The Sun-Earth-Moon System 9

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_ Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. L 1 _ 8 8 9 4 0 edn setas h u-at-onSse System The Sun-Earth-Moon Reading Essentials The Sun andtheSun Earth Earth’s Motion SystemThe Sun-Earth-Moon thermal energy. small partoftheSun’s energyreachesEarthaslightand at theSun’s surface,thetemperatureis about 5,500°C. A the Sun’s coretemperatureismorethan15,000,000°C.Even nuclear fusion.Nuclearfusionproducessomuchenergythat produce hugeamountsofenergy. Thisprocessiscalled energy. InsidetheSun,nucleiofatomscombineto greater thanEarth’s mass. Earth’s diameter. TheSun’s massismorethan300,000times The Sun’s diameterismorethan100timesgreater million kmfromEarth.TheSunismuchlargerthan how energyfromtheSunspreadsoutoverEarth’s surface. Summer turnstowinterbecauseEarth’s motionchanges again. TheseasonschangeasEarthmovesaroundtheSun. Earth. As Earth spins,daychangestonightandback moves aroundtheSun.Earth’s motioncauseschangeson be moving.ButEarthisalwaysinmotion.Itspinsand is moving. Theground,trees,andbuildingsdonotseemto 7 this lesson,reread thestatements to seeifyou have changedyour mind. if you agree withthestatement oraDifyou disagree. After you’ve read whether you agree ordisagree withthem.Place anAintheBefore column What doyou think? . i n eoeSaeetAfter Statement Before d d The Sunisagiantballofhotgases.Itemitslightand The neareststartoEarthistheSun.Sunabout150 If youlookaroundyou,itdoesnotseemasifEarth

1 2. 1. hasseasonsbecauseitsdistance from Earth the Sunchangesthroughout theyear. sunrises andsunsets. Earth’s movement around theSuncauses Readthetwo statements below anddecide effect ofnuclearfusion? to review thelesson. head. Use your highlighting the that explainorsupport paragraphs underthehead highlight keywords inthe color. Use anothercolor to eachheadinone Highlight Identify MainIdeas • • • Key Concepts 1. Explain the Sun? moves around as Earth Why dotheseasonschange poles? equator andcolder atthe warmeratthe Why isEarth move?How doesEarth Reading Check CHAPTER 20 What isone LESSON 1

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January 3 Earth is closest the Sun. to A spinning Earth’s Orbit Earth’s km 147 million Earth’s cycle of day and Earth’s rotation of Earth takes about Gravitational Gravitational pull of the Sun a counterclockwise a counterclockwise direction, Sun Earth orbits the Sun in an the Sun in Earth orbits The line on which an object rotates is The line on which an object rotates orbit.

The path an object follows as it moves as it moves an objectThe path follows km Earth rotates on an imaginary line 152 million Earth rotation.

Earth makes one complete revolution around the revolution one complete Earth makes rotation axis. rotation If you could look down onto Earth’s North Pole, you If you could look down onto Earth’s Earth orbits the Sun because the Sun’s gravity pulls on Sun’s Earth orbits the Sun because the the orbit around the Sun, shown above, is like Earth’s As Earth revolves around the Sun, it spins. The motion of one object around another object another one object of The motion around is called

July 4 Earth is farthest the Sun. from Earth’s motion Earth’s without the Sun’s pull gravitational 24 hours. One rotation completes night. It is daytime on the half of Earth that faces the Sun. It is nighttime on the half of Earth that faces away from the Sun. and Earth stopped suddenly, Earth would fly off into space and Earth stopped suddenly, straight line. in a motion is called that runs through its center. the would see that Earth rotates in from west to east. One complete depends on the masses of the objects and the distance depends on the masses of the more mass has a greater pull between them. An object with less mass. Likewise, gravity’s of gravity than an object with closer together. pull is greater on objects that are a string. The string pulls on motion of an object twirled on If the string breaks, the moves it in a circle. the object and gravity is like the a straight line. The Sun’s object flies off in around the Sun in a string. Gravity keeps Earth revolving If the pull of gravity between the Sun orbit. nearly circular Earth. The strength of gravity’s pull between two objects Earth. The strength of gravity’s revolution. Sun every days. 365.24 object another is an around Earth’s Rotation Earth’s The Sun’s Gravitational Pull Gravitational Sun’s The Earth’s Orbit Earth’s almost circular path. Earth’s orbit is shown below. is shown below. orbit path. Earth’s almost circular What is the 2

