DOCUMENT RE UME
ED 054 927 SE 011 306 AUTHOR Kaben, Jerrold William TITLE How Far a Star. A Supplement in SpaceOriented Concepts for Science and MathematicsCurricula for Intermediate Grades. INSTITUTION National Aeronautics and Space Administration, Washington, D.C. SPONS AGENCY Office of Education (DHEW), Washington, D.C. PUB DATE 69 NOTE 112p. EDRS PRICE MF-$0.65 HC-$6.58 DESCRIPTORS *Aerospace Technology; *Astronomy;Instructional Materials; 4-Intermediate Grades;*Mathematics; Measurement; Resource Materials; *ScienceActivities; Scientific Principles
ABSTRACT Space science-oriented conceptsand suggested activities are presented for intermediate gradeteachers of science and mathematics in a book designedtoltelp bring applications of space-oriented mathematics into the classroom.Concepts and activities are considered in these areas:methods of keeping time (historically); measurement as related to time,distance, and astronomy, including lunar photographs andmeasurement activities; communication in space, sound, and satellites;measuring the atmosphere; and measuring and interpretingthe light from stars. A glossary of space terms, an aerospacebibliography, and a subject index are included. (PR) EDO 5494 -
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------HOW FAR A STAR
A SUPPLEMENT IN SPACE ORIENTED CONCEPTS FOR SCIENCE AND MATHEMATICS CURRICULA FOR INTERMEDIATE GRADES
Prepared fr9m materials furnished by the National Aeronautics and Space Administration in cooperation with. the Unitfi: States Office of Education by a Committee on Space Science Oriented Mathematics
1969
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Chapter I THE MYSTERY OF TIME 1 History of Time, Early Timekeepers,Sundial Model, Mechanical Time- keeperi, The Foucault Pendulum,Time in Space, Review ofScientific Notation, Rendezvous in Space
Chapter II 17 MEASURING THE UNKNOWN - Time Standards, Need for BetterTimekeeDers, Units of Time, Limits and Errors, Earth as a Timekeeper,Rotation and Revolution, Sideral and Solar Days, The Moon, Phasesand gotions, Measuring withthe Vernier ahd Ruler, Distances in Space,Errors in Measurement, Satellite Orbits, Ranger Photographs, MoonMeaSurernents with Scale, Moon Atlas, Measurement Techniques Chapter III 67 "EMPTY" SPACE Discussion of Space, Communicationin Space, Sound, SatelliteCom- munication, Weather Satellites, Weatherover Earth Chapter IV 79 THE MEASURE OF OURATMOSIIFIERE History, Atmospheric Levels, Natureof Cases, Weather Observations, VoEume, Density, and Pressure,Measurenient of the Upper Atmos- phere, Density, Temperature, Instrumentsof 'Measurement Chapter V 97 WHAT LIGHT CAN TELLUS - Stars, Brightness and Magnitude, Measurement, Direct and Indirect, Identification of Celestial Coordinates, Spectraof Light, Wavelength, Spectra, Model Spectroscopeand Its Aiicatior Chap rer Vi 109 TO THE FUTURE People and the Space Program 111 GLOSSARY r, 121 BIBLIOGRAPHY 123 . INDEX...... rT.4 0 g
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4 ,,Tottitv,, rItromirrrwrovi,,,,,f.v. orior-r. woo: a result, hmar calendars (Figure I-6), needed ilateabout that 28 twelve or 29 an extra month every few years in order to 348 days which match the seasons and make time predic- , day Babylonian tions more exact. asonal year_ .A.s Certain lunar measured calendars have been -retained for use today_The calendar used in some sections of India, the Hebrew religious calendar, and the Christian method for fixing the date of Easter emplo-cs phases of the moon as a means of nieasuring tiine.Probably no one in all Babylonia, Egypt,a clock, Greece yet these or Rome people had could ever thought measure of the passage of time, appropriate to the needs of their culture.
