Name Gravity and the Solar System (source Dartmouth.edu)
Quicker (activity from Astronomy for Every Kid by Janice Van Cleave) Materials Long stick Short stick Modeling clay Procedure 1. Place a walnut-sized ball of clay on the end of the long stick and one on the end of the short stick. 2. Hold the long stick and short stick up and down, sideby-side, with the edge without the clay ball on the ground. 3. Release both at the same time. 1. Explain what happened when you dropped the sticks. 2. From your notes, you know that planets nearer the Sun revolve faster than planets away from the Sun. Explain how activity demonstrates that concept. 1
Spinner (activity from Astronomy for Every Kid by Janice Van Cleave) Materials Paper plate Paper plate cut in half Marble Safety Concerns: Scissors. Discuss safe and proper use of scissors. Procedure 1. Place the marble in the paper plate and move the marble around the plate. 2. Place the marble on the cut edge of the half plate. 3. Set the plate down on a table and slightly tilt it so that the marble moves quickly around the groove on the plate. 1. Describe what happens as the marble moves along the edge of the full plate. 2
2. Describe what happens as the marble moves along the edge of the half plate. 3. Explain why the marble moves as it does. Select and answer one of the following in the space below. (Your response must be complete, neatly written, and fully cover the topic. A sentence or two will not adequately answer the question): How does this activity represent the planets as they revolve around the Sun? Explain how this activity demonstrates the effect of gravity on the Solar System. 3
Materials Calculator Procedure More or Less (activity from Janice Van Cleave s Solar System) 1. Complete the table you have been given by calculating each planet s mass ratio, which is the ratio of a planet s mass to the mass of Earth. NOTE: The mass of planets is measured in trillion trillion kilograms (kg). For example, the mass ratio of Mercury is: mass ratio = planet s mass Earth s mass =.33 5.986 =.06/1 Mercury s mass ratio is.06/1, which means that Mercury s mass is.06 (6%) that of Earth. Mass Ratios of the Planets to Earth Planet Mass (trillion trillion kg) Mass Ratio (planet/earth) Mercury.33.06/1 Venus 4.87 /1 Earth 5.98 /1 Mars.64 /1 Jupiter 1,899 /1 Saturn 569 /1 Uranus 86.9 /1 4
Neptune 103 /1 Staying Up While Falling Down Materials Plastic golf ball Straw Different size washers Safety Concerns: Moving plastic golf ball. Discuss safe procedures for twirling ball and pulling washers. Procedure 1. Thread the string through the straw. DO NOT tie a washer to the other end of the string. Your set up should look like the diagram below (except no washer). 5
2. Hold the straw and swing the ball in a circle so that it orbits the straw. (Be sure to keep moving your hand at a constant speed.) Record below what you see happen. 3. Tie a small washer to the end of the string. Hold the straw and swing the ball in a circle so that it orbits the straw. (Be sure to keep moving your hand at a constant speed.) Record below what you see happen. 4. Tie a medium sized washer to the end of the string. Hold the straw and swing the ball in a circle so that it orbits the straw. (Be sure to keep moving your hand at a constant speed.) Record below what you see happen. 5. Tie a large washer to the end of the string. Hold the straw and swing the ball in a circle so that it orbits the straw. (Be sure to keep moving your hand at a constant speed.) Record below what you see happen. We have your rovers. If you want them back, send 20 billion in Martian money. No funny business or you will never see them again. - Seen on a hall wall at NASA's Jet Propulsion Labs 6
6. Tie two or more large washers the end of the string. Hold the straw and swing the ball in a circle so that it orbits the straw. (Be sure to keep moving your hand at a constant speed.) Record below what you see happen. 7. Explain how this experiment demonstrates planets revolving around the Sun. What if Gravity Disappeared? You let go of your dirty socks and they hit the floor. You kick a soccer ball and no matter how hard or high you kick it, a moment later it is back on the ground. Objects have an irresistible attraction to Earth caused by the force called gravity. But, what if gravity suddenly disappeared? We know it won t happen, but WHAT IF? We are so used to living with the effects of gravity, can you even get your brain to think about what would be different if gravity was gone? Well, stretch your brain and give it a try! Many of your everyday activities depend on gravity. Do you realize all the ways that if affects how you do things? For each of the actions in the following list, decide whether or not the action would be the same without gravity. If the activity would be different without gravity, describe the ways it would change. (Let s assume the air stays just like it is.) After describing ways the activity would change, describe how you could do it if there was no gravity. 7
