics course 5 th Module Let s observe and think rationally about the SKy This module introduces students to the study of the dimensions and of the distances of the bodies of the Solar System, beginning with the Sun-Earth-Moon System. Users: Fifth/Sixth Grade Students. Total amount of time: 20 hours. Teaching proposal and educational material, cards for students.

2 Introduction This Teaching Unit is addressed to fifth grade or to sixth grade students. The expected time is around 20 hours, which we suggest to spread out over some months in the school year. By studying the Sun-Earth-Moon system, students will make important steps in achieving confidence in data interpretation. The aim of this part of the course, is to have students develop a critical attitude, an ability in formulating hypothesis, in grasping the essential elements of a phenomenon, which later characterize its model. As you can see, the aims are big and ambitious, but their achievement is possible and it gives students enthusiasm and self-confidence. In this module, different instruments and models are supposed to be built. You have to prevent students from focusing their attention on the instrument or on the model rather then on the phenomenon. This means, that when they are building either an instrument or a model, they should keep in mind the phenomenon, and they should think about the limits of the instrument or of the model. Limits concern both applicability and utilization. The first T.U. is a catch-up unit. Later on, students will be introduced to Moon s observations. Moon s observations are fundamental as far as relative positions of three bodies, point of view and importance of the reference system. It represents the end of the observation part, which began back in the first module. The next part will involve abstraction of fundamental elements. As a matter of facts, in order to allow for a better understanding, natural phenomena will be reproduced by means of simulations and models. In order to raise students interest in observing the Moon and its aspects, either a small telescope or a binocular is what you need. You will use them to observe the Moon and its surface also during school hours. Other ways for raising their interest are through group works and through instrument and model construction. Often, students will build them by themselves. We strongly suggest to build and use the instrument as described in T.U. 5.1 (the thingscope ). Two more things are important. It is students first time to meet the problem about dimensions in space (in this case, in our Solar System). Dimensions and distances is a conceptual nucleus among the most important ones as far as Astrophysics, if we are allowed for a hierarchy in this field. The dimensions (of celestial bodies)/distances (in the Universe) relation is not at all clear to students. Moreover, mediameans and even textbooks, have a part in making it even more confusing. From this concept and from realizing that space is empty as far as matter a correct mental set up arises. It allows, later on, for example, for understanding the gravitational field and its forces. Sometimes, you can find images, which fits the entire Solar System in just one page, without keeping into consideration the right scale factor. Remember that first of all, it is a wrong representation, second it is misleading for students, and it allows for misconceptions. After building the Sun-Earth-Moon System, in the last T.U. students will build a Scale Solar System model. Students like it, and it shows in a very effective way the previous concepts. The last step of the construction of the model consists in placing the planets in their proper positions in a field or in whatever large place. It is possible to involve parents, too, but they just have to look. Daylight observations of the Moon allow for consolidating the fact that the Moon shows always the same face to the Earth. This activity is a starting point for understanding the inclination of the Moon s orbit with respect to the Earth s one. This time, the Night Under the Stars represents an evaluation activity for what knowledge students acquired. In fact, after their methodical observations, they have to be able to understand the phases of the Moon. The Night should take place at the end of the module, and it can take place by an astronomical observatory. It allows students for observing the planets, too, which can be seen in that period in the Sky and therefore, they consolidate the knowledge, which they acquired.

3 What some of the teachers, who tested this module, think about it No child had ever though that the Sun could be so big if compared to the planets, that the Moon could be so little if compared to the Earth, that the distance between two planets could be so large, and that, as far as eclipses, such a small satellite could obscure such a big star!. They saw it clearly thanks to the scale model. This experience turned out to be very positive. Students were highly enthusiastic in carrying out handson activities, in finding out the right scale factor for the model. It is not always that easy, to learn this concept from images in textbooks. I think that the part about Moon observation was very important for students. It was quite hard to carry it out, and you have to take into consideration the different position of the school buildings. I chose to have it carried out as homework. Therefore, the problem we had to face was to put together all the observations. This was useful for pointing out again to students how important it is to have a reference frame: an observer should always collect his data with respect to something. We also chose to measure the height of a star. Every child carried out by him/her self at least three individual observations, while at home, in the months between January and May. Everybody noticed a change among the values they measured.