In which What produces What produces

d d n i . 7 0 4 9 8 8 Key Concept Check Concept Key _ 1 Reading Check L Visual Visual Check _ near circle near circle circle a straight line Sun-Earth-Moon The System Reading Essentials E R _ 7 346 4. Identify 4. Identify

3. Identify 3. Identify c. a. b. 2. Describe shape of Earth’s orbit around around orbit shape of Earth’s correct the the Sun? (Circle answer.) direction does Earth rotate? Earth’s revolution around the around revolution Earth’s Sun? 0 0 _ 1 0 0 _ 3 9 1 CC193_001_007_RE_L1_889407.indd 2 CC193_001_007_RE_L1_889407.indd 3 1 9 3 _ 0 0 1 _ 0 0 7 _ R E

_ Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. L 1 _ 8 8 9 4 0 rotation causesapparenteast-to-westmotioninthesky. due toEarth’s west-to-eastrotation.Earth’s west-to-east and starsalsoseemtomovefromeastwestacrossthesky appear tomovefromeastwestacrossthesky. TheMoon causes theSun’s apparentmotion. is movingaroundEarth.Infact,itEarth’s rotationthat move acrosstheskyfromeasttowest.ItseemsasifSun edn setas h u-at-onSse System The Sun-Earth-Moon Reading Essentials Energy Received by a Tilted Surface Temperature andLatitude The Tilt ofEarth’s Rotation Axis Motion The Sun’s Apparent when thesurfaceismoretiltedrelativetolightbeam. on thesurfacewithinlightbeamreceiveslessenergy carries alsospreadsoutmoreoverthecard’s surface.Anarea out onthecard’s surface.Theenergythatthelightbeam away fromthebeamoflight,lightbecomesmorespread shines inacircle onthecard.Asyoutilttopof thecard energy. parts ofEarth’s surface getdifferentamountsoftheSun’s that partbecomes.BecauseEarth’s different surfaceis curved, sunlight thatreachesapartofEarth’s surface,thewarmer Earth thatfacestheSun.Sunlightcarriesenergy. Themore rotation axisisawayfromtheSun. During theotherhalfofEarth’s orbit,thenorthendof the orbit, thenorthendofrotationaxisistowardSun. rotation axisdoesnotchange.Duringone-halfofEarth’s tilted, asshowninthefigurebelow. ThetiltofEarth’s 7 . i n d d Earth rotatesfromwesttoeast.ThismakestheSun Suppose youshineaflashlightontoflatcard.Thebeam As EarthorbitstheSun,Sunshinesonhalfof

3 December March N N S S Earth Earth’s orbit Eachday, theSunappearsto Sun Earth’s rotationaxisis Rotation axis September June N N S S Sun thanotherparts? get more energy from the ofEarth’ssome parts surface away from theSun? end ofEarth’s rotation axis which monthsisthenorth across the sky? across thesky? the Sun’s apparent motion 6. Identify 5. Describe 7. Summarize Visual Check Reading Check Reading Check Between What causes

