Focus on California 8th Grade Physical Science Textbook Chapter 15 Stars, Galaxies and the Universe

Chapter Stars , Galaxies , and the Universe ( Standards Preview , wse ( hinges in , a ( on understanding Ihis Student know the rule ! An and me shapes , and A and an be from ing and galaxies Ind ( huh . A ) a luv this . know galaxies nu ! and may have mum . Stud know Nu ! Ihr Sun is our ul mam an the Wav gab my and that stars max we ( and Students know how to use normal and light years as ! sun , Ind Earth Students know that are the scams or in all ( in warn and the Moon and planets by um by awn ( I is made by question and investigations As A basis lot this concept me In the other Ihm , should own and perform . I ' and 01 data dark , as ! hydrogen gas . 5340

Hillel ! Preview Sum . Galaxies , and the Universe What is the structure and composition of the universe ?

Check What You Know Suppose you shine the beam of a flashlight against the wall of a darkened room . You then measure the size of the circle made by the beam on the room . What do you think would happen to the size and brightness of the circle if you moved closer to the wall ?

Farther from the wall ?

Explain your answer . Chapter 15 5115 Focus ont The images shown here represent some of the key in this chapter . Vou can use this skill to help you understand the meaning of some key terms in this chapter . A suffix IS a letter or group of letters added to the end of a word to change its meaning and often its part of speech . For example , the suffix means a place for . The suffix added to the verb observe harms the noun observatory . An observatory is a place used to observe stars and planets through a telescope In this chapter , you will learn key terms that have the , and . Suffix Meaning I Part Key Terms 11 Apply It ! Complete the sentence below with the correct form ol the word ) A theory in is a concept that is based on evidence . when you come across an unfamiliar word . look at the suffix to help you determine its meaning . Then check the in the glossary or a dictionary .

IE 15 Vocabulary ( rad ! ua uI . Lowe wavelength ( Section ( on year parallax Russell a ' mam sequence Section ' star planetary mu dwarf Section , star , globular galaxy Section . big bang solar , Hubble law dam mane dav , Energy ran Web ( ode , 15 537 Identify Supporting Evidence textbooks often the evidence that supports a theory or hypothesis Remember that scientific evidence data and facts that have been confirmed by observation oi experiments . You can use a graphic organizer like the one below to help you understand how supporting evidence is related to a theory . When you draw a graphic organizer , include a title supporting evidence on the left the hypothesis or theory on the right This chapter the theory of how the universe was formed . distant are moving away , from us and from each , The universe formed in an instant in an enormous explosion . I Apply It ! What IS a good title tor this graphic organizer ?

What kind of information would you include in the ovals on the left ?

As you read Section , complete the graphic organizer explaining the big bang theory , , Star Stones Many years ago , people created stones to the patterns ol stars they saw the sky . In your , you learn how the names of these constellations ( the ( of the people who named them . Your Goal To complete thus you learn the star patterns of at least three the myths that gave one Its name create your own star myth Plan It ! by a Inst of ( that you have heard about Then use the star charts in Appendix on pages 656 and 657 to locate in the night sky . The that are mange from season to season and over the ( ourse of a night . So read the the carefully to learn how to use the star charts . On ( you are familiar with the charts , find a sate , unobstructed area to VIEW the stars . Make a sketch of the that you locate Choose one , and ( the myths that gave it its name Draw a new picture for the star pattern your , and ( house a name for . a story about your At the end at the chapter , you will present your and a story that Its name . Chapter 15 599 I

Section Tech 61 Design and Students know that stars are the source of light for all bright objects in outer spate and that the Moon and planets shine by ed sunlight not by their own light What are the regions al the spectrum ?

What are telescopes and how do they work ?

Where are most large telescopes located ?

Key Terms radiation I tIl light wavelength ' I ( I retracting telescope convex lens I I radio telescope observatory Galileo 590 Telescopes Standards How Does Distance Affect an Image ?

Hold a plastic hand lens about an away from your eye and about an away from a printed letter on a page . Move the lens slowly back and until the letter is in clear torus . Keep the letter about from the lens as you move your eye bark to about 20 from the lens Then , keeping the distance between your eye and the lens constant . slowly move the object away from the lens . Think Over Observing What did the letter look like through the lens in Step compared with how it looked without the lens ?

How did the image ( hange in Step ?

Ancient up in at the many points light in the night sky . But they could ' my details with their eyes alone . was not until the til the in that people could observe in the sky more . Recall that telescope is a device that makes distant ( to ho , The ' now had a tool that allowed them to see many in for the tint time . Although Galileo was not the tirst person to use a telescope . made it he his to the sky . his . saw things that no out had even dreamed all lie was the tirst to see sunspots . the four large moons of . Galileo could see fine details . such as the munn . which can not be clearly by the , Galileo . astronomers have built ever larger and more powerful ' have lI ' up at whole universe of wonders that would have amazed even Galileo .

Electromagnetic Radiation ' understand how telescopes work , it useful to understand the nature of electromagnetic radiation . Light is a form of electromagnetic . or energy that can travel through , um . aim space in the form of waves . Stars produce such radiation ing the process of nuclear fusion . You can see stars when the light that they produce reaches your eyes . Go Forms of Radiation All the colors that you can see are visible light . Visible light is just one of many types of electromagnetic radiation . Matty objects give off radiation that you ca see . For example . in addition to their reddish light , the glowing coils of an electric heater give oft infrared radiation , which you feel as heat . Radio transmitters produce radio waves that carry signals to radios and televisions . Objects in space give oil all types radiation . the Electromagnetic Spectrum As shown in , the distance between the crest of one wave and the crest of the next wave is called a wavelength . Visible light has very short wavelengths . less than one millionth of a meter . Some magnetic waves have even shorter wavelengths . Other waves have much longer wavelengths , even several meters long . if you shine white light through a prism . the light spreads out to make a range of colors with different wavelengths , called a spectrum . The spectrum of visible light is made of the colors red , orange , yellow . green , blue . indigo , and violet . 55 The electromagnetic spectrum includes the entire range The Electromagnetic Spectrum of radio waves . infrared radiation . visible light . ultraviolet 77 ! Um 48 Ye ?

wavelength gamma rays . Interpreting Diagrams Are infrared waves longer or shorter , What is electromagnetic radiation ?

than ultraviolet waves ?

Radio Infrared Ultraviolet Gamma Red Orange Yellow Green Blue Indigo Violet Gunter 15 591 Types of Telescopes On a clear night , your eyes can see at most a few thousand stars . But with at telescope , you can see many millions . Why ?

The light from stars spreads out as it moves through space . and your eyes are too small to gather much light . Telescopes are instruments that collect and focus light and other forms of electromagnetic radiation . Telescopes make distant objects appear linger and brighter . A telescope that uses lenses or mirrors to collect and focus visible light is called an optical telescope . The two major types of optical telescopes are refracting telescopes and reflecting telescopes . Modern is based on the detection of forms of electromagnetic radiation besides visible light . Non scopes and focus different types of electromagnetic tion , just as optical telescopes collect visible light . Telescopes A telescope uses convex lenses to gather and focus light . A convex lens is piece of trans parent glass . curved so that the middle is thicker than the edges . Figure shows a simple telescope . This telescope has two convex lenses . one at each end of a long tube . Light enters the telescope through the large objective lens at the top . The objective lens focuses the light at a certain ' front ' the lens . This is the focal length of the lens . The larger ' the objective lens . the more light the telescope can collect . This A ( waning um , easier tor astronomers to see faint . am , A The smaller lens at the lower end of a telescope IS 35 ' Minot in called the eyepiece . The eyepiece the image produced ' the objective . Telescope Reflecting Telescope Focal length of objective lens ' Eyepiece Light rays Eyepiece objective lens Flat mirror Curved mirror 5920

Home Four Views of the Crab Nebula Different types of telescopes collect electromagnetic radiation at different wavelengths Astronomers are able to learn a great deal about the Crab Nebula by examining these different images . The images are shown at different ales , Reflecting Telescopes 1668 . Isaac built the first telescope . A reflecting telescope uses a ( to collect and focus light . Like the ' lens in telescope . the mirror in reflecting telescope focuses a large amount onto a small area . larger the mirror . the more light the can collect . The largest optical telescopes today are all telescopes . Radio Telescopes Devices used to detect radio waves from objects in space are called radio telescopes . Most radio scopes have curved . reflecting to 305 meters in . These surfaces radio waves the way the mirror in at reflecting telescope focuses light waives . The cou the faint radio waves space onto small like those on radios . As with optical telescopes , the larger zi radio telescope is . the more radio ' it can collect . other Telescopes Some telescopes detect infrared tion , which has longer wavelengths than visible light hut shorter wavelengths than radio waves . are aim detect the shortest , and rays . Who built the first reflecting telescope ?

This Ac ' ity Locating Radio Waves You can use an umbrella to focus radio waves . Line the inside of an open umbrella with aluminum foil . Turn on a small radio and tune it to a station . Move the radio up and down along the umbrella handle , Find the position where the station is clearest , Radio waves oft the foil locus at this point . Tape the radio to the handle . Hold the umbrella at different angles . At which angle is the station the clearest ?

Inferring In which direction do you think the radio station transmitter is located ?

Explain . dilator 15 593 Observatories in general , an is a building that contains one or more telescopes . But some observatories are located in space . Many large observatories are located on or in space . Why ?

