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ABSTRACT

DOCUMENT RESUME

SE 051 526

More Science Activities. 20 Exciting Experiments ToDo!

Smithsonian Institution, Washington, D.C.ISBN-0-939456-16-888

156p.; For a related document, see SE 051 527.Galison Books, 36 West 44th Street, Room 910, NewYork, NY 10036 ($9.95).Guiaes Classroom Use - Guides (For Teachers) (052)

MF01/PC07 Plus Postage.Biological Sciences; *Elementary School Science;Elementary Secondary Education; Intermediate Grades;*Laboratory Procedures; *Middle Schools; PhysicalSciences; *Science Activities; Science Education;Teaching Guides

Science and technology affect every facet of humanlife. By the 21st century, society will demand that all of itscitizens possess basic competencies in the fundamentals of scienceand the use of technology. As science increasingly becomes thedominant subject of the work place, it is important to begindeveloping within children an understanding and appreciation ofscience early in their lives. This book provides suggestions forinteractive science activities that can be done in a variety ofsettings, using inexpensive and readily available materials. Theactivities are designed as supplementary curricular materials andeducational guides for use in teaching science. Each of the 20activities in this book includes a list of materials, some backgroundinformation, procedures, and suggestions for variations. Topics inthis volume include making ginger ale; boats; mak4..ng a strobe light;plants; flight; feeding birds; mud; nocturnal games; taste; making akaleidoscope; vegetables; fruit flies; nutrition; rockets; makingpaper; ice cream; parachutes; magic; light; and making a radio.(CW)

-?:

* Reproductions supplied by EDRS are the best that can be made* from the original document.

FROM THE SMITHSONIAN INSTITUTION

eto

20 ExcitingExperimentsTo Do !

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"PERMISSION TO REPRODUCE THISMATERIAL HAS BEEN GRANTED BY

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U S DEPARTMENT OF EDUCATIONOft. of Enucationel Research and improvement

Er) TIONAL RESOURCES INFORMATIONCENTER (ERIC)

This document has been reproduced asreceived from the person or organizationoriginating itMinor changes have been made to improvereproduction Quality

Points of view or opinions stated in this documen, do not necessarily represent officialOERI position or policy

REST MPY AVAIL AR! F

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FROM THE SMITHSONIAN INSTITUTION

ACTIVITIESGALISON BOOKS

GMG PUBLISHING, NEW YORKAND

SCIENCE LEARNING, INC.ANNAPOLIS, MARYLAND

Copyright 1988 in all countries of the sntemational CopyrightUnion by the Smithsonian Institution All rights reserved

A Galison BookPublished by GMG Publishing Corp25 W 43rd StreetNew York, NY 10036

ISBN 0-939456-16-8

Project Director John Falk, Ph DAuthors Megan Stine, Craig Gillespie, Gladys StanburyLaurie Greenberg, Jamie Harms, Sharon Mayes,Larry Malone, Carol Moroz-HenryReviewer Kathy Faggella

Designer Marilyn RoseDesign Assistant Christine KirkIllustrator Simms TabackEditor Cheryl SoliminiProduction Editor Nora GalvinPublisher Gerald Galison

Third Printing

I

CONTENTSGinger Ale 11

Boats Afloat 15Flash Dance 19Fancy Plants 23Just Plane Wings 27For The Birds 31

Mud Pies 35Night Moves 39A Matter of Taste 43Kaleidoscope 47Karate Chop Veggies 51

Shoo Fly, Fruit Fly 55Greasy Kid Stuff 59Rockets Away 63Marbleized Paper 67Ice Cream Machine 71

Skydiver 75Science Magic 79Color & Light 83Crystal Radio 87

INTRODUCTION

Science and technology touches nearly every facet of our lives today By the 21st century, oursociety will demand that all its citizens possess basic competencies in the fundamentals ofscience and the use of technology. As science increasingly becomes the dominant subject of

the work place, it is important to begin developing within children an understanding andappreciation of science early in their lives.

Learning can, and does, occur in many places and many situations. Learning occurs in school, athome, and on the trip between home and school. This book provides suggestions for interactivescience activities that can be done in a variety of settings, using inexpensive and readily availablematerials. Whether the activities are done in a classroom or in a home, they will provide adults andchildren with increased opportunities to explore natural phenomenon in an engaging ana excitingway. Included are experiments, activities, crafts, and games that allow you, whether teacher orparent, to learn science along with your children. The only requirements for success are thedirections provided with each activity, a few common household items, a little bit of time, andsome cunosity and imagination. The activities in this book are designed as curricular materials,educational guides for you to use in teaching science.

SOME SUGGESTIONS FOR TEACHERSThe activities in this book should be used as supplements to your normal classroom sciencecurricula. Since they were originally developed for use in out-of-school situations, they mayrequire some minor modifications to permit a larger number of children to participate.

Nonetheless, you will find tnat these activities lend themselves well to a fun-filled science lessonfor all participants.

An increasing number of school districts are exploring the use of "take- home" lessons in order tobuild stronger learning partnership bonds between parents and teachers, home and school Thesematerials have proven to be an excellent source for such "teal n-building" efforts. Both teachers andparents find these activities rewarding ways to provide quality learning experiences for children.

SOME SUGGESTIONS FOR PARENTS

0ne of the most important jobs that you have, as a parent, is the education of your children.Every day is filled with opportunities for you to actively participate in your child's learning.Together you can explore the natural world and maize connections between classroom

lessons and real-life situations. You will learn the value of asking good questions, as well as strategiesfor finding answers to those questions.

10

FOR BOTH TEACHERS AND PARENTSThe best things you can bring to each activity are your experience, your interest, and, mostimportantly, your enthusiasm. These materials were designed to be both educational andenjoyable. They offer opportunities for discovery, creative thinking, and fun.

HOW TO USE THIS BOOKThe science activities in this book can be successfully implemented by any interested adult,regardless of his of her science background. Accordingly, the above have been designed sothere is no one "correct" solution and no "right" way to do it. Do not be afraid to say "I don't

know!"There are twenty activities in this book; since every classroom and family is different, not all

activities will be equally suitable. Take the time to browse through the book and find the ones thatseem to make sense for your class or family. There is no prescribed order to these activities, nor anynecessity to do all of them. Once you have selectedan activity to do, take the time to read through itbefore you attempt to do it.

At the beginning of each activity is a list of all the materials you will need to do the project. Try toassemble all of these items before you begin. TI,' procedures have been laid out in an easy-to-follow, step-by-step guide. !f you follow these directions, you should have no difficulty doing theactivity. Once you have completed the basic activity, there are also suggested variations that youcan try, now or later At the end of each activity is an 'Afterwords"section. This section is for you, theadult. It is intended to provide additional information, not on how to help children but for theinterest of an adult participanttake some time to read it for your own enjoyment.

ASKING QUESTIONSEncourage your children to ask questions, even if you don't know the answers The essence ofscience is asking questions, and then trying to find out the answers Some of the answers canbe discovered in books, some through observation, and some, at present, are unanswerable

by anyone. Ask questions like:(before you start)"What do you think is going to happen wnen we do this experiment?"(during the activity)"What do you see?""Does this remind you of anything else you've ever seen?'(after the activity Is con ipleted)"What do you know about X now, that you didn't know before we started?"

1i

"Is there anything you don't understand? Haw can we find out the answc.?"Encourage all kinds of answers, and all kinds of questions. Sometimes the crazy ones are the ones

that work. Often there is more than one answer to a question, so be tolerant of diversity and open tomultiple solutions. Use the library or an encyclopedia to help answer questions and further yourunderstanding. Lead, or have a child lead, a discussion after the project is completed. This will helpto pull together what happened, why things happened, and what the activity was all about. Justremember that it may take more than one exposure for some of the ideas introduced in theseactivities to "sink in." These activities are beginnings, not endings. Finally, don't be afraid to be alearner yourself--that was a large part of why these activities were developed in the first place.They are for learning, adults and children together.

John H. Falk, Ph.D.

PresidentScience Leaming, Inc.

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Ginger ale takes about anhour and one-half to prepare.It must be bottled after sixhours Ginger ale will tastebest if you wait two daysbefore drinking.

YOU WILL NEED

Pot filled with 4 quartswater

3 Tablespoons ginger1/2 Lime

2Y2 Cups sugar

3 Tablesp( lns creamof to tar

1 Tablespoon baker's yeastCheesecloth or coffee filterFunnel, mixing spoon, stoveGallon jug with cap or cork

Have you ever wonderedwhat makes ginger ale fizzy?All the little bubbles you seewhen you open a bottle ofginger ale are carbon dioxidea gas that's in the air youbreathe. Because bubblydrinks have carbon dioxide,they are often calledcarbonated drinks.

But how does the carbondioxide get into the drink?The Key is something called

yeast. Yeast makes the differ-

ence between "flat" waterand fizzy soda See the differ-ence for yourself when youmix water, yeast and flavoringsto make your own ginger ale

WHAT IS YEAST?

Yeasts are tiny, living plants.

They are not active in yourrefrigerator because the coldkeeps them in hibernation.But when you put them in awarm, moist place and givethem sugar to eat, they get ac-tive and make carbon dioxidegas. This gas can make breadrise or drinks fizzy.

You can put a little yeastinto a closed jug with warm,sugary water. As long as theyeast have enough sugar toeat, they'll keep making car-bon dioxide. When the airspace above the water fillswith carbon dioxide, the gasbubbles can't escape andthey stay in the water. Thismakes the water carbonated.If the cap is loose, all the car-bon dioxide will escape fromthe jug. You'll get "flat"ginger ale.

Boil the water in thepot Add.

Three tablespoonsginger Use powdered gingerfrom the grocery store spicesection or pound fresh gingerroot from the produce section.

Juice squeezed fromone-half of a lime.

Two and one-half cupssugar. Mix it well with a spoonuntil the sugar dissolves.

Three tablespoons creamof tartar. Mix well again.

2Let the mixture coolto lukewarm. It is luxe-warm when you put a

drop on your wrist and it feelswarm, but not hot. Ask yourparents to show you how it isdone. (Be careful. If the mixtureis too hot, it will kill the yeast.It may also burn your wrist.)Once it's lukewarm, add 1tablespoon baker's yeast andmix well. Cover the pot andlet the mixture sit for six hours.

Now it is time to bottleyour ginger ale Startby straining it through

a coffee filter or cheesecloththat's set into the top of afunnel. Some bits and piecesmay slip through the cheese-cloth. That's okay. They willsettle to the bottom. Be sureto leave an air space at thetop of the bottle to collectcarbon dioxide. Without thespace, your jug may blowits top.

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4Once the ginger ale isin the jug, cap it tightlyend put it into the refrig-

erator. Make sure you keepyour ginger ale in the refriger-ator. If it's not kept cool, theyeast will be very active mak-ing carbon dioxide and alco-

hol. Alcohol may be fine insome adult drinks, but it is notfine in ginger ale. It will giveyour ginger ale an unpleasantflavor.

5You can drinkyour ginger aleright away, but it

will taste better if youwait two days. Whenyou take your gingerale out of the refrig-erator, look for thebubbles.

461.14

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Watch them rise to thesurface and release their car-bon dioxide. Slowly unscr'wthe top of the jug. Listen for aslow fizzle and then a POP!when the gas escapes fromthe jug. What does your brewsmell like? More important,how does it taste?

VARIATIONS

Give ;your ginger ale even

more flavor by adding a CUDof fresh, chopped mint leaveswhen you put the ginger in.Then just strain them out withthe ginger.

Try using honey to replacethe sugar called for in theexperiment.

For another taste treat, addyour homemade ginger ale tolemonade or fruit juices. Makeup your own variations. Withhomemade ginger ale, creativ-ity is always in good taste.

I "7 13

AFTERWORDS

Yeasts are very tiny plants.They are related to mush-rooms, molds, and otherfungi. Like other fungi, yeastscan t produce their own food.To get energy, yeasts must first

break down sugars and othercarbohydrates.

Yeasts Lake in sugar, a mol-

ecule high in energy, and breakit down into carbon dioxideand alcohol. This process iscalled fermentation. Yeastsuse the energy released fromthis breakdown to supporttheir own life processes.A similar reaction occurswhen campers set fire to apile of wood to release heat.

Through research andbreeding experiments scien-tists have teamed to produceyeasts that can make espe-cially large amounts of carbondioxide and yeasts that canmake especially large amountsof alcohol.

Bakers take advantageof yeast that makes high levelsof carbon dioxide in br1/4..,d-

making. The gas bubbles thatthe baker's yeast gives offmakes bread dough rise.

To make wine and beer,

brewers use a yeast that pro-duces high levels of alcohol.Since early times, brewer'syeast has also been usedto cure various illnesses. It

contains large amounts ofB-complex vitamins that canbe used by people. Baker'syeast does not.

The carbonation in yourfamily's ginger ale results fromthe same reaction that occursin your homemade bread orbiscuits. Baker's yeast createscarbon dioxide that makes thebread dough rise. In the caseof your ginger ale, the bottlecap keeps the carton dioxidebubbles from escaping. Theystay in the ginger ale solution,giving it that carbonated fizz.

Commercially made gingerale goes through a differentprocess. Instead of lettingyeast make carbon dioxidebubbles, ginger ale manufac-turers pump carbon dioxideinto the ginger ale solution.The whole process is doneunder pressure, so that thegas bubbles are forced intothe solution. Pi° end productis the samea fizzle whenyou open the bottle and bub-bles of carbon dioxide youswallow when you drinkginger ale.

Yeasts contribute to theproduction of several othercommercial food products.When fermentation is allowedto occur in the presence ofoxygen, the yeast producesvinegar instead of alcohol.A poorly sealed bottle ofwine may let oxygen into it,causing the wine to turn tovinegar. In the past, bacterialinvasions into yeast doughshave resulted in new breadvarieties. For instance, bothrye and sourdough breads aremade with a special "starter.'The starter consists of theyeast dough combined withunique bacteria that givesa distinct flavor to each ofthese breads.

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16

OATS FLO TPlanning an ocean voyage?Maybe you'd better take anhour to try this experimentbefore you set sail!

YOU WILL NEED

Plasticine or florist's clay1 or 2 Large pots, pans,

or basins1 Pound of 1" finishing nails,

or 2 or 3 dozen marblesall the same size,

or box of paper clipsCookie cutter or jar lid11/4 Cups salt

2 Cups cooking oil2 Bottle caps, 20" string,

tape, long (1" or more)pin, plastic soda straw,2 tal! drinking glasses

Drop a steel nail into the waterand it sinks right to the bottom.So how is it possible that ahuge steel ship floats? Youmay think it has somethingto do with air trapped incompartments in the bottom

of the ship. A little researchwill tell you if this is true or not.

IRoll a piece of Plasticineor clay into a ball aboutthe size of a golf ball.

What happens when youdrop the ball into a pot ofwater? Now take the ball andform it into a flat boat shape.Then take some small objectslike nails, marbles, or paperclips and drop them in theboat. How many weights willyour boat hold before it sinks?Now mold the same piece ofPlasticine or clay into differentboat shapes. What is the mostany of these boats can holdand still float? What shapeof boat seems to be ableto carry the most?

2Now organize a con-test to see whose boatcan carry the biggest

load. Use a cookie cutter or jarlid to cut pieces of Plasticineor clay that are all the samesize. Give each person a piece

and have them build theirown boats. Make up somecontest rules. You'll have todecide when a loaded boat isstill considered "floating":when it is halfway above thewater, a quarter of the way, orjust slightly under the water?Must the boat stay afloat for aminute or two after the lastweight is added?

3 Try this contest: Whocan build the smallestboat able to keep one

marble afloat? You may needto make a balance to help youdecide the winner of this con-test. (See, Making a Balance,on this page.)

4 See how saltwater canaffect your ships' abilityto float. Mix 11/4 cups

of salt with 1 quart of water(double these amounts if you

need to). Let the saltwaterstand for a while before youwork with it. Meanwhile, floatone boat in freshwater andwrite down how manyweights it can carry. Then putthe same boat in the saltwater.Does the number of weightschange? (Saltwater can berough on your hands, so usea plastic spoon to fish yourboats and weights out.)

5Now you've !earnedthat the type of wateritself works in helping

boats float. But what wouldhappen if you used 2 cups ofcooking oil i )stead of water?How many weights can yourboat cairy then?

MAKING A BALANCE

1. Cut the 20" string in two.Cross the two 10" strings ontop of a bottle cap and tapethem in place. Turn the bottlecap over and pick up the fourends of the strings. Knot themtogether about 3" away fromthe cap. This is one balancepan.

9 n

2. Make another balance pan.Then hang one on each endof a plastic soda straw. Tapethem in place. Push a long pinthrough the center, halfwaydown the straw. Stand twodrinking glasses or jars closeenough together so that thepin can rest on both rims andthe balance can move freely.(Wiggle the pin back and fortha few times if the hole seemstoo tight.)

3. If your balance isn't exactlylevel when it is empty, stickbits of Plasticine or clay onthe higher pan until it is levelwith the other. When you aretrying to fi 'd out whose boatis smallest for Experiment Step

2TALL DRINKING&LASSES ----a

3, put a boat in each of thepans. When you see which isthe lighter boat, leave it in onepan and set another boat inthe second pan. Continue toweigh the boats against eachother until you find the lightestonethe winner!

AFTERWORDS

Archimedes is probably themost famous bather of all time.He lived in Sicily more than2,000 years ago and was afriend of the king. The kingsuspected that his new crownwas not pure gold and askedArchimedes to investigate.

Archimedes could find outeasily how much the crownweighed, but he didn't knowhow to calculate its vaurne(the amount of space it tookup). As the story goes, Archi-medes was lowering himselfinto his filled bathtub when henoticed the water spilling overthe sides. Supposedly he wasso excited by his discoverythat he ran into the street yell-ing, "Eureka!"("I have foundit!" the answer to his prob-lem). He then dropped thecrown into a full basin ofwater, catching the overflow.Next he weighed it against anequal volume of pure gold.

2

His demonstration for the kingshowed that the pure goldwas heavier than the "gold"crown, thus proving that ithad been mixed with a lighter,cheaper metal. Some detec-tive work!

When a ship is loweredinto water, it displaces thewater, pushing it out of theway. It does this until tieweight of the displacementequals the weight of the ship

and the ship floats. Remem-ber how your ball of Plasti-cine or clay sank? But afteryou flattened it out and turnedup the edges, it floated. Theshripe of the thinner hull wasable to displace enough waterto equal the weight of thePlasticine plus its load.

Up until about 100 yearsago, a ship's owner couldhave loaded his vessel with asmuch as he pleased. Manyoverloaded ships and theircrews were lost when theboats sank in storms at sea.Then, in 1876, Samuel Plimsoll

persuaded the British govern-ment to pass a law to controlthe loading of ships. The lay.required that every ship bemarked with a horizontal lineon its side to show the safeloading limit.