4 5 th Module Scheme, First part 5 th MODULE TEACHING UNIT OBJECTIVES CONTENTS Let s observe and think rationally about the Sky Aims: To facilitate Astronomy concept learning, starting from a hands-on activity concerning observation. To develop a skill in observing and interpreting phenomena, which were previously observed. To develop a critical attitude and abstraction skills. 5.0 Sun, Earth and motions 5.1 The phases of the Moon and the Sun- Earth-Moon system To consolidate some concepts, which refer to the Earth s motions. To consolidate students awareness, that the motion of the Sky depends upon the reference system, which we consider. To introduce the peculiarities of the reciprocal positions of three bodies. To have students understand that the aspect of the Moon depends upon many variables. To observe the phases of the Moon. To have students understand that it is necessary for the Moon to be above the horizon, in order for us to see it. Relative motion of a body with respect to another one. Relative motions of three bodies. Changes in the face of the Moon. Sun s height and Moon s height above the horizon; relative positions. To learn how to choose the fundamental elements, which are involved in a phenomena, in order to build a model. To rationalize some astronomical concepts. To correlate different physical quantities. 5.2 Different dimensions, different surfaces; dimensions and distances of the Sun, of the Earth and of the Moon To measure linear and surface dimensions. To compare the Earth s and the Sun s diameter. To compare the Earth s and the Sun s surface (by taking these two bodies as if they were flat surfaces). To compare the Earth s and the Sun s volume. Measures of lengths, of surfaces. Measure unit for length, surface. Relations among units of measure. To have students approach the understanding of the dimensions of the Universe. To acquire the idea that the Sun-Earth System is empty as far as matter. To acquire a critical eye, in order to give the right meaning to information, which are spread by media means. 5.3 Let s think about the Sun-Earth-Moon system To have students understand that motion depends upon the observation point (observation point on the Earth, on the Moon and on the Sun). Reference system. Point of view. 5.4 How to build a scale Solar System To understand that interplanetary space is empty as far as matter. To understand that the dimensions of the bodies of the Solar System are negligible if compared to the distances among them. The structure of the Solar System. The concept of emptiness of matter inside the Solar System. The Night Under the Stars

5 5 th Module Scheme, Second part TEACHING UNIT EDUCATIONAL MATERIAL MATERIAL FOR STUDENTS EXPECTED TIME 5.0 Sun, Earth and motions Sample card for carrying out the activity. Sample card for data recording. Sample card for observation. 2 hours Sample of summing-up table. 5.1 The phases of the Moon and the Sun- Earth-Moon system Sample card for carrying out the activity. Sample card for learning evaluation. Instrument construction cards (sextant and bearings getter ). Model construction cards (the phases of the Moon and eclipses simulator ). 6 hours Instrument construction card straw sextant. 5.2 Different dimensions, different surfaces; dimensions and distances of the Sun, of the Earth and of the Moon Sample card for carrying out the activity. Table about dimensions of the Sun-Earth-Moon system. Sample card for learning evaluation. 4 hours 5.3 Let s think about the Sun-Earth-Moon system Sample card for carrying out the activity. Sample card for learning evaluation. Sample card for observation (for drawings). Sample card for observation (for texts). 3 hours 5.4 How to build a scale Solar System Sample card for carrying out the activity. Table about the dimensions of the bodies of the Solar System. 2 hours The Night Under the Stars Pieces of advice for a visit to an Astronomical observatory. 3 hours

6 Teaching Unit 5.0 Sun, Earth and motions (Catch-up Unit, concerning fundamental concepts) In order to carry out this T.U., it is necessary for students to have already acquired the concepts of horizon and reference point. This T.U. is divided into two parts. Part A is a catch-up or consolidation time, while part B takes up again the concept of relative motion in the Earth-Sun model, in order to encompass the Moon. Contents Relative motion of a body with respect to another one, relative motions of three bodies. Objectives To consolidate some concepts, which refer to the Earth s motions. To consolidate students awareness, that the motion of the Sky depends upon the reference system, which we consider. To introduce the peculiarities of the reciprocal positions of three bodies. Glossary Ecliptic, planet, satellite. Required time Around two hours, for a joint discussion. Needed material Part A Windows, where to observe from. Part B Observation card, for keeping a Moon diary. Pencils. Crayons. Tellurium. Procedure In order to arouse students interest in Astronomy and Physics, we suggest to carry out a research on the Internet or on textbooks, about information concerning planets of the Solar System ( Students are supposed to find out information, which they think are important (mass, diameter, distance to the Sun, etc.), to compare them and to organize them into a table. Part A (Consolidation or review of the concept of horizon: go back to T.U. 2.2 for further information and for catching up with these concepts). 1. Catch-up lesson, concerning the concept of horizon. All you have to do is have students stand in front of a window, and have them first describe and then draw, what they see. It would be better to carry out observations in a day, when we can also see the Moon. This allows for introducing a necessary condition, in order for a celestial body to be seen: i.e. it has to be above the horizon. 2. Have students move to the back of the classroom and from this position, have them describe and draw both what they can see and what is different from the first observation. You may also want to use a recording card for describing the objects, which can be seen, from a closer-to-the-observer point of view. 3. Have students compare the two drawings and have them discuss about the differences between the two observation sessions.

