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 Solar System Models
By Carolyn Hollis May 2011 SOLAR SYSTEM MODELS By Carolyn Hollis Scientists create models to explain and share their understanding of the world. Often these are descriptions in their mind of how systems work also known as conceptual models. They may also build physical model or design computer models. These models have their limitations. Physical models are constrained by the nature of the materials used and computer simulations are limited in their complexity. Here we will explore ten models of the solar system that can be used with young people. Each has its limits and its strengths. Each model tells us something about the solar system, but equally, each leaves out information. The final pages have the models in a format that can be printed off and given to youth to explore in small groups. You might want to flip ahead and familiarize yourself with each model. Some of these pages have an answer key, so think about when you want to give out that information. Discussion is really important to prevent misconceptions and develop a strong understanding. To assist with that discussion, the next section is a collection of discussion questions and presentation notes. Picture the Solar System notes: The simplest model, it asks the students to order the photographs of objects from the center of the solar system outward. This shares some similarities to the papier-­‐mâché solar system many of us made as children. It has the advantage of also giving visual information about these objects. As the teacher, you must decide which objects you want to include. I like to include a comet and an asteroid. Will you include Earth’s moon? Moons of other planets? Eris or other icy bodies beyond Pluto? As the students place the photos in order starting with the sun ask the students to share what they already know about each object. There are many sources of excellent images. Nasa.gov may be the most accessible. Extensions: Science: Learn how comets and asteroids are named. Explore why the planets look the way they do. What are they made of? What features are on them? How were the features made? Learn about telescopes and their light gathering ability. Choose a planet: what space missions have explored it? Learn more about a space mission. What instruments were included? Plan your own space mission. Where would you go? What equipment would you take? Language & Culture: Read about the Greek gods planets were named for. In US we see a man in the moon, what do people in other countries see in the moon? Read stories from other cultures about the moon. Look at the moon. What do you see? Write a story about how that creature came to be in the moon. Imagine a time in the future, you are the first team of astronauts to land on a planet. What problems will you need to overcome? What will you discover? Write a magazine article telling of your adventure. Drawing Planets notes: This model compares the diameters of planets. It combats misconceptions about the relative size of the planets. Most students do not realize how tiny Earth is compared to Jupiter. It is an excellent opportunity to develop the math concept of scale and develop skills in measuring with a metric ruler. Discussion questions: How many Earths would reach across Jupiter? How big would the sun be in this model? (The sun’s diameter is 100 times that of Earth) How are the rocky planets similar? Why are the outer planets called gas giants? Some scientists think Pluto should be designated a dwarf planet. Why do you think that is? Extensions: Science: Arrange the circles in order from the sun. Look up the diameter of Earth’s moon and moons of other planets. Convert the diameter to this scale. Draw circles to represent these objects. How do they compare to Earth? Make a bar graph to compare diameters. How does the graph relate to the circles? Ask if the students notice any patterns between the size of the planets and what they’re made of. Art: Color in the planets – show pictures for inspiration. Make a collage that represents the conditions on each planet. Sculpting the Solar System notes: In this 3-­‐dimentional model, students use clay to make planets. In the last model we compared area. In this model we compare volume. We do not include the sun in this model. The sun contains 99.9% of the matter in the solar system. Discussion questions: Which are the gas giants? How do the sizes of the rocky planets compare to the gas planets? Where are the rocky planets located? Extensions: Uranus is formed from two pieces of clay. Follow the directions to determine what fractional part of Uranus is the same size as Earth. This information can be used in conjunction with the Rice Model to compare density. More details are in the Rice Model extensions. Measure the volume of the planet by reshaping it into a rectangular prism. Measure each dimension and use V=L*W*H. Measure the volumes by submerging the clay in water. Measure the water level in a graduated cylinder before and after submerging the planet. Play clay may get sticky and may begin to dissolve. Compute the fraction of clay used in each planet. Write fractions to represent each division of the clay. Write