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_Figure 1-6
observingWhen man the movementfirst tried to of tell our time planet, by Earth,for you it to was tell astime difficult from a asclok it whichwould had be neither hands nor face_ Lost, forever in the years be-fore history was written, are the works of the early men who watched the moving shadows cast by the sun, and used them toLet's mark examine- the passage how of you time, can (Figure make I-7meaSurements ) similar to those of the "lost"' scientists.From sunrise to sunset, mark the end of 91d Mayan manuscript a shadow cast by a utility pole, flag pole, s of Venus over a 104 fence post or other vertical, staff. Record and position of the shadow at various times during the day. Keep a record for t.IT, school year then you can compare the positions and lengths of the shadows at the beginning of the school year, during the winter, dur- ing the spring and at the end of the school year. To help you understand the different shadow lengths, conduct the following investigation.Place an unshaded lamp, to serve as a sun, in the center of a darkened room.Attach a small stick or a figure made of pipe cleaners to a world globe. Place the globe about 2 or 3 meters from the "sun" so that its axis is tilted 231/2 degrees toward the "sun."Measure the shadow cast by the stick. Move the globe to the other side of the unshaded bulb, placing it exactly the same distance from the lamp as it was before. Do not change the tilt of the axis.It will now tilt away from the "sun."Measure the shadow's length. Was the shadow longer when the axis was tilted toward or away from the
Figuie 1-7 the length for every hour as in Figure 1-8. What means can you devise to accurately: determine the end of the shadow; measure thetimeintervals;and mark shadow lengths? What , kinds of tables, graphs, scale drawings, etc., can you develop to keep a record of your results? You can investigaie the way time can be determined by the sun s rays and how the tilt of Earth's axis causes sunlight to strike Earth at different angles. Using the methods developed for Figure 1-8, record shadows cast over a long period of time. If possible, mark the shadow's position directly on the surface of the playground, your driveway or other permanent location. If not, record them on a large piece of chart paper or wrapping paper. Again note the exact location of the pole's shadows at the same time each day and record the length sun? You can see that the actual shadow place on Earth which is receiving the most length will vary according to the object direct rays will have the shortest shadows. you placed on the globe.Remember the What would you hypothesize if you moved the globe (tilted the same amount and in the same direction)to other positions equidistant from the sun?
o: -ci ci 01 co CSI a.0 So
- Winter -9 1/2 hours of daylight
Summer - 15 hours of daylight
Autumn - 12 hours of daylight
Winter-9 1/2 hours of daylight
Figure 1-9
You also know from daily observations that the number of hours of daylight varies throughout the year. Figure 1-9 illustrates how the hours of daylight and darkness vary at the NASA/Goddard Space Flight Center, Greenbelt, Maryland, U.S.A. If we recognize that the changes in your shadows and the apparent position of the sun are due to the motion of Earth in space, we must notice that there are two distinct major motions.The first you have just investigated:the movement of Earth in its orbit around the sun, revolution. The second motion, of course, is the rotation of Earth on its axis (Figure I-10). Earth makes a complete rotation on its axis in about 23 hours and 56 minutes. We call this a sidereal or star day. Our solar day, however, is a few minutes longer than this because as Earth rotates it continues to
Y1, revolve around the sun, (Figure I-11). Due Figure I-I0 to variations in orbital speed our solar day Figure I-11 varies from 23 hours 59 minutes to alittle over twenty four hours. If we seek to det0-mine how far the sun will appear to move in the sky in onehour, we calculate that if Earthrotates a complete circle of 360° in twenty four hours,the number of angular degrees for eachhour of rotation equals 360/24 or 15° per hour.The CD sun then will appear to move15° per hour. Figure 1-13 If we select the point wherethe sun is shining directly on Earth as solar noon, we can tell the time atvari,3us points around the globe by moving 150 In eitherdirection (Figure 1-12).