7 Part B (Catch-up lesson, concerning concepts of T.U. 4.2; go back to this T.U. for further information). 1. By means of a tellurium with the Sun and the Earth, discuss the Earth s motion as seen from the Sun, and the other way around. If you do not have a tellurium, you can have a lamp stand for the Sun and a foam rubber little ball stand for the Earth. A skewer, pierced into the little ball, can stand for the Earth s axis. Picture Earth-Sun relative positions by means of a tellurium. S L T Picture An alternative model, in case you do not have a tellurium: you need two little balls, having different dimensions, in order to represent the Earth and the Moon. It would be better if the diameter of the smaller ball, which represents the Moon, were almost _ of the one of the bigger ball, which represents the Earth. Use a turned-on overhead projector as the Sun. Discussion about the validity and the limits of the model (for example, why can the Sun be replaced by a lamp, which is far away enough, for example two meters, from the Earth-Moon system?). 2. Place the tellurium (or the other model) under an umbrella. It would be better if it were transparent. On the umbrella, you have previously drawn some stars. It represents the celestial dome. Imagine the motion of the Earth projected against the starry Sky, and, if the umbrella is transparent, draw the ecliptic (the ecliptic represents the intersection between the celestial dome and the plane of the Earth s orbit. Therefore, for a terrestrial observer, the ecliptic is the great circle, which the Sun covers in one year, in its apparent motion with respect to the fixed stars). 3. While you are tracing the motion of the Earth around the Sun, have students notice that, from the Earth point of view, it is the Sun, which describes a path, which is projected against the starry background. It is important for students to keep in mind that the stars are in the Sky even during daylight. At this point, you can discuss about the differences between the motion of the Sun and the motion of the stars as seen from the Earth. 4. Now, include the Moon in your model, too, by adding another smaller ball: how are we supposed to make it move? Discussion with students: in order to earn information about the motion and the phases of the Moon, it is necessary to carry out some observations, first. Further discussion about the importance of the reference system in this new situation, in order to highlight the composition of motions, i.e. the motion of the Moon around the Earth and the motion of the Earth around the Sun. It can be useful to have three students reproduce this motion. Each student is one of the three celestial bodies, while the other students observe and draw, what they can see from their external position. 5. Discussion, which leads to a sample of observation card concerning the Moon. Its set up has to allow for homogeneous results (observation card). Didactic-methodological suggestions It is important that the models are a lot and different, so that to repeat the concept that they are just fiction. The observation card is just a sample. It would be better if the card and its look will arose from the discussion among students themselves. As far as the Moon is concerned, for students at this young age, the Web Site Il volto della Luna (The Face of the Moon) in turns out to be very interesting.

8 Teaching Unit 5.0 "Sun, Earth and motions Observation card Date Date Date Date Date Date Date Date Date Date Date Date Date Date Date Date Date Date Date Date Date Date Date Date Date Date Date Date Date Date

9 Teaching Unit 5.0 "Sun, Earth and motions Fill in the following card Recording card (for students) 1. Fix an observation point, close to the window. Describe what you can see, with respect to an object, which acts as a reference point. 2. Step back twice from the window. Describe what you can see, with respect to the same object of the previous step, which acts as a reference point. 3. Step back twice once more, moving even further from the window, and do all over again. 4. Compare your answers and point out the differences. End of Teaching Unit 5.0

10 Teaching Unit 5.1 The phases of the Moon and the Sun-Earth- Moon system This T.U. involves a yearlong observation. It provides students with an understanding of periodicity of Moon s phases. It involves measurements of Sun s and Moon s heights above the horizon, which will be carried out on well determined times, in order to allow for comparisons. Contents Changes in the face of the Moon. Sun s height and Moon s height above the horizon; relative positions. Objectives To have students understand that the aspect of the Moon depends upon many variables. To observe the phases of the Moon. To have students understand that it is necessary for the Moon to be above the horizon, in order for us to see it. Required time We scheduled observations over three lunations. They are supposed to be carried out in different periods of the year, for example October, December and March. On the whole, it requires 6 hours: two for discussions, some minutes every day for observations, and at least other three hours for instrument and model construction. Needed material Observation cards for the Moon. Hand-made instruments. Procedure This activity concerns protracted and methodic observation of the Moon. It will lead students to hypothesis formulation, starting from data, which they collected. They will be asked to foresee on what days it will be possible to observe the Moon during classes. Its positions in the Sky will be compared to the Sun s ones. Part A. First observation session concerning the Moon 1. By means of the card, students begin their first observation session, without any teacher s suggestion about what to observe and what to record. After some days, carry out a discussion with students. They are supposed to identify what variables have to be taken into consideration, in order to obtain useful data. These data (sunrise time, differences in shape, waning or waxing gibbous, ) are supposed to be compared later on. Have students notice that the variables involved in Moon s observation are more than those involved in Sun s observation. Once students identified these differences, you can modify the observation table, in order to improve it. From the discussion, it must arise how important it is to fix a position, where to observe from. The necessity of determining reference points must arise 2. Go on observing by filling in the Moon diary. Form the final discussion, it has to be clear that it is necessary to measure the position of the Moon in the Sky with respect to reference frames, by using proper instruments.