Earth atmosphere makes objects in space look blurry . The sky on some is clearer than at sea level and is not brightened much by city lights . Unlike optical telescopes , radio telescopes need to be on mountaintops because many radio waves can pass through the atmosphere . One of the best observatory sites on Earth is on the of Mauna Kea . a dormant in Hawaii . Mauna Ken is so tall that it is above 40 percent of Earth . Tech Design in History Development of Modern Telescopes During the last century . astronomers have built larger telescopes . which can collect more visible light and other types of radiation . Today astronomers use tools that could not have been imagined 100 years ago . 1931 Beginning of Radio Astronomy , an American engineer . was trying to find the source of static that was Interfering with radio communications . Using a large antenna . he discovered that the static was radio waves given off by objects in space . accidental discovery led to the beginning of radio astronomy . 5940

Advanced Telescopes , di are equipped with systems that improve the ity of images . Optical on Earth with ( ig , sky that rival ul optical bum ! in ( Some new are equipped with that correct for such as and in air or mirror . uw to in I Wri il ' I Science . shape of mirror is tally adjusted of times each second in to i Research one of these . Elam as gnome la telescope . Create a publicity brochure In which you describe the features . when and where it was built , and what types at 1930 Very Large Array research it Is used for . The Very large May is a . set of 17 radio telescopes in New . The telescopes ( an be moved ( lose together or far apart In are linked . spin 50 ) 35 Space Telescope they were one giant radio Space Telescope The , telescope 25 kilometers Th Hubble Spare . I , DOWN . in diameter . in Mi that surveys ' the sky in the infrared Al I . range ! the spectrum . sharp . 980 2000 2020 Chapter 15 595

Repairing Hubble Astronauts have repaired and upgraded the Hubble Space Telescope on several occasions . Section Vocabulary Skill What do you sec in the word ! What part speech does it indicate ?

Assessment Telescopes in Space , gamma rays . and most ultraviolet radiation are blocked by . To detect these wavelengths , astronomers have placed telescopes in space . Some space telescope are designed to detect visible light or tion . since atmosphere also interferes with the transmission of these forms of radiation . The Hubble Space Telescope is a scope with a mirror meters in diameter . Because the Hubble telescope orbits Earth above the sphere . it can produce vety detailed images in visible light . It also collects ultraviolet and infrared tion . The spectacular Hubble telescope have changed how astronomers view the universe . The hottest objects in space give oft . The Chandra Observatory produces images in the ray tion of the spectrum . Chandra images ate much more detailed than those of earlier telescopes . The most recent addition to lineup ol telescopes in space is the Spitzer Space Telescope . in 2003 , the Spitzer telescope produces images in the infrared portion of the spectrum . writing . Summarizing How does the radiation ?

Why are many large optical telescopes located on ?

Applying Concepts Would it make to Reviewing Key Concepts . Sequencing list the main types ot waves . from longest wavelength to shortest . Applying Concepts Why are images from the Hubble Space Telescope clearer than from ) Faith ?

Identifying What are the two maior types ol optical telescope ?

Explaining How does it retracting telescope . work ! i Comparing and Contrasting Use Figure to explain the maior between reflecting and telescopes . 99 place an or ray telescope on mountaintop ?

why or why not . in Science List the sequence needed to build and operate a reflecting telescope for a be included in a model telescope kit . Be sure to describe the shape and position of each of the lenses or minors . You may include drawings .

Technology Lab or Design Objective lens ( tape to the ' be ) Design and Build Paper towel a Telescope . tubes . Problem . Design and build a better telescope . Vour Can you design and build a telescope ?

mall ! larger than your first model from the same Skins Focus observing distance . should have markings on the inner tube to enable you to mi ' i the telescope for a given observing distance . Draw a design for your new telescope . List the . materials need . Obtain your teacher ' approval . Then build your new model . diameters several plastic objective lenses several plastic eyepiece lenses I meter stick Analyze and conclude foam holder for eyepiece transparent tape . Inferring Why do you need two tubes ?

Procedure . Observing if you focus on a nearby object and then focus on something farther away , do you have to move the tubes together or apart ?

Evaluating the Design How could you improve on the design of your new scope ?

What effects would different lenses . Insert the small eyepiece lens into the or tubes have on in performance ?

ing in the foam holder . Fit one of the paper towel tubes inside the other . Make sure you can move the tubes but that they will not slide on their own . Place the large objective lens flat against the end of the outer tube . Tape the lens in place , Redesigning Describe the most important . Place the foam eyepiece lens holder into the ram , in designing you , ule inner tube at the end of the telescope site to the objective lens . communicate . Tape a meter stick to the wall . Look through the eyepiece at the meter stick from away . Slide the tubes in and out to focus your telescope so that you can clearly read the numbers on the meter stick . Draw your telescope . On the drawing , mark the tube position that allows you to read the numbers most clearly . Use your telescope to look at other objects at different distances , both in your classroom and through the window . For each object you view , draw your telescope , marking the tube position at which you see the object most clearly . CAUTION Do not look at the sun . You will damage your eyes Write a product brochure for your new scope , Be sure to describe in detail why your new telescope is better than the first telescope .

( Standards Focus 09 ' Students that the Sun is one of many stars In the Milky way galaxy and that stars may dif ler In size , temperature . and ( Students know how to use and light years as measures of distance between the Sun , stars and Earth . How are stars ! UV ! distances to the stars ?

What is an diagram and how do astronomers use it ?

Key Terms I constellation I I apparent brightness I absolute brightness I I parallax I diagram I main Illustration , of Orion Characteristics of Stars Standards How Does Your Thumb Move ?

I . Stand lacing a wall , at least an arm length away . Stretch your arm out with your thumb up and your curled . Close your right eye and look at your thumb with your left eye . Line your thumb up with something on the wall . Now close yr ur left eye and open your right eye . How does your thumb appear to move along the wall ?

Bring your thumb closer to your eye . about half the distance as before . Repeat Steps and . Think It Over Observing How does your thumb appear to move in Step compared to Step ?

How are these observations related to how far away your thumb is at each step ?

How could you use this method to estimate distances ?

When ancient around the world looked up at the night sky , they that groups til stars formed pictures of people or animals . Today , we call these imaginary stars constellations . cultures gave names to the constellations . For example . a largo constellation in the winter sky is named Orion , the Hunter . alter a Greek myth . In this . Orion is seen with a sword in his belt and an arm . On the other hand , the ancient thought that the stars in Orion fanned the line of a sheep . and China . this group of stars was called probably because of the three bright stars in Orion belt . Astronomers use the of the tions lo locate in the night sky . But although the stars in a constellation look as if they are close to one , they arc just happen to lie in the same part of the sky as seen from Earth .

Classifying Stars sun . all hup , ut ' lug . Thu ) up ul . energy the ( of ( tu rung ) stun brightly . In their physical LlI . include color , composition , and brightness . Color and temperature It mu at the night , mu ' iu the ul . the star in . star in ) hot nu uth , us I ' watch up . you can we glow . wire light arc tut . the LU ( ul about 200 . Will ! Ul about ( IL ! alC . un appears yellow . he mu in the sky . with . I ( Sile When you lU ( at ' in the ' tu he , Il thu ' stats mu ! Ir . dI Luge than the . stats or uur sun is , it enough to the as out . nun about 20 in ' star ( Sun ) White dwarf Giant star . For ull Visit ( tum Web ( Star Site Stats vary . stars are typically 10 times than the sun and more than ( the me a white ( a 420 million How many ! I than rim sun , has of !

mutt spectrum of Four Stars Astronomers can line to identify the chemical elements in a star . Each element produces a characteristic pattern of spectral lines . Inferring The lines on the spectrum below are from three different stars . Each of these star spectrum is made up of an overlap of spectrum from the individual elements shown in Figure in star which elements can you detect ?

which can you find in star ?

In star ?

6000 Chemical Composition Stars vary in their chemical position . The chemical composition of most stars is about 73 percent hydrogen . 25 percent helium , and percent other ments by mass . This is similar to the composition of the sun . Astronomers use to determine the elements found in stars . A spectrograph ( graf is a device that breaks light into colors and produces an image of the resulting spectrum . Most large telescopes have The gases in a star atmosphere absorb some wavelengths of light produced within the star . When the star light is seen through a spectrograph . each absorbed wavelength is shown as a dark line on a spectrum Each chemical element absorbs light at particular wavelengths . Just as each person has a unique set of , each element has a unique set of lines for given temperature . shows the spectral lines of four elements . By comparing a spectrum with the of known elements . astronomers can infer how much of each element is found in the star . What Is a spectrograph ?

Brightness of Stars Stars also differ in brightness . the amount of light they give off . The brightness of I star depends upon both its sin and temperature . Recall that the is the visible surface of a star . Betelgeuse is fairly cool . so a square meter of its photosphere does give off much light compared to hotter stars . But Betelgeuse is very large . so it shines brightly . on the other hand . is very hot . so each square meter of photosphere gives oft a lot of light . Even though it is smaller than Betelgeuse . shines more brightly .

HUW bright a star looks on both ( Earth and how bright star truly is . ul Try This two it tur . of ii slur ( rind absolute . Apparent Brightness A st ir apparent brightness is in as , min , can lIlL easily using . ever . murli light star aft inst from the star . lust as a flashlight looks brighter the it is to you , a star it is to Earth . this still looks wry ' his ( not mean that the su ii gives off more light than all other stars . The sun so bright simply it is an . In ) sun is ( cit only il ' Absolute Brightness A absolute brightness . or is the brightness the would have if it were at st distance from . Finding ir ' is complex than ils apparent mus ! tho ) and its distance from . Thu can than the absolute . have that the iii star can vary . Thu ' are more than billion brighter than the stars ! ad . What is a star ?

Star Bright You can compare absolute and apparent brightness . Dim the lights . Put two equally bright flashlights next to each other on a table . Turn them on . Look at the flashlights the other side of the room . Think of the as two stars . Then compare them in terms of absolute and apparent brightness . Move one of the lights closer to you and repeat Step . Replace one of the flashlights with a brighter one . Repeat Steps and with the unequally bright Making Models How could you plate the flashlights in Step so that they have the same apparent Try it . Absolute Brightness The in this photo all give off about same amount 01 light , and so have about the same absolute brightness . Applying Why do the closer appear brighter than the more distant lights ?

