HONEY, I SHRUNK THE SOLAR SYSTEM

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1 OVERVIEW HONEY, I SHRUNK THE SOLAR SYSTEM MODIFIED VERSION OF A SOLAR SYSTEM SCALE MODEL ACTIVITY FROM UNDERSTANDING SCIENCE LESSONS Students will construct a scale model of the solar system using a fitness ball to represent the sun. They will calculate the appropriate diameter of the scale model planets and their distances from the sun. They will then make models of the planets out of clay and set up the model over a distance of approximately 1.7 km (not including Pluto) or 2.2 km (if including Pluto). If you do not have 1.7 km to walk with your students, there are two alternatives: Measure the longest distance they can use on the school grounds and use this to set their scale for planetary distances. You will then need to use a different scale for the planets' sizes. Students can walk the distance of Saturn (0.5 km or 0.3 mile). Use a large picture of the school and area from Google maps satellite view and mark the points where each outer planet would go. Grade span: 6-8 OBJECTIVES The students will be introduced to parallax and how it can be used to find planetary distances. Determine the distance to the object by sighting a distant object from 2 different locations and knowing the distance between those locations. Create a scale model of our solar system that includes distance from the Sun and the diameter of the planets. Use ratio and proportion to compare the size of the scale model solar system to the actual size of our solar system. Describe the parts of our solar system in terms of size, distance, and location. Match appropriate units with given situations and convert units within a system of measurement (kilometers and Astronomical Units).

2 MATERIALS For the Teacher: Dry Erase Markers, or Viscam Camera Masking Tape Fitness ball ( 53 cm in diameter ) For Each Group: Planetary Data Sheet Graph paper Activity Page Pencils Ruler Measuring Tape Protractor Air-Dry Clay Calculator Index Cards Toothpicks Time: Part I 30 min; Part II 60 min; Part III 30 min TEACHER BACKGROUND ON THE SOLAR SYSTEM Our solar system consists of a star, our sun, and 8 planets. Pluto was considered a planet until 2006 when the International Astronomical Union reclassified it as a "dwarf planet". For the purposes of this activity, we've included Pluto, but you can refer to it as a dwarf planet. The planets are (in order, from the Sun, outward): Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. A new mnemonic used to remember the planets in order is, "My Very Educated Mother Just Served Us Nachos." The solar system consists of eight planets orbiting around one star: the Sun. Neptune, the farthest planet from the Sun, orbits at approximately 30 astronomical units (AU) from the Sun. An astronomical unit is a unit of length used by astronomers. One astronomical unit equals the average distance from Earth to the Sun about 93 million miles (150 million km). The solar system also includes the Kuiper Belt, a comet-rich area that begins near Neptune's orbit and stretches far beyond it, to about 50 AU from the Sun. Part of Pluto's elliptical orbit extends far into the Kuiper Belt. Beyond Pluto's orbit is another region of icy objects in our solar system, called the Oort Cloud, which extends approximately 50,000 AU from the Sun. In addition, there is an asteroid belt that lies in the zone between the orbits of Mars and Jupiter.

3 PART I PROCEDURE: PARALLAX METHOD 1. Place the fitness ball in the middle row on the front desk just at eye level for your students while seated. Place an X mark on the board directly in front of the fitness ball also at eye level. Any students sitting in the same row as the fitness ball should be able to see the ball but not the X. 2. Ask the student in the back of the row furthest right to describe how they see the ball in relation to the X. They should say something like the ball is on the left and the X is on the right. Make a quick sketch on the board. Ask the student at the back of the middle row and the student at the back of the row furthest left to also describe what they see. Make a quick sketch of both of their views. 3. Explain that scientists describe this apparent shift as a parallax shift or just parallax for short. We often experience this in everyday life. Move the ball out of the way and have each student close their left eye, extend one arm, and cover the X mark with their thumb. Once the X is covered have the students open the left eye and close the right. The thumb will appear to move back and forth due to parallax. Parallax allows the brain to see two slightly different images (one from each eye) and combine them to produce a 3D image. 4. When astronomers measure the parallax of an object and know the separation between the two positions from which it is observed, they can calculate the distance to the object. Using observations on Earth separated by thousands of miles -- like looking through two eyes that are very far apart -- parallax measurements can reveal the great distances to planets. 5. Place the ball on the front desk. Ask the students to determine the distance to the ball. Mark two places, A and B, for instance by using masking tape. The points A and B, together with the ball at point C, form a triangle. Ask the students to measure the distance AB with the tape measure. 6. Ask the student to stand at point A and measure angle BAC, and then move to point B and measure angle ABC. 7. Then ask the students to draw a scale model of their measurements. The students will use their ruler and the scale, to calculate the distance from the baseline to the ball. 8. Ask students to compare the actual distance and the distance determined in Step 7. Discuss some possible sources of error.