11 Part B. Second observation session concerning the Moon and the Sun. 1. In this observation session, during daylight, students are supposed to measure the Moon s height above the horizon, for example by means of a sextant (instrument construction card 1). At the same time, they are supposed to measure the Sun s one, by means of a straw sextant (instrument construction card 2). 2. In order to measure the Moon s and the Sun s positions horizontally, with respect to a fixed point lying on the horizon, have students build instrument n.3 (instrument construction card 3). By using it together with the sextant, students will be able to measure two angles. These measures have to be collected in a summing-up table (data collection table). 3. During daylight, while students are observing the Moon, it is useful to have them look at it through either a small telescope or a binocular. The purpose is to identify a detail on the surface of the Moon, which will later be taken as a reference point for further observations. At the end of everything, it is useful to carry out a discussion about the data, which students collected. Part C. Third observation session 1. The third observation session is supposed to be carried out just like the second one. 2. Comparison among all the data, by means of a joint discussion. Students are supposed to point out the periodicity of lunar phases, so that they will be able to tell what phase and what position in the Sky the Moon will take for a given day. In order to consolidate this acquisition of theirs, it can be useful to build a model (instrument construction card 4). 3. Have students observe the Moon through a telescope. This observation is supposed to be carried out on two or more different days, so that children can draw what they see, they can choose a detail on the surface of the Moon, they can highlight it and identify its new position on a following observation with respect to the previous one (see didactic-methodological suggestions). For those who wish to build a simple telescope, as many schools did, go to Students, who did it, preferred to call this telescope as thingscope. It allows for safe sunspot observations, too. Didactic-methodological suggestions Moon s observation is quite hard to carry out during classes hours, often because of the position of the windows, which is not the right one. The risk of such a protracted activity is that students may forget what they observed and the reason why they observed. It is good to start from a Full Moon observation. In order to do that, teachers can have a look at a calendar, which has the Moon s phases, too. From their observations, students have to be able to foresee a day, on which they can see the Moon in the morning, during classes. Therefore they can easily observe it by means of a binocular, in order to notice that it presents always the same face to us. You can also divide the class in groups, and you can have each group observe the Moon on different times, for example in the morning, while coming to school, or while leaving from school, around midday and in the afternoon (in any case, students have to agree upon the times). In order to compare the relative positions of the Sun and of the Moon, students are supposed to use the horizon. Later, they can place both celestial bodies on it, according to the angles, which they measured. Measures obtained by students often carry along very big reading errors. This is due to the fact that instruments were built by students themselves. Some errors might be due to a mess, others to intrinsic limits of the instrument itself. The intrinsic limits can be a hint for a discussion or for a text or Internet research about under what conditions data collections can be improved, always by means of instruments of the same kind. We chose on purpose to provide you with two different, but quite similar, sextants. By means of the first one, students will learn how to sight, by means of the second one, they will learn how to place it in the proper position with respect to the incoming beam of sunlight. This also keeps them from looking straight at the Sun. Concept consolidation activities In order to consolidate the information, which they acquired, you can ask students to develop a project about how to improve the instruments for measuring the Sun s and the Moon s heights, or to develop new projects. For measuring the tilt of the Moon s orbit, you can have students build the eclipse simulator (model 2).

12 Teaching Unit 5.1: The phases of the Moon and the Sun-Earth-Moon system Data collection table Let s observe the phases of the Moon The Unit of measure is grade Observation date Moon s height above the horizon Moon s distance from a fixed object on the horizon Sun s height above the horizon Sun s distance from a fixed object on the horizon

13 Teaching Unit 5.1: The phases of the Moon and the Sun-Earth-Moon system Evaluation test Mark with a cross the right answer (or answers). 1. You are observing the Moon; from its shape you can understand: if on the next night you will see a smaller piece of the Moon; if the Moon is setting; if you will see it tomorrow when the Sun is up. 2. In winter time, with respect to the horizon, the Moon is: higher than the Sun; lower than the Sun; it is always in the same position, regardless of the season. You observed the Sky, looking at the Moon every day for three lunations. Starting from the data you collected in your recording cards, answer to the following questions. 3.Could you always see the Moon, during the observation nights? 4. In what days, could you see a full Moon? 5. Can you tell on what days of the next month you will see the Moon in the morning?