15 am noun Parallax at the Movies You and your friend are sitting behind a woman with a large hat . Applying Concepts Why is your view of the screen different from your view ?

6010 Measuring Distances to Stars imagine that you could travel to the stars at the speed of light . To travel from Earth to the sun would take about . not very much time for such a long trip . The next nearest star . is much away . A trip to ( at the spud oflight would ! The Distances on Earth are in . distances to the am so that are not very practical units . Astronomers typically use unit called the to measure distances between the stars . In space . light travel at a speed of about kilometers per second . A is the distance that light travels in one year . about million million kilometers . Now that the in a unit of . not time . To help you understand , an . you at meters per hour , it would take you I hour to go to mall IU kilometers away . You could say that the mall away . Parallax Standing on Earth looking up at the sky . it seem as it is no way to tell how far the stains arc . have found to ' those . Astronomers often use parallax to measure distances to nearby stars . Parallax is the apparent change in position of an object when you look at it from different places . For example , imagine that you and a have gone to movie . A woman with a large hat sits down in front of you . as shown in Figure . Because you and your friend are ting in places . the woman hat blocks parts . an sitting on her left . the woman hat appears to by in from of the large dinosaur . But to your friend on the , to in front bird . Have the woman and hat hail ?

No . But you are looking , from places . she irs to have moved . This you look from two positivity is parallax ' ID Slay as seen lrom Earth January Earth in January Parallax in Astronomy arc able to the parallax of nearby stars to determine their . As ) lI Ill , as at at nearby star is un one side sun . Then they at the star again six months letter . when Earth is on the opposite side of the sun . measure how much the star appears to move of stars that are much farther . They can then use this measurement In calculate the distance to the i ) star app to . farther it is . can use parallax In distances up to few ' ill . The parallax any star that is away is . to measure accurately with existing technology . How is parallax useful In astronomy ! i A Sky as seen from Earth in July FIGURE Parallax of The apparent movement 91 a star when seen from a different position is called parallax , Astronomers use parallax to the distance to nearby stars . Note that the diagram is not to Male Interpreting Diagrams Why da nearby appear to position between January and July ?

15 so COCO I ' A or Beta 10 The Diagram About 100 ago , two scientists working independently made the same discovery . Both EYE HURT sprung ) in Denmark and Henry Norris Russell in the United States made graphs to out if the temperature and the absolute brightness of stars are related . They plotted the surface temperatures of stars on the and their absolute brightness on the . The points formed a pattern . The graph they made is still used by astronomers today . It is called the . or ! diagram . Diagram ( ti The diagram shows the relationship between the surface temperature and absolute brightness of stars . Interpreting star has I hotter or Aldebaran ?

( Reviewing Key Concepts Astronomers use diagrams to classify stars and to understand how stars change over time . min sec in of the ' in mini area ( tilled the main sequence . than ) of . including mu , arc ( slurs . the main . an ) hut stars are located at the left at and cooler dish stars arc ( at the right of diagram . stair arc near the top iii an diagram , the mars are at the bottom , int and supergiant stars are very . can by found near the trip ' and right iii . arc hot . but not ci bright . so they at or ' at the di . naming , i What is the main sequence ?

section Assessment Betelgeuse FIGURE 11 Orion includes the red . the blue supergiant , and many other and giant stars . Vocabulary Skill ' du sci in What part dun it ?

I we Suiting ) a . Listing ' In . Comparing and Contrasting What Ihr between brightness and . Applying Concepts A and . but ' A ( ax . Summarizing What two ' i tics at . in an ?

Identifying ' um in ' us An . Classifying Th ' ul , I and an ) than . type or ?

In the ' Activity Star . Measuring a parallax ! from and . i ' would ?

Observing Orion With adult family members , go outside on a clear . dark night . Determine which way is south . Using the star charts in Appendix , look for the constellation Orion , which is visible in the evening during winter and spring . Find the stars Betelgeuse and in Orion and explain to your family why they are different colors . cos

How Far Is That Star ?

Problem How can parallax be used to determine distances ?

Skills Focus inferring , calculating . predicting Materials masking tape paper clips pen black and red pencils metric ruler paper I meter stick calculator lamp without a shade , with light bulb copier paper box ( without the lid ) flat rectangular table . about I wide Procedure PART Telescope Model . Place the lamp on a table in the middle of the classroom . Carefully use the tip of the pen to make a small hole in the middle of one end of the box . The box represents a telescope . position of box 6060 . At the front of the classroom , place the box on a flat table so the hole points toward the lamp . Line the left side of the box up with the left edge of the table . Put a small piece of tape on the table below the hole . Use the pen to make a mark on the tape directly below the hole . The mark resents the position of the telescope when Earth is on one side of its orbit . Start . Label a sheet of paper Star I and place it inside the box as shown in the drawing . Hold the paper in place with two paper clips . The paper represents the film in a telescope . Darken the room . Turn on the light to sent the star . with the red pencil . mark the paper where you see a dot of light . Label this dot A . Dot A represents the image of the star on the film . Move the box so the right edge of the box lines up with the right edge of the table . Repeat Step . The mark on the tape the position of the telescope six months later , when Earth is on the other side of its orbit . Earth six months later Earth on one side of orbit

, Focal Length . Diameter Calculated Calculated Actual Distance to Distance to Distance Star ( in in ) Star ( in ) to Star ( in ) Repeat Step using a black pencil to marl the second dot . Dot represents the image of the star as seen months later from the other side of Earth orbit . Remove the paper . Before you continue . copy the data table into your notebook . Measure and record the distance in meters between dots A and . This distance represents the parallax shift for Star . Measure and record the distance from the hole in the box to the lamp . This distance represents the actual distance to the star . Measure and record the distance from the hole ( lens ) to the back of the box in meters This distance represents the local length of your telescope . 14 . Measure and record the distance in meters between the marks on the two pieces of masking tape . This distance represents the diameter of Earth orbit . and 15 . Move the lamp away from the half the distance to the back of the room . The bulb now represents Star . Predict what you thinl will happen to the light images on your paper . Repeat Steps with a new sheet of paper to find the parallax shift for Star . Move the lamp to the back of the classroom . The bulb now represents Star . Repeat Steps with a new sheet ot paper to find the parallax shift for Star . Analyze and Conclude . Inferring What caused the apparent change in position of the dots of light for each star ?

Explain . Calculating Use the following formula to calculate the distance from the telescope to Star Diameter Focal length Parallax shift . Calculating Divide your result from Question by to get the distance to the light bulb in meters . Repeat Questions and for Stars and . Predicting was your prediction in Step 15 correct ?

Why or why not ?

Interpreting Data How did your calculation for Star compare with the actual distance ?

What could you do to improve your results ?

Communicating Write paragraph that explains how parallax shift varies with . Relate star parallax shift to its distance from Earth . Design an Experiment What would happen if you kept moving the lamp away lrom the box ?

Is there a distance at which you can no longer find the distance to the star ?

Design an experiment to find out . 15 607 00 Standards Focus ! Students knowthat the Sun is one of many stars in the Milky way galaxy and that stars may ler in size , temperature , and ( Students know that stars are the source of light for all bright objects in outer snare and that the Moon and planets shine by ed sunlight , not by their own light now does a star term ?

What determines how long a star will What happens to a star when It runs out ol fuel ?

Key Terms I nebula I protostar I planetary nebula I white dwarf I supernova ' neutron star I pulsar I hole Lives of Stars Standards What Determines How Long Stars Live ?

This graph shows how the mass of a star related to its how long the star lives before it runs out at fuel . How long does a star with times the mass of the sun live ?

How long does a star with times the mass of the sun live ?

Think It Over Drawing Conclusions the general relationship between a star mass and its lifetime . billions of years ) VI Mass of ( tampered to sun ) Imagine that you want to study how people age . You wish you Cuuld watch a few people for 50 . but your is ( next week ! You lo study a lot of people liar at short lime , and . the people into age groups . You may come up with groups like . and . You do have time In see single person go through all these stages . but you know the . have a similar in trying to how slurs ago . Thu ) ca watch at single star for billions ol . they study stairs and other in space . Over time . astronomers have nut that those different stages in the lives of stars . Three generations

The Lives of Stars du nut last lim ' slur ix burn . goes through its lift ( and ' diva . Of course . star arr really , The words burn , llI . and die are just helpful ' A Star Is Born their lives in part ut A nebula is ( and dual out in un . A him . on the ( up til ut ' itt it ' I . the purl . gravity pulls gas and dim . As the ( loud ' and dim coir tracts . it Hark to heat up A cloud of gait ( with to form star is 21 protostar . in Greek , 50 ' is the ( ol Matt . has , A star is born when the contracting gas and dust from a nebula become so dense and hot that nuclear fusion starts . that ( is the ( by which atomic nuclei ) ing ( rut . In the sun . for ( In . Lifetimes of Stars ( star lives on its mass . You might think that with more would List longer than stars with leu . But the reverse is true . You can think ' cur ill but it alw has at small engine that hut gen . large tun has A . but it also ha Luger ' lIlL that gnu rapidly . So the car can lI an tank ut ' than the car . stars use up their more than . have much longer lives . that than the sun use . and can live tut up to 200 billion . mass stars like the sun live for about It ) think the sun is old . it is its . Shir limbs than the suit times . A star is times as as the sun may live about ten million . may a long , time , it ( Itll IR ) sun . Find nu How long will a star that is the mass ot the sun live ?

FIGURE 12 Young Stars New stats ave in the nebula on top . The bottom photo shows a protostar in the Orion Nebula , Applying ( How do some of the gas and dust II ! a nebula is ?

a Video Held Tri . Stars . Galaxies . and the Universe 15 cos . IQ Hill Low ass or or star ) Foam 13 The Lives of Stars A star lite history depends on in mass . A star uses up its slowly and eventually be ( omes a white . A star uses up its fuel quI ( After its supergiant stage . it will explode as a supernova . producing a neutron star or a black hole . Interpreting Diagrams What type produces a planetary nebula ?