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0 1 / 2 / 4 224/2/10 13:11:09 Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. When the surface the When the light is tilted, out beam is spread area. a larger over shows line dotted The by covered the area beam before the light the surface tilted. was Surface is tilted. During the other half of Earth’s orbit, the north end of orbit, the north During the other half of Earth’s are cooler in the northern hemisphere and Temperatures You might think that summer happens when Earth is might think that summer You orbit, the north end of the During one-half of Earth’s are higher in the northern hemisphere and Temperatures Instead of being flat and vertical like the card shown flat and vertical like the card Instead of being warmer in the southern hemisphere. It is fall and winter the northern hemisphere. At the same time, spring and in summer occur in the southern hemisphere. lower in the southern hemisphere. Daylight hours last longer inlower in the southern hemisphere. the northern hemisphere. Nights last longer in the southern hemisphere. It is spring and summer in the northern hemisphere and fall and winter in the southern hemisphere. the rotation axis is away from the Sun, as shown in the left figure on the next page. Then, the northern hemisphere receives less energy from the Sun than the southern hemisphere does. on Earth’s distance from the Sun. In fact, Earth is closest to distance from the Sun. In fact, Earth is closest on Earth’s rotation axis and the Sun in January! The tilt of Earth’s to change. motion around the Sun cause the seasons Earth’s Then, the northern hemisphererotation axis is toward the Sun. than the southernreceives more energy from the Sun on the right on the next page. hemisphere does. See the figure above on the left, Earth’s surface is curved and tilted, Earth’s above on the left, becomes surface the card on the right. Earth’s somewhat like and toward move away from the equator more tilted as you Earth near the poles receive the poles. As a result, regions of is This is why Earth equator. less energy than areas near the at the poles. warmer at the equator and colder seasonal changes do not depend closest to the Sun. However, Fall and Winter in the Northern Hemisphere Winter and Fall Spring and Summer in the NorthernSpring and Summer in the Hemisphere Seasons The Tilt of Earth’s Curved Surface Curved of Earth’s Tilt The

Why When 1 km 0.62 miles ______

Is the light × 4

d d n i . 7 Surface is vertical. 0 4 9 8 8 Key Concept Check Concept Key _ 1 L Visual Check Visual _ Sun-Earth-Moon The System Reading Essentials E R 91,100,000 miles _ Math Skills Math 7 = the vertical surface? or tilted energy more spread out on spread more energy 348 10. Convert Units 10. Convert miles, multiply the distance multiply the distance miles, in km the conversion by factor. 147,000,000 km When Earth 147,000,000 km is far is the Sun, how from Earth the Sun in miles? from in the distance calculate To

9. Cause and Effect 9. Cause is Earth warmer at the equator at the poles? and colder

8. Determine Earth is 152,000,000 km from far is Earththe Sun, how the Sun in miles? from 0 0 _ 1 0 0 _ 3 9 1 CC193_001_007_RE_L1_889407.indd 4 CC193_001_007_RE_L1_889407.indd 5 1 9 3 _ 0 0 1 _ 0 0 7 _ R E

_ Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. L 1 _ 8 8 9 4 0 table onthenextpage. hemisphere. Earth’s seasonalcycleissummarizedinthe receive moresolarenergy. Thisiswinterinthenorthern and less.Asaresult,thenorthernhemispherestartsto rotation axisstillpointsawayfromtheSunbutdoessoless energy. Springtakesplaceinthenorthernhemisphere. a result,thenorthernhemisphereslowlyreceivesmoresolar rotation axisslowlypointsmoreandtowardtheSun.As edn setas h u-at-onSse System The Sun-Earth-Moon Reading Essentials December Solstice toMarch Equinox EquinoxSeptember toDecember Solstice EquinoxJune Solstice toSeptember March Equinox toJuneSolstice Solstices, Equinoxes, Cycle andtheSeasonal Fall takesplaceinthenorthernhemisphere. The northernhemispherereceiveslessandsolarenergy. the rotationaxispointsmoreandawayfromSun. energy. Thisissummerinthenorthernhemisphere. less. Thenorthernhemispherestartstoreceivelesssolar rotation axisstillpointstowardtheSunbutdoessolessand orbit, neithertoward oraway from theSun. equinox when Earth’s rotation axisisthemosttoward oraway from theSun.An Earth’s axisisspecialrelativetotheSun. changes. Thiscausestheyearlycycleofseasons. that Earth’s rotationaxisistowardorawayfromtheSun always pointsinthesamedirectionspace.Butamount 7 North end of rotation axis points away from the Sun. North endofrotation axispointstoward North theSun. endofrotation axispointsawayNorth from theSun. . i n d d As EarthtravelsaroundtheSun,Earth’s rotationaxis There arefourdayseachyearwhenthedirectionof