14 Teaching Unit 5.1: The phases of the Moon and the Sun-Earth-Moon system Instrument construction card 1 Sextant for measuring Moon s height above the horizon Aim To measure the Moon s height (or the height of whatever celestial body but the Sun) above the horizon: measure of an angle. Procedure-methodological suggestions Materials are inexpensive, therefore every student can build his/her own instrument. If every one has his/her own instrument, it will be easier to carry out observations. Materials For each instrument you wish to build, you need: A 15X15cm squared piece of plywood. A 20-cm-long string. A medium weight bolt. A photocopy with a 90 angle. On its circumference, draw one small line for each degree (picture 5.1.1). Glue. A nail. Two screw eyes. Assembling 1. Screw the two screw eyes on the same edge of the piece of plywood. They will be used as sights. 2. Glue the photocopy on the piece of plywood. 3. Make the piece of string go inside the bolt and make a knot. 4. On the other end of the string, make a ring and fix it at the vertex of the angle by means of a nail (at this point, the string with the bolt hangs down from the vertex). Picture Sextant for measuring the Moon s height above the horizon. How to carry out the activity Choose an object, of which you want to measure the height above the horizon. Hold the instrument, and sight the object by means of the two screw eyes. The weight of the bolt tightens the string. The string shows the amplitude of the angle between the object and the horizon. Carry out the observation more than once, in order to compare the different values, which you will obtain.

15 Teaching Unit 5.1: The phases of the Moon and the Sun-Earth-Moon system Aim Instrument construction card 2 Straw sextant for measuring Sun s height above the horizon To measure the Sun s height above the horizon. Material For each instrument you wish to build, you need: A 15X15cm squared piece of plywood. A 20-cm-long string. A medium weight bolt. A photocopy with a 90 angle. On its circumference, draw one small line for each degree (picture 5.1.2). Glue. A nail. A piece of white cardboard, to be used as a screen, where to project the Sun s image. A straw. Assembling 1. Glue the photocopy on the piece of plywood. 2. Fix the bolt at one end of the string. 3. By means of a nail, fix the other end of the rope at the vertex of the angle (at this point, the string with the bolt hangs down from the vertex). 4. Glue the straw on the sextant, on its upper edge (see picture 5.1.2). Picture Sextant. The straw focuses the light on the white piece of paper. It allows for identifying the position, where the Sun s image is the sharpest. By holding the sextant in this position, we will be able to read the angle, which shows the Sun s height above the horizon. How to carry out the activity It is similar to the previous one. You are supposed to point the straw towards the Sun. On the other side, move the piece of white cardboard closer to and further from the instrument, and find out the sharpest bright spot. In this position, measure the angle. Procedure-methodological suggestions Be careful: remember never to look straight at the Sun.

16 Teaching Unit 5.1: The phases of the Moon and the Sun-Earth-Moon system Aim Instrument construction card 3 "The bearings getter" This instrument was called bearings getter by the first class, which used it. It is meant for measuring the angle between a celestial body and a fix reference point on the horizon. Material A goniometer and two _ cm-thick-wooden sticks. Assembling On the backside of the goniometer, fix one of the two sticks. Then, by means of a nail, fix the second stick at the center of the goniometer, so that it can rotate, as shown in the picture below How to carry out the activity Picture While assembling the instrument. Point the end of the fixed stick towards the object, which you choose on the horizon. Then move the other one, until it points towards the other object. Finally, read the angle between the two sticks. If on the same time we use a sextant, we will come up with two angles, i.e. two coordinates. Picture How to measure the angular distance between a celestial body and a fix reference point on the horizon.

17 Teaching Unit 5.1: The phases of the Moon and the Sun-Earth-Moon system Aim Model number 1 The phases of the Moon It is meant for providing a further understanding of the lunar phases, therefore it can be considered as a consolidation time, too. Material A sheet of paper for drawing. A sheet of glossy paper. Compasses. Felt tips pen to write on glossy paper. Assembling Draw a circle on the sheet of paper, which represents the orbit of the Moon around the Earth (since the sheet is small, it is not necessary to draw an ellipse). Draw the Earth in the center and, on the orbit, draw some Moons. On the sheet of glossy paper, draw many parallel lines, which represent the beams of light coming from the Sun (be careful: this model does not respect any scale factor!). Picture The Earth and the Moon Sun Picture Overlapped to the previous drawing, the glossy sheet of paper allows for highlighting the part of the Moon, which is illuminated by sunlight (see the yellow parts). Be careful: the straight lines do NOT represent solar rays. They are just a way to represent the fact that the entire system is uniformly overwhelmed by sun radiation.

18 How to carry out the activity Overlap the sheet of glossy paper to the drawing. With the red color, highlight the part of the illuminated Moon, which can be seen from the Earth. Picture On the sheet of glossy paper, with the red color highlight the part of the Moon, which can be seen from the Earth.

