Glencoe Earth Science - SharpSchoolnewlondonscs.sharpschool.com/UserFiles/Servers/Server_327725/File... · The Nature Science is a process ... You also might wonder why rocks can

The Natureof Science

Science is a process ofobserving, studying, andthinking about things inorder to gain knowledge.

SECTION 1Science All AroundMain Idea Testing, orexperimenting, is an impor-tant part of science.

SECTION 2Scientific EnterpriseMain Idea Scientificknowledge has changedand continues to change asnew advances are made.

A 66-million-year-old hear t?Inside the chest of a small dinosaur nicknamed Willo is somethingamazing—what appears to be a heart preserved as stone. Scientistsstill are debating whether this clump of stone is a preserved heart,and more research will be necessary. But that’s the nature of science.

How do you think scientists could learn more about the clump ofstone that could be a heart?Science Journal

Dutheil Didier/CORBIS Sygma

55

Science Vocabulary Makethe following Foldable to helpyou understand the vocabularyterms in this chapter.

Fold a verticalsheet of notebookpaper from side toside.

Cut along every third line of only thetop layer to form tabs.

Label each tab with a vocabularyword from the chapter.

Build Vocabulary As you read the chapter, listthe vocabulary words on the tabs. As you learnthe definitions, write them under the tab foreach vocabulary word. Exchange yourVocabulary Foldable with a classmate and quizeach other to see how many vocabulary wordsyou can define without looking under the tabs.

STEP 3

STEP 2

STEP 1

Measure in SIBig and small are words people use a lot. But,the meaning of these words depends on yourexperiences and what you are describing. Earlyin human history, people developed ways tomeasure things. In the following lab, try someof these measuring devices.

1. Using only your hands and fingers asmeasuring devices, measure the lengthand width of the cover of this book.

2. Compare your measurements with thoseof other students.

3. Using a metric ruler, repeat the measure-ment process.

4. Again, compare your measurements withthe measurements of other students inthe classroom.

5. Think Critically Infer and describe sev-eral advantages of using standardizedmeasuring devices.

Start-Up Activities

Preview this chapter’s contentand activities at earth.msscience.com

Dutheil Didier/CORBIS Sygma

http://www.glencoe.com/

6 A CHAPTER 1 The Nature of Science

Apply It! Now that you haveskimmed the chapter, write a short paragraphdescribing one thing you want to learn fromthis chapter.

Learn It! If you know what to expect before reading, it willbe easier to understand ideas and relationships presented in the text.Follow these steps to preview your reading assignments.

Practice It! Take some time to preview this chapter.Skim all the main headings and subheadings. With a partner, discuss youranswers to these questions.• Which part of this chapter looks most interesting to you?• Are there any words in the headings that are unfamiliar to you?• Choose one of the lesson review questions to discuss with a partner.

1. Look at the title and any illustrations that are included.2. Read the headings, subheadings, and anything in bold letters.3. Skim over the passage to see how it is organized. Is it divided

into many parts?4. Look at the graphics—pictures, maps, or diagrams. Read their

titles, labels, and captions.5. Set a purpose for your reading. Are you reading to learn some-

thing new? Are you reading to find specific information?

6 B

As you read, use other skills,

such as summarizing and con

necting, to help you under

stand comparisons and

contrasts.

Use this to focus on the main ideas as you read the chapter.

Before you read the chapter, respond to the statements

below on your worksheet or on a numbered sheet of paper.

• Write an A if you agree with the statement.

• Write a D if you disagree with the statement.

After you read the chapter, look back to this page to see if you’ve

changed your mind about any of the statements.

• If any of your answers changed, explain why.

• Change any false statements into true statements.

• Use your revised statements as a study guide.

Before You Read Statement After You ReadA or D A or D

1 Science can be described as a process of observ-ing, studying, and thinking about things.

2 A hypothesis can be a possible solution to aproblem or a temporary assumption thatexplains something.

3 The different factors that can change, or vary, inan experiment are called variables.

4 Very few experiments require a control, or stan-dard, to which results can be compared.

5 For an experimental result to be considered reli-able, it must be confirmed by many tests.

6 A scientific problem requires variables that canbe observed, measured, and tested.

7 A scientific theory is an explanation backed byresults obtained from one test or experiment.

8 Usually, a scientific law explains why somethinghappens in a given situation.

As you preview this chapter, be

sure to scan the illustrations,

tables, and graphs. Skim the

captions.Use this to focus on the main ideas as you read the chapter.

Before you read the chapter, respond to the statements

below on your worksheet or on a numbered sheet of paper.

• Write an A if you agree with the statement.

• Write a D if you disagree with the statement.

After you read the chapter, look back to this page to see if you’ve

changed your mind about any of the statements.

• If any of your answers changed, explain why.

• Change any false statements into true statements.

• Use your revised statements as a study guide.

Print out a worksheetof this page at earth.msscience.com


6 CHAPTER 1 The Nature of Science

Mysteries and ProblemsScientists are often much like detectives trying to solve a

mystery. One such mystery occurred in 1996 when Japanese sci-entists were looking through historical records. They reportedfinding accounts of a tsunami that had smashed the coast of theisland of Honshu on January 27, 1700. That led to the question:What had triggered these huge ocean waves?

The Search for Answers The scientists suspected that anearthquake along the coast of North America was to blame.From the coast of British Columbia to northern California is anarea called the Cascadia subduction zone, shown in Figure 1. Asubduction zone is where one section of Earth’s outer, rigidlayer, called a plate, is sinking beneath another plate. In areaslike this, earthquakes are common. However, one problemremained. Based on the size of the tsunami, the earthquake hadto have been an extremely powerful one, sending waves rollingall the way across the Pacific Ocean. That would be a muchstronger earthquake than any known to have occurred in thearea. Could evidence be found for such a large earthquake?

■ Describe scientific methods.■ Define science and Earth science.■ Distinguish among independent

variables, dependent variables,constants, and controls.

Scientific methods are used everyday when you solve problems.

Review Vocabularyanalyze: to examine methodically

New Vocabulary

• hypothesis

• scientific methods

• science

• Earth science

• variable

• independent variable

• constant

• dependent variable

• control

• technology

Science All Around

Figure 1 Along the Cascadiasubduction zone, the Juan de FucaPlate is sinking under the NorthAmerican Plate.