C = Coastal ServiceTF = Tropical FreshwaterT = TropicalF = FreshwaterS = SummerW = WinterWNA = Winter North

AtlanticAB = American Bureau

of Shipping(the authority thatdecides where themarks should be)

Notice that the Plimsollmarks also show the safe-loading limits for ships in dif-ferent kinds of water and indifferent seasons. That's be-cause, if you have two identi-cal buckets and fill one withsaltwater and the other withfreshwater, the saltwater willweigh more. Saltwater is moredense, therefore heavier, thanfreshwater. Also, a bucket ofwarm saltwater from the Gulfof Mexico will weigh less thanthe same bucket filled withcold North Atlantic saltwater

because cold water is moredense than warm water. Watertemperatures also changeaccording to the season.

Remember that a loadedship floats because it displacesits own weight? Well, in densewaters (cold -r saltwater), theship won't sink as low into thewater. In warm or non-saltywaters, the ship has to dis-place more water in orderto float. So, if an ocean vesselloses its way and happens tochug up the freshwater Mis-sissippi River, it will sink lowerinto the! water.

18

255

1St

MI DANCEPut on your dancing shoesit's time to boogie! All youneed is a strobe to light upyour life and help you catchall the flashiest action! It shouldtake about 30 minutes to make.

YOU /ILL NEED

Empty cardboard box about16" by 16" by 9"or at least 2" narrowerthan the length of yourdrill and bit

Pencil and compass fordrawing a circle

Utility knife

Crank-type hand drill with1/4" drill bit

Piece of cardboard fromanother box, 12" by 12"

Scissors

Jumbo-size drinking strawMasking tapeRuler

Bright flashlightBicycle (optional)

Have you ever seen peopledancing in the light of a flash-ing strobe? Their movementslook jerky like they're mov-ing in slow motion. With astroboscope, you can createall kinds of special visual

effects. You can even makedrops of water seem to stopin midair! Just get ready...turnout the lights... and do theFlash Dance!

1To make your strobo-scope, or strobe light,you will need to cut

several holes in two sides ofyour cardboard box. Use thetwo biggest sides of the boxand consider one side the"front" and the other the"back!"

First, make a small holewith the point of your pencilin the ront of the box. Positionthe holc about 3" down fromthe top of the box, and cen-

tered between the corners.Then use a utility knife or scis-sors to cut a vertical openingin the back of the box, oppo-site the pencil hole.This verti-cal stash should start at thetop of the box and be about3" long. Make the opening11/2" wide or wide enoughso that the handle of your drillcan sit in the space you'vemade. Be sure to center theslash between the corners ofthe box. Now you should beable to push the drill bitthrough the hole in the front,and rest the drill handle in theslash in the back of the !,ox,as shown in the diagram.

2Use a compass to drawa circle 12" in diameteron the extra piece of

cardboard and cut the circleout with scissors. Draw a lineacross the circle, through the

center hole, to mark the diam-eter. Cut two slots in the disk,on the diameter line, eachstarting about one 'nch fromthe edge of the circle. Eachslot should be 2" long and1/2" wide. With a pencil, pokea hole in the exact center ofthe disk. Make the hole justbig enough to push the drink-ing straw through.

3Cut off a piece of thestraw, making it thesame length as the drill

bit. In one end of the straw,use scissors to cut 4 slashes,each about 1" long. Now youshould be able to bend thefour split ends of straw back-ward, to use as tabs.

4Push the straw throughthe hole in the disk,and bend the tabs flat

cur STRAW SAME LENGTH AS4-- DFULL. BITG=CatOzEN:

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26

against With masking tape,secure the tabs to the face ofthe disk. Remove the drill bitfrom the drill, and put the bitinside thE itraw, with thepoint of the bit going towardthe tabs. Now the drill bit is in-side the straw, and the strawis attached to the cardboarddisk. Stick the straw-and-bitcombo through the hole inthe front of the carton. Frominside the carton, tighten thestraw-and-bit combo in thedrill chuckthe place wherethe drill bit fits into the drill. Ifyou have done this correctly,you will be able to turn thecrank on the drill and see thedisk spin around.

5Next you will needto cut a square hole 2"by 2" on the front of

the carton. Ybu must make

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sure that the slots in the diskwill pass right over this holeas the disk turns. To mark theplace, hold the disk still andmake a line on the carton bydrawing through one of theslots. Then cut through themark with the utility knife.Now, working from the insideof the box, enlarge the holearound the cut you just made,so that the hole is 2" square.

6Another hole must bemade in the back of thebox, exactly opposite

the 2" square hole in the front

of the box. Make this last holejust big enough for your flash-light so that the flashlightcan be wedged tightly intothe hole. The flashlight shouldshine directly through the 2"square hole in the front.

INow its showtime!Turn out all the lights,and turn on the flash-

light. When you rotate thedisk by turning the drill crank,the light will shine out of thefront of the box in flashes. Thefaster you turn the crank, thefaster the strobe will flash.

s,

411

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You may need a friend ortwo to help vou experimentwith your strobe. One personcan hold the flashlight, to makesure the light is shining straight

through the 2" square hole inthe front. (Or balance the flash-light on some books set in thebox.)Another person can turnthe crank on the drill whileyou try these experiments:

Put on light-colored clothesand dance in the strobe-lightbeam! Can you figure out wi- /your movements look jerky?

Turn on a water faucet sothat the water comes out in athin stream of droplets. Thenturn out the lights and shineyour flashing strobe at thewater. Can you make thedrops hang in space? Canyou make the drops of waterappear to move upward?

Turn your bicycle upsidedown and spin the frontwheel. With all the lights out,shine your strobe at the spin-ning tire. If you vary the speedof the strobe light, you willbe able to make the wheelappear to stop spinning. Canyou make it look like the wheelis spinning backward? Canyou use your strobe to figureout how fast (how many rev-olutions per minute) yourbicycle tire is spinning?

Try using a slide projector,

3 0

instead of a flashlight, as thelight source in your strobo-scope. The stronger beamof light will give you moredramatic effects.

AFTERWORDS

Did your stroboscope reallymake drops of water hang inmidairor were your eyesplaying tricks? The answer is:both. Water does come out ofthe faucet drop by drop. Butwater moves so quickly thatnormally you can't look at justone drop: Another drop al-ways comes along before youeven get a chance to zero inon the first one! They all flowtogether in your mind, and infact they all flow togetheras they come out of thefaucet, too.

But if you turned thecrank of your stroboscope atjust the right speed, the dropof water you looked at seemedto hang in midair. And as ev-eryone knows, water dropsdon't do that; what you werereally seeing was a series ofdrops of water. First you sawdrop #1 suspended, let's say,about an inch below the fau-cet. Then the stroboscopefi irned out the light, and didn'tturn ft back on again untilanother drop of water drop#2 was in that same position!

Then the light went out, andcame back on again for drop#3. This created the illusionthat one drop was hanging inmidair, when really you wereseeing many drops, each fall-ing into the exact same posi-tion below the faucet.

By turning the crank evenfaster, perhaps you saw thedrops of water appear tomove up back into the fau-cet! Here's what happened:First you looked at drop #1,an inch below the faucet.Then you look at drop #2, butit was only 3/4" below thefaucet. When the light cameon again, drop #3 had fallento only 1/2" below the faucet.Each drop you looked at wascloser to the faucet, so thedrops appeared to be goingbackward.

The stroboscope pro-duces fabulous lighting effects,but the stroboscope businesswould probably flicker anddie out if those were the onlyuses for this fancy flashing

light. For instance, did youknow that auto mechanics usestrobe lights to work on yourcar engine? They use them tovisually stop the action of thecrankshaft, which is spinningaround rapidly while themotor is running. That waythey can check to see if the

engine timing is accuratein other words, they can makesure that everything is happen-ing at just the right moment tomake the car run smoothly.

Strobe lights also letmechanics in other industriesview their machinery while itis in operation, to check fordefects or to observe partsthat might need adjustment.For instance, huge gears in fac-tory equipment may appearto be meshing when the ma-chine is turned off. But underthe stress of operation, thegears could be coming to-gether incorrectly. The onlyway to check it out is to lookat the gears while the machineis running. Superstrobe to therescue!

In the newspaper indus-try, strobes are used to visually"slow down" the huge rollsof paper that fly across thepress. Pressmen can then readthe newspapers while theyare being printed, to makesure that the printing job isright. In the audio equipmentindustry, strobe lights are usedto view the vibrating parts ina loudspeaker. And with flashstrobe photography, biologistscan record and study suchthings as the movements ofa hummingbird's wings!

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F Y [ANTSIt'll take only 90 minutes to setup this activity, but you'll haveto wait a week or two beforeyour Fancy Plants take on thecolor of spring.

YOU WILL NEED

Scissors, pen1 SpongeA small plateGrass seed or ryegrass

seed, radish seeds,and mung beans

Plastic wrap, plastic bags1 Styrofoam cupCotton ballsPaper towelsEmpty egg carton, yogurt

container, or similar boxesSoil

Old shirt with pocketJar with a screw topBlack construction paper

Why do you think plants growin the ground? And why don'tthey grow on park benches,or on tabletops, or on theroofs of parked cars? If youranswer is "Plants need soil togrow in;' you'll be surprisedto find out that just isn't true!At least, it isn't always true.You can grow some plants

like grass, for instance in

sponges, on paper towels,and maybe even in a shirt!Use your imagination andcome up with as many differ-ent Fancy Plants as you can.

1Use a scissors to cut asponge into a 1" widesnake shape. Soak the

snake sponge in water, andput it on a small shallow plate.Carefully plant the spongewith grass seed, making sureyou push some of the seedsinto the holes in the sponge.Cover the plate with plasticwrap. Set the plate near awindow. Keep the spongewet, and watch for roots.Remove the plastic wrapwhen green appears. Waterthe snake-in-the-grass severaltimes a day!

q2talkei95.

2Now, let's see if thisexperiment works withother things. Draw a

face on the outside of a Styrcfoam cup. Fill the cup withcotton balls soaked in water.Sprinkle grass seed on top of

the cotton balls and seal thewhole cup in a plastic bag.When the green grass- "hair"grcws, remove the plastic bagand water the grass frequentli.

3Fill the sections of anempty egg carton withvarious soil substitutes,

such as sand, crumpled tis-sues, tiny pebbles, sawdust,clean cat litter, loose tea, mar-bles, or whatever else youcan think of. Fill one section ofthe egg carton with soil. Thiswill be the "control" part ofthis experiment. Plant someradish seeds in each sectionof the egg carton. Water everyday. What do you notice aboutthe roots? Do the radishesgrow better when you put theegg carton in a closet for thefirst few days? Which part ofthe plant grows better in thedark the leaves or the roots?

4Try planting sorre grassseed in the pocket ofan old shirt. Hang the

shiri on a hanger and water ormist it frequently. Seal it ina plastic bag until the grasssprouts.

5Watch seeds grow byplanting mung beans ina screw-top jar lined

with a sheet of black construc-tion paper. The seeds shouldgo between the black paperand the jar. Fill the center ofthe jar with wet paper towels,and add 1/2" of water to thejar to keep the whole thingmoist. Screw the lid on andlay the jar on its side. You'll beable to see roots and shootsgrowing against the black-paper liner within a week.

STAY IN CONTROL

With any science experiment,it's important that you, the sci-entist, remain in control. Youmust control the conditions ofthe experiment and you con-trol the "variables" the"L.'ngs that could change andaffect the results of the experi-ment. That's why it's a goodidea to have what scientistscall the "c.Dritrol group" inyour experiment. For instance,in Fancy Plants, you will plantgrass seed in a sponge. Butwhat if it doesn't grow? Is it

THOU6NTFOR THE MONTI.

the grassIS alwaysgreetiec-,qhein you'vEgrown ityourself!

because the sponge isn't agood place for the seeds, orbecause there isn't enoughwarmth and light? Is there toomuch water, or not enough, inthe sponge? The only way tofind out for sure is to plantsome of the same kind of grassseed in soil and take care of itin exactly the same way andat the same time as you doyour experiment. This will beyour control group. Set thecontrol group in the same loca-tion with the seeded sponge.Water them both at the sametime, with the same amount ofwater. Now you are in controlof the experiment. If the grassplanted in soil grows betterthan the grass planted in thesponge, you'll know that thesponge was the only reasonfor the difference in the results!

AFTERWORDS

As easy as it is to start grassor radishes in such unlikelyplaces as a sponge or a shirt,these plants won't live longwithout constant attentionand nurturing. You probably

wouldn't want to spend thetime it would take to keepyour grass snake growing

forever. But sometimes it isworthwhile to invest the extratime and technology neededto grow plants wi'; lout soil.This method is callea hydro-ponics. By looking at the tech-niques used in hydroponics,you'll discover why soil issuch a perfect place for plants.

Water, air, light, warmth,nutrients, and stability. In justabout that order, those are thethings plants need to growand thrive. With water at thetop of the list, it's not surpris-ing that some of the first ex-periments with soil substitutesinvolved using plain water asthe growing medium. In fact,the word hydroponics comesfrom the Greek word forwater. But, as early research-ers soon found, there are anumber of problems with try-ing to grow plants in a big tubof water.

The first problem is thatwater does not support a rootsystem. To give plants stability,

they must be suspendedabove the water tank by somesort of structure or base.Another problem is that waterdoesn't allow oxygen to flow

freely to the roots. To copewith that deficiency, somehydroponic systems add airto the water with a motorizedpiece of equipment, a lot likethe one you might use on atropical fish tank. But thenthere's the question of nutri-ents. Elements like nitrogen,potassium, phosphorus,magnesium, and calcium areneeded in relatively largeamounts, and trace elementslike iron, copper, and zinc areneeded in t.ny amounts. Waterdoesn't have a rich supply ofthese elements, and no matterhow long the plants grow, thewater won't be able to pro-duce the nutrients or renewthem over a period of time.They must be purchased andadded in carefully controlledamounts, over and over again.

These drawbacks ledmany hydroponic growersto switch from just water towater and gravel as a growingmedium, because gravelmakes a sturdy base for theroots. But since gravel doesn'tcontain any nutrients anddoesn't retain water, thismethod presents a whole

new set of problems thatmust be overcome.

Now how does all ofthis compare with the time-honored method of growingplants in soil? Not too well.Without any supervision fromthe grower, good soil givesplants stability for their rootsystems. It also allows plentyof oxygen to reach the roots,and it contains most of thenutrients needed for growth.And unlike sand, gravel, loosetea, cat litter, sponges, andwhatever else you might haveexperimented with in FancyPlants, good soil can hold ontothe water it receives for morethan an hour. Generally speak-ing, good soil just naturally pro-vides the things plants need.

But admittedly, not all soilis good soil. And in some partsof the world the time andexpense needed to make theland ready for planting is over-whelming. In those regions,hydroponics is a "natural"choice a way to supplylocally grown crops at alower cost.

26

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JUSTDon't be a sore loserbe asoaring winner, with thesepaper airplanes that help youreach new heights. It willtake you only a few minutesto make your airplanes, butyou may want to test-flythem all day!

YOU WILL NEED

Several sheets of 81/2" by 11"paper

Paper clipsRuler

ScissorsPlastic straws

What one thing do jet fighters,

bumblebees, bluejays, andpaper airplanes all have incommon? The answer iswings, of course. Wings arethe one thing you've got tohave if you're doing to fly Butdon't be surprised if somewings look a little bit dif-ferent from others!

STUNT FLYER

Th;- is the best paper air-plane ever! It will loop-the-loop, do a barrel roll, orglide for long distances on a

40

E WINSgentle breeze. And best ofall, it has a snub nose, so youcan zo, n it at your friendswithout ilurting anyone.

1Start with an 8W by11" piece of paperFold it in half length-

wise, then open the paperup again. Bring the two topcorners to meet on the mid-dle fold, in diagram 1.Then fold the top triangledown across line A-B, as indiagram 2

2.

2Fold up the point ofthe triangle, point Cso that it is about an

inch long, as in diagram 3

3Now fold points Aand B in toward thecenter line, so that

they meet on top of thesmall triangle. They shouldtouch the triangle a little lessthan halfway up from its fold.See diagram 4.

y.

4Bring he foldededges of the plane(line X and line Y on

the diagram) to meet in themiddle. Diagram 5 showsthe airplane after one sidehas been folded rin. The dotted 44

line shows wherethe other sidewill be folded.

5Now the paper air-plane is ready to fly!Simply fold it in half

lengthwise, along the centerline, and hold the airplanefrom underneath The snub-nosed end is the front, ofcourse Fly the airplane as itis a few times, and then adda paper clip just under thenose Does your plane flybetter with or without thepaper clip? Where dues theclip work best? When youtry the stunts below, be sureto try them with and withoutthe paper clip.

4i

StuntsTo make your stunt plane

do a barrel roll, bend or curlone tail piece up about aninch, and bend or curl theother tail piece down aboutan inch

To loop-the-loop (yourplane will curve down andcome back to you), bendboth tail pieces down Itmay take some practice tothrow the Stunt Flyer prop-erly. If you want it to comeright back to ,our hand, aimupward when you throw it.

The Stunt Flyer cure loop-the-loop the oppositewayby curving up andaroundand then it willkeep on going! To do thisstunt, bend both tail piecesup, and snap your wristwhen you fly the plane. Itwill take some practice, butit's worth it!

HELICOPTER

This paper flyer moves justlike the blades of a heli-copter. Try making very smallpiper helicopters and verylarge ones. Stand on a chair

28

and drop two different onesat the same time. Do theyboth descend at the samespeed?

1To make a paper heli-copter, cut a strip ofpaper 11" long and 2"

wide. Following the diagram,cut along the solid lines.There are only three cut,. tobe made. Cut #1 is 5" long,and the other two cuts areeach about V3" long.

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2Now make the twolong folds, along thedotted lines These

folds cause the body of thehelicopter to be folded inthirds, with the two sidesoverlapping the center. Foldthe bottom of the helicopterup a half inch and then

another half inch, to makethe bottom heavier You canalso put a paper clip on thebottom to weight it

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3Last, fold the bladesof the helicopter inopposite directions.

One should point towardyou and the other shouldpoint away

4Drop your helicopterfrom a high place, orstand on a chair and

let it go What makes it twirl?How is your helicopter dif-ferent from a real helicopter?Hint Can your helicopterever go up?

WHIRLY TWIRLER

You can make a Whirly Twirlerwith only a dr .nking straw

and a smail piece of paper.

1wide

Cut or Lear a piece ofpaper to make a rec-tangle about 11/2"

and 61/2" long Fold the

Os"

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BEND pRopsempg uPSEND PROPS Amo DAWN.

paper in half lengthwise Cutor tear along the fold fromeach end toward the mid -die, leaving the center of thepaper untorn. Now you have

PROP YOURHEL/ C 0 P TE R

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PLACE

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four propellers.

2Bend one propeller upand the other downon one side of the

paper Bend the oppositepropellers up and down onthe other side of the paper,as shown in the diagram.

POKESTRAW

nifty CENTER

3Poke the straw throughthe center of the pa-per and your Whirly

Twirler is done! Let it fall froma high place and see whetherit spins faster or slower thanthe paper helicopter

SUPER LOOPS

For this amazing glider, youneed one plastic straw andtwo strips of paper, each 11/4"wide

1Cut one paper strip 7''long and the otherstrip 9" long. Make the

strips into loops by overlap-ping the ends about an inchor so and taping them closed.