19 Teaching Unit 5.1: The phases of the Moon and the Sun-Earth-Moon system Aim Model number 2 Eclipses simulator To have a chance of tilting the orbit of the Moon, in order to understand its motion and to simulate eclipses. Procedure-methodological suggestions The model is very easy to build, if the pieces of cardboard are stiff enough. Materials 2 pieces of cardboard (a, b) Thin and transparent nylon thread A glass bead having living colors Assembling 1. Take one piece a of cardboard. 2. Draw the Earth s orbit on it. Since the piece of cardboard is very little, you can draw a circumference. 3. Draw the Sun in the center. Draw the Earth. 4. Close to the Earth, cut out two holes, one in between the Earth and the Sun, and the other one on the outer part of the Earth s orbit, at the same distance from the Earth than the previous hole. 5. Make a piece of thread go through the holes. Make it go through the bead as well (on the front side of the drawing) and then knot it, in order to have a ring. The ring simulates the Moon s orbit around the Earth, and the bead represents the Moon. 6. Draw a second Earth, 90 far away from the previous one, and do the same. Picture While the Earth goes around the Sun, the plane of the Moon s orbit keeps always the same orientation. Therefore, eclipses can occur only when the line, which connects the Earth to the Sun, intersects the Moon s orbit, and the Moon is close to one of the nodes. 7. On the other piece b of cardboard, make a quite deep cut. Slide it towards the thread-ring: it has to be tilted with respect to the a piece of cardboard, as shown in picture Have students notice the nodes, as intersection points between the plane of the Moon s orbit and the Sun-Earth plane.

20 How to carry out the hands-on activity Move the piece of cardboard with the deep cut. It has to keep always the same orientation. The purpose is to have students notice that there are only two positions, in which the line of the nodes is aligned with the Sun. Picture We wish to remind you that the plane of the Moon s orbit keeps always the same orientation, and therefore it can be simulated by a dark cardboard. In this picture, the Moon s orbit is represented by a piece of string, so that it can be seen, and the knot represents the Moon. The Earth goes around the Sun on a circular orbit. End of Teaching Unit 5.1

21 Teaching Unit 5.2 Different dimensions, different surfaces; dimensions and distances of the Sun, of the Earth and of the Moon This Teaching Unit introduces students to a comparison between the Sun s and the Earth s dimensions. It starts with a comparison between the projections of two objects on a surface. Eventually, it leads to a scale model concerning the Sun, the Earth and the Moon, and to a scale model concerning a system with these three bodies. Contents Measures of lengths, of surfaces. Measure unit for length, surface. Relations among units of measure. Objectives To measure linear and surface dimensions. To compare the Earth s and the Sun s diameter. To compare the Earth s and the Sun s surface (by taking these two bodies as if they were flat surfaces). To compare the Earth s and the Sun s volume. To acquire the idea that the Sun-Earth System is empty as far as matter. Glossary Length, surface, volume, scale relations, emptiness of matter. Required time Around four hours. Needed material Either some sheets of paper, with little squares, or some packs of colored confetti (0.5 cm in diameter). Either a lot of foolscap sheets of paper, with little squares equal to the first one, or a sheet of wrapping paper. Procedure Part A Comparison between the Sun s and the Earth s diameter. 1. Imagine working with a flat Earth. Take its dimensions as if they were equal to a confetti or to a circle, which you can draw inside one of the little squares. Have students read the value of the Earth s and of the Sun s diameter and of the Sun-Earth distance from the research, they carried out in T.U Have students represent the Sun s diameter either by gluing on a line 109 confetti, one next to the other, or by drawing 109 little squares, one next to the other (109 is the approximate value for the ratio between the Sun s and the Earth s diameter). Picture While comparing linear dimensions. 2. Joint discussion. Students are supposed to point out that the diameter alone is not enough, in order to compare the dimensions of two bodies. At least, you have to compare surfaces.

22 Part B Comparison between the Sun s and the Earth s surface, taken as flat objects. 1. Draw a circumference. Its diameter has to be equal to the previous one. Have students count how many little circles can fit inside this circumference (or have them count how many confetti can fit inside it. Have students glue the confetti on the circle). 2. Have students notice that between one confetti and the next one, as well as between two little circles, there are empty spaces. Therefore, our final value is an approximation. a) b) Picture Comparison between two surfaces. How many confetti (Earths) do you need to cover the whole flat Sun? 3. Joint discussion. Students are supposed to point out that the surface is not enough, in order to compare the dimensions of two bodies. It is necessary to compare volumes. 4. Construction of spherical scale models concerning the Sun-Earth-Moon system. Students are supposed to choose an appropriate scale factor. Picture A tri-dimensional model of the Sun The Sun was built by using two (or more) double sheets, which were sewn together as to form a huge pocket and filled it with empty plastic bottles. It shape is not perfectly spherical, but it fits well our purposes anyway. The color of the sheets does not represent the color of the Sun. Anyway, it is better if it does not. As a matter of facts, we are dealing with a model. Its fundamental elements are dimensions and distance. Therefore, the less real everything looks, the more we can focus students attention on the concepts we are dealing with. 5. Discussion about the models, which students built. Students are supposed to point out that in order to represent the Sun-Earth-Moon system in a correct way, we have to introduce distances, too.