Predicting Find Algal , Sirius and Polaris in Figure 10 , the diagram . What type of star is each of these now ?

Predict what the next stage in each star lite will be . 610 Deaths of Stars its lung a star ( through gen intu helium in its core . thi star slay on the main . when the star to run out core and in sequence . un its . the red or . At this stage , begins to time in the . The fusion of such as carbon and . moat ' stars , ax ( 215 iron ' hy nuclear ' All stars red giant or . As shown in Figure , red giants and evolve in very difterent ways . After a star runs out of fuel . it becomes a white dwarf , a neutron star . or a black hole . Planetary Nebulas stars and stars like the sun take billions of use up their nuclear fuel . to run out mi fuel , expand . and they giants . Eventually . the ( ruler parts grow larger lill and drift out into spam . they form cloud of gas called a planetary nebula . Many . such as Nebula on 631 , are in . Reading . I what a planetary nebula ?

Planetary nebula . star ' Supernova White Dwarfs A core at am ! is lull behind ' nebula . his am gradually cools and becomes white dwarf . White are only the we ul . but they ' as much as sun . Since I as sun but only one the volume . iI is one million tunes as dame as the un . A spoonful of while dwarf has as much luau as . nu plum in white . they lo for of years leftover energy . Supernovas The life cle of a high star is quite from the lift ' ur . When mus out 01 . it can . Within hours . he slur millions ul limes . Thu is called supernova . A , produces enough Lu that art than irun . such as and gold . Along with when elements that form in . from fusion . art flung into space by This may part 411 ' nth . ula . The nebula i In form il new , partly star . sun began as a nebula lhat a than exploded billions of ' ago . This means that Earth . and even your body . arc inside . hole The uf Stars activity Visit ( um Code ( 15 an

FIGURE Pulsars emu steady . beaten , appears to pulse when is beam swoops sums Earth 612 Neutron Stars Am , at the ' from ' may farm . 411 ' and than . the sun but he ' about 13 , the at A at ) In Ivor . Bull , an in ' In guy . of ix , the lu ' tum on and than all in , might . emu ( in ' i , Ihr ' who I ' Pulsars Arr pulsars , for pulsating shown in do nul ull ol . beams . mules , the , warn In , um ul that , I . Thus , arc AM ?

In ' pulsar nine ' win ul Linn ) What is pulsar ?

Rotation am Black Holes The most having more than times the of the black holes when they die . A hole is ill ! object with gravity so strung that , not even light , can escape . a ' star dies in supernova sion . more than times the ofthe sun may be left . The gravity of this mass is so strung that the gas is . packing gas into it smaller and space . The gas becomes so densely packed that its intense gravity will not light to escape . The star ) No light , radio . or any other form of can 55 out black hole . so it is not possible to ' i black mad . Th hole directly . But can detect black holes indirectly . me ' For . gas a black is SH strongly that it , faster faster black . Friction heats hole pulling ' the gas up . can detect coming tron ) hot ' The . I an LI 10 15 . iin at us hula Conan is near a black hole . can calculate the mass at the , go a 5134 hart . from the effect of its gravity on the star . Scientists directly , how do astronomers find have dozens of black holes with the . They have also detected huge black holes that arc millions or billions of times the sun mass . section Assessment i til til Reading Skill Identify Supporting a . Comparing and Contrasting is Evidence the text under heading Black white ?

Haw is it different from a Holes . Create it showing neutron star ?

evidence the hypothesis that ) Why some mil . Il whit and Reviewing Key concepts neutron slats ur black holes ?

I I . What Will happen to the sun I ' when it runs nut fuel ! Explaining How does star lrom ii . A ' ting in Science I ?

Contrasting 12 i , i description HINT ' of one of the stages in motif of a star . such ' as a nebula . red giant , supernova , or white . Applying A star is massive on haw formed as the sun . Will its . in he or the as that til the sun ?

Explain .

00 Star Standards Focus BA a Students galaxies are clusters of billions of stars and may have different shapes I ) Students know that Sun is one of many Stars in the Milky Way galaxy and that stars may ler in size , temperature . and color . What is a star system ?

What are the major types of galaxies ?

How do astronomers the scale ol the universe ?

Key binary star I ( open ( luster globular cluster I galaxy spiral galaxy I galaxy I galaxy I quasar I ( notation Systems and Galaxies War ' Why Does the Milky Way Look Hazy ?

Using a pencil , carefully poke at least 20 holes close together in a sheet of white paper . Tape the paper to a chalkboard or wall . Go to the other side of the room and look at the paper . From the lar side of the room , what do the dots look like Can you see individual dots ?

Think Over Making Models How is looking at the paper from the far side ol the room like trying to see many very distant stars that are close together ?

How does your model compare to the photograph of the Milky Way below ?

up On ( Il ' iii ( can light ( the ski . This is Way . It looks as if is . ally . is inside Milky ! Milky ii milky OI Earth the slim tim lor your lu sec . The in the are of dust that black light the stars behind them .

16 Binary Algal an star system of a star and a dim . the dim star passes from of the one , Algal appears dimmer When dues Algal appear ?

Bright star Star Systems and Clusters Our ( Ills the Most stars are members of groups of two or more stars , called star cyst . If on plane ! in one star . at you ' sun would . Multiple Star Systems Slut lull ' called cure on binary stars . I ' he In , with three ' arc ' slur . nearby purl two ' A ( turm star ! arc ( ix part ur um ' In mu . unc slut in at star is much and ( anl ! binary even one at the can be seen from . can IN dun In lent Ivy ring thu the dim ' Mound bright ' dim ' In and . pair dancers who are twirling each ( that lI , Binaries 15 nut the clue that dun . in nun in ' i and ' it . binary sun would . in one star it ' light Ix eclipsing binary . In ' the star Algal i actually an ing , Dim companion nut Flaunt 17 Invisible Partners If you saw someone dancing but couldn see a partner , you tould infer that the partner wasthere by the damn ! you ( ould see Astronomers use a method stars star systems Chapter 15 615

FIGURE 18 Stav ( The stars in a ( above ) me mi about the same age and the same distance from Earth The ( mart ) Seven is an open ( luster 616 Planets Around Other Stars In 1995 . di . planet another ' star . A usul in studying binary stars , I that ' and hum us . They knew that the didnlt ' to be a stat . inc ) that it he . have than Ii ) I . limu . ut ' least the A small be ' it ( on the it . Could lite on in ?

Sonic it , tum . using ' to . tch that could not mme might he ' i nut I ( I . Star Clusters stun tu . All at the stare in A formed from the same nebula ume time and are about the same from . are two mum lI up ( ten and . clu tex Open clusters have . and ( nu ' mam ( much and Just . In tram . globular clusters are , at older stars . are round and ( with than million slurs . Hid ) What is a globular cluster ?

Galaxies nul pact . you . In , 11 Lu . In . 011 an , 11111 Galaxies in Space A galaxy 11 , 11111 . 111111 , and Ivy . In center . I here in ' I and the , 11111111 ' in . pic . uur , is purl ul i the ! he I ! the sli . 41 ! Aw ' Quasars ( I ! at three ! 1111111111 ( like . 111 1111 ' 11111111 uN , be . 111 ?

hula haw ' grunt . I ' I . hole , 111 up and . Andromeda Galaxy The 15 the to our own Way . hundreds of stars . Fur nu Visit nu . Web Code . 617 Chapter 15 Galaxy Irregular Galaxy Flaunt 20 Types of Galaxies There are three of galaxies . elliptical . and irregular 613 Types of Galaxies In , and . Astronomers classify galaxies into three main spiral . elliptical , and irregular . I Ell examples of each . Spiral Galaxies lo a in the and that spiral . lilac ' Such galaxies are spiral galaxies . spiral ' null and . new in in the spiral arms . few . galaxies . ies , iI gas that paw . Spiral ban in ' Elliptical Galaxies Not all spiral Elliptical galaxies . lulls , ur null , ut gas and . la gas or , nu . only old . in aim . Irregular Galaxies galaxies do not have regular . are known an irregular galaxies . Irregular ) than ul . They generally , and iota oi gas and In new . The large ( is All , galaxy ( I , nur . mu in ' gul ar are class In . pull ul . In spiral galaxies . when are most new stars located ?

Side View Sun About The Milky Way Our solar system is located in it spiral galaxy called the Way . Figure . the of the Milk ) ty ( on your point . From the side . Milky ' would look like i . disk with large in ' But trip lIt ' Milky Way have at , shape . You see this spiral shape at Milky Wily from Earth ( our solar is inside the galaxy Ill one at the spiral . The solar lAll ( ahout 233 million years to orbit the galactic center . Way is spiral . suggests that is te . you the . til night luring , the summer . you arr looking ( galaxy . til galaxy is about a ' but by clouds and gas . lI ( can . using . and waves . and . How far away is the center ol the galaxy ! FIGURE 21 oi the Milky Way From the side . the Milky Way appears to be a narrow disk with a bulge in the middle . The spiral is only lrom above or below galaxy Interpreting Diagrams Where in the galaxy is the sun located ?

A Spiral Galaxy You ( an make a model of nut galaxy . Using pipe cleaners , make a pinwheel with two spirals . View the spirals along the surface of the table . Sketch what you see . Next , view the spirals from above the table and sketch them . Observing The sun is inside a spiral galaxy . From Earth position on the flat surface . is it possible to get a good view of stars in the spiral arms ?

Why or why not ?