',TAPE LOOPSTo STRAW

2Next tape the loops tothe straw, as shown.Where are the wings?

To fly this plane, hold it withthe smaller loop facing for-ward, and the straw on thebottom. It will glide andsometimes even spiral as itsoars across your living room.

ROCKET BOMBER

Can a rolled-up piece ofnotebook paper fly? Try itand find out.

ITake an 8V2" by 11"shee. of paper androll it into a tube with

a 1" diameter. Use tape tokeep it closed. Try to fly itacross the room

2Now roll up anotherpiece of paper thesame way and tape it

closed. Cut a 2" slash in oneend. Cut sideways from the

30

slash in two directions, sothat a tail is formed, as in thediagram.

la....da...L._-..3S CUT HUE TO FORM 7411-

3Fly the Rocket Bomberwith the tail towardthe back. Does the

Rocket Bomber have wings?Do real rockets have wings?Do they have tails?

AFTERWORDS

For thousands of years,people have wanted to beable to fly like the birds. Buchave they succeeded?Technically, no Even today,no one has mastered the artof flying the way birds doby flapping their wings.

Flapping wings areunique to birds, althoughmany people have triedand failedto imitate themStill scientists dreamed offlight for many yearsLeonardo da Vinci made adrawing of a design for ahelicopter--almost 500years before it was invented!And Sir Isaac Newtonunderstood the principles offlight, but he ended up

predicting that peoplewould never fly!

Modem scientists havestudied the flapping motionof birds wings, and foundout just how tricky flappingflight is. For one thing, abird's wing does not merelygo up and down in twoevenly timed movements.The downward motion issmooth and slow, while theupward motion is faster andincludes a flicking motion.If you watch a bird flying,you'll notice that it's easier tosee the wings' downbeat,because it lasts longer.

Although no one hasmastered flapping flight,airplanes do glide and soarusing some of the samedesign elements found onbirds An airplane's wings arecurved at the front andtapered at the back, like abird's And flaps on anairplane wing can be movedup or down to increase thecurvature of the wing duringtakeoff and landing. Thoseadjustments are similar to thechanges you made whenyou changed the position ofthe tail pieces on your paperairplane. Of course you canonly make a few adjustments

in the wings or tad pieces ofyour paper flyers, comparedwith the hundreds of tinyadjustments that birds make.

Another similaritybetween birds, planes, andpaper airplanes is the needfor a tail. The tail is used forsteering and for balanceWithout a tail, birds andplanes would tend to gotopsy -turvy and take anunscheduled nose dive.That's probably whathappened to your RocketBomber when it was just apaper tube without a tail.

Whether you're flyinga paper Stunt Flyer or aDC-10 commercial jet, theprinciples of flight remainthe same The airplane mustgo fast enough to createsomething called lift. Lift isthe result of air flowing overthe wings of a plane at agreat speed. The air pressureabove the wing is less thanthe air pressure below thewing, so the plane goes up.Why can't your paperairplane just glide onforever? Because it doesn'thave a motor . and as itstarts to slow down, the airpressure above the wingincreases. No more liftand no more flight!

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T"E BIRYou don't need to take outan ad in the Bird Gazette tolet the birds in your neighbor-hood know that you care! Justput out a bird feeder. It willtake about 30 minutes to makea simple feeder. Then you canwatch the action for hours.

YOU WILL NEED

Empty milk carton, sodabottle, or bleach bottle

Duct tape or other hemwaterproof tape

Scissors or knifePipe cleanersPopsicle sticksColored paper for decorating

feederGlueRope or clotheslineBirdseed

In winter, the insects, seeds,and berries that songbirdseat are scarce, and snowoften covers the groundMany birds will starve orfreeze if they don t findenough food to eat. You canmake a bird feeder and putit in your yard, in a park, or

out along the roadside, tohelp feed the winter birds.Do it now, because that waythe birds will learn to cometo your feeder before thecold weather arrives. Andkeep your feeder filled intothe spring, because the birdshave learned to count onyou for food!

If you live in a warmerpart of the country, you'relucky. Many songbirds arethere all year ro.ind. Having abird feeder 's a great way tomeet them!

1Wash out an empty1-quart milk carton,a 2-liter soda bottle,

and/or an empty bleach bot-tle with a handle. Be sure thecontainer is well rinsed be-fore you begin.

2Seal the original open-ing with duct tape. Ifyou are using a milk

carton, close it and tape thetop tightly shut. If you areusing a plastic bottle, screwthe cap on tightly and sealwith duct tape. Remove anylabels from the bottle.

3With your scissors, cuta small door or open-ing in the container

about 5 inches from the bot-tom There are lots of waysto construct a feeder. If youare using a soda bottle, youcan lay it on its sid' and callthat the bottom. In that case,you might want to make twodoors. They can open side-ways, like a door, or upwards,like a tent flap. Make the doorssmall if you want to discour-age larger birds. Large birdssometimes scare the smallerbirds away. If you make ahuge hole in your feeder,you'll probably end up feed-ing squirrels instead!

4Tie the door openwith a pipe cleanerPut a small hole in the

door and a small hole in thefeeder. Put a pipe cleanerthrough the hole in the doorand knot it or twist it. Put theother end through the hole inthe bottle and knot it.

5Make a perch for thebirds to stand onwhen they come to

32

your bird feeder. You willneed two Popsicle sticks foreach perch. Use scissors or aknife to make a small slitabout 1/2" below the openingin the feeder. Make anotherslit about 1/2" below the firstslit. Push one Popsicle stickthrough each slit until onlyabout 2" of each stick re-mains outside the feeder.Tape the two sticks togetherwith duct tape to form awedge-shaped perch. (Ifusing a milk carton, also dec-orate the outside of yourfeeder. Glue on some col-ored paper)

6You will need to makehandles or straps tohang up your bird

feeder. Where you put thehandles will depend onwhat style of feeder youdesigned. For a bleach-bottle bird feeder, you cansimply put a rope throughthe handle and suspend itfrom a tree branch. For asoda bottle turned on itsside or for o milk carton, youwill need two pipe-cleanerhandlesone at each end

of the top of yoJr feeder.Poke two holes in the topleft side of your feeder andpush one pipe cleanerthrough both of them. Twistthe ends together or knotthem. Do the same at theright end of the top.

IFill your bird feederwith seeds. Make surethe birdseeds come

all the way up to the open-ing, so that small birds canreach themwithout havingto climb into the bottle!

8Make two or morefeeders and find outwhich kind the birds

like best. Do they want to beable to see the seeds inside?Or are they more attracted toa colorfully decorated birdfeeder? Even if you madetwo bird feeders, use thesame kind of birdseed ineach one. That way you willknow that it is the differencein shape or color of thebottleand not the foodinsidethat explains whybirds do or don't come toeach feeder. Later, you canexperiment with differentkinds of food.

WHERE TO HANGYOUR BIRD FEEDER

Bird feeders should be hungat least 5 feet from ;heground, so that dogs andcats cannot reach the birdswhile they are feeding. You'llalso want to hang the feederaway from bushes orbenches, so that squirrels

cannot jump to the birdfeeder and eat all the food.Suspend the feeder from awire attached to a treelimb . .or hang it from aclothesline.

WHAT TO FEED THE BIRDS

What do birds like to eat?Different birds like different

DECORATEMILK

CARTON

kinds of seed. Many birdswill also eat bread crumbs,fruits, nuts, and suet (beeffat). This list will help youdecide what kind of foodto use.Bread Crumbs: Scatter freshwhite bread crumbs (orsmall pieces of white bread)on the ground to attractbirds.Black-striped SunflowerSeeds. These seeds will at-tract bluejays, chickadees,grosbeaks, tufted titmice,finches, and cardinals.Mixed Seeds: This is themost easily available kind ofbirdseed.Fruits: Put out some raisins,apple slices, pieces of ba-nana, and orange slices, es-pecially in summer.Suet: This beef fat is avail-able in the grocery store. Itwill attract woodpeckers,which eat insects in summer.Roasted Peanuts (in theshell): These are good forbluejays.

MAN&FEEDERS

Ai LEAST5 FEET

FROMGROUND

USE PIPE CLEANERSTo NANG FEEDERS

WITHOUT, HANDLES

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Peanut Butter: Plain peanutbutter is too thick for birdsto swallow. Use 1 cup ofcornmeal to every 1/4 cup ofpeanut butter. Add enoughvegetable shortening tomake it less sticky. You cansmear the mixture directly ona tree trunk, or on a pineconeand hang it from a tree.Water: Birds need water, soput out a saucer for them, orfill one of your extra feederswith water and cut a largeropening. Change the waterfrequently.Grit: Mix a little sand or gritin with your birdseed. Birdsmust have grit to digest theirfood. They also like crushedeggshells for the calciumthey contain.

CARE FOR YOUR FEEDER

P-- let the birdseed iny..or feeder get wet, soggy,or moldy. Birds can get adeadly disease from eatingwet birdseed. Clean out thefeeder and scrub it wellabout once a weekormake a new feeder withanother soda bottle It's easy!

AFTERWORDS

Have you ever heardsomeone say, "You're eatinglike a bird?" They probablymeant that you weren't

eating much. But birdsactually eat quite a lot. Infact, most songbirds will eatmany times a dayespecially in winter, whenthey need the extra fuel tokeep warm And birdsgetting ready to migrate candouble their own bodyweight in only a few days!They store up fat to use asfuel for their journey south.

But if adult birds eat alot, baby birds eat more,especially just before theyleave the nest. They must befed every 15 to 30 minutesduring the first few weeks oflife! Their parents spend thewhole day flying back andforth to the nest, bringingfood The baby that stretchesits neck up the farthest andopens its mouth the widestis always fed first. That's justnature's way of making surethe hungriest bird gets whatit needs.

Birds have excellenteyesight, which is how theyfind food. Did birds come tofeed more quickly at yourclear plastic soda-bottlefeeder than at your less-transparent feeders? That'sbecause they spotted thefood from the air.

Of course, not all I biroseat seeds, but birds of prey

such as vultures and eaglesalso rely on their eyesight tolead them to food. Someowls and eagles' eyes areactually larger than humaneyes, and hawks are thoughtto see 10 times better thanhuman beings. Birds havesuperior vision for a numberof reasons. They have adouble set of muscles sothey can focus more easilyon objects at differentdistances. They also havemore cones and rodsthecells in the eye that aresensitive to color and light.

If you're not sure what acertain species of bird eats,you can ofteii figure it out bylooking at the tird's beak.Each beak shape is suited toa specific purpose. Forinstance, the hooked bill of ahawk is used for string andkilling prey animals. Thewoodpecker's pointed bill isused to dig insects out oftrees The cone-shaped beakfound on many songbirdscan crack open or crushseeds. And the long, taperedbill of the hummingbird isperfect for reaching deepinto flowers and sucking outnectar.

Although seed-eatingbirds have no teeth, they doneed to grind up their food,

the way animals and peopledo when they chew. That'swhy these birds eat gritsand or small pebbles. Thisgravel stays in the bird'sstomach, or gizzard. Whenthe digestive muscles go towork, grinding and mashingup the food, the gravel actslike a hard, grinding surface.

What do songbirds eatwhen people aren't feedingthem? In summer, many birdseat seeds and berries thatare plentiful then. The seedsfrom pine trees are one oftheir most important sourcesof food. They eat the berriesfrom almost every kind ofbush imaginable, and alsolike acorns and cherries.Most important of all, manybirds eat insects. If it weren'tfor birds, the world wouldbe overrun with insects!Some farmers and gardenersput up bird feeders toattract these insect-eaters.The birds then take upresidence in the area andhelp to control the insectsthat would otherwise do alot of damage to crops.

Thanks to birds, thebalance (If nature ismaintained And thanks toyour bird feeder, many birdswill live through a coldwinter.

34 5i

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MUUmmmm, delicious! A nicebig plate of mud! Take about30 minutes to dig the holeand plant the seer' . Wait1 to 11/2 weeks for them to

sprout and find out who likesmud pies better plantsor kids!

YOU WILL NEED

4 Aluminum pie pans(disposable)

Shovel to dig soil, or large bagof potting soil

Pencil

Paper

Transparent tapeNail

Popcorn kernelsWaterLarge plate

A brick or piece of sandstonePaper bagHammerDried-up modeling clayDried leaves, roots, and twigsFood scraps such as carrot

peelings, bread crumbs,and eg;,shells

Sand

lbWhat could be mushier,squishier, and gushier thana nice big mud pie! But plantsare usually found in rich soilnot mud. What's the differ-ence between mud and , oil?Make your own mud pies addfind out. And while you'rewaiting for your garden piestn sprout, you can also findout how long it takes natureLo "make" soil out of thet.: rigs that go into it.

11If you can get permis-sian to dig in your yard

aik or somewhere in yourneighborhood great! Gooutside and dig a hole about18" deep. Take enough soilfrom the hole to completelyfill 3 alurnnum pie pans. Makesure the soil doesn't haveplants already growing in it.(If you are digging in a grassyarea, throw the grassy partaway, and use the dirt belowthe grass roots.) Put soil fromnear the top of the hole thetopsoil into twc, of the piepans. Put soil from the bottomof the hole the subsoil intothe third pie pan. Label the firsttwo pies "Topsoil" and the

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third pie "Subsoil:'If you can't find a place

to dig, use potting soil from agarden shop for this activity.Fill only one pie pan withpotting soil and label it "Soilwithout drainage holes!' Thengo on to Step 2.

2Use a nail to punchabout 20 to 30 holesin the bottom of an

empty aluninum pie pan. Fillthis pie pan with topsoil trans-ferred from one of the othertwo pans, or use potting soil.or this pie, make a new label

that says "Soil with drainageholes!'

3Sprinkle 1 or 2 table-spoons of unpoppedpopcorn kernels on

each mud pie. Mx the pop-corn into the dirt, so that thekernels are underneath the soil.Now water each of the threepies thoroughly, but first putthe pie with drainage holeson a large plate to catch thewater that drips out. Set allthree mud pies in a sunnyplace. Water them oftenenough to keep the mud piesmuddybut do not over-water the one with drainagehobs

Which pie is the first oneto sprout? Does the pot,:orngrow better in the subsoilmud pie, in the topsoil mudpie, or in the topsoil pie withdrainage holes? What do youthink plants in the pie withdrainage holes get that theydon't get in the mud pie that isconstantly soaked with water?

4While you're waitingfor your mud pies toturn into popcorn pies,

try making some soil of yourown! First you will need to"weather," or break down,some rocks. Since you don'thave a million years and anocean full of water to do this,you'll have to use a hammerinstead. Take a brick or largepiece of sandstone outdoorsand put it in a paper bag ontree ground. Through the bag,Hammer the brick or stone un-til it crumbles into tiny pieces.Put the crushed rock into anempty pie pan.

Do the same thing witha dried-up piece of clay.Hammer it until it is powderyand add it to the crushedrocks. Add some dried leavesand grass, dead bugs, roots,vegetable scraps, a little bitof sand, and then water thewhole thing. Use just enoughwater to keep the contentsmoist, but not soupy. Stir upthe pie. Now let your piestand for how long?A week? A month? How longwill it take to make soil? Mixthe pie up every few days,and sprinkle with water if itdries out completely. Even if itnever really looks like soil, tryplanting popcorn in it to seewhat happens.

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AFTERWORDS

The story of soil is a long

one, starting back to whenthe Earth's crust was first cool-ing. There was no soil or dirtthen just rock. But over aperiod of thousands of years,little bits and pieces of rockwere broken off. Some rockswere worn down by the rainand wind. Others were dis-solved by adds in the waterof lakes and oceans. Andmany huge boulders werecracked again and again intosmaller and smaller piecesby thT changes in tempera-ture from tt-,ezing winterto scorching summer.

But crushed rocks aren'tthe only ingredient in soil. Youalso need water, oxygen, andorganic material, which is whatwe call things that either arealive or were alive. So herecomes the big question:Where did organic material,like plants for instance, comefrom if there wasn't any soilto grow them in?

Scientists think that lifebegan in the oceans and creptslow' `oward land. It tookeons ...ir the tiny bacteriaand protozoa of the water toevolve into forms of life thatcould survive on land. Stepby step, inch by inch, largerlife-forms developed. When

38 5-8

they died, they became theraw material to form soil,which in turn became a goodplace for even larger plantsto grow.

Dead plants and animalsare important ingredients ofthe soil, but live plants andanimals play a primary role,too. Take worms, for instance.Without worms, many of thedead leaves from plants andcrops would just lie there ontop of the field, or be blownaway. But earthworms takelittle bits of dried leaves withthem down into the earthas they tunnel around. Onescientist found that the wormsin a 3-foot-square area couldtake as much as 20 pounds ofdead leaves underground injust six months time!

In moist soils, ear hwormsare numerous. In some partsof the world, there are 2 mil-lion earthworms per acre!An average acre, though,would only have about 50,000worms in it, all working to mixup the ill. Their burrowingalso brings minerals from thelayers of subsoil up to thetopsoil. And their movementopens up air passages andkeeps the soil loose so thatwater can enter the ground

and plant roots can growmore easily. Other animalsthat live undergroundsuchas moles, ants, and beetlesdo the same job. But whatturns the dead leaves andinsects into soil?

Bacteria are microscopicplants that are present every-where on Earth. If you thoughtthere were a lot of earth-worms in an acre, just thinkof this: As many as 50 billionbacteria are in one drop ofwater! A rule in science saysthat the smaller an organism is,the more of them you'll findand the greater an effect they'llhave on the environment.That law is definitely truewhen it comes to bacteria.

Bacteria perform twomain jobs in helping to makesoil and keeping the soil"healthy" so that plants cangrow. First, bacteria causedead plants and animals todecompose, or break downinto simpler elements. Withoutbacteria, dead things wouldn'trot or decay. Second, a gasin the soil cz " i nitrogen isessential for all living things.Some bacteria are called nitro-gen "fixers.; which meansthey help plants to use thenitrogen present in the soil.

So the next time you wantto make mud pies, go rightahead. But do it 'with a littlerespect! Aftcr a'1: It took theearth a long time to producethat beautiful black stuff youcall mud!

V.

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4

VIGHT

MOVES

4

NI. 1 "OYESThe first game in Night Moves

can be played in 30 minutesor less. The second game isenough fun to fill up severalhours on a steamy summer

night. Just be sure to listenfor the screech of a bat orthe hoot of an owl wh0000might want to join in yourexperiment!

YOU WILL NEED

Clean laundry, especiallysocks

Paper and pen or marker1 Piece of lightweight

cardboardTape

Flashlight

Blindfold (optional)A small empty can

Owls, bats, raccoons, deer,skunks, mice, and porcupinesall get around in the dark verywell. That's because they'reall nocturnal animals, whichmeans that they're up all nightand they sleep all day. Youmay live that way sometimes,tooespecially in the sum-

mer. But that doesn't mean

you're really adapted to thenight the way nocturnal ani-mals are. For one thing, youdon't have the sharp hearingand keen eyesight that noc-turnal animals have. And youprobably don't need them.After all, you don't have tofight off vicious animals to geta decent snack during a late-night raid on the refrigerator!