addition problems to represent the amount in each planet. Use the fraction of the total ball of clay to compare the sizes of the planets. Keep this model available if you’re going to do the gravity models. Bead and String Model notes: This is a distance model. It is important to note that the scale is different than in Drawing Planets. The sizes of the planets are not in scale. Each planet is represented by an identical bead. If the solar system were shrunk to this scale the planets would not be the size of beads – they would no longer be visible. The distances are listed in astronomical units (AU). One AU is equal to the average distance from the Earth to the sun. Toilet Papering the Solar System gives these distances in km. Since planets travel in elliptical, not circular orbits, the table gives average distances from the sun. A common misconception is to imagine the planets are evenly spaced. Help the students notice the first four planets are crowded together relatively speaking. Discussion questions: What is the Asteroid Belt? Which planets are close together? In this model how much farther from the sun is Mars than Earth? How many times as far from the sun is Jupiter than Earth? What fraction of the distance to Pluto is Earth? Extensions: Tape the model to a wall and label each bead with the planet’s name. How far is the nearest star outside our solar system? If you were to add it to the model, how much string would you need? Advanced String Model notes: This model shows the relative distances of the planets from the sun. The Bead and String Model lines up the planets along a single string. This is the usual arrangement of planets in solar system models. Unfortunately this tends to create the misconception that planets in our solar system are similarly arranged. In this model, students can place the planets in all directions around the sun. Since the asteroid belt encircles the sun, it is not represented in this model. Remind the students the planets and sun are not to scale. You may also want to point out that orbits of the planets are elliptical not circular. Discussion Questions: In this model how close can Mars come to Earth? What does that distance represent? What is the maximum distance between Earth and Mars? If 1 AU = 93,000,000 miles, How far is Mercury from the sun? How far is Mars? Read the discussion questions for the Bead and String Model for more ideas. Extensions: This can be modified to create a large playground size model. With a larger model, students can walk through the revolution of the planets around the sun. Simply multiply all of the model distances by 10. (Thus the scale distance for Mercury would be 40 cm) You will need to add extra cord to each measurement for knots. For the regular model, I added on an additional 10 cm of string to each piece so the strings would be the right length after tying the notes. When you change to a courser rope and larger beads for the playground model, you will need to add on additional rope for the knots. When acting out the motion of the planets, remind students that the time it takes for a planet to travel around the sun is that planet’s year. Each planet has a different length year. This is not just because the orbits are different lengths. Students are often surprised to learn the closer a planet is to the sun the faster it moves. Toilet Papering the Solar System notes: This is another distance model. At this scale, Jupiter would be size of grain of salt and other planets would be invisible. This is great for students who have difficulty measuring – it requires counting not measuring. It does not require the dexterity of the Bead and String Models. Just like the Bead and String model, all the planets are lined up. In the solar system, the planets are not lined up – this is a major misconception See also Bead and String Model and Advanced String Model for additional back ground information. Discussion Questions: See Bead and String Model and Advanced String Model for discussion questions. Extensions: Is Pluto a planet? How is Ceres classified? What criteria do astronomers use to classify objects as planets? What other objects orbit the sun? How many planets have been found outside our solar system? Research an extrasolar planet. What is its orbital distance? Rice Model notes: This is a mass model. It asks students to compare the relative mass (weight) of the planets. Easy and inexpensive to make, this model needs to be prepared ahead of time. It is particularly valuable for people who learn by touching and doing (also known as kinesthetic learners). It is convenient to measure the volume of rice to create the bags for each planet. However, it is the mass of the planets we want students to compare. Focus on the weight of the bags, not how they look. It is important that the students handle the bags. They need to feel the weight of each bag, not look at the volume. Discussion questions: Feel how much more “stuff” is in Jupiter as compared with Earth. How does Earth compare to Pluto? Which planets are about the same size? What planet is roughly the same size as Earth? How does Mars compare to Earth? Extensions: Mass: Use a scale to weigh the “planets”. Have the students create a table of planet