Activity What Would Happen? Walking Taking a bath Writing a letter Riding a bicycle Tossing a tennis ball Mixing cookie dough with an electric mixer Using a thermometer Drinking orange juice Doing sit-ups Using the toilet Sleeping Lighting a candle Getting a haircut 8
Shooting a squirt gun Looking For Planets Without Seeing Them (an activity from NASA PlanetQuest) When astronomers look for planets around other stars, one thing they look for is if the star appears to be wobbling. Planets would cause the star to appear to wobble. This activity will help you understand why a star could wobble. Materials Strong piece of string Drinking straws Clay Procedure 1. Make a little solar system model from a string, drinking straw, and clay. Tie one end of a piece of string around a drinking straw, allowing the knot to slide back and forth along the straw. 2. Put a golf-ball-size lump of clay around one end of the drinking straw. This represents the Sun. 3. Put a marble-size lump of clay around the other end of the straw. This represents a planet. 9
4. Move the string until it looks like the diagram above. Gently turn the model. Observes what happens. 1. What happens when you turn the model? 2. Does the Sun stay in one place or does it move? 3. Observe the turning model from across the room. Can you see the wobble? 4. Hold a drinking straw vertically at arm s length between your eye and the little spinning solar system. Can you see the wobble now? 5. Why do you think stars with planets wobble, but stars without planets do not? Does the motion make a shape? What is the force called that causes planets and the Sun to move this way? 10
6. Explain how gravity of the planets would affect our Sun. Chaos Among the Planets Kate Ramsayer From Science News for Kids June 1, 2005. Once upon a time, many, many years ago, the giant planets in our Solar System took different paths around the Sun than they follow now. Jupiter, Saturn, Uranus, and Neptune were once bunched together and closer to the Sun, says an international team of scientists. Under the influence of gravity, the planets broke out of their original orbits and began violently rearranging the outer Solar System. A new theory suggests that the four giant planets, shown here in their current orbits around the Sun, were once much closer together. Nature 11
It's "a fairy tale of the early Solar System," says Hal Levison. He's a planetary scientist with the Southwest Research Institute in Boulder, Colo., and was one of the researchers who developed a computer simulation of the planets' movements. As the scientists tell it, the tale starts a few million years after the Solar System's birth. At first, the four giant planets had compact orbits. Neptune, for example, was only half as far away from the Sun as it now. A slowly circulating band of ice, dust, and gas lay beyond these planets. Ice, dust, and gas might not seem like much of a match for huge planets. But the researchers say that the pull of gravity between the particles and the planets caused the planets to gradually break out of their tight-knit group. Jupiter moved a bit closer to the Sun, and the other three planets moved further away. All was peaceful in the solar kingdom until the orbits of Saturn and Jupiter aligned so that Saturn took exactly twice as long as its neighbor to go around the Sun. The increased gravitational tug of the two planets acting together caused an avalanche of effects. Saturn's orbit changed shape slightly, which threw off the orbits of Uranus and Neptune. The orbits of these two planets started looking like squished ovals. At times, the two planets even crossed paths. And that's when things got really crazy. Uranus and Neptune started hurtling through the band of ice, dust, and gas, scattering the debris throughout the Solar System. The planets themselves ended up in their current orbits. In the meantime, some of the scattered material became trapped around Jupiter, the scientists suggest. This could account for the presence of objects, known as the Trojan asteroids, that both lead and trail the planet. Some of the debris could have been flung closer to our home, slamming into the Moon and the Solar System's inner planets. This bombardment may have created the huge craters on the Moon and elsewhere. No one knows for sure whether all this really happened. But, by using computers to play complex games of "what if," scientists can get a better sense of what might have happened to create the Solar System as we know it. 12
Questions 1. According to the article, these four planets were bunched together and nearer to the Sun. a. b. c. d. 2. This force caused the violent rearrangement of our Solar System. 3. orbit changed shape slightly, which threw off the orbits of. 4. This is the group of asteroids that both lead and trail Jupiter. 5. Debris flung towards the inner planets may have created the huge on the Moon and elsewhere. 6. Scientists are positive this really happened. True False 13