But, heywhy feel inferi-or to these nighttime prowlerswhen you haven't even testedyourself in the dark? By play-ing these two games andmaking some Night Moves,you can find out just how dif-ferent you and the wildlife are!

GAME No.1:SEEING IN THE DARK

IHave ready a pile ofclean, unsorted socksand a few shirts. Turn

out all the lights in the roomand close the blinds so thatjust a little light from the streetcomes in.

2Look around the dark-ened room and talkabout which things

you can see clearly and whichthings you cannot see. Canyou read a book title in thedark from 12 inches away?Have someone stand on thefar side of the room, and holdup a shirt. Can you identifywho it belongs to right away?Just wait...your eyes may nothave completely adjusted tothe dark.

3Start sorting throughthe clean socks andtake turns deciding

what color each sock is. Put allthe blue socks in one pile, allthe red ones in another pile,and so on. Use the paper andpen or marker to make a signlabeling each pile of socks bycolor. Do you find yourselfholding each sock up veryclose to your face to see thecolor better? Why do youthink that is?

4When you're finishedsorting the socks, lookaround the room again.

You'll notice that you can seemuch more now than youcould when you'd only beenin the dark for five minutes.Can you read the book titlenow?

5Turn on the lights andcheck out the piles ofsocks. Most likely, you'll

ind some red socks in theblack pile or some gray onesin the beige pile. And youmight even find some thingsthat aren't socks in the sockpile! As a matter of fact,maybe you should have araccoon sort your laundryfrom now on!

GAME No.2:HEARING IN THE DARK

1Use a lightweight pieceof cardboard to makea cone with a 1" open-

ing at the small end. Tape thecone over the end of a flash-

40 6

light. This will narrow the beamof the flashlight so that thelight shines on a smaller area.

2Go outside after dark,or turn out all the lightsin your living room, and

choose someone to be "It:' Ifyou are playing this game out-side, try to find a grassy spotto play it in. Have the personwho is It sit down on the

ground, either blindfolded orwith his or her eyes closed,and let him or her hold theflashlight. Place an empty cana few feet behind the personwho is It.

3Have all the other play-ers stand about 10 to15 feet in front of the

person who is It. These play-ers are called the Creepers.

As quietly as possible, theCreepers must try to sneakpast the person who is It.

4Whenever the personwho is It hears aCreeper coming, he or

she points the flashlight in theairection of the sound andturns it on. Sweeping the flash-light back and forth is notallowed. If the flashlight beam

actually shines on the Creeper,the Creeper must say Yougot me," and go back to thestarting line. But if the lightdoesn't touch the Creeper,then the Creeper may staythere, remain silent, and creepagain. The person who is Itshould not remove the blind-fold or open his or her eyesuntil the end of the game.

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5When all the Creepershave made it to theempty an behind the

person who is It without get-ting caught in the flashlightbeam, the game is over. Then itis someone else's turn to be It.

VARIATIONS

Play the game in a woodedspot; the leaves on bushesand the twigs on the groundwill make it much harder tosneak around quietly.II Have the person who isIt cover one ear during thegz. ne. Can he or she still tellwhere the creeping soundsare coming from? Do ycthink you need both ears coaccurately sense the directionof sounds?

Set a limit on the numberof times the flashlight may beturned on.

Now that you've played bothgames, what do you thinkabout nocturnal animals?If you were an animal, wouldyou rather have excelle:I nightvision or terrific hearing?

AFTERWORDS

More than half of the world'sanimals are active at night.

Considering how hard it is toget around in he dark, andhow much easier it is to dothings in daylight, the bigquestion is: Why? Why are somany animals either nocturnal,which means they are activeonly at night, or arrhythmic(without rhythm), whichmeans they can be just as ac-tive at night as they are in thedaytime? Scientists believethe answer to that questionhas to do with the relationshipbetween the predatory, or"hunting': animals and the ani-mals that are their prey, the"hunted:'

Here's how the theorygoes. Long ago, when theanimals we know today werefirst evolving, the prey animalsfound that if they wanderedaround in the daytime lookingfor food, they were easilyseen by the predators, whoquickly attacked. So the preyanimals remained still duringthe day, whether they weresleeping or not. When theprotective night came, theywent looking for food. But inthe dark, the animals neededexcellent night vision and su-perior hearing to find a decent

meal for themselves and stillavoid becoming someoneelse's dinner. Within each spe-des, a few animals did havesuperior senses and they sur-vived the longest, passingtheir traits along to their off-spring. Meanwhile, the preda-tory animals were staying upat night, too, and over timethey developed the samegood hearing and night visionas well. So they're all backto where they started!

With many animals, youcan tell just by looking at themwhether they have good nightvision, supersensitive hearing,or both. All you have to do isobserve the size of their earsand eyes. Big ears, which cupforward like a bell or a horn,"catch" more sound wavesand direct them down intothe animal's inner ear. Big eyesallow more light to enter theeye and strike a light-sensitivemembrane called the retina.But even animals with smallears or small eyes can oftensee and hear better than people can, because the irkemalstructure of their sense organsis so highly developed.

Consider the differencebetween a nocturnal animal'sretina and yours, for example.

Both types of retinas are madeup of two different kinds ofcells that can receive light.These cells are callea rods andcones. Because they are muchmore sensitive to light, rodsfunction in the dark or at night.Cones function during the dayor in bright light because theyare less sensitive. But a noc-

turnal animal's retina has manymore rods than yours does.There may be as many as onemillion tightly packed rods toevery 1/25 of an inch of retina!That's why most nocturnalanimals can see things in thedark that people aren't everaware of.

But even if you had asmany rods in your retina as ananimal does, you still wouldn'tbe able to see colors in thedark. That's because rodsaren't sensitive to color at all.Only cones are sensitive tocolor. When you played NightMoves, you weren't supposedto be able Lo sort the sockscorrectlyand if you could,it's because you had enoughlight in the room to stimulatethe cones in your retina.

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NATTER OF T S EMost people love to eat! Partof the fun in eating dependson how lood tastes. Can youimagine a hot dog withoutmustard or 'dish? Boring!These taste treats shouldtake about an hour.

EXPERIMENT No.1:MAPPING YOUR TONGUE

All of our tastes can be putinto 4 main groups: sweet(sugar or honey or molasses),

:;our (lemons or limes or vine-s'ar), salty (table salt) and bitter(baking chocolate or instantcoffee). Your taste-testeryo Jr tongue can be groupedinto 4 parts, too. Here's how.

YOU WILL NEED

Salt

SugarVinegarInstant coffeeLarge paper cupsSmall paper cupsCotton swabs (0 Tips)Paper and pencilMirrorBlindfold (handkerchief

or scarf)

44

41

Look in a mirror andstick out your tongue.Make a sketch of your

tongue that looks like this.Make it about as big as thepalm of your hand.

2You will need separatesolutions of salt, sugar,vinegar, and instant

coffee. Put 2 level teaspoonsof each substance into halfa cup of water and stir. Theseare your "stock solutions"; la-bel them. Next, label 4 smallercups and pour a teaspoon ofeach stock solution into the

proper cup. Put a cottonswab in each cup.

3Blindfold a friend andtell him / her to stickout his/her tongue.

Then take the swab out ofone of the smaller cups, butdon't tell your friend whichone. Gently touch this swabto your friend's tongue in re-gion 1. What does your friendtaste when the swab firsttouches the tongue: sweet,like sugar; sour, like vinegar;salty, like tosiie salt, or oitter,like coffee?

4Record your friend's an-swer by writing one ofthe following symbols

Of i your sketch of a tongue:"SW" for sweet; "SR" for sour;"SA" for salty; and "B" forbitter.

5Do the same thingon regions 2, 3, and 4(in tnat order,. Then

have your friend rinse themouth with clean water andspit it out into another bigpaper cup. Repeat step 3 foreach of the other 3 solutions.

6Repeat testing all 4

solutions at least onemore time, but the

more times the better. Testother people, but be riirr_ touse clean cups and swabs foreach subject you test. Whichparts of the tongue seem tobe best for tasting each of the4 tastes? How much do thetaste regions overt3p?

EXPERIMENT No. 2:NAME THAT TASTE

Now use your trusty tongueto see if it can identify differentkinds of foodseven if youcan't see or smell them!

YOU WILL NEED

Some different hard fruitsand vegetables (suchas potato, pear, apple,carrot, onion, squash,radish, turnip, parsnip,rutabaga, broccoli stem,cauliflower stem, sweetpotato, or whatever otherfoods like these you haveat home)

Paring knife

Paper cupsToothpicksBlindfold

1Peel each of the fruitsand vegetables, andcut them up into little

pieces about the size of theeraser on a pencil. Put eachfood in a separate cup andlabel the cup.

2Blindloici your friendand tell him/her topinch his/ her nose

shut. Then use a clean tooth-pick to feed your friend asmall piece of one of thefoods. What does yourfriend think the food is?

3Keep a record of yourfriend's guess by writ-ing down the name of

the food and putting a +beside it if he/she gets it right.(You may want to write down

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what he/she thought it was,if they don't guess right.)

4:lave your friend rinsehis/her mouth withclear water between

tests of each of the foods, sothere's no leftover taste on thetongue. How many foods didyour friend guess correctly?

5Repeat steps 2, 3, and4, but this time don'thave the nose pinched

shut. How many did yourfriend guess correctly thistime? How does your senseof smell affect your sense oftaste? Repeat all steps withanother friend, but don't for-VA to use a clear. toothpickwith your next customer.

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VARIATIONS

Try feeding your blind-folded partner a piece ofapple while you hold a pieceof pear (or onion) close underhis/her nose. What doeshe/she think is being eaten?

Suck an ice cube for a fewminutes. How do things tastewhen your tongue is cold?

Pinch a copper penny,

sandwiched by a small pieceof aluminum foil, betweenyour thumb and first finger.Touch the free ends of thetwo metals (the edge wherethe foil was cut) to the tipof your tongue. How doesit taste?

How well :an you tell thetaste of sugar solution from

artificial sweeteners? (Try theregular brand of some popand the diet brand of thesame pop.) Which one doants and flies so for?

Repeat Experiment No. 2but this time don't use a blind-fold or pinch your nose. Putsome potato in a blender, addsome green food coloring(Happy St. Patrick's Day?),and mix well. Do the samewith other light-colored foods,like pear, apple, radish, turnip.How does color affect yoursense of taste? Your enjoy-ment of food?

7'\,

AFTERWORDS

What does rotten meat haveto do with the discovery ofAmerica? Well, back in thetime of Columbus there wereno refrigerators, so fresh meatspoiled very quickly 6:111

smelled and tasted "bad:' Buteven spoiled meat was toovaluable to throw away, sopeople started to add spicesand herbs to hide the rottentaste. These seasonings had tobe brought from the Far Eastand Africa and this made themexpensive. Columbus waslooking for a quick way to theFar East when he bumpedinto America.

How do you like yourchili? Hot? The sense of tastevaries from person to person.Stick out your tongue andlook at it in the mirror. You willsee bumps and ridges be-tween them. Within thesebumps there are thousandsof tiny taste buds. These arespecialized cells connectedby sensory nerves to yourbrain. When chemicals (food)are dissolved in the liquidon the surface of your tongue,they stimulate the taste budsand the nerves carry the mes-sase to the brain. Your brain

then lets you know what youare tasting. 1 here are 4 kinds

of taste cells, one for each ofthe main tastes. Taste budsfor sweet things are mostlylocated at the tip of yourtongue. You taste most bitterthings with taste buds at theback of your tongue. Sourand salty things are mostlypicked up by taste buds onthe edges of your tongue.

If you touch a penny or apiece of aluminum foil to yourtongue, you feel a taste that isnot caused by food. In thiscase, your taste buds areelk Irically stimulated by aweak electric current that isproduced by the two differ-ent metals and your saliva.(Don't try this with any otherkinds of electricity!)

How do things tastewhen your nose is stuffed upwith a cold? Much of whatwe taste has to do with oursense of smell. In great-grand-mother s time a favorite medi-c;ne was Castor Oil. It smelledrotten. Whenever she gavesome to a child, she wouldpinch the child's nose shut.How good an idea was this?What part of your tongueshould you avoid if you everhave to take bitter medicine?

77t,

You can tell right away if afood is too salty. But you mayfind that a piece of lemondoesn't taste sour until youactually bite down on it andsome juice comes out. Howwell and how quickly you cantaste something dependsupon how well it dissolves inthe liquid on your tongue. Saltdissolves very quickly. Solidlemon does not dissolve asquickly as lemon juice.

How do you like yourpizza, hot or cold? Most peo-ple prefer hot foods becausethey seem to taste better. Forone thing, hot foods give offmore odors, which help topep up your sense of taste.Warm foods also help to stim-ulate your taste buds. Whathappens to your sense of tasteafter you suck on an ice cubefor a while?

Long ago, rich people andrulers, like kings and queens,were afraid that someonemight try to poison them,so they would hire "officialtasters" to sample food beforeit was eaten. Even today thereare professional "tasters" whotaste various blends of tea orwines to get the "blend ofseveral different tea leaves orwine grapes just right. Whata tasty way to make a living!

Ii I 1

For at least 150 years, kaleido-

scopes have been turning outmany beautiful patterns. Withtwo mirrors and some bits ofplastic, you can create somecolorful images of your ownin about 1 hour.

YOU WILL NEED

2 or 3 Identical mirrors, any

size between 11/2" to 3"wide and 6" to 12" long(You can get these froma glass shop; tell the sales-

person what you are mak-ing and ask to have themirrors' edges polished.If the glass shop doesn'tpolish the edges of themirrors, you will also needsome fine sandpaper,

emery cloth, or an emeryboard, and a small blockof wood.)

Glass cleanerTissues

Pencil

Ruler

Some strips of cardboardlarger than your mirrors

Scissors

Black construction paperor black tempera paint

Quick-drying glueMasking tape1 Clear plastic notebook

divider or a clear plasticfood container lid

Scraps of colored plastic orunwanted color film slides,or confetti

1 TranslucenYfood containerlid (one that you can seelight through, but youcan't see throughcompletely)

1Safety first! If the edgesof your mir rs are notpolished, handle them

very carefully and polish themyourself. Wrap some fine sand-paper or emery cloth arounda small block of wood andcarefully san6 the sharp edgesand corners. Or you can usean emery board (you won'tneed the wood block) to dothe same thing. When theedges are smooth and safeenough to be handled, clean

le mirrors with glass cleaner.

24 Now, before you make

your kaleidoscope, trythese mirror experi-

ments to find out how kaleido-

scopes work. Draw a lineabout 1" long on a piece ofpaper. Stand your two mirrorson their edges and make a"V" shape around the line,with one end of the line touch-ing the point of the "V," asshown. What seems to hap-pen to the line? Stand a pencilat the other end of the line.How many images of thepencil can you see? Changethe angle between the mirrors

make the "V" wider or nar-rower andand see how manyimages are formed.

3Cut a piece of heavycardboard to measureabout 1" wider than

the mirrors you are using, andjust as long. Cover the card-board with black constructionpaper and glue it in place.Or use black tempera paint

to make one side of thecardboard black.

4Now decide how bigan angle how wide a"V" you want your

kaleidoscope to have. (As youfound in Step 2, you can v lrythe number of reflected im-ages by changing the angle.)Make sure the shiny sides ofthe mirrors are facing eachother, and tape two long sidesof your mirrors together in the"V" shape you want.

5Measure the widestdistance across theopening between the

two mirrors. Trim the width ofthe black cardboard so that itmeasures the same as theopening between the mirrors.Tape the cardboard to themirrors with the black sidefacing in, forming a three-sided "tube:' You may needa friend to help you hold thethree pieces while you tapethem. Wrap the tape aroundas shown in the diagram.

Cover one open endof the tube with a cleartriangle of plastic cut

from d notebook divider orfood-container lid. Secure itin place with fast-drying glueand tapebut don't let toomuch tape show on the plastic.

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bB AteIMeasure and cut threepieces of heavy card-board, each one 1/4"

wider and longer than the

triangular tube. These will bethe covering for your kaleido-scope. At.ach them to theoutside of the tube so thatthey stick out 1/4" beyond theplastic-covered end of thetube. Important: Don't putglue on the backs of your mir-rors. You can glue one card-board cover to the black card-board side of the tube, andthen use tape to attach theother two cardboard covers.

8Cut some pieces ofunwanted color filmslides or transparent

colored plastic into small

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shapes. You can also use con-fetti. Stand your kaleidoscopeon end, with the clear plasticwindow facing up. Put abouta dozen of these pieces ontop of the clear window.

9Find a "frosted" lidfrom a food containerone that lets light

through, but that you can'tsee through completely. Cut atriangle of this plastic just bigenough to cover the end ofthe tube. With the confettiand colored bits still in placeon the clear window, placethe frosted window on top ofthem. Glue or tape it in place.The confetti is now sandwich-ed between the frosted win-dow aid the clear window.

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Finally, cut a triangle

of heavy cardboardbig enough to cover

the other end of the kaleido-scope, and make a peepholein it about as wide as a penciland off center closer to onecorner than the others. Glueand tape this triangle in place,with the peephole closest topoint of the "V" made bythe mirrors.

11Aim your kaleido-scope at a light (notdirect sunlight) and

look through the peephole.What do you see? Turn yourscope slowly as you lookat the light. What are ycurchances of seeing the samepattern twice?

VARIATION

If you want to try the

deluxe kaleidoscope model,use a third mirror instead ofthe black cardboard floor.

AFTERWORDS

Your kaleidoscope is similar toone designed and patentedby a Scottish physicist, SirDavid Brewster, in 1817. Brew-ster's invention was sc popu-lar he sold more than 200,000of them in the first few months.Brewster also came up withan even more fascinating ver-sion: a kaleidoscope with aconvex lens mounted in theend instead of the plastic bitsand confetti. Viewed throughThis device, the whole worldbecomes a series of symmetri-cal patterns, and even theplainest images look likeblossoming flowers!

But kaleidoscopes can bemore than toys. Until recently,a designer might use a kaleido-scope to create new patternsfor such things as fabrics, car-pets, and wallpaper. Now,however, designers moreoften use a computer todo the same job.

Your kaleidoscope alsodemonstrates some physicalconcepts, such as opacity:the ability of a substance toblock out light. If you hold apiece of plywood betweenyourself and a burning candle,

you won't see the candleor the light coming from theflame. That's because ply-wood is opaque: It doesn'tlet any light or sight through.

The opposite of opaqueis transparent. Ordinary win-dow glass is a good exampleof a transparent material.If you hold a piece of glassbetween you and the candle,you can see not only the lightcoming from the candle, butalso the details of the candle'sshape, size, color, and posi-tion. Transparent materialslet light and sight through.

But what happens whenyou look at a burning candlethrough a sheet of waxedpaper? You can see somelight coming from the candle

certainly enough to tellwhether or not the candle islit. But you can't see any ofthe details. Waxed paper isa good example of a translu-cent material: It lets throughsome light, but not sight. Howmany other examples of trans-lucent substances can youname? How would you de-scribe the opacity of a glass ofmilk? The glass just after youfinish drinking the milk?