4 PART II PROCEDURE: CLAY MODEL 1. Ask students "Why do we build models?" to generate discussion of models. 2. Then ask the students to name the planets on our solar system. Write the names up on the board in the correct order from the sun. Ask them how big the planets are and how far away they are. After some struggle with this, offer up the solution of building a model to help. 3. Show them the fitness ball and ask them how big each of the planets would be if the sun was the size of the fitness ball. Ask for a few volunteers to come up to the board and draw and label each of the planets compared to the fitness ball. 4. When this drawing of the solar system is complete, ask students how far apart each of these planets would be if the sun were a fitness ball. Would they fit in this room? Would they fit in the school? Write up some of their guesses about the size of the solar system on the board and make sure you can keep the answers there until the activity is completed. 5. The class needs to figure out what their scaling factor will be for the solar system if the fitness ball is going to represent the sun. Explain that you will need to measure the fitness ball and compare it to the real diameter of the sun. Then you can determine how many km each cm of the fitness ball represents. Ask for a couple of volunteers to measure the fitness ball. 6. Show students the measurements in the Planet Data Sheet table in the "Materials" section. Do the scaling factor calculation by dividing the actual diameter of the sun by the diameter of the fitness ball. Explain that the answer represents the number of km in every cm of your model. 7. Explain that we will use this scaling factor to figure out the sizes and distance from the sun of all the planets in our model. Demonstrate how to use the scaling factor to determine the diameter and distance from the sun of a hypothetical planet (so that you leave the real planets for the students. 8. Pass out clay, index cards, and ruler to each group. Instruct them to label the 8 index cards with the names of the 8 planets and to make a model of their planets with the correct diameter out of the clay. 9. When all the planets are represented, have the whole class take a look at their model. Refer back to their drawings on the board from Step 2. Ask the class, "What can we learn from this model? Take this opportunity to discuss the value of models in science. NOTE: If you are unable to walk the distances of this model solar system or to use Google maps to place them on a map, you can stop here and simply make these clay models into a mobile or other permanent display.

5 PART III PROCEDURE: PLANETARY DISTANCES 1. After this brief discussion, announce that you need to complete the model by placing the planets at the correct distances from the sun. Ask students to give you the model distances they calculated. They will be in AU, which will be difficult for students to imagine. Take Mercury as an example and convert it into something the students will have a better feel for, like feet or meters. Ask students how far away this distance is. In the classroom? Outside? If outside, where? How far from the classroom? 2. Have the students count how many paces it takes for them to walk a distance of 2 meters on a marked practice area. You can then tell them the multiplying factor to reach Mercury and do this for each planet. For example, if Mercury is going to be 22 meters away and they measured their pace for 2 meters, they will need to multiply their pace by 11 to find how many paces to take. 3. The total distance of the model will be roughly 1.7km, so you need a wide, open space you can walk this distance and leave the clay planets. Have the student count their paces from the start (where you've left the fitness ball sun) to each planet. At Mercury's distance you'll leave the planet on the toothpick and continue to the next planet. Continue from there, leaving each clay planet at its appropriate distance. 4. When you reach the end, have students look back and try to see the sun and each planet. Have a parent volunteer or teaching assistant stay at each place and then hold up the sun and each planet so that everyone can get a good look at the model. They will not be able to see most of the planets. You can add in that if we included Pluto, it would be 2.2km away from the sun. 5. Return to the classroom, take a second look at the distances from Step 4 in Part II. Ask students again what they learned from this model. Point out again that models are useful in this way in science. Sometimes scientists construct scale models to: study particular aspects of a complex system build a basic understanding of a system narrow one's focus and/or eliminate possibilities gain a more intuitive understanding of a system figure out what questions to ask about a complex system or problem help us visualize systems that are too large or too small to see Reflection: Ask students to reflect on this activity and the use of models in science: How did building the model of the solar system change the way they visualize the solar system? What additions or changes would they make to the model if they could do it again? What other models have they seen or used?

6 PLANET DATA SHEET INNER PLANETS Planet Mercury Venus Earth Mars Distance from Sun km 58,000,000 km 108,000,000 km 150,000,000 km 228,000,000 km Distance from Sun in AU Scale Distance in cm Diameter in km 4,878 km 12,104 km 12,755 km 6,790 km Scale Diameter in cm Avg. Surface Temperature

7 PLANET DATA SHEET OUTER PLANETS Planet Jupiter Saturn Uranus Neptune Pluto Distance from Sun km 778,000,000 km 1,429,000,000 km 2,875,000,000 km 4,504,000,000 km 5,900,000,000 km Distance from Sun in AU Scale Distance in cm Diameter in km 142,796 km 120,660 km 51,118 km 49,528 km 2,300 km Scale Diameter in cm Avg. Surface Temp In August 2006, Pluto was reclassified as a dwarf planet.