23 Part C: scale model of the Sun-Earth-Moon system 1. The purpose of this activity is to build a scale model. Therefore, the first thing to take into consideration is the place, where you want to carry out this activity. Have students make a table about the Sun, the Earth and the Moon, according to the research they did back in T.U (Or have them use the Table about distances and diameters of the bodies in the Sun-Earth-Moon System). 2. According to the dimensions of your place, have students make a table showing scaled numbers. 3. By means of plasticine or something else, build these bodies and place them in their right-scaled positions. Have students verify what follows: if the dimensions are properly (proportionally) scaled, you will be able to see (and simulate) eclipses; if the three bodies lie on the same line, eclipses occur twice every Moon s revolution around the Earth. 4. Discuss with students about what needs to be changed in the model, in order for it to be consistent with reality, i.e. eclipses do not occur every month. Didactic-methodological suggestions Building and placing the three bodies is for sure more effective and clarifying than any description or image about things, which others did. What material you use for building the celestial bodies is of no importance. The only thing, which is taken into consideration in this model, is the relation between dimensions and distances among these objects. Therefore, evaluation tests must concern these concepts. Whatever other change you wish to do in the model, it must aim to an understanding of the relation between dimensions and distances. The Sun, in picture is covered by almost confetti.

24 Teaching Unit 5.2: Different dimensions, different surfaces; dimensions and distances of the Sun, of the Earth and of the Moon Table about distances and diameters of the bodies in the Sun Earth Moon System. The distance available for our model is meters. Therefore, the scale factor, which we use, is Object Diameter (km) Scale diameter (cm) Distance from the Sun (km) Scale distance (m) Sun Earth Distance from the Earth (km) Moon

25 Teaching Unit 5.2: Different dimensions, different surfaces; dimensions and distances of the Sun, of the Earth and of the Moon Evaluation test 1. The Sun s diameter is around Km, and the Earth s one is around Km. Which scale factor will you choose, if you want the Sun to be represented by a 10 meter diameter sphere? Which will be the Earth s dimension, scaled by this factor? 2. If the Earth s diameter were 10 cm, what would be the value of the Sun s diameter, scaled by the same factor? 3. Now, assume you want the Sun to have smaller dimensions: you want to represent it with a 100-cm diameter sphere. What would be the value of the Earth s diameter? (Choose the answer you think is closer to the right one). o o o 1 cm 10cm 3 cm End of Teaching Unit 5.2

26 Teaching Unit 5.3 Let s think about the Sun-Earth-Moon system This T.U. aims to focus students attention on what would be the motion of a body, if it were observed from another body. In this situation (relative motions among three bodies), you have to keep in mind one thing. The pretend that -situation is not that easy to carry out. Contents Reference system, point of view. Objectives To have students understand that motion depends upon the observation point (observation point on the Earth, on the Moon and on the Sun). Glossary Tellurium, Planetarium. Required time Around three hours on the whole. Two are needed to have students try to use the tellurium or something similar (see picture 5.3.2). One goes for a discussion. The time required for a visit to a Planetarium is extra. Needed material Tellurium. Either a Planetarium or an umbrella. An instrument, which replaces the tellurium. It is made up of a fixed lamp and two little foam rubber balls, having different dimensions: one represents the Earth and the other one the Moon. Procedure 1. Use the tellurium without the Moon. a) Go close to the Earth and from here observe the Sun s motion. b) Under the same conditions, go close to the Sun and from here observe the Earth s motion. 2. With the Moon. a) Go close to the Moon, and from here observe the Earth s motion. b) Go close to the Earth, and from here observe the Moon s motion. c) Go close to the Moon, and from here observe the Sun s motion. d) Go close to the Sun, and from here observe the Moon s motion. 3. Every student is supposed to collect data in the observation tables: one is for drawing, and the other one is for describing the motions. 4. Have students describe the motion. 5. Final discussion. Students are supposed to notice the relativity of the reference system, from which we carry out our observations. Have students make one poster. S L T Picture An alternative model, if you do not have a tellurium. You need a smaller and a bigger ball in order to represent the Earth and the Moon. It would be better if the diameter of the ball, which represents the Moon, were around _ of the one of the ball, which represents the Earth. Replace the Sun by an overhead projector. Discuss about the validity of the model and about its limits (for example: why can the Sun be replaced by a lamp, which is far enough, for example two meters, from the Earth-Moon system?).