JUAN DE FUCA PLATE

PACIFIC PLATE

NORTH AMERICANPLATE

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SECTION 1 Science All Around 7

Gathering Evidence Evidence of a large earthquake in thedistant past did seem to exist along the coasts of Washingtonand Oregon. Much of the coast in that area had sunk, submerg-ing coastal forests and killing thousands of trees. However, dat-ing the earthquake to a specific year would be difficult.

A Possible Solution One scientist, whose field of study wastree rings, thought he knew how the earthquake could be dated.He made an educated guess, called a hypothesis, that tree ringsin the drowned trees could be used to determine when theearthquake occurred.

What is a hypothesis?

The hypothesis was based on what scientists know about treegrowth. Each year, a living tree makes a new ring of tissue in itstrunk, called an annual growth ring. You can see the annualrings in the cross section of a tree trunk shown in Figure 2. Twogroups of scientists analyzed the rings in drowned trees alongthe coast, like the remains of cedar trees shown in Figure 3.Their data showed that the trees had died or were damaged afterAugust 1699 but before the spring growing season of 1700. Thatevidence put the date of the earthquake in the same time periodas the tsunami on Honshu.

Importance of Solving the Mystery In addition to solv-ing the mystery of what caused the tsunami, the tree rings alsoprovided a warning for people living in the Pacific Northwest.Earthquakes much stronger than any that have occurred inmodern times are possible. Scientists warn that it’s only a mat-ter of time until another huge quake occurs.

Figure 3 Growth rings fromthese and other trees linked ahuge earthquake along the coastof Washington to a tsunami inJapan that occurred more than300 years ago.

Figure 2 You can see thegrowth rings in this tree trunk.Determine How much time doeseach ring represent?

(t)Michael Habicht/Earth Scenes, (b)Michael Wilhelm/ENP Images


Scientific Methods When scientists try to solve a mystery like what caused the

tsunami in Japan in 1700, they perform problem-solving proce-dures called scientific methods. As shown in Figure 4, some ofthe scientific methods they use include identifying a problem,gathering information (researching), developing hypotheses,testing the hypotheses, analyzing the results, and drawing con-clusions. When you use methods like these, you are solvingproblems in a scientific way.

ScienceScience means “having knowledge.” Science is a process of

observing, studying, and thinking about things in your world togain knowledge. Many observations can’t be explained easily.When people can’t explain things, they ask questions. For exam-ple, you might observe that the sky appears to be blue duringthe day but often appears to be red at sunset and sunrise. Youmight ask yourself why this happens. You might visit or see apicture of Devils Postpile in California, shown in Figure 5, andnotice that the dark rock is divided into long, thin, six-sidedcolumns. Many fallen columns lie at the base of this mass ofrock. You might wonder how and when this strange-lookingrock formed. You also might wonder why rocks can be smoothor rough, shiny or dull, and can be so many different colors. Sci-ence involves trying to answer questions and solve problems tobetter understand the world. Every time you attempt to find outhow and why things look and behave the way they do, you areperforming science.

What is science?

Figure 5 The columns in DevilsPostpile rise between 12 m and18 m from the valley floor. Thisunusual formation was createdwhen hot lava cooled and cracked.

Identify aproblem

Gather information(research)

Make hypotheses

Test the hypotheses

Analyze the results

Draw conclusions

Figure 4 By using scientificmethods, you can solve manyproblems.

Richard Cummins/CORBIS


Earth Science Science is divided into different areas of study.The kind of science you will learn about this year is Earth sci-ence. Earth science is the study of Earth and space. Some Earthscience topics include rocks, minerals, soil, volcanoes, earth-quakes, maps, fossils, mountains, climates, weather, ocean water,and objects in space. Some of these topics are represented inFigure 6. Much of the information you’ll learn about has beendiscovered through the ages by people who conducted scientifictests or investigations. However, many unanswered questionsremain and much more is waiting to be discovered.

What topics do Earth scientists study?

Working in the Lab Testing, or experimenting, is an important part of science,

and if you really want to learn from an investigation, the exper-iment must be carefully designed. Suppose that after listening toadvertisements for several dishwashing liquids, you want toknow which brand of dishwashing liquid cleans dishes the best.To find the answer, you would need to do some library orInternet research on dishwashing liquids. After researching, sev-eral thoughts might go through your mind. For example, youmight hypothesize that brand X will clean dishes better than anyother brand. You also might consider that there might be no dif-ference in how well the different liquids clean.

Next, you would design an experiment that tests the validityof your hypotheses. You would need to think about which dish-washing liquids you would test, the amount of each dishwashingliquid you would use, the temperature of the water, the numberof dishes you would wash, the kind and amount of grease youwould put on the dishes, and the brand of paper towels youwould use. All these factors can affect the outcome.

Figure 6 Earth science includesthe study of climate, volcanoes,space, and much more.Identify Which Earth sciencetopics are represented here?

Topic: Earth ScienceVisit for Weblinks to information about thedifferent areas of Earth science.

Activity Prepare a collage thatillustrates what you learn.

earth.msscience.com

John Heseltine/Science Photo Library/Photo Researchers



Variables and Constants The different factors that canchange in an experiment are variables. However, you want todesign your experiment so you test only one variable at a time.The variable you want to test is the brand of dishwashing liquid.This is called the independent variable—the variable that youchange. Constants are the variables that do not change in anexperiment. Constants in this experiment would be the amountof dishwashing liquid used, the amount of water, the water tem-perature, the number of dishes, the kind and amount of greaseapplied to each dish, the brand of paper towels that were used,and the manner in which each dish was wiped. For example, youmight use 20 equally greasy dishes that are identical in size,soaked in 20 L of hot water (30°C) to which 10 mL of dishwash-ing liquid have been added. You might rub each dish with a dif-ferent dry paper towel of the same brand after it has soaked for20 min and air dried, as the student in Figure 7 is doing. Ifgrease does not appear on the towel, you would consider thedish to be clean. The amount of grease on the towel is a measureof how clean each dish is and is called the dependent variable. Adependent variable is the variable being measured.