mass. How many times greater is the mass of Uranus to the mass of Earth? Compare your results to the volume model of Sculpting the Solar System. Density is the ratio of volume to mass. Why do Earth and Uranus have different densities? Relate this to either the Sculpting the Solar System or Drawing Planets. Density: Use the mass data in conjunction with Sculpting the Solar System volume data (computed by the students in extensions) for these activities. Find the ratio of Earth volume to a gas giant. Find the ratio of mass of these two planets. Are they the same? Why or why not? What is the ratio of mass to volume for these planets? This ratio of mass to volume is called density. Which planets would you expect to have similar densities? Why? How High Could You Jump? notes: This is a gravity model. Every object exerts a gravitational force on every other object. The strength of that force is determined by two things: mass and distance. The greater the mass, the greater the force of gravity. If you double the mass you double the force. If you could take 2 earths and squeeze them together into a ball the size of the earth, aliens standing on that world would experience twice the gravitational pull. Distance from the center of an object reduces the gravity by the square of the distance. In other words if you move 10 times further away from the center, the gravity is reduced by 100 times. (This is called the inverse square law.) If you imagine the earth as a marshmallow in the cosmic microwave, when it puffs up to twice the diameter the creature living on Marshmallowland will experience ¼ gravity. When we look at the gravitational force of planet, we need to take into account both the mass and the density. Working with two variables makes this a more complex idea. These variables work opposite to each other. The mass of Uranus is approximately 15 times that of earth –increasing the gravity by a factor of 15. How ever the diameter is approximately 4 times greater – decreasing the gravity by a factor of 16 (that is 1/16 of the original gravity). In the case of Uranus these factors nearly balance out giving a gravitational force close to Earth’s. Discussion Questions: Where can you jump highest? If you played basket ball on another planet, how would this effect the game? What changes might you want to make to the court or the rules? How would the gravity effect astronauts studying another planet? Which planets’ gravity are close to Earth’s? Extensions: Have the students jump 3 times and average their results before computing their jumping ability on other planets. Have students graph their data. Students can average class data or graph class data. Find high jump records. Use this data to compute high jump records for each planet. Find the mass and diameter of the sun. Compare these to Earth and compute the gravity relative to Earth. If Uranus were squeezed to the size of Earth, we noted that the gravity would be 15 times that of earth. If Jupiter were squeezed the same way, what would the gravity be on the surface? What if we inflated Mercury to earth size? What Would You Weigh? notes: This is another gravity model. If you’re not familiar with the relationship between mass and distance as it relates to gravity, please read the notes for the previous activity, How High Could You Jump? Discussion Questions: On which planet would you weigh most? Least? How much more would you weigh on Jupiter than Mercury? How many times greater is your weight on Jupiter than Mercury? Extensions: What would it be like to move on another planet? What would other objects weigh? How would weight effect tasks we do? Show video clips of astronauts walking on the moon. How do they move? Is the gravity of Moon greater or less than that of Earth? What effect might gravity have on evolution? What adaptations might plants or animals develop under different gravitational force? Hiking the Solar System notes: This makes a great culminating activity. In this activity the same scale is used both for the sizes of the planets and the distances between the planets. Previously, we’ve focused on either the relative the sizes of the planets or their distances from the sun but never both at the same time. It is helpful to write the name of each planet on large cards ahead of time. For the inner planets you might want to have a student stay at the spot holding the sign and planet. It is great if the hike starts where you can leave the sun behind. Students look back and see how small it is. Helps them get sense of distance. At Mars, the students with the first 3 planets can hurry and join up to the group. Extensions: At each planet have students review what they have learned about each planet. Assign teams to research each planet. They can present brief reports at each stop. Look back towards the sun at each stop. How big does the sun look? This is the size it would appear in the sky to an astronaut on that planet. Imagine what this does to the temperature of each planet. Ask students how far it would be to the nearest stars. (In this model, the nearest stars would be in Greenland and Cairo. Hand out mock plane tickets.) Questions to Think About: What information do you get from each model? What difficulty