5 is adaywhenEarth’s rotation axisisleaningalongEarth’s N SS

Northern hemisphere Northern receives lesssunlight. receives more hemisphere Southern sunlight. The north end of the Thenorthendofthe Thenorthendofthe Thenorthendofthe A Thenorthendof solstice Southern hemisphere Southern receives lesssunlight. is aday receives more hemisphere Northern sunlight. northern hemisphere. northern summer orwinter inthe to indicate whetheritis affect Earth? the tiltofEarth’s rotation axis and equinoxes. each seasonanditssolstices organize information about two sheetsofpaperto aboundbookfromMake 11. Label 12. Conclude Visual Check Key Concept Check

September Equinox N

December Solstice December the left figure the left

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0 1 / 2 / 4 224/2/10 13:11:21 Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. March Equinox March September Equinox are equal distances from the Sun. the from equal distances are hemisphere. hemisphere. are equal distances from the Sun. from equal distances are hemisphere. hemisphere. September 22 or 23. and 12 hours of night daylight everywhere on Earth. 20 or 21. hours of night and 12 daylight everywhere on Earth. • Both ends of Earth’s rotation axis rotation • Both ends of Earth’s about 12 hours of are There • in the northern begins • Fall • in the southern begins Spring • The March equinox is on March is on March equinox March The • axis rotation • ends of Earth’s Both about 12 hours of are There • • in the northernSpring begins in the southern begins • Fall on is September equinox The • Earth’s SeasonalCycle Earth’s losest to the Sun. The The Sun. the losest to June Solstice December Solstice December As the seasons change, the Sun’s apparent path across the As the seasons change, the Sun’s hours, and summer begins. hours, number of daylight the fewest begins. and winter hours, or 21. leaning c south end is farthest away. number of daylight the greatest greatest number of daylight greatest and summer begins. hours, December 21 or 22. December leaning farthest the Sun. from south end is closest.The hours, number of daylight fewest begins. and winter • The southern hemisphere has hemisphere southern The • • The southern hemisphere has its southern hemisphere • The is on June 20 June solstice The • axis is • northThe end of Earth’s northernThe has • hemisphere • The December solstice is on solstice December • The axis is north • The of Earth’s end northern• The has its hemisphere sky also changes. In the northern hemisphere, the Sun’s path hemisphere, the Sun’s sky also changes. In the northern the the June solstice. Similarly, through the sky is highest on path is lowest on the December solstice. Sun’s Changes in the Sun’s Apparent Path Path Apparent Changes in the Sun’s the Sky Across 6

When is the d Highlight in one d n i . 7 0 4 that begin on each that begin 9

8 8 _ 1 Reading Check L Visual Check Visual _ Sun-Earth-Moon The System Reading Essentials E R _ 7 equinox in the northernequinox a different Use hemisphere. highlight the to color seasons color the seasons that begin the seasons that begin color and each on each solstice 350

14. Recall 13. Show 13. Show northern hemisphere? Sun highest in the sky in the solstice and equinox in the and equinox solstice southern hemisphere. 0 0 _ 1 0 0 _ 3 9 1 CC193_001_007_RE_L1_889407.indd 6 CC193_001_007_RE_L1_889407.indd 7 1 9 3 _ 0 0 1 _ 0 0 7 _ R E

_ Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. L 1 _ 8 8 9 4 0 edn setas h u-at-onSse System The Sun-Earth-Moon Reading Essentials 2. 1. revolution: orbit: equinox: Mini Glossary 7 . i What doyouthink n Did you changeyour mind? agree withthestatement oraDifyou disagree. lesson. Fill intheAfter column withanAifyou Reread thestatements atthebeginning ofthe d revolves.Thencompletetheotherpartsoftable. In thetwoboxesinfirstcolumn,drawEarthtoshowhowitrotatesand describes howsolsticesandequinoxesdiffer. Review thetermsandtheirdefinitionsinMiniGlossary. Write asentencethat d object Earth’s orbit, neither toward noraway from theSun

7 the path an object followsthe path asitmoves anobject around another Earth’s Revolution a day whenEarth’s rotation axisisleaningalong Earth’s Rotation the motion of one object around anotherobject the motionofoneobject

Rotation isthespinningofan object around anaxis.object What isrevolution? What isrotation? solstice: rotation axis: rotation: lesson’s resources. and access your textbook to findthis Log onto ConnectED.mcgraw-hill.com away from theSun C onnect a day whenEarth’s rotation axisisthemosttoward or a spinningmotion the line on which an object rotatesthe lineonwhichanobject ED

What doesEarth’s What doesEarth’s revolution cause? rotation cause? seasons LESSON END OF 351 224/2/10 13:11:23 4 / 2 / 1 0

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Content Vocabulary LESSON 1 Earth’s Motion Directions: Explain the differences between/among each set of terms. Then explain how the terms in each set are related.

What is the difference Terms How are the terms related? between/among the terms? Revolution, rotation

Orbit, revolution

Rotation, rotation axis, equator

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Lesson Outline LESSON 1 Earth’s Motion

A. Earth and the Sun 1. The diameter is more than 100 times greater than Earth’s diameter. a. In the Sun, atoms combine during , producing huge amounts of energy. b. Some of the Sun’s energy reaches Earth as thermal energy and . 2. is the movement of one object around another object. a. The path a revolving object follows is its . b. It takes approximately one for Earth to make one revolution around the Sun. c. Earth moves around the Sun because of the pull of between Earth and the Sun. 3. The force of gravity between two objects depends on the of the objects and how far apart they are.

4. The of an object is its spinning motion. Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. a. The line around which an object rotates is the . b. Looking at Earth from above the North Pole, Earth rotates in a(n) direction from west to east. c. Earth’s rotation makes the Sun appear to rise in the . 5. It takes one for Earth to complete one rotation. 6. Earth’s rotation axis is always in the same direction. B. Temperature and Latitude 1. The Sun shines on the part of Earth that the Sun. 2. When light shines on a tilted surface, the light is more than it would be on a surface that is not tilted. a. Because of the tilt of Earth’s axis, Earth’s surface becomes more tilted as you move away from the . b. As a result of this tilt, regions of Earth near the receive less energy than regions near the .

10 The Sun-Earth-Moon System

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Lesson Outline continued

C. Seasons 1. Earth’s change in a yearly cycle because of the tilt of its rotation axis and Earth’s around the Sun. 2. The end of Earth’s that is tilted toward the Sun receives more energy from the Sun. a. The part of Earth tilted toward the Sun experiences seasons of spring and . If the northern end of Earth’s axis leans toward the Sun, it is spring or summer in the hemisphere. b. The part of Earth tilted away from the Sun experiences seasons of autumn and . If the southern end of Earth’s axis leans toward the Sun, it is fall or winter in the hemisphere. 3. During a(n) , Earth’s rotation axis is the most toward or away from the Sun. a. Solstices occur each year. b. The June solstice is the first day of in the northern hemisphere. c. On the December solstice, the end of Earth’s rotation axis leans the most away from the Sun. 4. During its revolution, Earth’s axis does not lean toward or away from the Sun during a(n) . a. The September equinox marks the first day of in the southern hemisphere. b. The March equinox marks the first day of in the northern hemisphere. 5. The Sun’s apparent path through the sky in the northern hemisphere is near the June solstice and near the December solstice. Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc. The McGraw-Hill of a division © Glencoe/McGraw-Hill, Copyright

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