Another principle at workin your kaleidoscope involvesthe reflection of light. Firstof all, light tends to travel in

straight lines. Light entering amirror in a straight line will re-flect off the mirror in a straightline. But if the light hits the mir-ror at an angle, it will bounceoff the mirror in the oppositedirection, but at the sameangle. This is the law of reflec-tion: fhe angle going in has toequal the angle coming out.You can test this law by stand-ing in front of a mirror that isonly half as tall as you are.

Surprisingly, you will be ableto see your whole body, eventhough the mirror does notseem to be tall enough todo that job.

Most kaleidoscopes useabout a 60-degre?. angle,which produces a six-sidedpattern. Each side is an equal"slice" of the circle. The small-er the angle, the more imagesit creates. For instance, mirrorsangled at 45 degrees will re-flect eight equal images. Youcan figure out how many im-ages you'll see with any givenangle by measuring the anglewith a compass and dividingthe size of the angle into 360the number of degrees in acull circle. But as you probablynoticed, too many repeatedimages can look too confus-ing. So cut down on thenumber of "slices" in yourkaleidoscope pie!

50 80

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lili E ("MIL IEHfititittlyaa! Karate-chop yourveggies and watch themgrow. You don't have to be akarate expert or own asamurai sword. All you needis 15 minutes to set up thisexperimentand earn aBlack Belt in indouigardening!

YOU WILL NEED

Several root vegetables suchas carrots, beets, turnips,parsnips, radishes, andrutabagas

Knife

Pebbles or gravelSever& shallow bowls1 Very large carrotF .cavy string or Mole2 Sweet potatoesc.. Empty jars or large glassesbothpicks

Is there food in the roots of aplant? There must be, be-cause carrots, radishes, andbeets are all roots that weeat. They have sugar andstarch in them. If people canuse that food as fuel orenergy, then maybe theplants can use it too. Find

out how much energy isavailable by growing KarateChop V. les this month.

1Look at several rootvegetables, s ch ascarrots, beets, turnips,

parsnips, and radishes.Which side do you think is"up" when they are in theground? Which is the top?Figure out where the leavescome out on each vegetable.That is the growing tip Ifthere are leaves alreadygrowing on the veggies, re-move them without cuttinginto the growing tip. With aknife (you might ask an adultto help you), chop oil thebottoms of the root vegeta-bles, leaving only about 1" or2" of vegetable below thegrowing tip. (Save the vege-table bottoms to use in theRoot-a-Bake recipe shownbelow.)

2Choose several shai-low bowls to growyour Karate Chop Veg-

gies in. Put a layer of peb-b!es or gravel in elch bowl.

Set me vegetable top ineac; '-:owl, push i-2 ,'IP: cutend do, ..n into the gray °I toanchor it. Keep each bowlfilled with 1/2" of water. Newleaves should grow out ofthe top

Will leaves gr^w up-side do' . ? Find outby mu- 8 a nang:ng

carrot basket. Use a verylarge, fat carrot. Cut off thebottom half, leaving about 5"of the fattest part, includingthe top. Hold the carrot cut-side up and hollow out asection big enough to holdsome water. The widest partof the carrotthe growingtipwill be on the bottom.Make a rope hanger for thecarrot using two pieces oftwine or heavy string. Tie thestrings together in the middleand then pull them uparound the carrot, as shown.Hang the carrot basket froma hook or a bent coat hanger,near a window. Fill hollowed-out section with water. Theleaves should sprout out ofthe bottom. But will theygrow down?

HAN6THECARROTwalt2 PIECESOFTWINETIED INMIDDLEANDHAN&NEAR AWiN00"

4Which end is "up" ona sweet potato?Where will the leav

grow from? Look at twosweet potatoes. One end ismore round than the other.Ore end has more "f "scab"or scar than the other. Planteach sweet potato in a jar orglass of water to find outwhich end is the root. Plantone with the round enddorm. Plant the other withthe round end up. Stick tweetoothpicks into the sides ofthe sweet potato as "arms"to support it in the glass.Keep the bottom third of thesweet potato covered withwater. Set both jc.:s in awarm, dark place until ioots

are formed. Then give theplants a little light, gradually.After a frw days, you canplace the sweet potatoesnear a windch / for full tight.When the sweet potato hassprouted many leaves, youcan transfer it to a pot orthe garden.

VARIATIONS

Chop off the top of apineapple and grow it inpebbles or soil. If you useonly pebbles and water, theleaves will continue to growfor a week or more. In soil,you can start a whole newplant.

Cut a potato into severalpieces. Make sure that eachpiece has an "eye." Planteach piece in a separate potof soil or in the garden.

ROOT-A-BAKE

2 Large carrots2 Large parsnips1 Large turnip3 Tablespoons butter

Cup brown sugarSalt and pepper

Preheat oven to 350°. Use thevegetables above or use theleftover bottom parts of yourKarate Chop Veggies; anycombination of root veceta-bles will do. Cut the vegeta-bles into sticks about 3"by 1/2 ". Cook 10 minutes, or

unto tender, in boiling waterDrain. Butter a small, shallowbaking dish and arrange thevegetables in it. Sprinklebrown sugar over them anddot with more butter. Addsalt and pepper to taste.Bake at 350° for 20 to 25minutes, until the brownsugar and butter form aglaze.

AFTERWORDS

Have you ever Seen a carrotflower? Probably not, andneither have most of thefarmers who grow acres andacres of carrots each year.But carrots do have flowersand they do bear fruit. Theproblem is: The are biennialplants, which means that ittakes them twc. years tornmplete their growingcyue. They don't flower untilthe second year. And sincecarrots are grown mainly forthe edible root, they are

8 E3

pulled up out of the groundafter just one growingseason, before the flowerever has a chance todevelop.

Tumips, rutabagas,parsnips, and beets are alsobiennial plants. But in mostcases, these vegetables tooare harvested after only afew, months of growth.Usually these plants aregrown for their roots, whichstore up large amounts ofstarch -.tid sometimes sugar.The let 's of the youngplants di, small, and thestems are ;port. If harvestedearly, these plants becomefood for c zople. But if theyare allowed to remain in theground for another year, all ofthe food stored in theseplants is then put to use bythe plants themselves, and thestored starch is used toproduce more leaves on ataller stem. In your KarateChop activity, you coaxedthe vegetables into using upthe food stored in the rootto produce more leaves Ifthe can ot had remained in

the ground, it would haveproduced more leaves andeven a flower or two.

Most root vegetables aregrown just for the root, buttumips are an exception. Inthe South, many people eatthe turnip greenstheleaves from the top of theplantand throw the rootaway' In oth:_. parts of thecountry, people eat the rootand throw the turnip topsaway!

Red beets are grown forthe root, but another beet isgrown mostly for its greentop, called Swiss chard. Athird kind of beet is one thatyou probably eat almostevery day. You sprinkle thisroot on your cereal. You bakecookies are cakes with thisroot. Can you guess what itis? It's the sugar beet, fromwhich much of the world'ssugar is made. In fact, thesugar in sugar beets isidentical to the sugar in sugarcane. Both form a crystallinesugar when the juice isextracted from the plant

Is a white potato a root?No, although sweet potatoesare Whize potatoes areca:Ir:d tubers and they are

8 , ,

actually , idergrounci stems.Each "eye on the potato islike a bud on a twig. That'swhy farmers are able to cutup potatoes into severalsmall pieces and plant thepieces to start new potatoplants. As long as each piecehas an e. e, or bud, thepotato wl grow new leavesand more tubers.

Although quite a fewroots are edible, most plantsdo not store food in theirroots. In most plants, theroots are mainly an anchorfor the plant and a system forcarrying water and mineralsto the stem. And the biggerthe plan, the bigger the rootsystem must be. Some treeshave lateral root systems,spreading out horizontally,that are almost twice as wideas the tree is tall. A 37-foot-tall oak might have rootsreaching out 60 feet from thebase of the tree! A good ruleof thumb is that the rootsusually extend farther thanthe branches do. So nexttime you're standing under alarge tree, look at the spreadof the branches. Then walkjust until you are no longerunder the tree. More likelythan not, there are rootsunder your feet!

54

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§1100 FLY, FDon't say "Shoo, fly!" to fruitflies. They may be pesty, butscientists love to study themand so will you. You canraise two whole generationsof fruit flies in a month (butit's best to try it in a summermonth). It will take you 15minutes to set up a habitatfor them, and 30 minutes toobserve them up close.

YOU WILL NEED

3 Large empty glass jarsVery ripe grapes and

bananasPaper towelsAbsorbent cotton (large

pieces, not cotton balls)Sheet of notebook paperTransparent tapeVery small clear glass or

plastic lootte, such as anasp,rin bottle

Aluminum to ;lMagnifying glass

Have you ever seen a bowlof fruit with fruit flieshovering around it? Did youwonder where the fruit fliescame from? And why dothey always seem to appearout of nowhere when fruitgets very ripe? It's easy tofind out the answers bysetting up a scientific experi-ment with two jars of fruitone jar sealed up, the otherjar open. Maybe the fruit fliesare attracted to the ripe fruit.Or maybe the fruit-fly .:3gsare on the fruit itselfjustwaiting to hatch. Which is it?

1Place half of a veryripe bananawiththe peel still onin a

large, clean glass jar. Addsome very ripe grapes and acrumpled paper towel.Close the mouth of the jarwith loosely packed absor-bent cotton, as shown. Makesure there are no holes aroundthe edges, so that fruit fliescan't get in or out.

I2

Use a sheet of note-book paper and trans-parent tape to make a

paper funnel that will fit inthe mouth of the second jar.Let the small opening of thefunnel be about A" wide. Putsorri very ripe grapes andthe other half of the bananain another jar, along with acrumpled paper towel. Setthe paper funnel in themouth of the jar This forms asort of trap, so that fruit fliescan get into the jar but won'tfind tht .1. way out so easily.

3Set both jai in awarm, bright spot, butnot in direct sunlight.

Within a few days, youshould see some fruit flies.Are there fruit flies in bothjars? Where did they comefrom? When you see 5 to 8fruit they, in the jar with thefunnel, remove the funneland plug the inouth of the jarwith absorbent cotton sothey can't get out.

4Watch the life cycle ofthe fruit flies in yourjars. The eggs will be

too tiny to see. But you can

LTwatch for the larvaethecrawlirr, worm-like stage inthe development of the fruitfly. You might see them onthe crumpled paper towel.They will eat the fruit forabout a , veek and thenchange into the pupae stage.The pupae are almost adults,but not quite. When thepupae become adults, theywill mate and then lay eggs.A few days after that, youwill see new larvae, and thecycle will start all over againFruit flies live about fourweeks all together. Count thefruit flies in your jar and seehow fast they multiply.

5Carefully transfer oneor two of the newfruit flies to a very

small empty jar, like an aspirinbottle. Wrap aluminum foilaround the top two-thirds ofthe bottle, to make it darkinside The fruit flies willmove, toward the light at theuncovered end of the bottle.Use a magnifying glass toobserve them. Females arelarger than the males. But

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males have a larger, darkerblack band on the end ontheir abdomens. Can you tellwhich is which? If you thinkyou have a male and femalein your small bottle, transferthese fruit flies to the thirdlarge glass jar and add somefruit. Plug the opening withabsorbent cotton. If youwere right, these two fruitflies will mate and lay eggs.You can raise a whole newgeneration of fruit flies thisway.

VARIATIONS

In Place fruit in a jar but donot cover it at all. You maywant to place the jaroutdoors. Do fruit flies hoveraround the fruit? For howmany days? Will they layeggs and start a newgeneration? Does the fruit-flypopulation increase?

Try to raise fruit flies usingdifferent kinds of fruit. Findout whether or not you willget fruit flies with an apple, apear; some cherries, or apeach.

AFTERWORDS

No matter how annoying it isto sa, a swarm of fruit fliescircling around a beautifulbowl of fruit, scientists have

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often been willing to put upwith the little buggers becausehuit flies are perfect for onething: the study of genetics.Genetics is the study ofgenes, and how differentcharacteristics are passedalong from parents to off-spring. With fruit flies, whichlive for only about fourweeks, a geneticist can fol-kw 25 generations of fruitflies in a year! Fruit flies arealso easy for scientists toobtain. Since fruit flies thrivein a warm environmentsuch as overripe fruitscientists have a constantsupply.

The fruit flies you raisedare called Drosophilathesame species used in thestudy of genes. Imagine thatyou had a male fruit fly withcurly wings and a femalefruit fly with normal wings.Will their children have curlyor normal wings? It onlytakes four weeks to find out,because the whole life cycleof the fruit fly is complete inthat amount of time.

Drosophila have verylarge chromosomesalthough all chromosomesare microscopicwhich

makes them easy to study.When the genes for severaldifferent traits are locatedtogether on one chromosome,scientists say that thosegenes are linked. So whathappens if the gene for curlywings is linked to the malesex gene? In that case, onlythe male offspring of the fruitfly will have curly wings.Scientists have found that thefruit fly has more than 400different genes, many ofthem linked together, so thatthere are a great number ofvariations in the ways fruitflies develop

Can you see the color ofyour fruit flies' eyes? Believeit or not, they come in red,purple, white, apricot, andbrownnot to mention the"bar-eyed" fruit flies and theones with no eyes at all!Some of these colors aredominant, meaning that ifonly one parent passes thatgene along to the child, thechild will ' the dominanttrait. Other ey, colors arerecessive traits, meaning thatboth parents must pass thegene along in order for thechild to have that trait. Thesame is true in human beings.Some eye colors are domirintbrown, for instance. Othereye colors, such as blue, are

recessive.

Surprisingly, some genesfor eye color in fruit flies arelinked to the gene that deter-mines life expectancy. Howlong will a purple-eyed fruitfly live? Only about 27 days.Fruit flies with normal eyes willlive about 10 days longer.

Of course, fruit flies arepests, and they've done enor-mous amounts of damage aswell. The Mediterranean fruitfly took hold in Florida in the1920s, threatening to destroyacres upon acres of fruit.Eliminating the Mediterraneanfru!' fly cost $6 million andthe effort lasted for severalyears--only to have the"Med fly" pop up in Califor-nia again in the 1970s.

Another damaging spe-cies is the Mexican fruit fly,which attacks citrus ft _itsThen there s the apple mag-got, the cherry fruit fly, tnemelon fly, and others thatattack walnut-, celery, as-paragus, and olives And it'svery hard to get rid of ',I tern.

LurAily for you, it's prettyeasy to get rid of your fruitflies. Just dump the projectin the trash, sell itandkeep you+ fruit in the re-frigerator from now oni

58

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GREASY IEven if you don't like steak,french fries, or butter, youmay be living off the fat of theland. Find out which foods arehigh in fat content by doingtwo easy kitchen experiments.You'll burn 110 calories of fuelor fat in the one hour it takesto complete this activity.

YOU WILL NEED

Brown paper bagVarious test foods such as:

butter, banana, apple,hard-boiled egg,uncooked frankfurter,potato, avocado, tomato,cottage cheese, cookies,nuts, cola, orange, limabeans, peanut butter,potato chips, etc.

Pen or felt marker

Have you heard all about thefour food groups and theirrole in planning a healthy,

well-balanced diet? If so,you know that you should eatFruits and Vegetables, Milkand Dairy Foods, Meats/Fish/Poultry/Dried Beans, andDreads and Cereals every day.But there's another rule aboutnutrition that is just as impor-

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60

tant for good health, and thatis the rule about fats in yourdiet. Health experts suggestthat no more than 30% to 35%of the calories you eat shouldcome from fats.

But before you can plana healthy, low-fat meal, youneed to find out which foodsare high in fats, and whichfoods are not. Greasy Kid Stuffwill help you sort out the "fat"foods from the other ones!

DEFINITIONS

Calorie: This is P unit ofmeasure that rerers to theallount of heat or energy afood will produce. Differentfoods will produce differentamounts of energy. Ounce forounce, fats will produce a lotmore heat or energy thanproteins or carbohydrates,and so fats are high in calories

Carbohydrates: Almost allcarbohydrates come fromplants. There are two mainkinds of foods in the carbo-hydrates group sugars andstarches. Peaches and berriesare sugary carbohydrates,while peas and potatoes arestarchy carbohydrates. Wheat,

STUFFrice, and the other grains areprimarily starch as well.

Protein: Every living cell con-tains protein, which is whymeats, fish, and poultry aresuch good sources of thisimportant kind of food. Milkand dairy products are alsovery rich in protein, and soare dried peas and beans.Protein's main job is to helpthe body grow.

Fats: The oily or greasy partof meat, poultry, fish, nuts,seeds, and so on.

1Cut open a large brownpaper bag and lay itflat. This will be your

Fats Chart. Cut off a small pat

of butter and rub it on at thetop of the paper-bag chart,until the butter stains. Writethe word "Butter" under thestain, and put a number 10beside it. Buter will make thegreasiest stain, since it isalmost all fat.

2Next, look at all of thefoods you're going totest, and try to decide

which one has the least fat init. Rub that food on the bag

near the bottom. Write thename of the food underneaththe stain it makes, and put anumber 1 beside it.

3Now try to decidewhere the other testfoods fit in the scale

from 1 to 10. If you thinkpeaches are very fatty, putthem near the top of the chartand give them a high number.Continue testing foods for fatby rubbing each food on thebag and numbering the stains.With dry foods like cookies,you oy want to warm themin your hands first, and thenrub hard to make a mark. Labeleach stain by writing the nameof the food underneath it.

4Look at the bag a fewhours later or the nextday when the wet

stains have dried. Hold thebag up to the light and youwill see a greasy, see-through

mark by each food that con-tains fat. The more fat in thefood, the greasier the stainwill be. Did you put all of thefoods in the right order? If so,you will have a column of

9 .'

stains that goes from verygreasy to not greasy at all.If you find a big greasy marknear the bottom of your scale,or a "blank" space near thetop, you guessed wrongabout the fat content ofthe foods!

Does the mark from thebanana surprise you? Howabout the stain above theword cheese? Did you knowthat many nutritious foodsare very high in fat?

HOW TO LOSE FATFAST!

When it comes to cookinghamburgers, there's a great

way to cut your own fat in-take. It's called broiling. Findout how much fat you canlose from a hamburger patty,that is by trying this dinner-time experiment.

Divide a pound of groundbeef into four hamburgerpatties, each weighing about1/4 pound. Try to make thepatties as equal in size aspossible.

Fry two of the hamburgersin a skillet on top of the stove.

Broil two of them in a broilerpan in the oven.

When the hamburgers arecooked, look in the pans tosee how much fat they've lost.Which cooking method re-moved the most fat from thehamburgers? Measure the fatin the broiler by scooping itout a tablespoon at a time.

Then do the same with the fatin the frying pan if there isany! If there isn't any fat in thefrying pan, where is it?