Controls Many experiments also need a control. A control isa standard to which your results can be compared. The controlin your experiment is the same number of greasy dishes, placedin 20 L of hot water except that no dishwashing liquid is addedto the water. These dishes also are allowed to soak for 20 minand air dry. Then they are wiped with paper towels in the samemanner as the other dishes were wiped.

Why is a control used in an experiment?

Figure 7 Wiping each dishin the same manner with a differ-ent paper towel is an importantconstant.Explain why it is necessary to havea constant in your experiment.

Soil Experiment Supposeyou wanted to designan experiment to findout what kind of soil isbest for growing cactusplants. What would beyour variables and con-stants in the experiment?

Aaron Haupt


Repeating Experiments For your results to be valid or reli-able, your tests should be repeated many times to see whetheryou can confirm your original results. For example, you mightdesign your experiment so you repeat the procedures five timesfor each different dishwashing liquid and control. Also, thenumber of samples being tested should be large. That is why20 plates would be chosen for each test of each dishwashing liq-uid. The control group also would have 20 plates. By repeatingan experiment five times, you can be more confident that yourconclusions are accurate because your total sample for eachdishwashing liquid would be 100 plates. If something in anexperiment occurs just once, you can’t base a scientific conclu-sion on it. However, if you can show that brand X cleans best in100 trials under the same conditions, then you have a conclu-sion you can feel confident about.

Testing After you have decided how you will conduct anexperiment, you can begin testing. During the experiment, youshould observe what happens and carefully record your data ina table, like the one shown in Figure 8. Your final step is to drawyour conclusions. You analyze your results and try to under-stand what they mean.

When you are making and recording observations, be sure toinclude any unexpected results. Many discoveries have beenmade when experiments produced unexpected results.

Figure 8 Arranging your data ina table makes the information eas-ier to understand and analyze.

Designing anExperimentProcedure1. Design an experiment to

test the question: Whichflashlight battery lasts thelongest?

2. In your design, be sure toinclude detailed steps ofyour experiment.

3. Identify the independentvariable, constants,dependent variable,and control.

Analysis1. List the equipment you

would need to do yourexperiment.

2. Explain why you shouldrepeat theexperiment.

Aaron Haupt


Technology Science doesn’t just add to the understanding of your natu-

ral surroundings, it also allows people to make discoveries thathelp others. Science makes the discoveries, and technology putsthe discoveries to use. Technology is the use of scientific discov-eries for practical purposes.

When people first picked up stones to use as tools orweapons, the age of technology had started. The discovery of fireand its ability to change clay into pottery or rocks into metalsmade the world you live in possible. Think back to the LaunchLab at the beginning of this chapter. Measuring devices like themetric ruler you used are examples of technology.

Everywhere you look, you can see ways that science and tech-nology have shaped your world. Look at Figure 9 to see howmany examples of technology you can identify in each of the pic-tures. Figure 10 shows a time line of some important examples oftechnology used in Earth science. Notice how different cultureshave added to discoveries and inventions over the centuries.

Figure 9 Examples of technol-ogy are all around you.Identify What are some waysthese examples affect your life?

(t)Michael Dwyer/Stock Boston, (c)Tim Courlas, (b)Mark Segal/Stock Boston

Figure 10

VISUALIZING THE HISTORYOF EARTH SCIENCE TECHNOLOGY


For thousands of years, discov-eries made by people of manycultures have advanced the

study of Earth. This time line shows milestones and inventions that haveshaped the development of Earth sci-ence technology and led to a greaterunderstanding of the planet and itsplace in the universe.

10,000 B.C.: First pottery (Japan)

7000 B.C.: Copper metalworking (Turkey)

80 B.C.: Astronomicalcalendar (Greece)

A.D. 132 (CHINA) Thisearly seismographhelped detect earthquakes.

650: Windmill (Persia)900: Terraced fieldfor soil conservation(Peru)

1090:Magneticcompass(Arabia,China) 1000 (NORWAY) Streamers

tied through holes in Vikingwind vanes indicated winddirection and strength.

1592: Thermometer (Italy)

1998–2006: INTERNATIONAL SPACE STATION With partici-pants from 16 countries, theInternational Space Station ishelping scientists better under-stand Earth and beyond.

1814 (GERMANY) A spectro-scope allowed scientists todetermine which elementsare present in an object or substance that is givingoff light.

1943 (FRANCE) Breathingfrom tanks of compressedair lets divers moveunderwater withoutbeing tethered to an airsource at the surface.

1926: Liquid-fuel rocket(United States)

1880: Modern seismograph (England)

3500 B.C.: Bronze tools and weapons(Mesopotamia)

1538: Diving bell (Spain) 1957:Spacesatellite(formerU.S.S.R.)

A.D.100

1000 B.C.

2000

Streamer holes

(t)Science Museum/Science & Society Picture Library, (cl)reprinted by permission of Parks Canada and Newfoundland Museum, (c, cr)Dorling Kindersley, (b)NASA


Self Check1. Define the term hypothesis. Why must it be testable?

2. Define the term Earth science.

3. Explain why it is important that scientists perform anexperiment more than one time.

4. Think Critically Why is it important to use constants inan experiment?

SummaryMysteries and Problems

• Scientists develop and test hypotheses toexplain phenomena they observe.

Scientific Methods

• Scientific methods consist of a series ofproblem-solving procedures.

Working in the Lab

• Scientists experiment with independent anddependent variables, constants, and controls.

Technology

• Technology uses scientific discoveries for prac-tical purposes.

5. Communicate In your Science Journal, write a para-graph about how you would try to describe a moderndevice such as a TV, microwave oven, or computer to someone living in 1800.

Using Technology Most people immediately think of com-plex and exotic inventions when the word technology is men-tioned. However, the use of scientific knowledge has resulted insuch common yet important things as paper, can openers, buck-ets, aspirin, rubber boots, locks and keys, microfiber clothing,ironing boards, bandages, and scissors. It also has resulted inrobots that check underwater oil rigs for leaks and others thatmanufacture cars. Technology also includes calculators andcomputers that process information.