Gupta 15 619 Girl Height I Scientific Notation The bright star IS about from Earth To express this number in first insert a point in the original number so that you have a number between one and ten In this case , the number Is . To determine the of 10 , count the number of places that the decimal point moved Here the decimal point moved three plates 123 105 Problem The sun takes about years to revolve once around the center at the galaxy . Express this length ot time in 620 The Scale of the Universe ' I ) in it . The is . As far ' hey study such . that iii ' may also ( i uI ' lint , with the Since the numbers astronomers use are often very large or very small . they use scientific notation to sizes rind distances in the universe . Scientific Notation notation , ten in will . it text I iii . I ' and lit and ( i ' I Ix It ) ix ) il , tI , there are digit alter the tint digit . in is It The of the ' in the ' in the ' that mu art , verse . Rater Figure 31 as you take your ' trip at the with girl through . She ix ' the right turd thi mil by ( or ) You nun . luau to the ' ul . 10 . As you ) tutti left in ' the scale ' the ) Ui )

i i Cat Eye Nebula Andromeda Galaxy Virgo Diameter ii 10 in ' ii 10 Diameter 10 Flaunt 22 Scientific Notation use ( helo the was ! i iii . i UI ix ( i ' many Iii ' iii ' than Faith ( in ' HI ( in ili , The ii ! a verse is about Him ZhI ' solar . iii ' ix about . How large is the observable universe ?

Section Assessment Vocabulary Ski ( i Ili ( Va ( I ( I , i ! IM mu ' Lil do ?

i i ' i ' i ' iii ) ii ' In ' I . Explaining is ?

HINT iii ?

i Reviewing Key Concepts MINT a Defining is ' INT i ' COn ( Ep ( il ' ii . IX term i ' i Hui wii ' your AI . HINT a . Listing ' ii ' Chapter 15 621 HINT Practice . Notation The star has a diameter is 427 years Write ea ( oi HINT these in notation .

000 xi students the rule at gravity in hunting and the shapes oi planets , stars . and the solar system Students know galaxies are clusters of billions of stars and tray have shapes What is the big bang theory ?

How did the solar system ( Wnat do about the at the Key Terms I Hubble I solar I dark matter ' dark energy The Expanding Universe , Standards How Does the Universe Expand ?

Use a marker to put 10 dots on an empty balloon The dots represent galaxies . Blow up the balloon . What happens to the distances between galaxies that are ( lose together ?

Galaxies that are lar apart Think Over It the universe is expanding , do galaxies that are close together move apart faster or slower than galaxies that are far apart Explain ( the mint rye this has ' fur million years Earth . When that light your eyn . the ) looked . Irs ( galaxies that air of Light rum ( able to in the . How the Universe Formed . i the ' ul ago . At that time , the part of tun we was the end at this . tiny ' was il ( hot and dense . The universe then ( in what ( tI ) this big bang . Nearly every visible object in this image is a distant galaxy .

According to the big bang theory , the universe formed in an instant . billions of years ago . in an explosion . hi . of ( Itl is ' early in its . i , il i . My . Jud to . hug is , expect in rind in You ( that the maxim hurled hu lug lung mil he . You alw In ind the . Moving Galaxies , iCI ' iCI ) hi . In the , of galaxies at ' Faith . By ' spectrum , could tell the galaxy ix and il ) it Hubble di . ul ( All arr min us and mull . round that there ii relationship the ' In ' and its ' Li . law ( it is iy us . big Lung ' Galaxies A of the distant gala astronomers haw are moving vapidly away from Du ! and ham each other Chapter 15 623

moi Statistics . om . and I III Use the graph to answer the questions below about moving clusters of galaxies . Reading Graphs How far away is the Bootes cluster ?

How fast is it moving ?

Reading Graphs which galaxy is moving away the fastest ?

Which galaxy is closest to Earth ?

Drawing ( How are the distance and speed of a galaxy related ?

Predicting Predict the speed of a galaxy that is billion from Earth . From Earth ( Killian ) Galaxy Movement as BOMB ! Spud ( Ursa Major To understand how the galaxies are moving . think of raisin bread dough that is rising . If you could shrink yourself to sit on a raisin , you would see all the other moving away from you . The farther a raisin was from you . the faster it would move away , because there would be more bread dough to expand between you and the raisin . No matter which raisin you sat on . item ! 24 all the other raisins would seem to be moving away from you . 35 ! You could tell that the bread dough was expanding by watching The galaxies in the universe are the other raisin like the raisins in rising bread . dough akin How The like the bread dough . the raisins in the does rising raisin bread dough dough . the galaxies in the universe are moving away from each resemble the di other . In the universe . it is space that is expanding , like the universe ?

dough between the raisins . Cosmic Background Radiation In . two American , physicists , Amo and Robert Wilson . accidentally detected a faint radiation on their radio telescope . This mysterious glow was ' coming from all directions in space . Scientists later concluded that this glow . now called cosmic background radiation , is the leftover thermal energy from the big bang . This energy was in every direction as the universe expanded . Universe Since astronomers can measure approximately how fast the universe is expanding now . they can infer how long it has been expanding . Based on careful measurements of how fast distant galaxies are moving away from us and the cosmic background radiation . astronomers estimate that the universe is about billion years old . 6240

Formation of the Solar System After the big bang , matter in the universe separated into galaxies . Gas and dust spread throughout space . Where the solar system is now , there was only cold , dark gas and dust . How did the solar system form ?

The leading hypothesis is explained below . The Solar Nebula ( About billion years ago , a giant cloud of gas and dust collapsed to form our solar . A large cloud of gen and dust such as the one that formed our solar is called at solar nebula . Slowly , gravity began to pull the solar nebula together . As the solar nebula shrank . it spun faster and faster . The solar nebula . forming a rotating disk . Gravity pulled of the gas into the center of the disk , where the gas eventually hot and dense enough for nuclear fusion to begin . The sun was born . in the outer parts of the disk . gas and dust tanned small and called . These formed the building blocks of the . collided and grew larger by ing together . to form the . the Planets When the formed , were very high . It was so hot close to the sun that must ( and other simply . Most gases escaped the gravity of the planets that were forming in this region . As result . the inner planets are relatively mall and Farther from the un it was much cooler . As the ets in this region grew . their gravity increased and they were able to capture much of the hydrogen and helium gas in the surrounding space . As it result . the gas very large . Most comets formed near and Saturn . They were later out to the outer solar tem . Beyond the gas giants . a huge disk of ice and other substances formed . Pluto also formed in this region . Evidence The composition of the inner and outer planets provides strong evidence or the solar nebula theory . Other evidence includes the position of the sun at the center of the solar system and the that all of the planets revolve around the in the direction . What is a solar nebula ?

A cloud gas and dust a spinning . Gas In the ( enter at the disk collapsed to form the sun . The , gas and dust the planets . The solar system the sun , and belts of rod , Ito , and dust . Focus 25 How the Solar System Formed The solar system formed from a cloud of gas and dust . 625

Go INKS , For Links on the universe Visit Web ( ode 26 Van Astronomer Vera Rubin observations helped prove the of dark matter . The Future of the Universe What will happen to the universe in the future ?

One possibility is that the universe will continue to expand . as it is doing now . All of the stars will eventually run out of fuel and burn out , and the universe will be cold and dark . Another possibility is that the force of gravity will begin to pull the galaxies back together . The result would be a reverse big bang , or big crunch . of the matter in the universe would be into an enormous black hole . of these possibilities is more likely ?

Recent discoveries have led to a surprising new view of the universe that is still not I understood . New observations lead many astronomers to that the universe will likely expand forever . Dark Matter Until fairly recently , astronomers assumed that the universe consisted solely of the matter they could observe directly . But this idea was disproved by the American mer Vera Rubin . Rubin made detailed observations of the tion of spiral galaxies . She discovered that the matter that astronomers am see . such as stars and . makes up as tle as ten percent of the in galaxies . The remaining exists in the form of dark matter . Dark matter is matter that does not give off radiation . Dark matter can not be seen directly . However . its can be inferred by observing the effect oi its gravity on visible objects . such as stars , or on light . Astronomers still do know much about dark matte , it is made of or all places where it is found . An Accelerating Expansion In the late ) mers observed that the expansion of the universe appears be accelerating . That is . galaxies seem to be moving apart at faster rate now than in the past . This observation was puzzling . as no known Force could account for it . Astronomers infer that 21 mysterious new force . which they call dark energy , is causing the expansion of the universe to accelerate . Current estimates indicate that must of the universe is made of dark energy and dark matter . think that only a small fraction of the than composed of normal matter that they can see . Astronomy is one of the oldest sciences , but there are still many discoveries to be made and to be solved about this universe of ours ! What is the Hun of dark energy ?

27 Dark Matter Astronomers measured the Wart gravity on ight to this computer image of how dark matter ( in blue ) Is distributed a of galaxies 529 a section Assessment Ski a . Defining dink Evidence , Explaining Him ilu kin i HINT ( I ihr the , In ' Ke ( once , 47 ' my big lung ! did Iii ?

Describing I pi ' flab lira ! Iii lug ' 1009 MINT Summarizing Him ix Ihr ' Relating Cause and Effect , i ?