Did you know that mostbutcher shops and meatdepartments add chunks ofwhite fat to the beef beforegrinding it into hamburger? Bylaw, hamburger may contain

61

as much as 30% added fat.That's in addition to the fatthat is already present in thered part of the meat;

VARIATIONS

Go on a Supermarket Safarilooking for fats! Read the in-gredients labels on cookies,crackers, cakes, frozen dough-nuts, breakfast cereals, etc.You'll be surprised how manydessert foods contain beef fator other animal fats. Next, readand compare the nutritioninformation labels on manydifferent foods. Make a chartshowing how many grams offat there are in a single servingof whole milk, low-fat milk,cottage cheese, one pat ofbutter, various canned soups,frozen dinners, potato chips,breads, and so on.

w/hich foods are most satis-fying? Eat a meal that is entire-ly fat-free. You may want toconsult your brown bag chartof grease stains and yourSupermarket Safari list to helpyou decide what your fat-freemeal should have in it. Afteryour fat-free meal, how longis it until you are hungry again?

The next day, eat a starch-freemeal and make a note of whenyour hunger pangs return.

AFTERWORDS

Fats have fallen into disfavorrecently, especially amongpeople who are concernedabout heart disease and goodhealth. Nevertheless, fats are anecessary and important partof any diet. For one thing, fatsprovide a good source ofenergy. They also slow downthe rate of digestion, whichmeans that you will feel "satis-fied" longer after eating a high-fat meal. Fats carry the fat-soluble vitamins A, D, E, andK; these vitamins can be dis-solved only in fat and not inwater like the other vitamins.And lastly, many fats containan essential nutrient, linoleicacid, that is necessary for nor-mal growth and healthy skin.

The problem is that mostAmericans eat too many fats.Since the early 1900s, Ameri-can consumption of fat hasrisen 25%, while consumptionof carbohydrates has fallen bythe same amount. This trend isprobably an unhealthy one,because there seems to bea connection between theamount of saturated fat youeat and your chance of get-ting heart disease and certainkinds of cancer. For this reason,

many nutrition experts recom-mend that fats account for no

more than 30% to 35% of thecalories consumed daily. Theaverage American diet, how-ever, currently contains about45% fat.

In any plan 'o reduce fatsin your diet, the It word Issaturated. Saturated fats arethought to contain largeramounts of cholesterol thanpolyunsaturated fats. Andalthough the question of cho-lesterol levels is still beingdebated, many doctors sug-gest that people with a historyof high blood pressure and /orheart disease should cutdown on high-cholesterolfoods.

But how do you knowwhich fats are saturated andwhich fats are not? Here aresome easy guidelines to helpyou answer that question.Saturated fats are usually solidat room temperature, andtney come primarily from ani-mal sources meat, milk anddairy product 3, and eggs.Polyunsaturated fats, on theother hand, are usually liquidat room temperature. Theycome from vegetable sourcessafrlower oil and corn oil aretwo examples and they arethought to help decrease

the level of cholesterol in theblood. The two monounsatu-rated fats, olive oil and peanutoil, also have a positive effecton cholesterol levels.

For people who want tocut down on cholesterol, itsanimal fats that must be elimi-nated. This can mean switch-ing from butter to marga1 ine,cutting down on the numberof eggs eaten each week,choosing skim milk instead ofwhole milk at mealtimes, andeating leaser cuts of meat.

But in any discussion ofnutrition its important to re-member that no single nutrientshould be completely elimi-nated from the diet. Choles-terol is a good example of thisrule. In fact, cholesterol is

needed by the body for diges-tion and for the formation ofhormones and vitamin D. Yourbody can probably manufac-ture all the cholesterol youneed. But it would still bea mistake to cut out all foodsthat contain cholesterol, be-cause many of those foodsprovide other valucble nutri-ents that are of great impor-tance in a well-balanced diet.

62

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OC EIS ILW YDo you have dreams of beingan astronaut? First you haveto learn how to get yourrocketship off the ground.You'll be airborne in only30 minutes!

YOU WILL NEED

A plastic tennis-ball can orplastic soda bottlewith cap

Large nail or pencilScissors

Soda straws of 3 differenttypes: jumbo, superjumbo, and flexible(see Note)

Tape

Paper

Several small pieces ofhook Velcro

A "woolly" blanketA plastic bag, about

10" by 12"Some fishing line,

6- or 8-pound testA few balloons, long rather

than roundVinegarBaking soda

Note: Most large drinkingstrawsthe kind you getat burger jointsare jumbostraws. However; a few fast-food places Burger Kingor ice-cream parlors that servethick milk shakes) have evenlarger straws superjurnho.For this activity you will needa few of each arid the jumboshould be able to passsmoothly througn the superjumbo. You might also wantto get some flexible straws(ones that have a bend like anaccordion partway down thestraw); they're available at thesupermarket.

You can use air power to learnsome rules that are importantfor understanding flight andtrajectory (the path your rock-etship will take in space). Getset to make your own rocketsand a launcher!

1Poke a hole in the lid ofthe plastic tennis-ballcan with a large nail or

pencil. If using a soda bottle,you might have to use a drillto make a hole in the cap.Or try using the pointed end

of a pair of scissors. (Ask a

grown-up for help if youneed it.)

2Cut the end of the flexstraw on an angle andrun it through the hole

in the lid or cap. The strawshould fit very snug. Put thelid or cap back on the canor bottle.

3Stick ajumbo straw intothe end of the flex strawand tape it in place.

The flex straw will allow youto adjust the angle of launchduring later experiments.Your rocket launcher isnow complete!

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4Now, make some rock-ets. Fold over V? of theend of a super jumbo

straw and tape it down. Slidethe super jumbo over thejumbo launcher straw, aim,

and give the can or bottlea sharp squeeze. The superjumbo should take off! Prac-tice launches to see if you canland your rocket in a box orwastebasket. Try it from differ-ent locations around the room.Then put some obstacles in itspath to see if you can getyour rocket high enough tosail over them.

VARIATIONS

Stabilizers are often attach-ed to flying devices to helpthem fly straight. Find out howvarious stabilizer designs helpor hinder the straight flight ofyour rockets. Tape on paperfins (2, 3, or 4), cones, orother designs.

Does a short rocket flyfarther than a long one? Makedifferent rockets (21: 4", and 6"long), fit them all with identicalstabilizers, and find out whichflies best.

A target makes all of theexperiments more interesting!at a bit of hook Velcro andtape it to the front tip of yourrockets. Search around thehouse for a blanket that the

64

Velcro-tipped rocket will eas-ily stick to. Hang the blanketover a door. Now launch therocket and try to stick it to theblanket. How high can youstick a rocket? What is thegreatest distance from whichyou can stick the rocket tothe blanket?

Make a Beeline Rocket

Message Delivery System.Tape the soda straw to theside seam of a plastic bag.Run a length of fishing linethrough the straw long enoughto tie one end of the line tosomething in one room, andthe other end of the line tosomething in another room.Write a message and put it inthe bag. The open end of the

bag should trice away fromwhere you want your mes-sage to go. Blow up a balloonand pinch the opening shut,put it into the bag with themessage, and release it. Yourmessage will rocket into thenext room!

Real rockets don't run on air,of course. They use fuel thatburns, or combusts, and thepower sends them off intospace. You can make yourown rocket fuel. Pour 1 cup ofvinegar into the can or bottle.Then take 2 tablespoons ofbaking soda, roll it up into apaper napkin, and insert it inthe can or bottle. Replace thelid or cap and swirl the con-tainer to mix the ingredientstogether. Zoom!

AFTERWORDS

Real rockets don't fly or com-pressed air power. Real rock-ets have internal combustionengines and carry both fuel toburn and 9 source of oxygento help the combustion. Be-cause rockets carry their ownoxygen source, they can oper-ate even in the deep reachesof space where very little airexists.

Rocket propulsion worksbecause of a very basic lawof physics: For every action,thereif Ngclual, and oppo-

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site, reaction. Fuel is burnedin a dosed chamber. The hotgases that result from thecombustion rush out the noz-zle at great speed. The fast-moving gases the', ore pro-pelled out the end of therocket are the "action:' Theopposite "reaction" movesthe rocket fL,rward. This sim-ple principle drives rocketsto the moon and beyond!

Your soda-straw rocketcarries no fuel for propulsion;the driving force behind therocket is air pressure. Whenyou squeeze the flexible plas-tic bottle, the air in the bottleis compressed into a smallerspace and the pressure insideincreases. The air pushes outin all directions with equalforce. When gee ;ricreasedforce pushes against theclosed end of the rocketstraw, the force is strongenough to send the rocketoff into space.

If the force is applied fora short time, the rocket willmove slower. Me longer theforce acts on the rocket, thefaster the rocket will be goingwhen it lean fs the launcher.

This fact suggests that a longerstraw rocket will fly faster(therefore farther) than a shortone. Did you figure that outyourself?

For a brief moment duringthe launch of a soda-strawrocket, it acts like a real rocket.Precisely when .he rocketleaves the launcher and thepressure inside the straw isvented through the open endof the straw, it acts just like afull-fledged rocket. For a splitsecond, air will rush out theopen end of the straw as itleaves the launcher. This actionwill have the reaction of add-ing a little thrust to the strawrocket. The effect will be small,but nonetheless the thrust willhelp the rocket move. The restof the rocket's flight can beattributed to the push givento the rocket by the actionof compressed air.

Another force to be dealtwith in rczketry is air. Air is likea fluid; it has mass and occu-pies space. It must be pushedout of the way if an object isto pass through it. Therefore,the more streamlined youmake your rocket, the moreeasily it will push through theair. Put this force to work foryou. In order to keep therocket on course, place stabi-

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lizers, or fins, at the back ofthe rocket. As long as therocket travels straight forward,the sharp edges of the fins cutefficiently through the air andkeep the rocket steady. it

the rocket starts to pitch orroll, the broad side of the finwill start to make contact withthe air, creating more air resist-ance. Increased resistance willtend to slow down that sideof the rocket, which correctsthe rocket's flight automati-cally. Now your rocketsshould make it safely totheir destinations!

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How would you like to makewrapping paper that lookslike real marble, with swirls ofcolor? You don't have to he agreat artist. Just put science towork for you and in about30 minutes you can createa work of art.

YOU WILL NEED

3 Drinking glassesWater

Small amounts of assorted

beverages (milk, juices,soft dririls) andhousehold liquids(vinegar, detergents)

TeaspoonSalt

Vegetable oilFood coloringNewsp6per;A large rectangular baking

dish, tray, dishpan, ordisposable e.luminumroast:lg pan, big enough

to hold the paperHobby paints: oil-based,

in various colors(available in smallsquare jars wherevermodel airplanes are sold)

Stick or paint stirrerWhite notepaper and sheets

of paper large enoughto be used as gift wrap(pads cf artist's "layoutbond" work well)

Dishwashing liquid

Salad oil or turpentine orpaint thinner for clean-up

Paper towels

Maybe you've heard that oiland water don't mix. But arethere other liquids that won'tmix with water? Is there away to force oil and water tomix? When you find out theanswers to those questions,you'll understand why mar-bleized paper is easy to make.

68

1Fill a drinking glass half

full of water and add asmall amount of milk.

Stir. Do the two liquids mixtogether or do they separate?Rinse out the glass and try theexperiment with other bever-ages. Do all liquids mix withwater? Can you find a liquidin your kitchen that will not mixwith water? CAUTION: DONOT DRINK THE EXPERIMENTS!

2Clean the glasses andbegin again. Fill oneglass with cold water

and one glass with hot water.At the same time, add a tea-spoon of salt to each glassand stir. Which glass of waterdissolves the salt faster? Pour1/2 cup of vegetable oil into thethird glass, add a teaspoon ofsalt, and stir. What happens?

3Find out whether ornot you can make oiland water mix! Start

with a clean glass, filled half-way with water. Add a fewdrops of food coloriri_ soyou'll be able to tell the waterfrom the oil more easily. Nowadd a few teaspoonfuls ofvegetable oil and stir madly!If you stir fast enough, will theoil and water finally mix?Does the food coloring mixbetter with the oil or water?

1

4Now it's time to takeadvantage of the GreatOil and Water Feud and

make beautiful marbleizedpaper! Spread newspaperson the floor near your work-space to use as a drying area.Fill your flat baking dish, tray,or disposable roasting panhalf full of water. Add a smallamount of hobby paint to thewater. See how it floats on thesurface? Use a stick to swirl

HOBBY PAINT WILLFLOAT ON5t/RFAcfr-

the paint around. You canmarbleize your paper now, oradd more colors first. Whenthe floating paints look goodto you, lay the paper on thesurface of the water for a fewseconds. (Until you get thehang of it, experiment withthe small notepaper beforeyou go on to the larger paper.)Work quickly Ind don't soakthe paper. That way it won'twrinkle. Lift it off and look atyour designs! You'll probablybe able to marbleize one ortwo more sheets of paperbefore you need to add morepaint. Experiment with stirring

the water rapidly and thenquickly putting the paper onthe surface while the paintand water are still moving.

5Find our how soap af-fects the oil-and-watercombination by adding

a squirt of dishwashing liquidto the mixture. What happensif you add the soap withoutstirring the paint and water?What happens if you stir it upfirst? Can you get differentmarbleized effects this way?

6Let -your marbleizedpaper dry, paint-sideup, on newspapers for

several hours before using it.If the paper is slightly wrinkled,you can iron it between twosheets of plain paper. Use alow setting cn your iron.

IClean your marbleizingtray and utensils withsalad oil or paint thinner.

VARIATIONS

You can marbleize vases,cardboard and plastic boxes,pencils, and other objects thathave a smooth, solid-colorsurface. Boxes can be marble-ized in the tray by simply lay-ing the box on the surface ofthe water, one side at ?. time.For other objects, i is:. a bucketof water instead of a tray, and

get the water moving beforeyou dip the object.

Create special designs byswirling a marbleizing "comb"through the floating paints.You can make the comb your-self: Use a strip of heavy card-board about 1" wde and 8"long; push some pins throughthe cardboard in a straightrow, spaced 1/2 inch apart.

Or use toothpicks stuck intoa piece of Styrofoam.

To make marbleized notecards and envelopes, usesheets of stationery folded inhalf. If you dip the envelopes,don't use too much paint andbe sure to keep the gummedflaps dry. You can write onyour marbleized paper if thepaint isn't too thick.

Make book covers fromyour marbleized paper. Orbetter yet, "publish" yourown book and paste the mar-bleized paper on the insideof the front and back covers.That's the way it's done forspecial editions of handmadebooks.

AFTERWORDS

Marbleized paper was cre-ated in Persia 400 years ago,and it hts been made justabout the same way eversince. In France, England, Italy,

and, later, in the United States,

beautiful marbleized paperswere often used as endpa-pers: the decorative papersthat are pasted down on theinside front and back coversof books. For an example, youmight check your local publiclibrary and/or school library.If they have old copies ofWebster's New InternationalDictionary Second Edition,the endpapers will probablybe marbleized paper.

Other old books in yourlibrary might have a variationof marbleized paper: marblededges. Even as recently as the1950s, apprentice bookbind-ers were taught how to mar-bleize book edges by hand.The pages of the book wereheld tightly together in aclamp, and then dippedquickly into the multicoloredpaints floating on the surfacein a vat of water. Master book-binders knew how to usecombs and rakes to createspecific standard patternswith names like Peacockand gate..

Today marbleized end-papers and edges are rarelyused, but when they do ap-pear, they are still made byhand, aria still use the princi-ple that oil and water won'tmix. But water mixes well withmost other substances. In fact,water can dissolve so manysubstances that chemists callit a universal solvent. The sub-stance a solvent dissolves iscalled the solute, and themixture that results is calleda solution.

Your kitchen is full of solu-tions that you drink every day.Lemonade, coffee, tea, appleiu:ce, and soft drinks are allsolutions with one or moresolutes dissolved in them.Have you ever noticed thatsugar dissolves more easily inhot tea than in iced tea? That'sbecause the solubility of asolid in other words, theability of a solid to dissolveincreases when the tempera-ture of the solvent goes up.

But here's a surprise:The opposite is true when thesolute is a gas. With gases, thecolder the solvent, the moresoluble the gas is. Maybe youdidn't even know that gases

could be dissolved! Well, theycan and that's how softdrinks c.re made. The gas

carbon dioxide is actuallydissolved in water, along withsugar and some other flavors,to make the fizzy carbonateddrinks people love. Now thatyou know how temperatureaffects the solubility of gases,you can understand why so-das left out in warm weatheralways taste flat!

One beverage you'll findin your refrigerator isn't a solu-tion at all. Scientists call milk acolloid, rather than a solution,because there is something inmilk that can't be dissolved.Can you guess what it is? It'sthe butterfat, of course! Fiftyyears ago, before milk washomogenized, the creamwhich has most of the butter-fatwould separate from themilk and rise to the top of thebottle. (That was in the dayswhen milk came in bottles.)Though cream looks thickerand "heavier" than milk, thetiny particles of fat in creamare lighter than the rest ofthe milk.

Today, however, the but-terfat never separates frcmthe milk because homogeniza-tion is standard in the UnitedStates. During this milk-pro-

1 1 .

cessing method, the small par-ticles of butterfat are forcedthrough a valve and madeeven smaller. Once the butter-fat particles are the right size,they neither rise nor sink,because they aren't lighteror heavier than the rest ofthe milk.

So next time you sirsa glass of milk, you can say

thanks to teLi urology for thehomogenization that givesyou a smoother drink. Butwhen it comes to makingmarbleized paper, there is noneed for technological tricks.The natural conflict betweenoil and water brings abouta more beautiful creation.

70

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ICE (RE CINEWhich is colder: ice or icecream? You'll find out whenyou get the scoop on theamazing Ice-Cream Machine!From mixing to tasting shouldtake about 45 minutes.

YOU WILL NEED

Empty coffee can withplastic lid

Scissors

Wooden spoonIngredients for Vanilla Cookie

Ice Cream (see box)

;

MAN

COOKIEVVAM444 of,ior

4:11VAN ILLA

BowlElectric mixer5-Pound bag of iceBrown grocery bagHammer A,

NewspapefsBucket

RACHELS1o4 HomEmADE lo 4

ICE CREAM

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S PR WALES

2 to 21/2 Cups table salt

Empty plastic container orice-cube tray

Homemade ice cream andclear roads during a winterblizzard what do these twothings have in common? They

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both depend on the specialrelationship between ice andsalt Salt melts ice That's whyit's spread on icy roads in thewinter. But salt also causes thetemperature of water to godown. You'll use salt to meltice and lower the temperatureof the water in your Ice-CreamMachine. Believe it or not, thewater will get colder than 32degrees Fahrenheitbut itwon't freeze! Pretty cool, huh?

72

ckz.9E3AND _AN

TEIL-NE Li,t4" E

RE Prii

INGREDIENTS FORVANILLA COOKIEICE CREAM

(adapted from a recipe pub-lished in Consumer Reportsmagazine)

1 Egg

2 Cup sugar1 Teaspoon vanilla1 Cup heavy cream2 Cups half-and-half3/4 Cup of your favorite

cookies, crushed by hand

1Before you begin, haveready all the ingredientsfor Vanilla Cookie Ice

Cream and al! of the equip-ment listed. Wash and drythe empty coffee can andlid. Using a scissors, poke asmall hole in the plastic lid.Make sure the hole is offcenter. Enlarge the hole bypushing ti ., wooden -spoonhandle through the hole. Don'tmake the hole too big: Thespoon handle should fit tightlyin the hole. With the scissors,trim away the rough edges ofplastic around the hole.