Transferable Technology Technology is a natural outcomeof using scientific knowledge to solve problems and make people’slives easier and better. The wonderful thing about technology isthat it is transferable, which means that it can be applied to newsituations. For example, many types of technology that are nowcommon were originally developed for use in outer space.

Scientists developed robotic parts, new fibers, and micro-miniaturized instruments for spacecraft and satellites. Afterthese materials were developed, many were modified for usehere on Earth. Technology that once was developed by the mili-tary, such as radar and sonar, has applications in the study ofspace, weather, Earth’s structures, and medicine.

Earth scientists rely on information from weather satelliteslike the one in Figure 11 to gather weather data. But biologistsalso use satellites to track animals. A tiny radio transmitterattached to an animal sends signals up to a satellite. The satellitethen sends data on the animal’s location to a ground station.Some researchers use the data to track bird migration.

Figure 11 Weather satelliteshelp forecasters predict futurestorms.Predict How might this sametechnology be used to protectendangered species?

earth.msscience.com/self_check_quizRuss Underwood/Lockheed Martin Space Systems


SECTION 2 Scientific Enterprise 15

A Work in Progress Throughout time, people have been both frightened by and

curious about their surroundings. Storms, erupting volcanoes,comets, seasonal changes, and other natural phenomena fasci-nated people thousands of years ago, and they fascinate peopletoday. As shown in Figure 12, early people relied on mythologyto explain what they observed. They believed that mythologicalgods were responsible for creating storms, causing volcanoes toerupt, causing earthquakes, bringing the seasons, and makingcomets appear in the sky.

Recording Observations Some early civilizations went sofar as to record what they saw. They developed calendars thatdescribed natural recurring phenomena. Six thousand yearsago, Egyptian farmers observed that the Nile River flooded theirlands every summer. Their crops had to be planted at the righttime in order to make use of this water. The farmers noticed thatshortly before flood time, the brightest star in the sky, Sirius,appeared at dawn in the east. The Egyptians developed a calen-dar based on the appearance of this star, which occurred aboutevery 365 days.

Later, civilizations created instruments to mea-sure with. As you saw in the Launch Lab, instru-ments allow for precise measurements. Asinstruments became better, accuracy of observationsimproved. While observations were being made,people tried to reason why things happened the waythey did. They made inferences, or conclusions, tohelp explain things. Some people developedhypotheses that they tested. Their experimental con-clusions allowed them to learn even more.

Scientific Enterprise

■ Explain why science is alwayschanging.

■ Compare and contrast scientifictheories and scientific laws.

■ Discuss the limits of science.

Science helps you understand theworld around you.

Review Vocabularyobservation: act of using thesenses to gather information

New Vocabulary

• scientific theory • ethics

• scientific law • bias

Figure 12 Early Scandinavian and Germanic peoplesbelieved that a god named Thor controlled the weather.In this drawing, Thor is creating a storm. Lightningflashed whenever he threw his heavy hammer.

Todd Gustafson/Danita Delimont, Agent


The History of MeteorologyToday, scientists know what they know because of

all the knowledge that has been collected over time.The history of meteorology, which is the study ofweather, illustrates how an understanding of one areaof Earth science has developed over time.

Weather Instruments As you have read, ancientpeoples believed that their gods controlled weather.However, even early civilizations observed andrecorded some weather information. The rain gaugewas probably the first weather instrument. The earliestreference to the use of a rain gauge to record theamount of rainfall appears in a book by the ruler ofIndia from 321 B.C. to 296 B.C.

It wasn’t until the 1600s that scientists in Italybegan to use instruments extensively to study weather.These instruments included the barometer—to meas-ure air pressure; the thermometer—to measure tem-perature, shown in Figure 13; the hygrometer—tomeasure water vapor in the air; and the anemome-ter—to measure wind speed. With these instruments,the scientists set up weather stations across Italy.

What instruments were used exten-sively in Italy in the 1600s to studyweather?

Weather Prediction in the United StatesBenjamin Franklin was the first American to suggest thatweather could be predicted. Franklin read accounts of stormsfrom newspapers across the country. From these articles,Franklin concluded that severe storms generally move across thecountry from west to east. He also concluded that observerscould monitor a storm and notify those ahead of its path that itwas coming. Franklin’s ideas were put to practical use shortlyafter the telegraph was invented in 1837.

By 1849, an organized system of weather observation siteswas set up and weather reports from volunteer weatherobservers were sent by telegraph to the Smithsonian Institution.In 1850, Joseph Henry, secretary of the Smithsonian Institutionin the United States, began drawing maps from the weatherdata he received. A large weather map was displayed at theSmithsonian and a weather report was sent to the WashingtonEvening Post to be published in the newspaper.

Figure 13 This photo showsa replica of a 1660 Italian alcoholthermometer.

Smithsonian Institution


National Weather Service By the late 1800s, the UnitedStates Weather Bureau was functioning with more than 350observing sites across the country. By 1923, weather forecastswere being carried by 140 radio stations across the UnitedStates. In 1970, the bureau’s name was changed to the NationalWeather Service and it became part of the National Oceanic andAtmospheric Administration (NOAA).

Today’s weather is forecast using orbiting satellites, weatherballoons, radar, and other sophisticated technology. Each dayabout 60,000 reports from weather stations, ships, aircraft, andradar transmitters are gathered and filed. Figure 14 shows instru-ments used to gather data at a weather station. All the informa-tion gathered is compiled into a report that is distributed to radiostations, television networks, and other news media.

Today, if you want to know about the weather anywhere in theworld—at any time of day or night—you could watch a televisionweather channel, listen to a radio news station, or check aninternet site. If you live in an area that has tornadoes, hurri-canes, or other severe weather conditions, you know it isimportant to have weather watches and warnings available toyour community.

Rain gauge collects and measures rainfall over 24 hours.

Automatically records the amount of rainfall on a chart.

Traps water and then records the rate at which it evaporates.

Measures wind speed near the ground.

Thermometers and hygrometers, which record temperature and humidity, are kept in here.

Transmitsdata

Contains radarequipment

Figure 14 Some weather stations areoperated by meteorologists, but many arenow automated. Data from automated sta-tions are transmitted to a central office,where they are studied.

Topic: Weather ForecastingVisit for Weblinks to information about weatherforecasting.