Han ark ! of with Iii ! In hymn ?

ear IL . se ( an lie Shiv ( locate the Milk ) Way ' mi . fusion ii ) sun . and some interesting stars that you have learned about Explain to you ! family what you know about the Milky Way and ( that you observe Chapter 15 611 Chapter 15 Telescopes Key The includes radio , light , and rays . are and fonts light and other torn radiation . Many large Ul ) are located on ) or in . Key Terms visible light spectrum radiation lem ' Characteristics of Stars ( Key Concepts . used to classify stars include , and . The brightness of slur depends upon both its size and temperature . use unit called the to ' the . use ( distances to ' use diagram to cla . if ' start and to over nine . Key Terms I I I apparent brightness I I I I diagram I main St ' Study Guide learn about the structure and of the universe by studying stars . galaxies . and other oblem in spate . Lives of Stars Key Concepts . A star is born when and dust a heroine no dense and hat that nuclear fusion starts . How long a ' live un ils man . After star rum uut uf fuel . it ) white star . or a black hole . Key Terms I nebula I I planetary nebula I white dwarf I I star I pulsar I black ! star Systems and Galaxies Key Concepts in . I Mast stars are members . classify I ! galaxies types spiral , elliptical . and irregular . Our is located in a spiral called the Milky ) rue violation describe sizes and in ( Key Terms I binary star I open cluster I I galaxy I quasar I galaxy I elliptical galaxy I irregular I ! I The Expanding Universe Key Concepts a . In the big bang theory , the formed in an ofyears ago . About year giant cloud of gas and nur system . New ) lead In that the universe will likely . Key Terms I big bang I law I I nebula I dark matter I dark

Go ' um For Visit ( om Web Review and Assessment Evidence Target Reading Skill , Identify Supporting Evidence , as ( a graphic of a get or , the ' the mat I . I ! loud of gas , dust . Reviewing Key Terms Choose of the ! Complete the following sentences so that your clearly explain the key ' light form . radiation . by the , 90 , i Li . background . i ' are on surf . An diagram is graph ! I . am . Man are in , huh are MINT , main sequence . live Milky ' is an example of galaxy , absolute brightness . 10 . fur the big bang cosmic I , sequence i inn while . I . mu Science . star in which one blocks the mu . magi you an a ! is ?

vying ( mem in ' astronomy . Write an mid blick are . how they form , and how they binary ' an be , binary . that ' began . ses me in an enormous lhe nebula . and the big bang , 15 529 Review and Assessment Checking Concepts is lune ?

12 , the star ix ' 13 . the evolution oh ' born ?

14 . Where in nu plan ! 15 . What is Hubble law ?

detect dark matter it they observe it ?

Math ' 17 . Calculating Thu , star Spica about 261 ) from our . How ' 18 . Notation lhe star is , twin Earth . Write this in . Th Critically 19 . might locating a telescope . such as the mic . on the moon ?

20 . Applying ( real world and ' car at 6300 21 . Relating Cause and Line a . 22 . Comparing and Contrasting ( the led to the terrestrial planet with those that led to the of the gas giants . Skills Use the data in the ! diagram below to answer Questions . Diagram Main 50 ! Sinus A in Sun . an Alpha or ' white ovum , COD Surface Temperature ( 23 . Interpreting Diagrams Which tar greater ) ur Sirius ?

14 . Interpreting Diagrams Which stars have higher ' Sirius ?

25 . Applying Concepts hit . mu is . lac . Sirius . or ?

26 . Comparing and ( the terms we . iy , Performance Assessment ( heck the story fur . i ( will present your story . ur . could make , your story . or perform it As a slut or .

Choose the letter of the best answer . You can stars at nigh ! humus A ) light from . Ilia ) light urn . they have exploded . A oxygen . hydrogen . helium . all in must . The main the of a A ( ma . I wuuld ( listener in A light years . is . The table below gives an estimate of the distribution of stars in the Milky Way galaxy . Use the table and your knowledge of menu to answer Question . Type of Star of Total Mam Red Giant White Dwarf ul in Milky air A . white dwarfs . ige above shows few no new . is sin ) A spiral galaxy . spiral gain ) following ( star from young to uld ?

A while . giant . xur , dwarf . mIai ' Mar . dwarf . red , star , white . Win ! pulled together in the solar In ?

A dark energy gravity . lac oi Milky iy you wuuld we ii from and rum ' or ihr dun galaxy from ' points ?

a 15 531 Chapter 12 Earth , Moon , and Sun The motions of Earth and the moon and their position relative to the sun result in day and night . the seasons . phases of the moon , eclipses , and tides . How does Earth move in space ?

What two factors combine to keep the moon and Earth in orbit ?

What causes the phases of the moon , eclipses , and tides ?

What are some characteristics of the moon ?

Chapter 13 Exploring Space THESE Scientists have learned much about the solar system through various types of space missions . How does a rocket work ?

What were the major events in human exploration of the moon ?

What are the roles of space shuttles , space stations . and space probes ?

How has space technology benefited modern society ?

Chapter 14 The Solar System The solar system includes the sun , the planets and their means . and smaller objects such as comets . asteroids . and . What are the layers of the sun interior and its atmosphere ?

What characteristics do the inner planets have in common ?

What characteristics distinguish each of the outer planets ?

What are the characteristics of comets . asteroids . and ?

Chapter 15 Stars . Galaxies . and the Universe Astronomers learn about the structure and evolution of the universe by studying stirs . galaxies . and other objects in space . How are stars classified ?

How does a star form ?

What are the major types of galaxies ?

What is the theory ?

Unit Assessment Imagine an adventurous group ol astronauts in the far future going on a grand tour of our solar system . They might time their trip to start just after a big event . such as a solar eclipse . They would need a rocket to get them oft Earth surface and beyond Earth gravitational pull The astronauts would visit Mars , pass through the asteroid belt , and then delight at the gas giants Jupiter , Saturn , Uranus , and Neptune . They might spend a lot of time studying Jupiter and its four large moons And no grand solar system tour would be complete without enjoying a ( view of Saturn lovely rings After a stop at tiny , cold Pluto , the astronauts would head back toward the center of the solar system , passing Venus and Mercury until finally they would get as close to the sun as they possibly could . They might take note of how well the sun supports lite on Earth . Not every star in the galaxy has a system of planets , and of those that do . many may not support life as we know it . For a solar eclipse to occur . what must be . Which of Jupiter largest moons is thought the moon phase ?

Chapter 12 ) to have the conditions necessary for lite to new moon first quarter develop ?

Chapter ) i . full moon . third quarter lo . Europa Ganymede . To leave Earth gravitational pull , the astronauts rocket had to reach which 01 . What kind of star is the sun ?

Chapter is ) the following ?

Chapter 13 ) white dwarf terminal velocity giant supergiant orbit . Write a paragraph that summarizes the conditions necessary for a planet to support Give examples of places In our solar system where each of these conditions exist . orbital velocity ( escape velocity 633

Think Like a Scientist Scientists have a particular way at looking at the world . or habits of mind . Whenever you ask a question and explore possible answers . you use many of the same skills that scientists do . some of these skills an described on this page . Observing When you use one or more of your senses to gather information about the world , you are observing . Hearing a dog bark . counting twelve green seeds , and smelling smoke are all observations . To increase the power of their senses . scientists sometimes use microscopes . telescopes . or other instruments that help them make more detailed observations An observation must be an accurate report of what your senses detect . It is important to keep careful records of your observations in science class by writing or drawing in a book . The information collected through observations is called evidence . or data . Inferring When you interpret an observation . you are inferring . or making an inference . For example . if you hear your dog barking . you may infer that someone is at your front door . To make mu inference . you combine the the barking your experience or know that your dog barks when strangers reach a logical conclusion . Notice that an inference is not a fact it is only one of many possible interpretations for an observation . For example , your dog may be barking because it wants to go for a walk . An inference may turn out to be incorrect even if it is based on accurate observations and logical reasoning . The only way to find out if an infer once is correct is to investigate further . Predicting When you listen to the weather forecast , you hear many predictions about the next day the temperature will be . whether it will rain . and how windy it will he . Weather forecasters use and knowledge of weather patterns to predict the weather . The skill of predicting involves ing an inference about a future event based on current evidence or past experience . Because a prediction is an inference . it may prove to be false . in science class . you can test some of your predictions by doing experiments . For example . suppose you predict that larger paper airplanes can fly farther than smaller planes . How could you test your prediction ?

Activity Use the photograph to answer the questions below . Observing Look closely at the photograph . List at least three observations . Use your observations to make an inference about what has happened . What experience or knowledge did you use to make the inference ?

Predicting Predict what will happen next . On what evidence or experience do you base your prediction ?

Classifying ( ould you imagine searching for a book in the library if the books were shelved in no particular order ?

Your trip to the library would he an eve Luckily , librarians group together books on similar topics or by the same author . Grouping together items that are alike in some way is called classifying . You can classify items in many ways by shape . by use . and by other important characteristics . Like use the skill of classifying to information and things are sorted into groups . the relationships among them become easier to understand . This student is using a model to demonstrate what causes day and night on Earth . what do the and the tennis ball in die model represent ?

look like the thing works . Communicating Whenever you talk on the phone . write a report , or listen to your teacher at school . you are communicating . Communicating is the of sharing ideas and information with other people . Communicating requires many skills . including writing . reading . speaking . listening . and making models . Scientists communicate to share results , information , and opinions , Scientists often communicate about their work in . over the telephone , in letters . and on the Internet . Classify the In the photograph into two groups based on any characteristic you choose . Then use another characteristic to classify the objects into three groups . organize Making Models Have you ever drawn a picture to help someone stand what you were saying ?

Such a drawing is one type of model . A model is at picture . diagram . computer image . or other representation of a complex or process . Making models helps people understand things that they can not observe directly . Scientists often use models to represent things that are either very large or very small . such as the planets in the solar system , or the parts of a cell . Such models are physical , or th structures that real thing . models are mental equations or words that describe how also attend meetings where they share their ideas with one another in person . on a sheet of paper . write out I , clear . detailed directions for tying , your shoe . Then exchange directions with a partner . Follow your partner directions exactly . successful were you at tying your shoe ?

How eould your partner have more clearly ! Skills 635 Making Measurements By measuring , scientists can express their observations more and communicate more information about what they observe . Measuring in SI The standard system of measurement used by scientists around the world is known as the international System of Units . which is ated as Si ( System International , in ) units are easy to use because they are based on multiples of IO . Each unit is ten times larger than the next smallest unit and one tenth the size of the next largest unit . The table lists the used to name the most common SI units . Length To measure length . or the distance between two points . the unit of measure is the ( In ) The distance from the floor a knob is approximately one meter . Long distances , such as the distance tween two cities . are measured in kilometers ( on , Small lengths are measured in centimeters ' or millimeters 100 ( Scientists use metric rulers and meter sticks to measure length . The larger lines on the ruler in the picture show centimeter divisions , while the smaller . unnumbered lines show divisions . How many centimeters long is the shell ?