would we have presenting all this information in one model? What age level is each model appropriate for? Picture the Solar System By Carolyn Hollis Materials: Collection of photographs Directions: Can you identify these objects in our solar system? With your team, place them in order from the sun. What do you know about these objects? Are all of them planets? Which objects are most alike? Drawing Planets By Carolyn Hollis Materials: Paper, pencils, metric rulers Directions: 1. On separate pieces of paper, draw a circle to represent each planet. Be sure to label each of your drawings with a planet letter. Use the scale column of the chart for the diameter of the circles. Your group only needs to make one set of circles. Strategy: There are many ways to draw circles. Here is one. 1) With your ruler draw a line the length of the diameter. 2) Turn it into an X by drawing a similar line across it. 3) Draw a circle by connecting the ends of the X. 2. Discuss the model with your group. Think about what you already know about the planets. Decide which circle represents each planet. Can you arrange the planets in order from the sun? Planet Data Planet letter Planet Diameter Scale Diameter Name of planet A 12.76 K km 13 mm B 143.0 K km 143 mm C 6.79 K km 7 mm D 4.88 K km 5 mm E 49.5 K km 50 mm F 2.37 K km 2 mm G 120.5 K km 121 mm H 51.1 K km 51 mm I 12.1 K km 12 mm Answers: (Planets are listed alphabetically) A Earth; B Jupiter; C Mars; D Mercury; E Neptune; F Pluto; G Saturn; H Uranus; I Venus Sculpting the Solar System Adapted by Carolyn Hollis* Materials: 2 pounds of play clay, 3 pieces of paper, plastic knife. Directions: 1. Prepare a mat for each planet. On 3 sheets of paper draw lines to create 3 sections. Write each planets name in a different section. You will put clay on these mats to form scale models of each planet. 2. Roll the clay into a fat hotdog shape. 3. Cut the clay into 10 equal parts. Put 6 parts on Jupiter mat and 3 parts on Saturn mat. 4. Cut the remaining piece of clay into 10 equal parts. Add 5 parts to Saturn mat. Put 2 parts on Neptune mat. Put 2 parts on the Uranus mat. 5. Cut the remaining piece into 10 equal parts. Add 9 parts to Saturn mat. 6. Cut the remaining piece into 2 equal parts. Put one part on Earth mat. 7. Cut the remaining piece into 10 equal parts. Put 9 pieces on Venus mat. 8. Cut the remaining piece into 10 equal parts. Put 9 parts on Mars mat. 9. Cut the remaining piece into 10 equal parts. Put 9 parts on Mercury mat. Put 1 part on Pluto mat. 10. Roll the clay on each mat into a sphere to represent the shape of the planet. Line up the planets by distance from the sun. What did you discover about the sizes of the planets? TM
*Based on Worlds in Comparison by Dennis Schatz, 2001 Project Astro , Astronomical Society of the Pacific, 390 Ashton Avenue, San Francisco CA 94112 Bead and String Model of the Solar System By Carolyn Hollis Materials: 10 beads plus 1 sun bead, 4 ¼ meters of string, meter stick Directions: 1. Tie the special bead on one end of the string. This will represent the Sun. 2. Using the scale distances from the chart, tie a bead on the string to represent each planet. Notice these are distances from the Sun. Be sure you are making all of your measurements from the Sun bead. 3. Discuss your observations. What have you noticed about the solar system? How does this model compare to other models you have made? Planet Data Planet Distance from sun Scale distance from Sun Mercury 0.4 AU 4 cm Venus 0.7 AU 7 cm Earth 1.0 AU 10 cm Mars 1.5 AU 15 cm Asteroid Belt 2.8 AU 28 cm Jupiter 5.0 AU 50 cm Saturn 10.0 AU 100 cm Uranus 19.0 AU 190 cm Neptune 30.0 AU 300 cm Pluto 39.0 AU 390 cm Advanced String Model of the Solar System By Carolyn Hollis Materials: 9 pony beads for planets, 12 meters of string, meter stick, scissors. Directions: 1.Use the chart to cut 9 pieces of string. 2. Tie a bead on one end of each string to represent the planets. 3. Next you will tie the strings together in a bundle. Gather together the ends of the strings that do not have beads. Line them up evenly. Holding it as if it is one thick rope, make an overhand knot close to the end. 4. The knot you have just formed at the end represents the sun. 5. Label the planets. 6. Spread out the string to place the planets at the correct distance from the sun. In this model do the planets need to be in a line? Are the planets lined up in the solar system? Discuss your observations. What have you noticed about the solar system? How does this model compare to other models you have made? Planet Data Planet Distance from sun Scale distance Length of string from Sun Mercury 0.4 AU 4 cm 14 cm Venus 0.7 AU 7 cm 17 cm Earth 1.0 AU 10 cm 20 cm Mars 1.5 AU 15 cm 25 cm Jupiter 5.0 AU 50 cm 60 cm Saturn 10.0 AU 100 cm 110 cm Uranus 19.0 AU 190 cm 200 cm Neptune 30.0 AU 300 cm 310 cm Pluto 39.0 AU 390 cm 400 cm Toilet Papering the Solar System Adapted by Carolyn Hollis* Materials: roll of toilet paper, marker Directions: • Practice writing on toilet paper. Then throw the test sheet away. • Make a dot between the first and second sheets of toilet paper. Label it Sun. All distances will be measured from here. • Using the chart below make dots to represent each planet. Be sure to label the dots. • Remember, all distances are measured from the sun. Object Squares of toilet paper Average distance from from sun sun in km Mercury 1.0 57,910,000 Venus 1.8 108,200.000 Earth 2.5 149,600,000 Mars 3.8 227,940,000 Ceres 7.0 414,436,000 Jupiter 13.2 778,330,000 Saturn 24.2 1,429,400,000 Uranus 48.6 2,870,990,000 Neptune 76.3 4,504,000,000 Pluto 100.0 5,913,520,000 TM