Activity Prepare a detailed fore-cast for an imaginary snowstormusing information based on theresearch you have conducted.

earth.msscience.com



Continuing ResearchScientific knowledge continues to change as

scientists develop better instruments and testingprocedures. As it changes, scientists have agreater understanding of nature. As you saw inFigure 14, scientists use a variety of technologiesto study weather. Scientists have similar tech-nologies to study Earth’s interior, the oceans,environmental problems, and space. How couldthe technology shown in Figure 15 be used byEarth scientists?

It is impossible to predict the types of instru-ments scientists will have in the future. But it iseasy to predict that as research continues andinstruments improve, knowledge will grow.Perhaps one day you will make a scientific break-through that changes people’s understanding ofthe world.

Scientific Theories As you learned earlier,scientists test hypotheses. If data gathered over along period of time support a hypothesis, scien-tists become convinced that the hypothesis isuseful. They use results from many scientists’

work to develop a scientific theory. A scientific theory is anexplanation or model backed by results obtained from manytests or experiments.

How can a scientific hypothesis become ascientific theory?

Examine how one hypothesis became a theory. Comets oncewere believed to be the forecasters of disaster. People often wereterrified yet fascinated by the ghostly balls appearing in the sky.Slowly over the years, comets lost much of their mystery.However, from the 1800s until 1949, most scientists hypothe-sized that comets were made of many particles of different kindsof materials swarming in a cluster. Based on this hypothesis, acomet was described as a swirling cloud of dust.

In 1949, American astronomer Fred L. Whipple proposed ahypothesis that a comet was more like a dirty snowball—thatthe nucleus of a comet contains practically all of a comet’s massand consists of ice and dust. If a comet’s orbit brings it close tothe Sun, the heat vaporizes some of the ice, releasing dust andgas, which form the comet’s tail. Dr. Whipple’s hypothesis waspublished in the March 1950 Astrophysical Journal.

Figure 15 The GlobalPositioning System (GPS) can pin-point a person’s location on Earth.A radio receiver gets signals fromseveral orbiting Navstar satelliteslike this one. By comparing howfar the receiver is from each satel-lite, the receiver’s position can bedetermined and displayed.

NASA/MSFC


Hypothesis Supported Before it became an accepted the-ory, Dr. Whipple’s hypothesis was subjected to many years oftests and observations. Some of the most important were the1986 observations of Halley’s comet, shown in Figure 16. Agroup of astronomers from the University of Arizona, headed byDr. Susan Wyckoff, studied the composition of the comet. Dr.Wyckoff observed the comet many times, using giant telescopesin Arizona and Chile in South America. At other times, she stud-ied the observations of other astronomers, including those whostudied data collected by the Giotto and other spacecrafts. Allthese observations and data supported Dr. Whipple’s originalhypothesis. With so much support, Dr. Whipple’s hypothesis hasbecome an accepted scientific theory.

Scientific Laws A scientific law is arule that describes the behavior of some-

thing in nature. Usually, a scientific law describes what will hap-pen in a given situation but doesn’t explain why it happens. Anexample of a scientific law is Newton’s first law of motion.According to this law, an object, such as a marble or a spacecraft,will continue in motion or remain at rest until it’s acted upon byan outside force. According to Newton’s second law of motion,when a force acts on an object, the object will change speed,direction, or both. Finally, according to Newton’s third law, forevery action, there is an equal and opposite reaction. This lawexplains how rockets that are used to launch space probes tostudy Halley’s comet and other objects in space work. When arocket forces burning gases out of its engines, the gases pushback on the rocket with a force of equal strength and propel therocket forward.

Figure 16 The view of Halley’scomet from the Giotto spacecraftallowed scientists to determinethe size of the icy nucleus, and thatthe nucleus was covered by a blackcrust of dust. Jets of gas blastedout from holes in the crust to formthe comet’s tail.

Observing aScientific LawProcedure1. Cut one end from a shoe

box.2. Put the box on the floor.

Place a rubber ball in theclosed end of the box.

3. Pushing on the closedend of the box, movethe box rapidly acrossthe floor. Then suddenlystop pushing.

Analysis1. What happened when the

box stopped?2. How does Newton’s first

law of motion explain this?

European Space Agency/Science Photo Library/Photo Researchers


Limits of Science Will science always provide answers to all your questions?

No, science doesn’t have answers to all the questions and prob-lems in the universe. Science is limited in what it can explain.For a question or problem to be scientifically studied, theremust be variables that can be observed, measured, and tested.Problems that deal with ethics and belief systems cannot beanswered using these methods. Ethics deals with moral valuesabout what is good or bad. Belief systems deal with religiousand/or other beliefs. Examples of ethical and belief-system ques-tions that science cannot answer are: Do humans have morevalue on Earth than other life-forms?, Should the federal gov-ernment regulate car emissions?, and Should animals be used inmedical experiments? Look at Figure 17. What’s your opinion?

Why can’t science be used to answer ethicalquestions?

Doing Science Right Although ethical questions cannot be answered by science,

there are ethical ways of doing science. The correct approach todoing science is to perform experiments in a way that honestlytests hypotheses and draws conclusions in an unbiased way.

Figure 17 Ethical questionscan’t be solved by using scientificmethods.

These animals live on theAfrican plains.Form an Opinion Shouldthey be hunted as trophies?

Helmets reduce serioushead injuries.Think Critically Shouldthe government requiremotorcycle riders to wearhelmets?

Disease-carrying mosqui-toes can live in this swamp.Debate Should swamps bedrained, even if otherspecies lose their habitat?

Science Ethics The ques-tion of whether or not touse humans in medicalresearch studies is matterof ethics. As a class, dis-cuss and list some pros andcons of using humans astest subjects. Explain whythere is no right or wronganswer to this question.

