The Pull of the Planets

Transcription

1 The Pull of the Planets Overview The Pull of the Planets is a 30-minute activity in which teams of children model the gravitational fields of planets on a flexible surface. Children place and move balls of different sizes and densities on a plastic sheet to develop a mental picture of how the mass of an object influences how much effect it has on the surrounding space. This series is appropriate for children ages 10 to 13. What's the Point? Gravity is the force that keeps planets in orbit around the Sun. Gravity alone holds us to Earth's surface. Planets have measurable properties, such as size, mass, density, and composition. A planet's size and mass determines its gravitational pull. A planet's mass and size determines how strong its gravitational pull is. Models can help us experiment with the motions of objects in space, which are determined by the gravitational pull between them. Materials For each group of up to 30: Computer and projector to show an animation of Juno orbiting Jupiter or an artist's rendering of Juno in orbit, printed preferably in color. Examples could include: o o For each group of four children: 1 (20" by 12" or larger) embroidery hoop Something to support the edges of the embroidery hoop, such as foam bricks or books 1 thin stretchable plastic sheet, like a plastic garbage bag or sheets of plastic-wrap 2 4 (1/2" wide) small marbles 1 (2") Styrofoam ball Half a can of Play-Doh For each child: "The Pull of the Planets" page 1 pencil or pen Preparation Prepare the gravity fields: stretch the plastic sheets (plastic wrap or garbage bags) around the inside of the embroidery hoops, then add the outer hoop, keeping the plastic stretched tightly.

2 Activity 1. Ask the children to connect what they have learned about gravity to the motions of objects in the solar system. Ask the children to recall from Heavyweight Champion: Jupiter! Which properties cause a planet to have more or less gravity? Planets that are massive and have the largest diameters have the most gravity. Which properties do not influence gravity? The presence of an atmosphere, temperature, and distance from the Sun do not affect a planet's gravity. Are the objects in the solar system still or are they in motion? The Sun's gravity pulls the planets in orbit around it, and some planets pull moons in orbit around them. Even spacecraft are in motion through the solar system, either in orbit around the Earth or Moon, or traveling to further worlds, because of gravitational forces. The Juno mission will be pulled into orbit around Jupiter by Jupiter's intense gravity. How does gravity influence the movements of objects such as planets in the solar system? Has anyone seen or played with a "gravity well?" How does a "gravity well" model gravity in the solar system what part of this model is the Sun? The planets? The center of the gravity well is the Sun, and the coins or marbles are a model of the planets. The closer the planet is to the Sun, the greater the pull of the Sun's gravity, and the faster the planet orbits. This model fails in that objects in stable orbits do not fall into the Sun. (Comets are objects with orbits that can easily become unstable and fall into the Sun.) Facilitator's Note: There are many different misconceptions about gravity; children may think that it is related to an object's motion, its proximity to Earth, its temperature, its magnetic field, or other unrelated concepts. Guide conversations cautiously and listen carefully to what the children say to avoid supporting their misconceptions. 2. Tell the children they will make a model of how objects like planets interact in space. Have any of the children played on a trampoline? What happens to the surface of the trampoline when you sit on it? What would happen if a friend tried to roll a ball on the surface with you sitting on it? Explain that space can act much like the surface of the trampoline. The indentations made on the surface represent the "gravity wells" created by massive objects in space. 3. Invite the children to experiment with the same effects on smaller scale models. Separate the children into groups and give each group a prepared embroidery hoop, suspended in the air on bricks or books. Explain that they will use marbles and Play-Doh balls to model the effects of gravity on objects in space. What will happen to the plastic sheets (space) if they add a marble to it? It will stretch out and the marble will roll. What will happen if there are two marbles on the sheet? The marbles will roll toward each other. Facilitator's Note: Gravity is a universal force, like magnetism and electricity. However, it becomes important only at large scales. Gravity determines the interactions stars, planets, and moons. In the model, the balls are too small to exert a significant gravitational pull on each other. However, they are gravitationally pulled toward Earth! They move toward each other because the weights of heavier objects distort the sheet and lighter objects roll "downhill."