2Make the ice-creammix by putting the egg,sugar, and vaniila into

a bowl and beating with anelectric mixer for 1 minuteon a medium speed. Add thecream and half-and-half, and

mix on low speed for 3 min-utes. (You'll add the crushedcookies later.) Set the ice-cream mix back in the refriger-ator until your bucket of iceis ready to go.

3Now you need tomake crushed ice. Putthe 5-pound bag of ice

inside a brown grocery bag,fold the bag end closed, andpound the ice with a hammeron the kitchen floor. It mighthelp to cover the grocery bagwith a layer of newspapers,to keep the hammer frombreaking through the paperbag. Pour about one-thirdof the crushed ice into thebucket. Cover the ice withabout 1/2 cup of salt. Put the

coffee can on top of the ice,in the middle of the bucket.Add ice and salt in layersaround the can until you haveused up all of the ice. Butdon't use all of the salt

SOChE

,OFFEEt_AN,

IL E,

yet. You may not need itall, or you may need toadd some later.

4Pour about two-thirdsof the ice-cream mixinto the coffee can.

Pour the rest of the mix intoa plastic container or emptyice-cube tray and stick it inthe freezer right away. Thispart of your ice-cream experi-ment is what scientists call the"control": It gives you anothermethod of freezing your mix-ture so you can compare andsee which method works best.When you have finished mak-ing ice cream, immediatelycheck the control portion inthe freezer. Is it frozen yet?Can you figure out why?

5Stick the woodenspoon into the coffeecan with the ice-cream

mix. Snap on the plastic lid,letting the spoon handle stickup through the hole. Thewooden spoon has two jobsin your ice-cream machine:It's a handle for turning thecan, and a dasher for stirringthe ice cream. Now grab thishandle and start turning thecan. Every 2 or 3 minutes,stop spinning the can andhold it still so you can use thedasher (the "bowl" of the

wooden spoon) to stir theingredients inside. Try to mixin as much air as you can:Move the dasher in a circularmotion around the bottomof the can and the side. Don'tremove the lid to do this.

After about 10 or 15 min-utes of spinning the can, takethe lid off and add the crushedcookies. Replace the lid andcontinue as before. You cancheck on your progress everyonce in a while, but don't takethe lid off too often. You'llnotice when you're stirringthat the mixture is getting thick-er. All together, it will probablytake about 25 to 30 minutesto make ice cream. But don'tworry: It's not hard work! Youcan keep the can spinningwithout much muscle power.And it never hurts to have ahungry friend handy, to helpyou take "turns"! Remember:When the ice cream is done,check the control portion inthe freezer.

12.,

HINTS FOR SUCCESS:

2 Make sure all the ice-creamingredients are cold whenyou start.

If the ice doesn't seem tobe melting in the bottom ofthe bucket, add a small amountof water to get it going.

Don't add too much salt atfirst: You can always add morelater if you need it. The moresalt you use, the faster the icewill melt. If the ice melts toofast, ice crystals will form ant:the mix will harden too soonbefore you have a chanceto stir enough air into it. Airis what gives ice cream itssmooth texture. Air also keepsyo,. from noticing how coldthe ice cream is! Is your home-made ice cream colder thanstore-bought ice cream?Which do you think is themost "airy"?

Be patient. At first, the icecream may not seem to besolidifying, but after about20 minutes, you'll noticethe change.

AFTERWORDS

Ice cream is the delicious re-sult of some important scien-tific principles. N.., one knowsfor sure when ice cream wasinvented, but frozen dessertshave been around for a longtime. The Romans had fruitices, and Marco Polo claims tohave eaten some ice milk dur-ing his travels to the Far East.

If you've eaten ice milk orfruit ices, however, you knowthat they just aren't...well, ascreamy as ice cream. So whoput the creaminess in icecream? Probably the Euro-peans. In the 1700s they dis-covered that salt could lowerthe temperature of iceandthat meant that frozen dessertscould be frozen much morequickly. When milk and creamare frozen quickly, ice crystalsdon't have time to form.

In your ice-cream experi-ment, you probably foundout that it's hard to get theperfect balance betweenfreezing the mixture quicklyenough so that ice crystalscan't form, and freezing itslowly enough so that youhave time to incorporateplenty of air. "Overrun" iswhat ice-cream manufactur-ers call the air that is mixedinto ice cream. Using hugemachines with gigantic dash-

ers, they can double the vol-ume of ice cream by addingas much air as there is cream,sugar, and milk! Ice creamwith a lot of overrun doesn'tweigh very much, and it'spretty frothy in your mouth,too. But ice cream without airis too hard and too cold: It'smore like frozen milk. Themixed in air actually keepsyou from noticing how coldthe ice cream is!

To keep manufacturersfrom cheating the public byputting huge quantities of airinto ice cream, the govern-ment requires that a gallon ofice cream weigh at least 41/9

pounds. Next time you're inthe grocery store, cc, nparethe less-expensive ice creamswith the higher-priced ones.You can probably tell justby lifting them which onesare full of air. When you thinkabout the fact that you're get-ting more food and less airin the heavier ice creams,doesn't it make the high pricea little easier to swallow?

Modern-day manufactur-ers use huge freezers insteadof salt and ice to freeze !he icecream ingredients. But beforefreezers were invented, peo-ple needed ice to make icecream. Without refrigeration,

though, it was hard to get icein the summer. Some people,who lived near rivers or lakes,had icehouses to store ice in,and they could make ice creamin the summer. In winter, theytook huge chunks of ice fromthe river and packed the giantice cubes in hay for insulation.The ice lasted for months thatway but by August, it wasoften melted. In those days,ice cream was eaten moreoften in December than in thegood old summertime. Quitea chilly treat!

People often wonderhow salt can melt snow andice on the roads if it actuallymakes ice water colder. Andif the melted ice is colder than19 degrees, then why doesn'tit freeze again right away?The answer is that as the icemelts, it dissolves the salt andmakes saltwater. Saltwaterdoesn't freeze at 32 degreesthe way plain water does:It freezes at a lowertemperature.

Now that you're an expertabout ice cream, you mightwart to go into the ice-creambusiness. Maybe you'll be thefirst person to come up witha ,;avor no one's ever thought(.4 yet. What a sweet life! Justtry not to lick up all yourprofits!

74

S/Eh

What goes up must comedown but wearing a para-chute makes landing easier!This activity will take 30 min-utes, plus a few hours dryingtime for your papier-macheparatrooper.

YOU WILL NEED

Small piece of cardboardScissors

Pipe cleanersFiourWaterBowl and spoonNewspapersTempera or hobby paintsPaintbrushPlastic from garbage bags,

dry-cleaning bags,or food-storage bags

Felt-tip markerNeedle

Heavy-duty thread

Did you know thateven themost experienced paratroop-ers sometimes get hurt whenparachuting out of an airplane?As the saying goes: "It's notthe fall that hurts it's thelanding!' Maybe you've won-derPdwhy these paratroop-as hit the ground so hard.

It seems like there should besome way to keep them fromfalling so fast. Well, you'll findout why parachutes are de-signed the way they are whenyou make your own test pilotwho's heaaing for a fall!

1Cut out a body foryour parachute manfrom a small piece of

cardboard, using the patternshown here. Your man shouldbe about the same size asthe pattern.

us!:FOR PAT LRNAN0 r-'41;,1 T 0alYOUR OWNFARAHL,T,t,

4*au

2Make a "loop" by twist-ing a pipe cleaner intothe shape of a script e,

as shown. (Later you'll tieyour parachute to this loop.)

Place the loop against thecardboard man's neck so thatthe two tails of pipe cleanerstick out to form arms. Thenwrap the arms around theneck once to attach the pipecleaner to 0 le man. This is the

MAIkE 5,RE LOOP:5 k.',1

BODY AVOFREEsituNC,To T

frame for the parachute man.

3Mix up some papier-mache paste by com-bining 4 tablespoons

flour with 6 tablespoonswater in a small bowl. Cutor tear strips of newspaperabc,:t1/9" wide. Dip a stripof newspaper into the pasteand then use your fingersto wipe off the excess. Coverthe arms, head, and body ofthe parachute man with stripsof papier-maché wrappingthem around and around to

build up a little bulk. But besure to leave the loop freeand uncovered! Let thepapier-mache man dry for afew hours or overnight. Thenyou can paint a face andoveralls on your parachutist.

4 While the paint is dry-ing, cut a circle out oflightweight plastic such

as a garbage bag, food-stor-age bag, or the plastic thatcovers your clothes whenthey come back from the drycleaner. This will be your para-chute. How big a parachutewill you need? Do you think aparachute could ever be toobig? You'll find out by experi-menting with circles of varioussizes. If your man is less than3" tall, you cen start with a

Parachute 12" in diameter.

1)

5Now it's time to attachthe lines to the para-chute, and then to the

man. first, look at your para-chute circle and pretend it isa clock. With a felt-tip marker,put a dot each, about 1/4" fromthe parachute edge, at 12o'clock, 2 o'clock, 4 o'clock,6 o'clock, 8 o'clock, and 10o'clock. Thread a needle witha single strand of heavy-dutythread and attach six lines tothe parachute, one at eachdot, as shown in the diagram.How long should the lines be?

'Form)CHUTEIS A

CLOCKTOMPH.;PCI

TACHATREAD

That depends on the size ofyour parachute. A good ruleof thumb is to make the linesapproximately as long as theparachute is wide. Onceyou have threaded the linesthrough the plastic, though,they will be double strandshalf the width of the para-

A./

,oftligi: THR)t L')CiPbAch

12t;

chute. When all six lines are at-tached to the chute, pull themtogether and make sure thatthey are all exactly the samelength. Knot them through theloop Dn the back of tne para-chute man's neck, as if theywere all one thick cord.

Time to bail out! Experi-ment with your para-chute man by tossing

him into the air, or droppinghim from the top of a ladder.But if you're going to climba ladder, be sure to have an

adult nearby. You also canthrow your parachute manout a window, but neverlean out the window! Havea friend waiting below towatch where iitr lands.

When you drop him froma high place; does your para-

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12;

chute man fall gently to theground or does he plummetto the earth? Does he swingfrom side to side as he de-scends? If so, cut a small holea little smaller than a dimein the very center of the chute.This air vent helps stabilize the

parachute's descent. Experi-ment with different-sizechutes on the same man. Canyou figure out why paratroop-ers don't want huge para-chutes, even though biggerchutes would allow themto land more gently?

VARIATIONS

Attach the parachute manto a helium balloon and let itgo. When the helium balloongets high enough, it will ex-plode, and the man will para-chute to earth. This is howone of the first parachutistsgot the chance to test his newinvention! If you write yourname and address on the para-chute in permanent markerbefore launching the balloon,you might get a letter or callfrom the person who finds it.

Before tying the lines(threads)to the man, arrangethem so that one is shorterthan the others. How doesthis affect the parachuteman's ).311?

I 9Av.+ ,

AFTERWORDS

Imagine: Long before peo-ple had thought of a wayto get themselves up off theground, Leonardo da Vincihad devised a way to landsafely: with a parachute. Hisdrawing of a man descendingin a square-framed parachutedates from around 1485a full 300 years before humanbeings first took to the skiesin hot-air balloons! But in 1783,a Frenchman named Sebastien

Lenormand actually built aparachute and tried it outhimself by jumping from atower in Paris. He survived,and is usually credited withhaving invented the parachute.

Ten years later, anotherFrenchman, Andre-JacquesGarnerin, constructed a para-chute of white linen, 23 feet indiameter, and attached it to ahot-air balloon. Then he wentup to 6,000 feet and cut thehot-air balloon free! Ascrowds of awestruck peoplewatched silently from theground, Garnerin came down.His descent was successful,but because his parachutehad been designed withoutan air vent, he was swungviolently from side to side. Hefainted from the nauseatingexperience!

Parachutes wouldn't benecessary at all if it weren't forone thing: gravity. Gravity isthe force that attracts twobodies to each other anytwo bodies, although most ofthe time we are only aware ofthe Earth's gravity. D;d youknow that the force of gravityis present between everythingeven between you andyour lamp? It's just that it isvery, very weak gravityso weak that no matter howclose you get to your lamp,it won't fall on you from theforce of your own gravitationalpull! Here's why: The mathe-matical equation that explainsthe force of gravity says basi-cally that the force of gravityincreases when the distancebetween the two bodiesdecreases. But it also says thatthe mass of the two bodieshow dense they are and howmuch they weigh has a lotto do with how strong thegravitational force is. You andyour lamp or any other ob-jects you get close to don'tweigh enough together tocreate a noticeable gravita-tional force.

Of course, there's gravityon the moon, too, but its forceis not as powerful as theEarth's. That's why you weigh

on Earth. Some people thinkthat gravity is weaker on themoon because its "way outin space' But that's not true.Gravity is weaker on the moonbecause the moon is smallerthan Earth, and so it's gravita-tional pull on e human beingis less. The moon would bea great place to practice para-chuting. Even if your para-ci IL:+e didn't open, it wouldn'thurt half so much when youcame down!

Stars, too, are subjectto the laws of gravity, andthey exert an enormous forceon the smaller bodies aroundthem. Take our sun, for in-stance, which is really a verynear star. The sun has so much

mass, it is able to attract theEarth and the other planets,and hold them in its power!If the sun were smaller andmuch less dense the Earthwould never have beenpulled into orbit around thesun. It might have flown outinto space and become ameteoroid instead. If the sunwere larger and more dense,the Earth would be pulled rightto the sun by the force of thesun's gravity, and burn up.Isn't it amazing that the sun'smass is just right to maintain its

safe gravitational relationshipless on the moon than you do with Earth?

18

Ai

Ar

SCIEN E MAGICHocus pocus! Its timefocu. xi magic! You canlearn to do all the tricks forthis magic act in about 45minutes. But it might take youlonger to perform the bestall-time disappearing trickthe one that makes yourstage fright disappear!

YOU WILL NEED

Tray for props5 Pennies

Plate

Raisins

Club sodaSeveral drinking glassesWaterHandkerchief

ADVICE TO AMATEURMAGICIANS

Some of the tricks you areabout to learn have beenused for many years byfamous magicians. And yetthey are very simple to dolBut the first time you trythese tricks, they may notseem totally amazing to yourfriends. Why not For tworeasons. One is that youneed to practice them

many times, so that youcan do them smoothly andconfidently. And the otherthing you need, in orderto really come off like apolished magician, is patterPatter is all the small talkmagicians make while theyare performing the trickorwaiting for it to work! So besure to use lots of snappypatter while performing yourtricks (But don't tell anyonewe told you---because that'sa trick of the trade!)

GOOD VIBRATIONS: AMIND-READING COINTRICK

Have 4 or 5 pennies ready,each with a different dateMake sure you don't handlethe pennies too much! Youmight even want to put themin the refrigerator for a fewminutes before the magicshow Put the pennies on aplate and ask someone fromthe audience to choose one,while your back is turnedTell them to hold the pennytightly to let their "vibrations"flow into the penny Then tellthem to look at the date on

the penny, so they'll knowwhich one they close. Afterabout 20 seconds, have theperson pass it to someoneelse in the audience and gothrough the patter againasking the second person tolet their "vibrations" flow intothe penny and to concentrateon the date. Now havethe second person putthe penny back on the plateand then tell you to turnaround. Quickly you willidentify the correct penny!

How It's Done:You will quickly pick up ortouch each penny until youfind the one that is warmerthan the others. Copper is agood conductor of heatand all those "vibrations"are really just body heat,transferred from the personto the penny!

THE LIVING RAISINS

This is a quick but dumbtrick, so don't spend toomuch time on it. Just try tomake your patter cute

Tell your audience that

1.j

you have trained six raisins tothink of themselves as fish.They are now, believe it ornot, The Living Raisins. Andyou can prove it by returningthem to their natural habitat:water. They love the water,you say, but like all fish theymust have oxygen to breathe.And since they don't havegills, they will have to cometo the surface fcr air. Also,you might add that TheLiving Raisins are fromCalifornia, and consequentlythey prefer mineral water orseltzer rather than plainwatEf.

Pour a glass of fresh clubsoda and drop six ordinaryraisins into it Then simplywatch the action! The raisinswill rise to the surface andthen sink again repeatedly.Announce grandly, "TheLiving Raisins, ladies andgentlemen!" And then moveon to another trick!

QUICKIE TRICKY

Choose a volunteer from theaudience and have the per-son come torward. Tell thevolunteer that you're going

80

to do a mind-reading trick.Then turn around so that yourback is to the person andclose your eyes. Tell the per-son to put one hand on hisor her head, and then toconcentrate on whicheverhand it is. Use a lot of patterfor this trickbecause youneed about 30 or 45 sec-onds for the trick to work.Keep saying, "Are you con-centrating on the hand?" Fi-nally, tell the volunteer to put

Pick IPENNYANDHOLD

TiGorlyAND.

his or her hand down. Thenturn around and quickly askto see both handspalmsup. Miraculously, you will an-nounce which hand was onthe person's head!

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How It's Done:The palm that is lighter incolor will be the one thatwas on the person's head.Why? Because blood didn'tcirculate as much in the handthat was up in the air.

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DRAGON BREATHTell the audience that youhave Dragon Breath, whichallows you to heat things upsimply by blowing on them.In fact, you say, you can makewater boil in a glass just bytouching it with your fingeronce your finger has beenheated up with Dragon Breath,of course.

To perform the trick, havea small glass of water and awet handkerchief ready. Theglass of water should beabout two-thirds full. Coverthe glass with the handker-chief and pusn it duwr. intothe glass until the clothtouches the surface of thewater. Then hold the glass asshown, with one hand flatover the mouth of the glassand the other hand tightlywrapped around the hand-kerchief and glass, near therim. Turn the glass overquickly A little water might

13,1

come out, but most of it willstay in the glass.

Now take away onehandthe one that was flatover the opening. Hold theglass and handkerchief nearthe rimstill upside downand breathe your DragonBreath on the index finger ofyour free, hand. Then pushdawn on the top of the glass(it's really the bottom, but itsupside down). Say, "Boil,boil, boil and bubble" Thewater should start bubbling,but if it doesn't, breathe onyour finger again and pushharder. Hold tight. The glassmust slip down a little butthe handkerchief must notmove for the "bc.!ing" effectto happen.

MAGICIANS NO. 1/ MOSTIMPORTANT RULE IN THEWHOLE WORLDNever repeat a trick!

AFTERWORDS

Here are the secrets to theother amazing tricks in yourScience Magic Show. It's upto you whether or not youwant to reveal to youraudience just how thesespectacule ricks work.

The Living Raisins

The club soda you used forthis trick contains a lot ofbubbles, which are really thegas carbon dioxide. Bubblestend to collect on thesurfaces of things. So whenyou dropped raisins into theglass, the bubbles collectedon the raisins and lifted themto the top of the liquid Butat the top, the bubbles breakand the car'', dioxide isreleased the air, so theraisins sink back dawn again.