(l)Frans Lanting/Minden Pictures, (c)Ted Levin/Animals Animals, (r)Al & Linda Bristor/Visuals Unlimited


Being Objective When you do scientific experiments,be sure that you design your experiments in such a waythat you objectively test your hypotheses. If you don’t,your bias, or personal opinion, can affect your observa-tions. For example, in the 1940s, Soviet scientist TrofimLysenko believed that individuals of the same specieswould not compete with one another. His ideas werebased on the political beliefs held in the Soviet Union atthat time. Based on his personal opinion, Lysenkoordered 300,000 tree seedlings planted in groups in areforestation project. He believed that the trees in eachgroup would aid one another in competing against otherplant species. However, the area where the trees wereplanted was extremely dry, and all of the trees were com-peting for water and nutrients. As a result, many treesdied. Lysenko’s personal opinion and lack of knowledgeturned out to be a costly experiment for the Soviet government.

Suppose you wanted to grow as many plants as possible in asingle flowerpot. Would you assume that all of the plants in thepot shown in Figure 18 could survive, or would you set up anexperiment to objectively test this hypothesis? Unless you testvarious numbers of plants in pots under the same conditions,you could not make a valid conclusion.

Figure 18 These seedlings arecrowded into a single pot.Predict How many do you thinkcould survive?

How can bias affect your observations?

RankingsWithout Hint

5 7

4 5

6 4

5 6

5 3

Average: 5.0

Rankings With Hint

7 8

8 9

9 8

10 8

7 9

Average: 8.3

Do you think bias can affect a person’sobservations? With the help of her

classmates, Sharon performed an experi-ment to find out.

Identifying the Problem Sharon showed ten friends a photo-

graph of an uncut amethyst and askedthem to rank the quality of color from1 to 10. She then wrote the words PrizeAmethyst on top of the photo and askedten more friends to rank the quality ofcolor.

Solving the Problem 1. Examine the tables. Do you think the

hint affected the way Sharon’s classmates

rated the amethyst? What effect did thehint have on them?

2. Do you think bias could affect the resultsof a scientific experiment? Explain. Howcould this bias be prevented?

Matt Meadows


Figure 19 Scientists takedetailed notes of procedures andobservations when they do scienceexperiments.Explain why you should do thesame thing.

Self Check1. Explain why science is always changing.

2. List ways a hypothesis can be supported.

3. Compare and contrast scientific theory and scientific law.

4. Determine What kinds of questions can’t be answeredby science?

5. Think Critically When reading science articles, whyshould you look for the authors’ biases?

SummaryA Work in Progress

• Early people used mythology to explain whatthey observed.

Continuing Research

• After data are gathered over a long period oftime to test a hypothesis, the informationmight be developed into a scientific theory.

• A scientific law is a rule that describes thebehavior of something.

Limits of Science

• Science is limited to what it can explain.

• Scientists need to remain open and unbiasedin their research.

6. Draw Conclusions Describe what would have hap-pened if the 1986 observations of Halley’s comet had not supported Dr. Whipple’s original hypothesis.

Being Ethical and Open People who perform science inethical and unbiased ways keep detailed notes of their proce-dures, like the scientists shown in Figure 19. Their conclusionsare based on precise measurements and tests. They communi-cate their discoveries by publishing their research in journals orpresenting reports at scientific meetings. This allows other sci-entists to examine and evaluate their work. Scientific knowledgeadvances when people work together. Much of the science youknow today has come about because of the collaboration ofinvestigations done by many different people over many years.

The opposite of ethical behavior in science is fraud. Scien-tific fraud involves dishonest acts or statements. Fraud couldinclude such things as making up data, changing the results ofexperiments, or taking credit for work done by others.

earth.msscience.com/self_check_quizBates Littlehales/National Geographic Image Collection


Scientists conduct investigations to learn thingsabout our world. It is important for researchersto share what they learn so other researcherscan repeat and expand upon their results. Oneimportant way that scientific results are sharedis by publishing them in journals and magazines.

Real-World QuestionWhat information about Earth science and sci-entific methods can you learn by reading anappropriate magazine article?

Goals■ Obtain a recent magazine article concerning

a research topic in Earth science.■ Identify aspects of science and scientific

methods in the article.

Materialsmagazine articles about Earth science topics

Procedure1. Locate a recent magazine article about a

topic in Earth science research.

2. Read the article, paying attention to detailsthat are related to science, research, and sci-entific methods.

3. What branch of Earth science does the arti-cle discuss?

4. Describe what the article is about. Does itdescribe a particular event or discuss moregeneral research?

5. Are the names of any scientists mentioned?If so, what were their roles?

6. Are particular hypotheses being tested? Ifso, is the research project complete or is itstill continuing?

7. Describe how the research is conducted.What is being measured? What observationsare recorded?

Conclude and Apply1. Explain Are data available that do or do

not support the hypotheses?

2. Infer What do other scientists think aboutthe research?

3. Are references provided that tell youwhere you can find more informationabout this particular research or themore general topic? If not, what aresome sources where you might locatemore information?

Understanding Scsence Articles

Prepare an oral report on the article you read.Present your report to the class. For morehelp, refer to the Science Skill Handbook.

LAB 23Aaron Haupt

Real-World QuestionA pendulum is an old, but accurate, timekeeping device.It works because of two natural phenomena—gravityand inertia—that are important in the study of Earthscience. Gravity makes all objects fall toward Earth’s sur-face. Inertia makes matter remain at rest or in motionunless acted upon by an external force. In the followinglab, you will test some variables that might affect theswing of a pendulum. How do the length of a pendulum,the attached mass, and the angle of the release of themass affect the swing of a pendulum?

Procedure1. Copy the three data tables into your Science Journal.

2. Bend the paper clip into an S shape and tie it to one end ofthe string.

3. Hang one washer from the paper clip.

Goals■ Manipulate variables

of a pendulum.■ Draw conclusions from

experimentation withpendulums.

Materials string (60 cm)metal washers (5)watch with a second handmetric rulerpaper clipprotractor

Safety Precautions

Testing Variables of a Pendulum


Table 1 Length of the Pendulum

Len Swings Per Stri age

Table 3 Angle of the Release of the Mass

An Swings Per MiRe erage

Table 2 Amount of Mass on the Pendulum

Un Swings Per MiM erage

Mark Burnett

Do not write in this book. Do not write in this book.

Do not write in this book.

4. Measure 10 cm of string from the washer and hold the string at that distancewith one hand.

5. Use your other hand to pull back the end of the pendulum with the washer soit is parallel with the ground. Let go of the washer.