3 4. Invite the children to experiment with their models of space by placing and dropping the marbles (together and separately) onto the sheet. 5. Ask the groups to each add a large, 2" round ball of Play-Doh to represent a large "planet" alone on the sheet. Ask the children to hypothesize what will happen if the marbles are dropped onto the sheet, and have them record their thoughts in their journals before they test them. After they have dropped the marbles onto the sheet, share that this "pull" toward the "planets" is a model of gravity. How does this model gravity? The marbles are pulled, or "fall," toward the planet. Does this large Play-Doh planet represent strong or weak gravity? This planet has strong gravity the marbles fall straight toward it. Facilitator's Note: The Play-Doh and Styrofoam balls used in steps 5 7 serve to create test "wells" on the sheets. They should remain stationary while the children roll the marbles to see how they move at each step. Encourage the children to only roll marbles, as the Play-Doh is sticky and will not model the motion accurately. 6. Ask the groups to place a very small round ball of Play-Doh (about half of the size of a marble), which represents a small asteroid, alone on the sheet. Have them note their predictions in their journals and then test what will happen to marbles added to the sheet. What will happen if marbles are added to the sheet now? Why? The marbles may take longer to reach the Play-Doh asteroid or may not move toward it at all. What type of gravity will a small asteroid have compared to a large planet? It doesn't have very much "gravity". 7 Ask the groups to place the Styrofoam ball alone on the sheet and, keeping records in their journals, experiment with its gravitational pull. What type of object might the Styrofoam ball model? It can represent a planet that isn t very dense, like Saturn. How does its size, mass, and density compare to that of the large Play-Doh "planet"? It is about the same size, but less dense and therefore less massive. What will happen when the marbles are added? Will they behave more like they did for the large or small Play-Doh planets? Again, the marbles may take longer to reach the low-density giant planet; they won t feel the pull of gravity as strongly as they did with the very large Play-Doh planet. Does Saturn have as much gravity as Jupiter? Saturn s gravity is not very strong compared to Jupiter s. Remind the children that the gravitational pull of a planet depends on its mass and size. Saturn is large in size, but it does not have nearly as much mass packed into its volume as Jupiter does. Facilitator's Note: Saturn does have plenty of mass, and as they explored in Heavyweight Champion: Jupiter!, it does have gravity. However, because it is not dense, a person standing in its cloud tops would only weigh about as much as they weigh on Earth. Saturn's cloud tops are far above the planet's bulky and gravitationally strong center. Because the force of gravity depends on both mass and distance, planets that are puffy and less dense have less gravity at their cloud-tops or surfaces, which are far above the bulk of the mass in their interiors. This is why planets like Saturn appear to have less gravity than Neptune, despite Saturn's greater mass. You may need to remind the children of what they learned in Dunking the Planets in order for them to understand these difficult concepts.

4 8. Invite the groups to experiment with dropping the marbles in different locations, and with different amounts of Play-Doh or the Styrofoam ball, in various locations on their gravity field. Do the marbles ever briefly circle the planet? Do they ever avoid the planet? Do small asteroids experience gravity? Asteroids and other small bodies, like comets, are also kept in orbit around the Sun by the Sun's large gravitational pull even when they are at great distances from the Sun. They can also be pulled into orbit around a planet like Mars' two moons or impact a moon or planet. 9. After the children have finished experimenting, discuss their findings. How did the marbles behave toward the largest Play-Doh planet? They rolled directly toward it. How was this like gravity? The large planet had a lot of mass, and, in our model, a lot of gravity. How did the marbles behave with the Styrofoam planet? They may have ignored it completely. Why? The ball did not have much mass, and so it had very little gravity in this model. Does a large object always have a lot of mass? No! If we can measure the gravity of a planet, and its size, what can that tell us about that planet? The gravitational pull of the planet can tell us more about that planet's mass, which helps us to determine its density and what its interior is like. Ask the children to draw in their journals, based on their models, how deep a gravity well the Moon, Earth, and Jupiter each create in space. Have them describe how their differences in gravity relate to each object's size and mass. 10. Invite the children to describe how this model of gravity resembles real gravity and how it fails. Do objects in the solar system move toward each other with real gravity, like they did in the model? Yes. Do objects roll toward each other in space because of gravity? No, they are tugged but they don't roll. Do planets in our solar system usually run into each other? No, they are very far apart and they are orbiting the Sun. Sometimes comets and asteroids collide with planets, though. Facilitator's Note: Children also may not understand that the planets are not being significantly pulled toward each other. They are strongly pulled toward the Sun, but since they are also moving, they move around the Sun in stable orbits. Smaller objects like comets and asteroids may have less circular orbits that cross the paths of planets sometimes resulting in a collision. Be careful when identifying the objects in this activity not to introduce misconceptions regarding planets' orbits and collisions.