Now many millimeters Common Si Prefix Meaning It I 100 A da A 10 Liquid Volume To measure the volume of a liquid , or the amount of space it takes up . you will use a unit of measure known as the liter ( One liter is the approximate volume of carton of milk . Smaller volumes are measured in milliliters ( Scientists use graduated cylinders to measure liquid volume . Common Conversion The graduated cylinder in the picture is marked In milliliter divisions Notice that the water in the cylinder has a surface . This curved surface is called the meniscus . To measure the volume , you must read the level at Ute lowest point of the What is the volume of water in this graduated ?

Man To measure mass . or the amount of matter in an object , you will use a unit of measure known as the grain ( One gram is approximately the mass of a paper clip . Larger masses are measured in kilograms ( Scientists use a balance to the mass of an object . Common Conversion lhe mass of the potato In the picture is measured in kilograms . What is the mass of the potato ?

Suppose a recipe for potato salad called for one kilogram of potatoes . About how many potatoes would you need ?

Converting SI Units To use the Si system . you must know how to convert between units . Converting from one unit to another involves the skill , or using mathematical operations . Converting between SI units is similar to converting between dollars and dimes because systems are based on multiples of ten . Suppose you want to convert a length of 80 centimeters to meters . Follow these steps to convert between units . Begin by writing down the measurement you want to this example . 80 centimeters . Write it conversion factor that represents the relationship between the two units you are converting . In this example . the ship is meter centimeters . Write this conversion factor as a fraction . making sure to place the units you are converting from ( centimeters , in this example ) in the denominator . Inquiry Skills To measure the temperature of a substance . you will use the Celsius scale . Temperature is measured in degrees Celsius ( using a Celsius thermometer . Water freezes at OT and boils at Time The unit scientists use to measure time is the second ( What is the temperature the liquid in degrees Celsius ?

Multiply the measurement you want to convert by the fraction . When you do this . the units in the measurement will cancel outwith the units in the denominator . Your answer will be in the units you are ing to ( meters . in this example ) Example I meters centimeters meters Activity Convert between the . 600 millimeters I meters . liters I milliliters . grams I kilograms 631

Conducting a Scientific Investigation In some ways . scientists are like detectives , piecing together clues to learn about a process or event . One way that scientists gather clues is by carrying out . An experiment tests an idea in a careful . orderly . Although experiments do not all follow the same steps in the same order . many follow a pattern similar to the one described here . Posing Questions begin by a tion . A question is one that can be answered by gathering evidence . For example . the question Which freezes ' water or salt water ?

is a question because you can carry out an investigation and gather information to answer the question . Developing a Hypothesis The next step is to form a . A hypothesis is a possible explanation for it set of observations or answer to a question . A hypothesis may incorporate observations . concepts , principles . and theories about the natural Hypotheses lead to predictions that can he tested . It prediction can be worded as an . than . statement . For example . a prediction might be If I add salt . the ' will take longer In . prediction worded this way serves as rough outline of the experiment you should perform .

Designing an Experiment Next you need to plan a way to test your . Your plan should be written out as a procedure and should describe the observations or measurements you will make . Two important steps involved in designing an experiment are controlling variables and forming operational . Controlling Variables In a experiment , you need to keep all variables the same except for one . A variable is any factor that can change in an experiment . The factor that you change is called the manipulated variable . In this experiment . the manipulated variable is the amount of salt added to the water . Other factors , such as the amount of water or the starting temperature , are kept constant The factor that changes as a result of the manipulated variable is called the responding variable . The responding variable is what you measure or observe to obtain your results . In this experiment . the responding variable is how long the water takes to freeze . An experiment in which all factors except one are kept constant is called a controlled experiment . Most controlled experiments include a test called the control . In this ment . Container is the control . Because no salt is added to Container you can compare the results from the other containers to it . Any difference in results must be due to the addition of salt alone . Forming operation I Definitions Another important aspect of a experiment is having clear operational . An operational is a statement that describes how a particular variable is to be measured or how a is to be . For example , in this experiment . how will you determine if the water has frozen ?

You might decide to insert a stick in each container at the start of the experiment . Your operational of frozen would be the time at which the stick can no longer move . Inquiry Skills , i ' AM no III to Container . Interpreting Data The observations and measurements you make in an experiment are called . At the end of an experiment , you need to analyze the data to look for any patterns or trends . often become clear if you organize your data in 21 data table or graph . Then think through what the data reveal . Do they support your hypothesis ?

Do they point out a flaw in your experiment ! Do you need to collect more data ?

Drawing Conclusions A conclusion is a statement that sums up what you have learned from an experiment . When you draw a conclusion . you need to decide whether the data you collected support your hypothesis or not . You may need to repeat an experiment several times before you can draw any conclusions from it . Conclusions often lead you to pose new questions and plan new to answer them . is a ball bounce affected by the height from it is dropped ?

Using the sup just described . plan a controlled experiment to this problem . 639 Technology Design Skills Engineers are people who use and technological knowledge to solve practical problems . design new products , engineers usually follow the process described here . even though they may not follow these steps in the exact order . As you read the steps . think about how you might apply them in technology labs . Identify a Need Before engineers begin designing a new product . they must first identify the need they are trying to meet . For example . you are a ber of a design team in a company that makes toys . Your team has a need lay boat that is inexpensive and easy to . Research the Problem Engineers often begin by gathering tion that will help them with their new design . This research may include articles in books . magazines . or on the Internet . It may also include talking to other engineers who have solved similar problems . Engineers often perform experiments related to the product they want to design . For your toy boat . you could look at toys that are similar to the one you want to design . You might do research on the . You could also test some materials to see whether they will work well in a toy boat . Drawing for a boat design Design a Solution Research gives engineers information that helps them design product . When engineers design new products . they usually in teams . Generating Ideas ( design teams hold brainstorming meetings in which any member can contribute ideas . Brainstorming is a creative process in which one leant suggestions often spark ideas in other group members . Brainstorming can lead to new approaches to solving a design problem . Evaluating constraints During storming , at design team Will often come up with several possible designs . The team must then evaluate each one . As part of their evaluation . engineers consider constraints . Constraints are that limit or restrict a product design . Physical characteristics . such as the properties of materials used to make your toy boat , are Money and time are also . If the in a product can a lot . or product takes a long time to make . the design may be impractical . Making Design teams usually to make . in a , give up one of a proposed design in order to obtain another . In designing your my boat . you will have to make . For example . suppose one material is sturdy but not fully waterproof . Another material is more proof , but breakable . You may decide to give up the benefit in order to obtain the of .

Build and Evaluate a Prototype Once the team has chosen at design plan . the engineers build a prototype of the product . A prototype is a working model used to test a design . Engineers evaluate the prototype to see whether it works well , is easy to operate . is safe to use . and holds up to repeated use . Think of your my boat . What would the be like ?

01 ' what materials would it be made ?

How would you test it ?

Troubleshoot and Redesign Few prototypes work perfectly . which is why they need to be tested . Once it design team has tested a prototype , the members analyze the results and identify any problems . The team then tries to troubleshoot . or fix the design For example . if your toy boat leaks or wobbles , the boat should be redesigned to eliminate those problems . You can use the technology design process to design and build a toy boat . and I . Visit the library or go online to research toy boats . Investigate how a toy boat can be powered , including wind . rubber bands . or baking soda and vinegar . Brainstorm materials . shapes . and steering for your boat . Design and Build . Based on your research , design a toy boat that I is made of readily available materials is no larger than long and 10 wide Inquiry Skills Communicate the Solution A team needs to communicate the design to the people who will manufacture and use the product . To do this , team may use sketches , detailed drawings , computer simulations . and word descriptions . includes a power system , a rudder , and an area for cargo travels meters in a straight line carrying a load of 20 pennies . Sketch your design and write a plan for building your boat . After your teacher approves your plan . build your boat . Evaluate and Test your boat , evaluate the results . and troubleshoot any problems . Based on your evaluation , redesign your toy boat so it performs better . 641

Creating Data Tables and Graphs How can you make sense of the data in I science experiment ?

The first step is to organize the data to help you understand them . Data tables and graphs are helpful tools for organizing data . Data Tables Calories Burned in so You have gathered your materials and set up Experiment your experiment . But before you start . you Hill ! I need to plan a way to record what happens . during the experiment . By creating at data table . you can record your observations and . ments in an orderly way . i ' Suppose . for example . that a scientist 60 ' 35 ducted an experiment to find out how many Calories people of body masses hum while doing various activities . The data table Experiment the number of Calories burned shows the results . while bicycling ) is the heading of the next Notice in this data table that the column . Additional columns were added for lated variable ( body mass ) is the heading of related experiments . one column . The responding variable ( for Bar Graphs To compare how many Calories a person burns . For each category , draw a solid bar using the doing various activities . you could create a bar scale on the vertical axis to determine the graph . A bar graph is used to display data in a height . Make all the bars the same width . number of separate . or distinct . categories . In Add that , me graph . this example . bicycling . playing basketball . and watching television are the three categories . Gnomes Burned by og To create a bar graph , follow these steps . Perm ' 30 ' On graph paper . draw a . or . axis and a vertical . or , axis . Write the names of the categories to be graphed along the horizontal axis . Include an overall label for the axis as well . Label the vertical axis with the name of the responding variable . Include units of . Then create a scale along the axis by marking spaced numbers that cover the range of the data collected .

