The Earth-Moon System The Earth-Moon System - Delta Education

activity5The Earth-Moon SystemOBJECTIVESTo further develop their understanding ofthe sizes and distances involved in theEarth-Moon system, students will create athree-dimensional scale model of the Earthand its natural satellite.The students estimate the size of the Moon in relation toa given Earth globe investigate the difference in volumebetween the Earth and Moon by seeinghow many Moons are needed to create oneEarth use models to demonstrate distancesbetween the Earth, Moon, and artificialsatellitesSCHEDULEAbout 40 minutesVOCABULARYartificial satellitenatural satelliteMATERIALSFor each student1 Activity Sheet 5For each team of four1 ball, foam, large3 sticks clay, modeling1 marble1 measuring tape1 ruler, metric*1 pair scissors*1 toothpickFor the class8 bags, plastic, reclosable4 photos, Earth from Moon4 photos, Moon from Earth1 poster, Moon Map1 roll string* provided by the teacherPREPARATION123Make one copy of Activity Sheet 5 for eachstudent.Use one of the pairs of scissors to cut alength of string 4 m (13 ft) long for eachteam of four.Display the Moon Map poster in theclassroom for reference during this andsubsequent activities.BACKGROUND INFORMATIONStudents often have misconceptions regardingthe actual sizes and distances involved in theEarth-Moon system, since most illustrationsare not accurate to scale. Even though theMoon is among the largest of the naturalsatellites in our solar system, it appearsrelatively small in size next to Earth. Thediameter of the Moon is one-quarter of Earth’sdiameter. The Moon’s volume is one-fiftieth ofEarth’s. And the distance from Earth to theMoon equals about 30 Earth diameters. Theseratios are visually impressive and are usuallyquite a surprise to students even if they knowthe numbers representing the measurements.delta science modules Earth, Moon, and Sun 45

4Guiding the ActivityHave students measure the string with theirmeasuring tapes and record its length ontheir activity sheets. Ask, How did the actualscale distance between Earth and Mooncompare with your predictions?Write satellite on the board. Ask, What is asatellite?Ask, Does anyone know the name of thefirst satellite to orbit Earth?Write natural satellite and artificial satelliteon the board. Explain that the Moon is anatural satellite. But point out that Earth alsohas many smaller manufactured satellites,or artificial satellites, that are used forcommunication, weather monitoring, andother data collection purposes.Have students predict on their activity sheetshow far from Earth most artificial satellitestravel.Then have teams take the tiniest dot of claythey can from their model Earth and hold itbetween Earth and the Moon, 20 cm (8 in.)from Earth. Explain that the position of thisbit of clay represents the altitude of some ofthe most distant Earth satellites! (See Figure5-3 for an accurate distance model of Earth’ssatellites.)Additional InformationAllow students time to express their surpriseor other responses. Students may beinterested to know that the true diameter ofEarth is about 12,800 km (8,000 mi) and themean distance from Earth to the Moon isabout 380,000 km (230,000 mi).Students may know that a satellite is anobject that orbits a planet.Students may answer with the name of anearly artificial satellite, but probably will saythat they do not know. The answer actually isthe Moon.Approximately 3,000 artificial satellites arecurrently in orbit around Earth.Each team also can hold up the Earth modeland a tiny speck of clay to demonstrate ateam prediction.This distance corresponds to an altitude ofabout 35,000 km (22,000 mi) and is thedistance of certain satellites that orbit Earthat the same rate at which Earth spins and,therefore, that maintain their position abovethe same spot on Earth at all times. The mostcommon satellites of this kind are theweather satellites that produce the picturesseen on television weather reports.the Earth, surrounded byartificial satellitesmost distant artificial satellitesthe Moon, Earth’snatural satellite Figure 5-3. An accurate distance model of Earth and its satellites (not accurate to size).delta science modules Earth, Moon, and Sun 49

Guiding the ActivityTell teams to insert their toothpick into theclay model of Earth until less than 5 mm(0.2 in.) extends from the clay. Explain thatthis represents 500 km (310 mi), the heightat which the space shuttle and most othersatellites fly above Earth.Ask, How do space shuttle launches compareto the feat of traveling to the Moon?Additional InformationAllow students time to discuss this revelationand to revise their drawings to represent thepositions of satellites accurately.The Apollo Moon missions were the farthesttrips ever made by human beings, more than1,000 times as far as the average spaceshuttle height.R EINFORCEMENTHave students examine the photos of Earthfrom the Moon and the Moon from Earth.Next, ask each student to observe Earth fromthe Moon and the Moon from Earth in theirscale models, by positioning their eye closeto the object from which they would view.Discuss why the models look different fromthe photos.Earth actually appears about four timeslarger in the Moon’s sky than the Moonappears in Earth’s sky. The fact that this isnot the case in the photos is an illusion.There is no lawn chair in the Moon shot tohelp us judge the difference in size!SCIENCE NOTEBOOKSHave students place their completedactivity sheets in their science notebooks.C LEANUPPlace one of the clay scale models ondisplay in the classroom throughout theremainder of the module. Put the rest ofthe clay in the plastic bags provided.Return all other materials to the kit.50 activity 5 The Earth-Moon System

ConnectionsScience ChallengeChristopher Columbus discovered that steadywinds, now called trade winds, blow fromeast to west in the southern Atlantic and fromwest to east in the northern Atlantic. Prior toColumbus’s discovery, most sailors believedthat winds were due to the whims of gods ordemons. Scientists did not learn why tradewinds exist until two centuries later.Challenge students to research EdmundHalley’s and George Hadley’s work to explainhow Earth’s rotation and orientation createthe trade winds.Science and the ArtsPerspective determines the apparent distanceof objects. Display examples of medieval art,created before formal rules for perspectivewere developed, alongside Renaissanceworks that demonstrate perspective.Then have team members take turns holdingthe model Moon at an appropriate distancefrom Earth while other team members viewthe model from various perspectives: a sideview, the viewpoint from Earth, the viewpointof someone traveling to the Moon, and theviewpoint from the Moon.the amount of parallax is greater for objectsclose to the viewer than for distant objects,an object’s distance can be determined by itsparallax.Have students trace two circles near oppositeends of a sheet of paper to represent theMoon and Earth. Earth’s diameter should beabout 2 cm (0.75 in.) and the Moon’s, about0.5 cm (0.2 in.). Then they should draw a dotbeyond and to one side of the Moon torepresent a star and two separate dots on theside of Earth facing the Moon to representtwo astronomers at different locations. Usinga ruler, students should draw four straightlines, one from each astronomer to the starand one from each astronomer along thecircumference of the Moon. Using aprotractor, students should measure theangle between the Moon and the star fromthe perspective of each astronomer. What isthe difference—the parallax—between them?Then have students tape sheets of papertogether so that the Moon can be 60 cm(24 in.) away, its actual scale distance. Howdoes parallax change as the distance to theMoon increases?Science and MathThe distance from Earth to the Moon wasfirst measured about 2,000 years ago byHipparchus, a Greek astronomer, usingparallax. He and a distant colleague bothmeasured the angle between the Moon anda particular star on a particular night.Have students hold a finger near the tip oftheir nose and view it, first closing one eyeand then the other. Have them view an objectacross the room and a distant tree or buildingin the same way. Do the distant views vary byeye as much as the nearby finger? Explainthat the difference between the view with oneeye and the other is called parallax. Becausedelta science modules Earth, Moon, and Sun 51