*Based on Toilet Paper Solar System by Suzanne, 2001 Project Astro , Astronomical Society of the Pacific, 390 Ashton Ave., San Francisco, CA 94112 Rice Model of the Solar System By Carolyn Hollis Materials: Prepared and labeled bags of rice Directions: Each bag represents the mass of one of the planets in the solar system. • Think about what you know about the planets. • Decide which bag represents each planet. • Arrange the planets in order from the Sun. Required Advance Preparation and Answer Key Materials: Rice, Ziploc bags, and measuring cups and spoons to prepare bags Marker to label bags Preparation Use this table to prepare the bags. This also is an answer key. It should not be given to students Planets Earth mass/ Amount of rice Label Conversion factor Mercury 0.055 8 grains of rice D Venus 0.814 2/5 tsp. of rice I (a scant ½ tsp.) Earth 1 ½ tsp. A Mars 0.107 16 grains of rice C Jupiter 318 3 ½ cups B Saturn 95.18 14 ½ Tablespoons G Uranus 14.54 2 ½ Tablespoons H Neptune 17.14 2 Tbs. 2 ½ tsp. E Pluto 0.0021 4/5 of a grain of rice F (a large piece of a grain of rice) How High Could You Jump? By Carolyn Hollis Materials: Tape measure hung vertically on a wall. The bottom needs to be in reach of all students. The top must be above jumping reach of the students. Directions: We can compare the effect of gravity by computing how high we can jump on different worlds. Gravity is an attractive force that holds us to Earth. If the gravity is less the strength of our legs will let us jump higher. If the force of gravity increases we can’t jump as high. All objects exert a gravitational force on every other object. The strength of this force is based on two things. 1) The size of the object. The greater the mass of the object the more force it exerts. 2) Your distance from the center of the object. The greater the distance from the center of the object the weaker the gravitational force it exerts on you. It is the relationship between the mass of a planet and its diameter that determines the gravitational force you would experience standing on its surface. First, work with a partner to determine how high you could jump on Earth. • Reach as high as you can on the tape measure. Record this reach number. • Have your partner watch as you jump and touch the tape measure. Your partner will tell you the jump number. • Subtract the reach number from the jump number to determine how high you can jump on earth. Write it on the earth line. Next, divide the height of your jump by the relative gravity or conversion factors listed on the chart to determine how high you could jump on other planets. Planet Relative gravity Height you could jump Conversion factor Earth 1 Mercury 0.4 Venus 0.9 Mars 0.4 Jupiter 2.4 Saturn 1.1 Uranus 0.9 Neptune 1.2 Pluto 0.1 How Much Would You Weigh? By Carolyn Hollis Materials: Bathroom scale, calculators Directions: We can compare the effect of gravity by computing how much we would weigh on different worlds. Weight is the effect of the force of gravity on a mass. Mass is a measure of the amount of matter we are made of. That remains constant as we travel through the solar system. The greater the gravitational force the more you weigh. All objects exert a gravitational force on every other object. The strength of this force is based on two things. 1) The size of the object. The greater the mass of the object the more force it exerts. 2) Your distance from the center of the object. The greater the distance from the center of the object the weaker the gravitational force it exerts on you. It is the relationship between the mass of a planet and its diameter that determines the gravitational force you would experience standing on its surface. • Use the scale to determine your weight on Earth. Write it in the chart for Earth. • Multiply your weight by the relative gravity/ conversion factors on the chart to determine how much you would weigh on other planets. Planet Relative gravity/conversion factor Your weight Mercury 0.4 Venus 0.9 Earth 1 Mars 0.4 Jupiter 2.4 Saturn 1.1 Uranus 0.9 Neptune 1.2 Pluto 0.1 Hiking the Solar System By Carolyn Hollis Total walking distance is about 1 mile. Scale 100,000 miles to 1 inch Approximate size Scaled size Sun’s diameter 800,000 miles 8 inches Earth’s diameter 8000 miles 0.08 inch 8/100 Sun to Earth distance 93,000,000 miles 930 inches (26 yards) Materials: Objects to represent the sun and planets as described in the chart. Additional yards Astronomical object Suggested model object 0 Sun 8-­‐inch ball 10 yards Mercury Mustard seed 9 yards Venus Peppercorn 7 yards Earth Peppercorn 13 yards Mars Mustard seed 31 yards Ceres in asteroid belt Too small to see 64 yards Jupiter 1-­‐inch wooden ball 113 yards Saturn Marble: ¾-­‐inch 249 yards Uranus Garbanzo bean 281 yards Neptune Garbanzo bean 244 yards Pluto Cake sprinkle