5 Ages: years Duration: 30 minutes Materials: Per classroom of 20 students 20 small paper plates 1 box of graham crackers 1 bag of butterscotch chips 2 cans of whipping cream 1 box of vanilla crème wafers 1 can of chocolate frosting-spray ~ LPI EDUCATION/PUBLIC OUTREACH SCIENCE ACTIVITIES ~ EDIBLE LITHOSPHERE AND ASTHENOSPHERE OVERVIEW The students will create an edible model of the lithosphere and asthenosphere, moving them and using a variety of materials to model different characteristics of interacting plate boundaries. OBJECTIVE The students will: Determine which characteristics of plate boundaries to model Discuss analogies for different types of volcanism Create a model for a type of plate interaction BEFORE YOU START: The students should be with the concepts of the lithosphere and asthenosphere, and the different types of plate tectonics interaction (subduction, divergent, convergent, and transform fault boundaries). ACTIVITY Invite the students to describe different types of plate interaction. Share with the students that they are going to model these interactions with food. Hand out items as needed. 1. Each student should pick a particular type of plate boundary in advance to model. 2. Each student should take a paper plate and fill it with 2 centimeters of whipping cream. 3. Students will use vanilla crème wafers to model continental crust, and graham crackers to model oceanic crust. 4. Butterscotch chips will be used for volcanos in subduction zones. 5. Chocolate frosting will be used for volcanos at divergent boundaries and hot spots. 6. Students should position their materials to create their boundary, and then participate in a group or classroom discussion: In what ways does the graham cracker model ocean crust? [thinner and denser] How does the vanilla crème wafer model continental crust? [thicker and less dense] What happens when two ocean plates collide? When they diverge? Which boundaries should have the volcanos? Where should they be? Which boundaries might have chocolate frosting? In what ways do these models succeed? In what ways do they fail? Time to eat!

6 TIES TO STANDARDS Scientific Processes The student is expected to analyze, review, and critique scientific explanations, including hypotheses and theories, as to their strengths and weaknesses using scientific evidence and information; represent the natural world using models and identify their limitations. Sixth Grade Scientific Concept TEKS (10) Earth and space. The student understands the structure of Earth, the rock cycle, and plate tectonics. The student is expected to: (D) describe how plate tectonics causes major geological events such as ocean basins, earthquakes, volcanic eruptions, and mountain building. Eighth Grade Scientific Concept TEKS (9) Earth and space. The student knows that natural events can impact Earth systems. The student is expected to: (B) relate plate tectonics to the formation of crustal features

7 Ages: 5 th grade high school Duration: 30 minutes Materials: A golf ball for each student (optional) one golf tee for each golfball (optional) hot glue gun A blacklight A darkened room An embroidery hoop or something similar (rigid and oval) for each team of students ~ LPI EDUCATION/PUBLIC OUTREACH SCIENCE ACTIVITIES ~ GOLF BALL PHASES AND EMBROIDERY HOOP ECLIPSES OVERVIEW In the first half, students explore the dynamics of lunar phases to develop an understanding of the relative positions of our Moon, Earth, and Sun that cause the phases of the Moon as viewed from Earth. Using a golf ball glowing under the ultraviolet light of a blacklight makes it easier to see the actual phase of the Moon. In the second half, students kinesthetically model the orbit of the moon relative to the Earth's revolution around the Sun to gain a deeper understanding of eclipses. OBJECTIVE The students will: Demonstrate the Moon s phases in their correct order using a golfball and blacklight to model the Moon and Sun. Demonstrate that eclipses occur during two periods each year, modeling the Earth- Moon system s motion around the Sun. BEFORE YOU START: Do not introduce this topic unless the students already understand the size and distance of the Earth and Moon to scale, the tilt of the Moon s orbit around the Earth, and the Sun s role as the source of light for Moon phases. Use a hot glue gun to glue a golf tee to the bottom of each golf ball. Prepare to darken the room by closing blinds, etc. ACTIVITY Step 1: Model the Moon s motion first for the students. 1. Choose a student to hold the golf ball representing the Moon. The child's head will represent our Earth. Choose another student to stand with the blacklight representing the Sun. Turn out the room lights. Before turning on the Sun, ask the students to observe the golf ball. Does the golf ball make its own light? (No) Does our Moon make its own light? (No) 2. Turn the light on and have the student with the golf ball hold it low in front of them, between the student and the light. Ask the student with the Moon to describe its appearance. What does he observe about the Moon? Is the part of the Moon we see from Earth illuminated? (No) What part is illuminated? (The part facing the Sun that they cannot observe from Earth ) Based on this observation, does the Moon really have a dark side? (No) What phase of the Moon is he observing from Earth? (The new Moon) 3. Ask the student holding the Moon to slowly turn 90 while raising the golf ball to shoulder-height, keeping the Moon at arm's length. As the Moon revolves around the Earth, what happens to its appearance? How does the illumination of the Moon change as viewed from the Earth? (It increases to 1 st Quarter)