6. Count the number of complete swings the pendulum makes in 1 min. Recordthis number in Table 1.

7. Repeat steps 5 and 6 and record the number of swings in Table 1 under“Trial 2.”

8. Average the results of steps 6 and 7 and record the average swings per minutein Table 1.

9. Repeat steps 4 through 8, using string lengths of 20 cm, 30 cm, 40 cm, and 50cm. Record your data in Table 1.

10. Copy the data with the string length of 50 cm in Table 2.

11. Repeat steps 5 through 8 using a 50 cm length of string and two, three, four,and five washers. Record these data in Table 2.

12. Use 50 cm of string and one washer for the third set of tests.

13. Use the protractor to measure a 90° drop of the mass. Repeat this procedure,calculate the average, and record the data in Table 3.

14. Repeat procedures 12 and 13, using angles of 80°, 70°, 60°, and 50°.

Conclude and Apply1. Explain When you tested the effect of the angle of the drop of the pendu-

lum on the swings per minute, which variables did you keep constant?

2. Infer which of the variables you tested affects the swing of apendulum.

3. Predict Suppose you have a pendulum clock that indicates an earliertime than it really is. (This means it has too few swings per minute.)What could you do to the clock to make it keep better time?

Graph the data from your tables. Title andlabel the graphs. Use different coloredpencils for each graph. Compare yourgraphs with the graphs of other membersof your class.

LAB 25Timothy Fuller

“The Microscope”by Maxine Kumin

Anton Leeuwenhoek was Dutch.He sold pincushions, cloth, and such.The waiting townsfolk fumed and fussedAs Anton’s dry goods gathered dust.

He worked, instead of tending store,At grinding special lenses forA microscope. Some of the thingsHe looked at were: mosquitoes’ wings,the hairs of sheep, the legs of lice,the skin of people, dogs, and mice;ox eyes, spiders’ spinning gear,fishes’ scales, a little smearof his own blood, and best of all,the unknown, busy, very small bugs that swim and bump and hopinside a simple water drop.

Impossible! Most Dutchmen said.This Anton’s crazy in the head!We ought to ship him off to Spain.He says he’s seen a housefly’s brain.He says the water that we drinkIs full of bugs. He’s mad, we think!

They called him dumkopf, which means “dope.”That’s how we got the microscope.

Respond to the Reading1. Do you think Anton was a scientist by

trade? Why or why not? 2. What did Anton find inside a water drop?3. Linking Science and Writing Write a

heroic verse or poem that rhymes. Pick ascientific method or discovery from yourtextbook.

Scientific instrumentscan increase scientific

knowledge. For example, microscopes havechanged the scale at which humans can makeobservations. Electron microscopes allowobservers to obtain images at magnifications of10,000� to 1,000,000�. In a microscope witha magnification of 10,000�, a 0.001-mmobject will appear as a 1-cm image.Microscopesare used in Earth science to observe thearrangement and composition of minerals inrocks.These give clues about the conditions thatformed the rock.

UnderstandingLiteratureRhyming Couplets A couplet is a poeticconvention in which every two lines rhyme.Some of the most famous poems that userhyming couplets describe heroic deeds andoften are epic tales. An epic tale is a longstory that describes a journey of exploration.Why do you think the poet used rhymingcouplets in the poem you just read?


Maxine Kumin

AP/Wide World Photos

Copy and complete the following concept map about variables andconstants.

Science All Around

1. Scientific methods include identifying aproblem or question, gathering informa-tion, developing hypotheses, designing anexperiment to test the hypotheses, perform-ing the experiment, collecting and analyz-ing data, and forming conclusions.

2. Science experiments should be repeated tosee whether results are consistent.

3. In an experiment, the independent variableis the variable being tested. Constants arevariables that do not change. The variablebeing measured is the dependent variable.A control is a standard to which thingscan be compared.

4. Technology is the use of scientific discoveries.

Scientific Enterprise

1. Today, everything known in science resultsfrom knowledge that has been collectedover time. Science has changed and willcontinue to change because of continuingresearch and improvements in instrumentsand testing procedures.

2. Scientific theories are explanations ormodels that are supported by repeatedexperimentation.

3. Scientific laws are rules that describe thebehavior of something in nature. They donot explain why something happens.

4. Problems that deal with ethics and beliefsystems cannot be answered using scientificmethods.

CHAPTER STUDY GUIDE 27

Possible Hypothesis:The amount of salt in water affects how fast brine shrimp eggs hatch.

the independent variable is

Length of time for eggs

to hatch

the dependent variable is

Amount of water

the constants are

earth.msscience.com/interactive_tutor(l)CABISCO/Visuals Unlimited, (r)Jan Hinsch/Science Photo Libray/Photo Researchers


Use what you know about the vocabulary wordsto explain the differences between the words inthe following sets. Then explain how the wordsare related.

1. constant—control

2. dependent variable—independent variable

3. scientific law—scientific theory

4. science—technology

5. hypothesis—scientific theory

6. science—Earth science

7. independent variable—constant

8. variable—control

9. Earth science—technology

10. ethics—bias

Choose the word or phrase that best answers thequestion.

11. Which word means an educated guess?A) theoryB) hypothesisC) variable D) law

12. The idea that a comet is like a dirty snow-ball is which of the following?A) hypothesis C) lawB) variable D) theory

13. Which of the following is the first step inusing scientific methods?A) develop hypothesesB) make conclusionsC) test hypothesesD) identify a problem

14. The statement that an object at rest willremain at rest unless acted upon by a forceis an example of which of the following? A) hypothesis C) lawB) variable D) theory

15. Which of the following questions couldNOT be answered using scientific methods?A) Should lying be illegal?B) Does sulfur affect the growth of grass?C) How do waves cause erosion?D) Does land heat up faster than water?

16. Which of the following describes variablesthat stay the same in an experiment?A) dependent variablesB) independent variablesC) constantsD) controls

17. Which of the following is a variable that isbeing tested in a science experiment?A) dependent variableB) independent variableC) constantD) control

18. What should you do if your data are dif-ferent from what you expected?A) Conclude that you made a mistake in

the way you collected the data.B) Change your data to be consistent with

your expectation.C) Conclude that you made a mistake

when you recorded your data.D) Conclude that your expectation might

have been wrong.