Line Graphs To see whether a relationship exists between body mass and the number of Calories while bicycling . you could create a line graph . A line graph is used to display data that show how one variable ( the responding variable ) changes in response to another variable ( the manipulated variable ) You can use a line graph when your manipulated variable is continuous , that it , when there are other points between the ones that you tested . In this example . body is a continuous variable because there are other body masses between 30 and 40 grams ( for example , Time is another example of a continuous variable . Line graphs are powerful tools because they allow you to estimate values for conditions that you did not test in the experiment . For ple . you can use the line graph to estimate that a 35 kilogram person would burn 68 Calories while bicycling . To create a line graph . follow these steps . I . On graph paper . draw a . axis and at vertical . or . axis . Label the horizontal axis with the name oi the manipulated variable . label the vertical axis with the name of the responding able . units of measurement . Create a scale on each axis by marking off equally spaced numbers that cover the range of the data collected . Plot a point on the graph for each piece of data . In the line graph above . the dotted lines show how to plot the first data point ( 30 kilograms and 60 Calories . Follow an imaginary vertical line extending up from the horizontal axis at the mark . Then follow an imaginary line extending across from the vertical axis at the . Plot the point where the two lines intersect . Inquiry Skills of Body Mass on Calories Burned While a Body Mass ( 30 ) Connect the plotted points with a solid line . In some cases , it may he more appropriate to draw a line that shows the general trend of the plotted points . In those , some of the points may fall above or below the line . Also . not all graphs are linear . it may be more appropriate to draw a curve to connect the points . Add a title that the variables or relationship in the graph . Cunt graphs to display the din from and Experiment In the data table . You read In the newspaper that a total at centimeters of rain fell In your area In June . centimeters tell In July . and fell in August . What type of graph would you use to display these data ?

graph paper to create the graph . skin 54 Circle Graphs like bar graphs , circle graphs can be used to display data in a number of separate categories . Unlike bar graphs . however . circle graphs can only be used when you have data for all the categories that up a given topic . A circle graph is sometimes called a pie chart . The pie represents the entire topic . while the slices represent the individual categories . The size of a slice indicates what percentage of the whole a particular category makes up . The data table below shows the results of a in which 211 teenagers were asked to identify their favorite sport . The data were then used to create the circle graph at the right . To create a circle graph , follow these steps . Use a compass to draw it circle . Mark the center with I point . Then draw a line from the center point to the top of the circle . Determine the size of each slice by setting up a proportion where equals the number of degrees in a slice . Note A circle contains 360 degrees . For example , to the number of degrees in the soccer slice . set up the following proportion Students who refer soccer Total Tot at of students degrees in il circle ?

sec and solve for . 24 360 The soccer slice should contain degrees . 6140 Sports that Teens Prefer . Use a protractor to measure the angle of the first slice . using the line you drew to the top of the circle as the ' line . Draw a line from the center of the circle to the edge for the angle you measured . Continue around the circle by measuring the size ofeach slice with the protractor . Start measuring from the edge of the previous slice so the wedges do not overlap . When you are done . the entire circle should be in . Determine the percentage of the whole circle that each slice represents . To do this . divide the number in a slice by the total of degrees in a circle ( 360 ) and multiply by ) For the soccer slice . you can the percentage as follows 20 ' I ( Use a color for each slice . Label each slice with the category and with the percentage of the whole it represents . Add at title to the circle graph . in a class of ! students . 12 students the bus In school , 10 mutants wall . and students ride their bicycles . run a circle graph on display these data .

Math Skills Math Review Scientists use math to organize , analyze , and present data . This appendix will help you review some basic math skills . Mean , Median , and Mode The mean is the average . or the sum of the data divided by the number of data items . The die number in set of ordered data is called the median . The mode is the number that appears most often in a set . Probability is the chance that an event will A scientist counted the number of distinct occur . Probability can be expressed as a ratio . a songs sung by seven different male birds fraction . or percentage . For example . when and collected the data shown below . you coin . the probability that the coin will land heads up is I in or , or 50 percent . Mal ?

95 The probability that an event will happen can be expressed in the formula . Tout number at possible wont To determine the mean number of songs . add the total number of songs and 538 50 15 bi ?

divide by the number arm orange and this case . the number of male birds . if ?

and pick a marble from the bag . what is ' the probability that it will be yellow ?

To the median number of songs . arrange the data in numerical order and ( the number in the middle ofthe series . 17182935363640 The number in the middle is so the , I 35 ' Each side of a cube has a letter on it . No Th is ' sides have three sides have and one I ' 36 side has ( I . If you roll the cube . what is twice . while each other item appears only , ha ! A win land on top once . Therefore . 36 songs is the mode . Find out how many minutes it takes each student in your class to get to school . Then the mean . median . and mode for the data . 645

Area The are of surface is the number of square units that cover it . The front cover of your book has an area of about 600 . Ann of I and a square To find the area ofa rectangle , multiply its length times its width . The formula for the area of a rectangle is Since all four sides of a square have the same length , the area of a square is the length of one side multiplied by itself . or squared . A scientist is studying the plants in at that measures 75 45 In . What is the area of the ?

Ana of I Circle The formula for the area of a circle is The length of the radius is by and the value of II is approximately . Find the area ofa circle with a radius of . Find the area of a circle that has a radius of Circumference The distance around a circle is called the circumference . The formula for finding the circumference of a circle is The radius of a circle is 35 . What is its circumference ?

What is the circumference ofa circle with a radius of 28 in ?

The volume of an object is the number units it contains . The volume of a , for example . might be about . Volume of a Rectangular Object To the volume of a rectangular . multiply the object length times its width times its height . Find the volume of a box with length 24 , width 12 . and height . What is the volume of a rectangular object with length . width 11 . and height ?

Fractions A fraction is a way to express a part of ti whole . in the fraction . is the numerator and ' is the denominator . Adding and Subtracting Fractions To add or subtract two or more fractions that have a common denominator . add or subtract the . Then write the sum or ence over the common denominator . To find the sum or difference of fractions with different denominators . first the least common multiple of the denominators . This is known as the least common denominator . Then convert each fraction to equivalent tions with the least common denominator . Add or subtract the . Then write the sum or difference over the common denominator . 11 Multiplying Fractions To multiply two fractions . multiply the two . then multiply the two denominators . Fractions Dividing by a fraction is the same as multiplying by its reciprocal . are whose and denominators have been switched . To divide one fraction by another . first invert the fraction you are dividing other words , turn it upside down . Then multiply the two . Solve the following Math Skills Decimals Fractions whose denominators are lot ) or some other power of It ) are often ex as . For example . the fraction can be as the decimal and the fraction ' can be written as . Adding and With Decimals To add or subtract . line up the mal points before you carry out the operation . Multiplying with Decimals When you multiply two numbers with decimals . the ber of decimal places in the product is equal to the total number of decimal places in each number being multiplied . one decimal place ) at ( two decimal places ) three decimal places ) Dividing with Decimals To divide a decimal by a whole number . put the decimal point in the quotient above the decimal point in the dividend , To divide a decimal by a decimal , you need to rewrite the divisor as a whole number . Do this by multiplying both the divisor and dividend by the same multiple of 10 . 41 yl at lli Multiply by skill 641

Ratio and Proportion A ratio compares two numbers by division . For example . suppose scientist counts 800 wolves and moose on an island . The ratio of wolves to moose can be written as a fraction . which can be reduced to The same ratio . A proportion is mathematical sentence saying that two ratios are equivalent . For proportion could state that turn I . I . You can set up a proportion to or estimate an unknown quantity . For example . suppose a enlist counts 25 beetles in an area of IO square meters . The scientist wants to estimate the number of beetles in 100 square meters . Express the between beetles and area as a ratio 775 , to . Set up a proportion . with representing the number of . The proportion can be stated , 05 . Begin by . In other words . multiply each tor by the other fraction denominator . To the value both sides by . The result is or 250 beetles in 100 square meters . Find the ) in the following proportion Percentage A percentage a ratio that compares a ber to 100 . For example . there are 57 granite rocks in a collection that consists of rocks . The ratio can be written as 37 . Granite rocks make up 37 of the rock collection . You can calculate percentages of numbers other than 100 by setting up a proportion . Rain falls on ( lays out of 30 in lune . What percentage of the days in lune were rainy ?

days 30 IN To the value of begin by cross , as for any proportion There are 300 marbles in jar . and 42 of those marbles are blue . What percentage of the marbles are blue ?

Significant Figures The precision of measurement depends on the you use to take the measurement . For example . ifthe smallest unit on the ruler is millimeters . then the most precise measurement you can make will be in . The sum or difference of measurements can only he as precise as the least precise ment being added or subtracted . Round your answer so that it has the saute number of digits after the decimal as the least precise ment . Round up if the last digit is or more , and round down if the last digit is or less . Subtract at temperature of from the temperature . I has the fewest digits after the decimal . so it is the least precise measurement . Since the last digit of the answer is round up to . The most precise difference between the is ( Add to Round your answer according to the precision of the measurements . are the number of nonzero digits in it measurement . Zeros between nonzero digits are also . For example . the measurements . and all have three . When you multiply and divide measurements . the one with the fewest determines the number of in your answer . Multiply I ) by 110 Because I ID has only two . round the answer to 630 Scientific Notation A factor is a number that divides into another number with no remainder . In the example . the number is used as a factor four times . An exponent tells how many times a number is used as a factor . For example . can be written as . The exponent cates that the number is used as a factor four . Another way of expressing this is to say that ill is equal to to the fourth power . notation uses exponents and powers of ten to write very large or very small numbers in shorter form . When you write a number in notation , you write the number as two factors . The first factor is any number between I and . The second factor is power of IO . such as 103 or ) The average distance between the planet Mercury and the sun is . To write the first factor in notation , insert a decimal point in the original ber so that you have a number between I and 10 . In the case of , the number is . To determine the power of 10 , count the number of places that the decimal point moved In this case . it moved places . Inn 10 in I Express in notation . skills !