27 Didactic-methodological suggestions The activity involving the tellurium is particularly easy. It would be even simpler if you worked with the replacing model and if you involved just the Earth s and the Moon s reciprocal motions. Highlight the importance of the reference point, from which phenomena are observed. Use a tellurium first without the Moon, so that you can study the Earth-Sun phenomenon. Then introduce the Moon. Every student has to carry out the activity by him/her self, or two by two at most. Therefore, you have to schedule the day properly before. As a sum-up activity, we suggest to visit a Planetarium. Ask to see the Sun s and the Earth s motion, as seen from the Moon, and the Earth s and the Moon s motion as seen from the Sun, projected on the dome. Concept consolidation activity Invent a planet X. Pretend it is the outer most one in the Solar System, and you are on it. Describe the Sun s, the Earth s and the Moon s motion as seen from X. If X were an inner planet, how would the motions of the other planets be, as seen from X? Children are supposed to find out dialogues and settings, in order to carry out an alive representation.

28 Teaching Unit 5.3: Let s think about the Sun-Earth-Moon system Table Observe, draw and describe motions Reference System Drawing about the motion Description of the motion From the Sun, I m observing the Earth motion From the Earth, I m observing the Sun s motion From the Moon, I m observing the Sun s motion From the Sun, I m observing the Moon s motion From the Moon, I m observing the Earth s motion From the Earth, I m observing the Moon s motion End of Teaching Unit 5.3

29 Teaching Unit 5.4 How to build a scale Solar System This Teaching Unit starts with a construction of a scale Solar System model. It will eventually lead students to the concept that the Solar System is empty as far as matter. It is the most important T.U. in the 5 th Module. It is fundamental, in order to have students understand that the entire Universe is empty as far as matter. Contents The structure of the Solar System. The concept of emptiness of matter inside the Solar System. Objectives To understand that interplanetary space is empty as far as matter. To understand that the dimensions of the bodies of the Solar System are negligible if compared to the distances among them. Required time Around two hours. Needed material Either plasticine or little balls, having the appropriate dimensions for a scale Solar System model. A metric tape. Glossary Planets, stars, satellites, measure unit. Procedure 1. Have students look in the Internet for the data, which they need, in order to build a scale Solar System model: dimensions and distances of the planets from the Sun (you can use the table we provided). 2. Choose a proper place in open air (for example a big field) where to put the scale Solar System model: have students measure the biggest distance in order to place the planets. 3. Have students determine scale dimensions and distances, keeping into consideration both the room, which they can count upon, and the construction of the planets. Have them fill in the table, which we provided. It will be useful later on. If the dimensions of the field are not the proper ones, you can skip the last planet (Pluto). In this case, it is important to have students identify anyway, what would have been its position in the surrounding space. For example: if we used 1: 3 billions scale, the Earth would be a 5mm-diameter ball, which would be 50 meters far away from the Sun, the Sun would be a 56-cm-ball, while Pluto would be more then two kms far away. 4. Students are supposed to build the planets and to place them on the field according to the dimensions and the distances they determined. If you prefer not to build the planets, you can use little cards, carrying the names of the planets, with sticks to put in the ground. 5. Tell students to walk inside the scale Solar System model, in order to highlight the emptiness of matter.

30 a) b) Picture After placing the Sun, (a), students measure the distances in order to place the planets (b). Picture After the Sun, students place the planets at the right scale distance. In this picture, you can see the cards carrying the names of the planets. Didactic-methodological suggestions It is a fundamental T.U. also as far as further concept acquisition is concerned. A research in the Internet about other scale Solar System models can represent a further consolidation activity. These models have to be analyzed and discussed upon with students, in order to verify if students really acquired the concept of emptiness of matter (see other experiences at It is not necessary to carry out any evaluation test, since the scale model and the placing of the planets themselves represent an evaluation test for the entire experience.

31 Teaching Unit 5.4: How to build a scale Solar System Table about scale distances and diameters of the Solar System bodies The distance available for our model is Object Diameter (km) Scale diameter (cm) Distance from the Sun (km) Sun Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto Scale distance from the Sun (cm) Note. Be careful at the origin point, with respect to which, calculations are carried out. End of Teaching Unit 5.4

32 5 th Module: The Night Under the Stars The Moon and others (plan for the Night Under the Stars) The Night Under the Stars should take place after the diurnal observations of the Moon. Actually, it should take place after the Module is over, after the scale model. In any case, it should be better to have the chance to see a tiny crescent Moon, just for going over the concepts once again, which, however, should have already been consolidated before. A visit to a professional Astronomical Observatory is recommended, in order to see not only the planets, which might happen to be visible, but also the instruments used. For any information about what observatory you can visit, to: cielo@pd.astro.it End of 5 th Module