8 4. Ask the student holding the Moon to continue moving and raising the golf ball, until the ball is 180 away from the blacklight and just over the student s head. What phase of the Moon is he observing when the Moon has orbited halfway around the Earth? (A full Moon) 5. Ask the student holding the Moon to slowly turn another 90 while lowering the golf ball to shoulder-height, keeping the Moon at arm's length. What phase of the Moon is he observing now, when the Moon has orbited three quarters of the way around the Earth? (3 rd quarter, or last quarter Moon) Step 2. Student Exploration 1. Once the students are comfortable with the motion of the Moon, starting low in front of the lamp and moving up to above their heads for full Moon, have each student take a golf ball and model the motions of the Moon, while the teacher holds the blacklight. 2. Have the students observe the changing illumination of the Moon, repeat the exercise so that each Moon phase is revealed. Start with the new Moon and have the students rotate in steps of 45 degrees, pausing at each of the eight phases (waxing crescent, 1 st quarter, waxing gibbous, full, waning gibbous, 3 rd quarter, waning crescent) to invite the students to make observations about the illumination and to identify the phase. Step 3. Modeling Eclipses 1. After the students are comfortable with the motion of the Moon, remind them that the Moon s orbit isn t a perfect circle it s an ellipse. What are some objects that have elliptical shapes? 2. Show the students an embroidery hoop. Hold the hoop at an angle to the blacklight that mimics the positions that the students have been moving their golf balls low in the front and high in the back. Ask the students about the effect this orbit has on the Moon s appearance. Will the Moon block the Sun for people on Earth when it moves in this orbit? Will the Earth block the sunlight from reaching the Moon in this orbit? (no) 3. Explain that the Moon s orbit remains tilted as the Earth orbits the Sun. Walk with the embroidery hoop around the blacklight, stopping when you have moved one quarter of the way around the Sun. Have a student demonstrate the motion of the Moon with a golf ball from this position for the class. Now when the Moon is low, what is its phase? Where will it be at new Moon? What will people on Earth see? (People on the right part of the Earth will see solar eclipse) Two weeks later, when the Moon is at full, what will people on Earth see? (A lunar eclipse, visible to everyone on the part of the Earth facing the Moon) 4. Continue moving the embroidery hoop around the blacklight, rotating the blacklight as needed. Stop at another quarter of the way around the Sun. Discuss the Moon s appearance with the class. Will the Moon block the Sun for people on Earth when it moves in this orbit? Will the Earth block the sunlight from reaching the Moon in this orbit? (no) 5. Continue moving the embroidery hoop around the blacklight, rotating the blacklight as needed. Stop at the 3 rd quarter of the way around the Sun. Discuss the Moon s appearance with the class. Now when the Moon is low, what is its phase? Where will it be at New Moon? What will people on Earth see? (People on the right part of the Earth will see solar eclipse) Two weeks later, when the Moon is at full, what will people on Earth see? (A lunar eclipse, visible to everyone on the part of the Earth facing the Moon) How much time has past since we had the last solar eclipse and lunar eclipse? (6 months) 6. Let the students practice moving their golf balls from these different locations, modeling both lunar and solar eclipses. Ask them to demonstrate the position of the Moon during a solar eclipse, and then a lunar eclipse. What is the Moon s phase for a solar eclipse? (new) What is the Moon s phase for a lunar eclipse? (full)