Figure 1-14 Prior to 2000 B.C., the firstknown shadow clock (Figure 1-14) was builtThis gave a measure to parts ofthe day. A stick was joined to along, narrow Figure 1-12 piece of wood to form a T (Figure15). These hour lines are the meridian& The The piece of wood had markingswhich Prime Mericfian which passes through Green- represented hours of the day. This took wich, England, serves as a starting point for up a lot of spaceand was later replaced measurement east and west aroundthe by the sundial which was both more con- globe. (Figure I-13.) venient and more accurate, To summarize, Earth rotates from west Based on observations thatthe length to east.Therefore, the sun's apparent of the shadow changed with the seasons, path is from east to west and your shadow the sundial was developed to Peatlit allow- records move from west to east. The sun's ances for position onEarth and the seasons of the year.You have seen, how your apparent motion across the sky canbe used could be used to tell to measure time. own shadow charts time.But a major difficulty would be to make charts that would be correct regard- less of the season or your position on Earth. You can build a measurement instrument that will record local sun time corrected for position and season. Your sundial will have four parts (Figure 1-16). The shadow stick or gnomon (pronounced nö'man), the equatorial ring on which to read gnomon shadows, the equatorialringsupport, and the base are the four parts of the sundial. Use stiff cardboard or flexible metal for construction of the gnomon, the equatorial ring, and support.If cardboard is used, a weather-resistantspraywillrna,ke your Figizyc I-1s
EQUATORIAL RING 1/2IN. OVERLAP SLIT 1 IN. DEEP SLIT 1/ IN. DEEP SLIT 1 IN. DEEP
3IN. P.M. 6 54 3 2 1 12 11 10 9 8 7 6 A.M. _L 24 IN. 2 IN.-I 21N.-11 1---"481 N.4
TO NORTH STAR
Figure 116 Figure 117 sundial more permanent. The base is made About 800 or 900 B.C. the water clock, of wood. a clepsydra (klep' se-dre), was developed. Note, when constructing the gnomon, It was a bowl- with a small hole in the the angle 0 (called "theta")should be bottom.When the bowl was filled, the equal to your local latitude.Your local water dripped out slowly. By marking the iatitude may be determined from a map. inside of the bowl with lines, time was Measure this angle carefully with a pro- measured as the water level became lower. tractor.In Figure 1-16, the distance AB is The trouble with the clepsydra (which given for a latitude of 40°. If your latitude means water thief) was that someone had is less than 40°, angle 0 will be ''s than to fill the bowl as soon as the water ran 40°.If your latitude is greater out.Then too, the rate of water flow angle 8 will be greater than 40°. changed as the reservoir emptied and, of After making the parts according 1..0 Ithe cousse, a frozen water clack was not a good dimensions in Figure 1-16, bend the cequa- mersuring device! torial ring into a circle with the madcf3ngs Aas the art of glass blowing progressed on the inside, and fasten the two inch duriag the 8th Century A.D., the sand lap with glue.Slide the gnomon into the glass or hour glass was invented.Using notch of the wooden base and insert -the sandi-instead of water, the grains emptied equatorial ring support into the gnomon.. out of one glass vessel through a hole into After the equatorial ring slits are hooked anotner glass vessel of the same size. The on the supports, your sundial should It>ok sanz glass proved best for measuring short like Figure I-17. peninds of time. A three-minute glass, for In use, your sundial should be on a love', inst=ce, may be used in your home to surface with the gnomon pointing due- time boiling eggs or telephone calls.But North. North may be determined at niakt you would need many many sand glasses from theposition of the North Sttar, to measure a whole day in hours, minutes, Polaris, or in the daytime by using a and seconds. And someone would have to compass. On sunny days, the time is read be there to turn the glass over when the from the position of the leading edge of the top vessel is empty. gnomon shadow on the equatorial ring scale. This will be your local solar time. Civilizations using sundials sought to overcome difficulties such as cloudy days and darkness by the use of devices that did not depend on Earth's rotation. Two such devices were water clocks and hour glasses. Both inventions were based on the principle of rate of flow.
Figure 1-19 Throughout the evolutionof better time keeping, more accurate mechanical devices have been sought. All mechanical clocks have several things in common: hands, dials, bells or other ways to mark the passing of time; the escapement or regulation devices; and a source of power. We often think of the pendulum in this connection. varies. A simple relationship of L to T is as follows: Li 11/7,1 L2 111.-- Your experimental results should be very cic.. _ to this relationship. They would be exact, except that the usual experimental errors in timing swings, measuring length, and det rmining the end of the swing will incurlilt differences. To ch--,Tck your observations, make a tableof your results like Figure 1-22. Notice that you have two variables !.h. the constructiten of your pendulum; the length of the pendulum, and the weight of the
Figure 1-20