28 CHAPTER REVIEW

bias p. 21constant p. 10control p. 10dependent variable p. 10Earth science p. 9ethics p. 20hypothesis p. 7

independent variable p. 10science p. 8scientific law p. 19scientific methods p. 8scientific theory p. 18technology p. 12variable p. 10

earth.msscience.com/vocabulary_puzzlemaker


CHAPTER REVIEW 29

19. Recognize Cause andEffect Suppose youhad two plants—acactus and a palm.You planted themin soil and wateredthem daily. After twoweeks, the cactus was dead. What scientificmethods could you use to find out whythe cactus died?

20. Think Critically How have advances in tech-nology affected society?

21. Explain what is meant by the statement,Technology is transferable.

22. Evaluate Why don’t all hypotheses becometheories?

23. Identify some scientific methods you useevery day to answer questions or solveproblems?

24. Identify and ManipulateVariables and ControlsHow would you setup a simple experi-ment to testwhether salt-crystalgrowth is affectedby temperature?

25. Form Hypotheses Youobserve twobeakers containingclear liquid and icecubes. In the first beaker, the ice cubes arefloating. In the second, the ice cubes areon the bottom of the beaker. Write ahypothesis to explain the difference inyour observations about the two beakers.

26. Recognize Cause and Effect Explain why scien-tific methods cannot be used to answerethical questions.

27. Draw Conclusions A laboratory tests a hypoth-esis through an experiment and publishesits findings that confirm the hypothesisis true. Ten other laboratories attempt toduplicate the findings, but none are ableto prove the hypothesis true. Give a possi-ble explanation why the labs’ results didnot agree.

28. Poster Research an example of Earthscience technology that is not shown inFigure 10. Create a poster that explains thecontribution this technology made to theunderstanding of Earth science.

Use the table below to answer questions 29–30.

29. A Color Experiment A friend tells you that darkcolors absorb more heat than light colors do.You conduct an experiment to determine whichcolor of fabric absorbs the most heat. Analyzeyour data below. Was your friend correct?Explain.

30. Variables Identify the independent variablesand the dependent variables of the experiment.

Color and Heat Absorption

Conn ature (°C)at 0 minutes

Re 4° 6°Bl 4° 8°Bl 4° 7°W 4° 5°Gr 4° 7°

earth.msscience.com/chapter_reviewPaul Silverman/Fundamental Photographs


Record your answers on the answer sheetprovided by your teacher or on a sheet of paper.

Use the illustration below to answer question 1.

1. The test tubes were left at room temperaturefor a week to see if algae would grow. Whichvariable is being investigated?A. the volume of water usedB. the temperature of the test tube’s

contentsC. the amount of chlorine presentD. the amount of algae present

2. Which of the following is the study ofEarth and space?A. life scienceB. Earth scienceC. physical scienceD. chemical science

3. Which of these is a factor to which experi-mental results can be compared?A. independent variableB. dependent variableC. controlD. constant

4. What is the use of scientific discoveries forpractical purposes?

A. biasB. scientific methodsC. scienceD. technology

5. Which of the following is an explanation ormodel that is supported by many experi-ments and observations?A. hypothesis C. theoryB. law D. estimate

6. Which is a rule that describes the behaviorof something in nature?A. hypothesis C. estimateB. law D. theory

Use the illustrations below to answer questions 7–9.

7. Which quality can be measured using thetools in group A?A. distance C. volumeB. weight D. mass

8. Which quality can be measured using thetools in group B?A. distance C. volumeB. weight D. mass

9. Which of the following belongs in group Babove?A. spring scale C. beakerB. thermometer D. stopwatch

Group A Group B

10mL

15mL

5mL

25mL

20mL

35mL

30mL

10mL

15mL

5mL

25mL

20mL

35mL

30mL

10mL

15mL

5mL

25mL

20mL

35mL

30mL

10mL

15mL

5mL

25mL

20mL

35mL

30mL

20 mL water0 mL chlorine




30 STANDARDIZED TEST PRACTICE

Standardized Test PracticeStandardized Test Practice

STANDARDIZED TEST PRACTICE 31

Record your answers on the answer sheetprovided by your teacher or on a sheet of paper.

10. What’s the difference between an inde-pendent variable and a dependent variable?

11. Which types of questions can be answeredusing scientific methods?

12. What can scientists do to ensure that theyperform experiments objectively?

13. Why is it a good idea to repeat anexperiment?

14. Would a scientist be convinced that his orher results were accurate after one trial?Why or why not?

Use the illustration below to answer questions 15–17.

15. Alicia taped the meterstick shown above toher bedroom wall and recorded her heighton her birthday for five consecutive years.The bottom of the meterstick was 1 mabove the floor. How many centimeters tallwas Alicia when she was 10 years old?

16. How many centimeters did she growbetween her 10th birthday and her 14thbirthday?

17. What was the maximum amount thatAlicia grew in any one year?

18. Describe the steps of the scientificmethod. Give an example experimentusing the steps.

19. Define the terms scientific theory andscientific law. Give an example of each.

Record your answers on a sheet of paper.

Use the graph below to answer questions 20 and 21.

20. Describe how the average high tempera-ture changes through the year inCharlotte, North Carolina. Which monthis warmest? Which is coldest? How muchis the difference?

21. How do you think the average temperaturedata for Charlotte, N.C. were obtained?What measurements were recorded? Whatcalculations were performed?

22. Why is it important to take good notesand record all data when performing anexperiment?

23. Why does science lead to better technol-ogy and technology lead to better science?

Average High Temperature, Charlotte, NC

46

20

8

28

101214161820222426

MonthTe

mp

erat

ure

(�C)

Jan.

Feb.

March AprilMay

June

July

Aug.Sept.

Oct.Nov.

Dec.

1 m above floor

cm 10 20 30 40 50Age 10 Age 11 Age 12 Age 13 Age 14

Your Experiences Remember to recall any hands-onexperience as you read the question. Base your answer on theinformation given on the test.

Question 21 Recall the procedure from the pendulum lab.Remember how the record of your data helped you completethe lab.

earth.msscience.com/standardized_test


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