9 7. Conclude by letting them know that sometimes the Moon brushes through just part of the Earth s shadow, resulting in a partial lunar eclipse, and sometimes the Moon only covers part of the Sun, resulting in a partial solar eclipse. There are a total of 5 to 7 eclipses each year; some of these are partial eclipses, often a month apart. EXTENSIONS Conduct the kinesthetic activity Paper Plate Moon, requiring the students to correctly position themselves and the Moon phase they carry relative to the Earth and Sun. BACKGROUND Understanding the cause of lunar phases is a spatially complex topic that confuses many people. Instructors should take care not to rely upon two dimensional models and should require all students to model the phases for themselves. Most activities, including this one, can accidentally reinforce misconceptions if not done carefully; for instance, if students do not hold the full moon high enough, they can create an eclipse that might be confused with the new moon. A resource that might be useful to examine before this lesson is Learning about Phases of the Moon and Eclipses: A Guide for Teachers and Curriculum Developers, TIES TO STANDARDS Connections to the National Science Standard(s) Content Standard D Earth and Space Science, (grades 5 8): Most objects in the solar system are in regular and predictable motion. Those motions explain such phenomena as the day, the year, phases of the moon, and eclipses. Principles & Standards for School Mathematics Geometry Standard for Grades 3-5: Specify locations and describe spatial relationships using coordinate geometry and other representational systems Reasoning and Proof: Instructional programs from PK through grade 12 should enable all students to make and investigate mathematical conjectures Texas TEKS Scientific investigation and reasoning. The student uses critical thinking, scientific reasoning, and problem solving to make informed decisions and knows the contributions of relevant scientists. The student is expected to: (A) in all fields of science, analyze, evaluate, and critique scientific explanations by using empirical evidence, logical reasoning, and experimental and observational testing, including examining all sides of scientific evidence of those scientific explanations, so as to encourage critical thinking by the student; (B) use models to represent aspects of the natural world such as a model of Earth's layers; (C) identify advantages and limitations of models such as size, scale, properties, and materials; 3 rd grade Science Concept Standards (TEKS) (8) Earth and space. The student knows there are recognizable patterns in the natural world and among objects in the sky. The student is expected to: (C) construct models that demonstrate the relationship of the Sun, Earth, and Moon, including orbits and positions 4 th grade Science Concept Standards (TEKS) (8) Earth and space. The student knows that there are recognizable patterns in the natural world and among the Sun, Earth, and Moon system. The student is expected to: (C) collect and analyze data to identify sequences and predict patterns of change in shadows, tides, seasons, and the observable appearance of the Moon over time. 8 th grade Science Concept Standards (TEKS) (7) Earth and space. The student knows the effects resulting from cyclical movements of the Sun, Earth, and Moon. The student is expected to: (B) demonstrate and predict the sequence of events in the lunar cycle; and (C) relate the position of the Moon and Sun to their effect on ocean tides.

10 Ages: years Duration: 30 minutes Materials: Per group of students ½ container of playdough ¼ cup of either miniature penne pasta or large almond slivers Plastic knives ~ LPI EDUCATION/PUBLIC OUTREACH SCIENCE ACTIVITIES ~ MODELING METAMORPHIC ROCKS OVERVIEW The students will model metamorphic processes and create a rock with aligned crystals. OBJECTIVE The students will: Demonstrate that pressure can align certain structures within a matrix. Model the formation of a metamorphic rock ACTIVITY Invite the students to create a metamorphic rock. Hand out materials as needed. 1. Each group of students should soften their playdough by squeezing it. 2. Have the students add their elongated crystals (either pasta or almond slivers) and fold and pull the combined materials apart and together until the crystals are mixed thoroughly and randomly oriented. 3. Ask the students to place their rock on a surface and apply pressure to the top. Invite them to discuss what is happening to the crystals. Pressure from one dimension will compress the rock and align the crystals in one dimension, forming layers. 4. Have the students pick up their rock and apply pressure from a different direction, squeezing the playdough into a tube. Continue applying pressure from the alternating sides; as the tube grows long, pull it into two tubes and join them, and repeat. 5. After sufficient pressure has been applied from two dimensions, cut the tube lengthwise with a plastic knife and examine the crystals. Discuss their orientation. When would a rock experience pressure from two dimensions? [when mountains are forming; there will be pressure from rocks above and from the sides] Further Discussion: What rock does this model? [metamorphic foliated rock, such as schist] In what ways does this model succeed? In what ways does it fail?

11 TIES TO STANDARDS Texas Science TEKS: Scientific Investigation and Reasoning (3) Scientific investigation and reasoning. The student uses critical thinking, scientific reasoning, and problem solving to make informed decisions and knows the contributions of relevant scientists. The student is expected to: (B) use models to represent aspects of the natural world such as a model of Earth's layers; (C) identify advantages and limitations of models such as size, scale, properties, and materials Sixth Grade Scientific Concept TEKS (10) Earth and space. The student understands the structure of Earth, the rock cycle, and plate tectonics. The student is expected to: (B) classify rocks as metamorphic, igneous, or sedimentary by the processes of their formation Eighth Grade Scientific Concept TEKS (9) Earth and space. The student knows that natural events can impact Earth systems. The student is expected to: (B) relate plate tectonics to the formation of crustal features