When he was only nineteen, Galileo is reported to have used his pulse as a means to measure time for the comparison of the swing times of a pendulum. A more de- tailed, account of Galileo's experiment is given-lin another book in this series, From LENGTH AVERAGE Here, Where? pp. 82 ff. EXPERIMENT IN TIME FORPERIOD FOR You can compare Galileo's measure- TRIAL CENTIMETERS 5 SWINGSONE SWING ments with experimental results of your 20 .own by constructing a simple pendulum. Tie a small Weight such as a bolt or lead 40 sinker, to a string about 10 to 15 inches 50 long and let it hang down as you hold the, other end of the string.Now pull the 80 weight, a pendulum bob, to one side :did releaseit(Figure I-21). Itwill ,begin 100 swinging back and forth. 160 Cut the string in half and repeat your observations. What change do you observe 180 in the period of time measured for a corn- 200 plete swing?The period will be shorter. The length of the string (t) arid the-Period 320 of the swing (T) are related. As the length of the string is changed the period of swing PIVOT POINT Figure 1-24 illustrates how these prine3- pies are applied to a mechanical clock. The pendulum regulates the motion and the hang:no weight provides the energy to overcomethe action of frictional forces. Yau may see a similar arrangement :;-.1 some "cuckoo" clocks. Oneof the cuckoo weights is for the pendulum mechanism, the other is to operate the cuckoo. "*". \ Figure 1-23shows how grairitational ST ART forces cause the downward movement of the bob and inertial movement forces it- to the end of its arc. You knowthat the force of gravity depends on many factors; altitude, the shape and density of Earth, and Earth's rotation. As a consequence, a 1GRAVITY pendulum clock moved from one location to another on Earth or in spacewould not Figure .1-23 keep the same time. Therefore, most clock pendulums have a screw adjustment to bob. As you use your pendulum, another correct for local variations. variable is the size of the arc used to start The movement of our Earth on its axis the pendulum swinging. We are interested in space also has another effect on the in measuring the time necessary for one motion o-f pendulums. The French phys- complete swing of the pendulum. icist Jean Bernard Leon Foucault used _ _ this motion to demonstrate that Earth Time fivesuccessive swings for the rotates on its axis. Perid-iihim lengths as in Figure 1-23. Meas- FOucault suspended a very long pendu- ure length from the pivotpoint to the. liim frOm the ceiling of a high room and center of the bob.Use a complete swing Set the-pendulum in incition. Aftet obServ- cycle (back and forth) of the bob as the ing the pendulum for many hours, he period.You will find that a support for discovered that the pendulum was not your pendulum, such as athumbtack over swinging in the same geographical direction a doorway or a ladder,will help your in- as it was when it started.That is, if his vestigation.From your measurement of pendulum was swinging back and forth fiveperiods,find the average for one toward one wall of the room, it gradually period. For example, if you obtained five complete swings in twelve seconds, the would appear to change its direction toward average period for oneswing would be 12/5 = 2.4 seconds. At The top of the arc, gravitational force directs the pendulum bob toward the center of Earth.The string acts as a control on the direction of fall.Inertia, according to Newton's first law of motion, carries the bob to the top of the other side of the arc (Figure 1-23).There the bob reaches the point where Earth's grairitational forces are gteater than inertial forces and the bob swings back. If no other forces acted on the pen- dulum, we would have perpetual motion. However, friction at the pivot and friction between the moving pendulum parts and PEN DULUM 'air molecules result in the pendulum grad- ually slowing to a stop. Figure 1-24 Eatth, the Equator, tl, woud be no apparent change in dire- non sina:e at this point Earth is no longr"turninkg under" the pemduium. What's up There?, aither boOk in this series will provide- yor with some useful infor, aation on applican. ,ns of pendulum princi'ples in satelllite inruments.Read particalarly the secthion or usirng -three pen- dulum accelerometfas tr: 2rovide measure- ment of satellite possition , pp. 61-67. How would yoia descm'be the distance between two cities?Wm_i_ your answer in units of miles or hours? If your response was in hours, yolu wouild be usingthe language of astrommers. kstronomers use the term light-year to imdkate tthe distance to nearby stars. A light-rear is the distance Figure 1-25 light would travel in one year at a rate of about 300,000 kilometer, per second. the next wall and so on unt.11 the pendulum Our closest star after :'he sun is Proxima Centauri.Proxima Centauhi is about 4.3 appedred to be swinging back in the direc- light years away, or thearne distance that tion of its starting point. light will travel in 4.3 y -:-ts at the rate of By doing the following project you can 300,000 kilometers per econd. How far examine Foucault's reasoning that Earth To and the observer are moving in relation to away is Proxima Centauri in kilometers? findout,firstcalculate how far light the direction of swing of the pendulum. travels in one year. To make this calcula- You will need:a rotating mechanism tion, you will need to multiply. 