Why do the bubbles liftthe raisins up? Because when

attach themselves to theraisin, they increase theraisin's volume withoutincreasing its weight verymuch. him/ that the raisin-plus-bubb!?.s is bigger, itdisplaces more water Thingthat displace enough waterto equal their own weightwill float So tL.e "bigger"raisin will float. When the

bubbles that were clingingto the raisin burst at thesurface, the raisin becomessmaller Now it doesn'tdisplace enough water toequal its awn weight, so itsinks. This trick can also bedone with salted peanutsand any carbonated softdrink.

Dragon BreathOooh ... there are so manymysteries about this trick!Why doesn't the water fallout of the glass when youturn it upside down? That'seasy: It has to do withsurface tension. Have youever noticed that you can filla glass of water past the rimand it won't overflow? Watermolecules tend to want tostay together rather thanseparate. So when youcarefully add more water tothe glass, the surface bulgesup but doesn't spill overbecause the moleculeswould rather stick togetherthan spread out all over theplace. That's surface tension.In the Dragon Breath trick,you've got surface tensioneven with the glass upsidedown. The water fills in eachtiny space between thehandkerchief, and creates

hundreds of little areas withenough surface tension tokeep the water in the glass.

But what makes thewater seem to boil? Airpressure, coming fromoutside the glass, is pushingup on the handkerchief andthe water. When you pusdown on the glass, youcause the water level todrop and you create a spacewhere there isn't any water.So air flows in through thehandkerchief to equalize thepressure inside the glass. Asthe air moves up through thewater to reach the "empty"space at the top of the glass,it looks like the water isboiling. And you look like amagician!

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COLOR & LIARRoses are red,

Violets are blue,We have a ColorActivity for you!You'll need about 45 minutesto make and experimentwith color wheels.

YOU WILL NEED

3 Flashlights (borrow fromfriends)

Balloons i four colors: red,yellow, green, and blue

ScissorsHeavy white paperCompass for drawing circlesRuler ard pencilCrayons or felt-tip markers

in all colorsHand-cranked drill and

drill bit

Note: If you don't have ahand drill, you can spin yourcolor wheels with a piece ofstring as shown on page 86

What color is white? Mostpeople think that white isno color. But the truth is thatwhite is the color you seewhen all the colors of therainbow are reflected atonce. You can trick your eyes

13:,

(and brain) into seeing whiteby looking at all of the rain-bow colas at the exactsame time. If the colors arespinning around so fast thatyou can't really see themseparately, your brain will putthem together and see white.Try it and see!

I,Is white light reallywhite? Or is it madeup of many different

colors? To find out, try mix-ing colored lights and seewhat you get. With the scis.sors, cut the necks oft ofsome colored balloons.Stretch a red balloon acrossone flashlight so that it makesred light Stretch a yellow orgreen balloon across anotherflashlight, and a blue balloonacross the ti-iird flashlight.Turn out the room lights andshine the rkd libr , at a whitewall or white piece of paperDo you see a red spot? Nowshine the blue flashlight atthe same spot, so that itoverlaps the red. What color

do you see? Add a thirdcoloreither yellow orgreenfrom a third flash-light. Which three colorsmixed together make thespot appear to be white?

LEAVE

HOLE

FOR

DRILLBITIN

CENTER

2Make a color wheelwith all the colors ofthe rainbow. Use a

compass to draw a circleak-)out 3V in diameter onhea,,y white pmer. With aruler and a pencil, divide thecircle into eight equal pie-shaped sections. Color eachsection a different color,starting with red and thenadding orange yellow, green,blue, ind.30, and violet.leave the last section white.Cut out your colored circle.Carefully poke the end of thedrill bit through the center ofthe color wheel. Don't make

1 3 .

a big hole in the paper, or itwon't spin on the drill. Standin front of a mirror, with thecolor wheel facing it, andtum the crank handle of thedrill as fast as you can. Doyou see all the colors sepa-ratelyor does your braincombine them to make an-other color? (If you don't seea pure white, it's probablybecause you've coloredone section darker than theothers.)

3Do you think that thecolors on the wheelare just spinning so

fast that any combination ofcolors would look likewhite? That's not the case,and you can prove it toyourself by making anothercolor wheel. But this time,make one half of the wheelred and the other half blue,ana spin it on the drill. Whatdo you see? Even thoughthis color wheel is spinningJust as fast as the other one,your brain can see the twoseparate colors flashing by.

84

4Make a color wheelthat will allow yourbrain to combine the

two colors. Divide the wheelinto eight sections. Colorevery other section red.Color the alternate pieshapes blue. When you spinthis disk, what color do yousee? Make another colorwheel using alternating or-ange and blue sections...or

red and green ...or purpleand yellow. Look at the ColorCombos chart to the rightCan you figure out why thesecombinations will make yousee white?

COLOR COMBOS

There are only three primarycolors: red, yellow, and blue.You can combine the pri-mary colors to make other

colors, called secondarycolors. But if you combine allthe primary colors, usinglight bearrs, you will getwhite light.

Primary SecondaryRed + Blue = PurpleRed + Yellow = OrangeBlue + Yellow= Green

14 ii

5Make a Fetchnerwheel like the oneshown here. The easi-

est way to do it is to use acompass. Hold the point ofthe compass in the center ofthe circle the whole time.

Draw a curved segment, thenclose the compass a little bit(in other words, move thepencil closer to the point)and draw another curvedsegment. Continue drawingcurves and then closing thecompass a little until youhave copied the Fetchnerwheel. Make the lines darkusing a black felt-tipped penor crayon Be sure that youcan see the white spacesbetween the curved lines.

Spin the Fetchner wheelat a moderate speed usingthe handcrank drill Don'tspin it too fast. Do you seesome thin lines of color?Spin the wheel in the op-

14.

posite direction and you willsee different colors. This isan unexplained phe-nomenascientists don'treally understand why itworks!

HOW TO SPIN A COLORWHEEL WITH A STRING

Use a piece of string that'sabout 4 feet long. Poke twoholes in the color wheel, oneon each side of the centerpoint. The two holes shouldbe about 3/4" apart. Threadthe string through the holes,as shown, and tie the endstogether. Hold one end ineach hand. Put a twist in thestring by spinning the colorwheel around and around ina jump-rope motion, asshown. Then pull outwardon both ends of the stringquickly and tightly. The stringwill untwist, and that willmake the color wheel spin.Watch it while it spins, to seewhat color it makes.

AFTERWORDS

If you've ever seen a rainbowor the colors reflected fromlight shining through a prism,you know that white light ismade up of many colorscalled a spectrum. Earlyscientists had observed thisalso, but Sir Isaac Newtonwas the first one tounderstand that if thesecolors could be separatedby a prism, they could alsobe recombined by a lens orprism to make white lightagain.

Later, scientists discoveredthat each color of light in thespectrum has a differenttemperature. By placing athermometer in the spacejust below the red part ofthe spectruma space thatlooks dark to us because wecan't see the light therescientists were able to dis-cover some invisible lightcalled infrared light. Theyknew it was there because itgave off some heat! Similarly,the space above the violetarea gave off heat too. Soscientists knev there was in-visible light above the vio-letultraviolet light

If light is like a wave, thelight "waves' from eachcolor of light would be dif-

ferent lengths. Ultravioletwaves are much shorter thaninfrared The shorter wavesare sent out at a muc:1 higherfrequency than the longerones. Therefore, ultravioletlight has more energ', thaninfrared In fact, the ultravioletrays from the sun have enoughenergy to give you a sunburn!

Infrared is a lower energylight wave, very similar to aradio wave. These waves areoften used to make lasers. Alaser is a beam of light inwhich the waves are all ex-actly the same length, and,more importantly, they are allin phasemoving along to-gether, like people in amarching band marching instep. This is called coherentlight. When a beam of co-herent light is focused into alaser beam, the energy andlight is concentrated in a waythat regular light rays are not.

In the spectrum, red hasthe longest wave length andthe lowest energy, and violethas the shortest and highestAs you go through the colorsin the rainbowred, orange,yellow, green, blue, indigo,violeteach subsequentcolor has more energy

Did you know that anobject's "color" is really theresult of which color of lightis reflected? Take a redapple, for instance. Whitelight, containing all thecolors, falls on the apple,but most of the colors areabsorbed. Only the red partof the spectrum is reflected,so you see the apple as red.But the apple doesn't haveany "red" in it.

But why does the sirylook blue? In outer space,the sky looks almost black,because there is noatmosphereno dust orgasto reflect the light raysfrom the sun But earth'satmosphere is composed ofdust, gases, and drops ofwater, which are able toscatter and reflect some ofthe light from the sun.Because of the wave lengthsof each color of light, it is theblue light that is scatteredmost easily. So we see thesky as blue. At sunset,however, we often see thesky as red, orange, or pink.That's partly because thedust in the atmosphere isdenser near the earth. Thedust scatters the blue,leaving the red and orangelight waves, to give us abeautiful sunset.

86

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4010"- -t:

CRYSTAL 10Tune in to what's happeningon your own homemadecrystal radio. No batteries re-quired! The radio can bemade in about an hour and a

half. And it can be listenedto foreveror at least untilbedtime.

YOU WILL NEED

1 Empty plastic film canister(the kind a roll of 35mmfilm comes in)

Scissors1 Piece of corrugated

cardboard, 7" by 18"Heavy-duty aluminum foilTransparent tapeMasking tape2 Sheets of 81/2" by 11" paper2 Spring-type clothespins, or

2 large, spring-actionpaper clips

From an electronics store,such as Radio Shack:50 Feet of 22-gauge solid,

insulated hook-up wire1 Germanium diode1 Phono input cable with

plug (one end of thecable should already bestripped)

I4'I t J

Note: You will also needaccess to a stereo amplifierand speakers, in order tohear the signal from yourcrystal radio.

What's a crystal radio? It's aradio made out of somewire, cardboard, aluminumfoil, and very little else. Theonly mysterious thing in acrystal radio is the germaniumcrystal diode--and its notreally so rnystenous. Germanium

is a metal that can help detectradio waves. In fact, under theright circumstances, many dif-ferent metals can detect radiowaves. Have you ever heardof someone getting radio sig-nals on the fillings in theirteeth? Or on their braces? Itcan happen!

However, let's just stick togetting radio signals on ahomemade radio You couldlisten to your radio by hookingup a small earphone. But with

an earphone, the signal wouldbe veryfaint. Even in store-bought crystal-radio kits, youcan hardly hear the radio sta-

tionsyou receive. That's whywe suggest using your stereoamplifier to make the signallouder.

1Start by making the coilfor the radio. Use thepoint of a scissors to

poke three holes in theempty film canister One holegoes in the bottom. Thesecond and third holes goon the side of the can, justY8" from the top and bottom,as shown in the drawing.

Now you want to wrapthe 22-gauge hook-up wirearound the film canister. Butfirst, push the end of thewire through the side holenear the bottom of the filmcan, and then push it out thebottom hole. Pull out about6" of wire and leave it dan-gling. Coil the rest of the wiretightly arc Jrid the film can in

a single layer, until you havefilled all the space up to thetop hole. The wire must betightly wrapped, with nospaces between the coils.There should be about 25 or30 "turns" in your coil. Cutthe wire, leaving about 1 footextra. Push the end of thewire through the top holeand pull it tight. For now,leave the extra 1 foot of wiredangling.

2Next you will makethe radio's capacitor.Cut a 7" by 18" piece

of corrugated cardboardfrom a carton. Try to cut thecardboard so that the ridgesor corrugations are goingacross the short (7") sideinstead of up and down the18" side. Measure up 8" fromthe long end, and draw aline. Use your scissors point

1 4 ., ;

to "score" (cut partwaythrough) the cardboardalong the line. Now you caneasily fold the cardboardbackward, along the line.

When the cardboard isfolded, it will make a"pocket." You will want toline the pocket with a singlepiece of heavy-duty alumi-num foil. The lining must alsocome outside the pocketand turn over onto the frontof the pocket, as shown inthe drawing. To do this, cut apiece of heavy-duty alumi-num foil 6" wide and 17"long. Lay the cardboard flatand tape the foil to it withtransparent tape, being sureto leave an inch or so hang-ing over the short end. Tapearound all sides. Fold the foilover the short end and tapethe edges down.

vSET ANSPARENT

APE,'LEAVE I" EXTRAFOIL FOR FLAP

Fold the cardboard inhalf with the foil inside toform the pocket. The extra 1"of foil will show as a flap onthe outside of the pocket.With masking tape, tape the

14r

pocket closed a;ong theedges, leaving the top of thepocket open. Try to tape thepocket together very tightly.

FOLD CARDBOARD CAPECLOSED EXTRA FOIL0440 DOWN

TAPE SIDES To FORM POGIce T

3Next you will need tomake a "tuner." Cut an8" by 10" piece of

heavy-duty aluminum foiland put it between twopieces of 81/2" by 11" typingpaper to make a sandwich.Fold all three in half like abook. The book will be 51/2"by 81/2".

40-1FOLD INHALF

LIKE ABook

PLAGEOx10" FO L. BETWEENSHEETS OF PAPER

4Get ready to wire it allup! But first ...youshould practice strip-

ping the insulation (the plas-tic coating) from the wire.For practice, use an extrapiece of wire and your scis-sors. Cut very gently, untilyou have cut through theplastic without cutting the

copper wire. Slide the in-sulation off the end of thewire.

Use transparent tape tomount your coil on top ofthe cardboard pocket. Put itright next to the aluminumfoil "flap."

Remember that you havetwo wires dangling out ofthe ends of the coil. One ofthem is 6" long. Strip off 4"of insulation from the end ofthis wire. Then tape it downtightly to the aluminum-foilflap.

The other dangling weis about 12" long. Strip off 4"of insulation from the end ofit. Now comes the hard part.You want to strip or bare a 1"section of this wire. Withyour scissors, gently cutthrough the insulation at apoint about an inch or sofrom where it comes out ofthe film canister. But insteadof pulling the plastic all theway off, just slide it downthe wire about an inch. Let'scall this the "bare spot."

Attach the end of thelong dangling wire to thetuner "book" you made outof typing paper and foil. Slipthe stripped end of the wire

into the book, near thecrease, and tape it to the foiltightly.

SNORT

ifeEFWLFLAP.ANDLDMIRETO TUNER

5Cut a new piece of22-gauge hook-upwire to be your an-

tenna. The antenna shouldbe about 30 feet long, al-though 20 feet is probablyenough. Strip one end of thewire and attach it to the"bare spot" by twisting itaround and around tightly.

Look at the phono cable.One end has two kinds ofbare wires sticking out of it.Find the one that is in thecenter and has its own plas-tic insulation.

Now look at the diodeand find the end that has apainted band around it. (Itwill probably be a blackband or ring.) Connect thebanded end of the diode tothe center wire of the phonocable, by twisting them to-gether tightly.

Attach the other end ofthe diode to the "bare sr:xi(where the antenna has al-

14.

8c,

FIND DIFFEF.ENT STATIONS BYSLIDING. THE TUNER UP& DOWN

oacty been attached.There is another wire

probably a twisted onecoming out of the phono:able. Tape it down tightly tothe aluminum flap on theoutside of the pocket.

6Slide the tuneryourpaper-and-foil bookinto the pocket. You will

tune in different stations bysliding the tuner in and out.

To plug your radio intoyour stereo amplifiei, first iumoff the power. Turn the volumeall the way off.

1 4

Unplug your phono turn-tab', from the amplifier. Plugthe phono cable from yourcry.Fc..l radio into that inputJac' ....X you can simply plugyour crystal radio into anauxiliary inp'.c, if your amphas

Turn on the power ar dset your amplifier to thePHONO or AUX setting Tumup the volume until you heara little noise. Slide the crystalradio's tuner in and out ofthe pocket to find variousradio stations. When youidentify a station, you candraw d line on the tunerpaper, and write dawn thestation's call letters or fre-quency.

If you have trouble re-ceiving stations, try pressingon the pocket so that th.aluminum foil lining piec.scome more closely together.You may need to put clothes-pins on the pocket to hold itmore tightly closed

AFTERWORDS

It seems amazing that a radiocan be made out of coiledwire, foil, and cardbo:::4 Butonce you understand a fewscientific principles, you'llsee why it orks

Principle No. 1 centersaround the relationshipbetween a coil and acapacitor, which are the twomain parts of your crystalradio. A coil made out ofcopper wire is capable ofstoring magnetic energy. Thealuminum-foil pocket capaci-tor is capable of storingelectric energy. When youconnect a coil to a capacitor,the magnetic energy in thecoil flows toward the cap-acitor, and the electricenergy in the apacitor flowstoward the coil. In otherwords, the energy oscillatesback and forth between thetwo. The circuit formed bythe two is called a tankcircuit, because it acts like a

storage tank for energy.But! Nv does the energy,

or the radio wavesget intothe capacitor in *.l'e firstplace? That brings us to prin-ciple No. 2. Radio waves areelectromagnetic. They don'ttravel on the air, like soundwaves do; they travel onthemselves by oscillating be-tween electric energy andmagnetic energy. Radiowaves sent out by radiostations oscillate at thefrequency (or speed) as-signed to them by theFederal CommunicationsCommission, a govemmentagency

When these radio waveshit your crystal radio's antenna,the ele-:*.ric pat of the signalstarts the electrons in theantenna moving back andforth. These electrons thenproduce a very tiny electricfield at the end of the wire.You'll notice that the end ofyour radio's antenna is at-tached to the same wire thatgoes into the tuner (theboW. Sc the signal from the

radio station is being deliv-ered through the antennato the tuner, which in turntransfers that signal to thecapacitor (the pocket). Andwhere do the radio wavesgo from there? They're trap-ped! Now all you need todo is to change those radiowaves into sound waves soyou can hear them.

That's where the diodecomes in. The diode allowsenergy tc flaw in one directiononly. It sends the signal toyour earphone or amplifierand speakers. Your speakersconvert the signal to so ,denergy instead of elec-tromagnetic energy andbingo! Out comes rock 'n'roll!

But how does your crys-tal radio tune in just oneradio station? Why don't youhear them all at once? Becausethe frequency of oscillationsbetween any coil and ca-pacitor depends on the sizeof each part. If you make thecapaLicor smaller or bigger, itchanges the frequency of theoscillations. You must makethe frequency of your tankcircuit match the frequencyof the station you want tohear.

In fact, your radio's "tuner"is actually just a movableplate in the capacitor. Whenyou slide the tuner out, youmake the capacitor smaller.When you slide It in, youmake the capacitor biggerWith a bigger capacitor, thefrequency of the oscillationsgets smaller, and vice versa.Look on your tuner: If you'vewritten down each radio sta-tion's number on the paper,you'll see that the numbersget lower as you push thetuner in.

If your favonte radio stationhas a very low frequencylet's say 850 on the AM dialthen you'll need a largercapacitor to receive that sig-nal. Why not make one?After all, it only takes a littlemore cardboard and foil!

15

NOTES

NOTES

154

NOTES

1 5 ',

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