300,000 (phonograph turntable, piano stool or lazy by the number of seconds in one min- Susan; .support. such as wood dowel; heavy ute (60), the number of minutes in one weight, such as a lead sinker; string; square hour (60),the number of hours in a wastebasket, ring stand or other support; day (24), the number of days in a year and clamps (Figure 1-25). _ (36514), = (300,000) x (60) (60) (24) Tie the weight to one end of a string (36514), = (300,000) x (31,557,600) = about 60 centimeters long. Attach the other 9,467,280,000,000 = 9..46728 x 1012 kil- end to a Ph foot piece of dowel or broom ometers. handle about 30 centimeters long.Place _ A generally used value for the Iiht the dowel across the top of a wastebasket, (read as ring stand or other support, allowing the year is 9.46 x 10" kilometers weight to swing freely. Place the support nine and forty six hundredths times ten to on top of the lazy Susan or pianostooL the twelfth power kilometers). Therefore, Set the pendulum in motion and then ro- the distance to Proxima Centauri would be tate the lazy Susan or piano stool very 4.3 x 9.46 (10" ) = 40.678 x 10' . In slowly. scientific notation, it is 40.67 (1012), and See if the swing direction changes with would be read as "forty and sixty seven respect to the platform.As Earth moves hundredths times ten to the twelfth power." under the pendulum, the pendulum appears rf you do'nof understand scien-tifiC-no- to change the direction of its swing. A tation, copy and complete Figure 1-26. swinging pendulum atthe North Pole Then read pp. 4-5 and p. 80 in What'. -11 would appear to make a complete turn, There, the first book of this series. 360°, in 24 hours.As you move toward In our space age, time is an important the Equator, the effect becomes less pro- factor to us. When do you launch a space nounced and a longer and longer period is vehicle so that it will get where you want it necessary to make a 360° change.At a to go, and arrive when you, wanted it to point exactly perpendicular to the axis of get there? For example, suppose you
1 3 Read As Power Means Equals 10 x 10 100 one hundred 102 1,000 one thousand 103 10 x 10 x 10 104 10 x 10 x 10 x 10 10S 106 1,000,000 102 10,000,000 Figure 1-26
planned to have your rocket rendezvousin TIMESCALE OF THE UNIVERSE Durations space with anotherspacecraft.Since a Ages or periods of time rocket carries only a limited amountof in seconds fuel and spends most of its time coasting in 1022 unknown outer limits of time leave Earth at space, you would have to 10" possible oge of the universe (?) position age of the eorth (5 billion years) just the right time to arrive in one revolution of the sun oround the galaxy along side the vehicle with which youwish to 10'S oge of younger mountain systenn duration of hurnon race (o million years) rendezvous. There would be no usearriving written history in orbit on one side of Earthwhen the 1010 age of a nation 0 year 0ne revolution of eorth around sun rendezvous vehicle was on the other side. a month /OS o day one rotation of the earth Let's suppose you wish to rendezvous an hour eating ale meol over a particular pointin the Atlantic a minute taking of a breath a second a heartbeat Ocean. Assume that an Agena target blink of an eye vehicle in orbit travels about 5 miles per MILLI vibration period of audible sound WS MICRO a flash of lightning second and that it takes about 90minutes dumtion of a muon particle NANO time far light to cross a room for Agena to orbit Earth. You can seethat le° vibration period of radar orbit at PICO time far on air molecule to spin once if you wish to meet the Agena in vibration period oF infra-red radiation one point over Earth'ssurface, you will 10-1S vibration period of visible light havethatopportunity once every 90 vibration period of x-rays minutes.In addition, if you do not want 10-20 vibration period of gamma rays to miss Agena by more than 5miles, your time far a proton to revolve once in the nucleus of an atom take-off will have to be accurate within one lo-25 unknown inner limits of time second.Every 90 minutes there will be a one second interval duringwhich you must Figure 1-27 launch to accomplish your rendezvous as planned. That one second time interval is more. By mastering theserhythms he de- called a launch window. veloped the art of measuring thne So now Figure 1-27 shows events which are.pos- he can measure time, not only forseconds, sible during different periods of time.One days, and years not only for centuries of the shortest periods we knowis the but for billions of years onthe one hand, length of time it takes a proton torevolve and a billionth of a second onthe other. once in the nucleusof an atom.The But his mastery of rhythm means more largest period of time we knowabout is than the measurement of time.It means our estimate of the ageof the universe. an increasingunderstanding of nature. His As man has passed throughtime for knowledge of rhythms not onlylights up many, many years on hisjourney to the hidden, dark corners ofthe past, but it civilization, he has learned that he lives also helps him to plan forthe future. in a world of many rhythms. Hefound Armed with knowledge of therhythms of rhythms high in the sky, and buried deep in the universe, man continues to passthrough the heart time. the rocks. He found rhythms in In the next chapter wewill see what of the atom, and out in the far reachesof time so space.And, besides those that he found has been done to standardize our in nature, he learned how to make many that we all can "be on timer'
_ r11 MEASURING THE UNKNOWN In order to describe the measure of outer Most people have a pulse rate of about space, we need to consider distance as it 72 pulses per minute. We will use this as a relates to time.We can experience, or standard for this exercise. Is your own rate "feel," the measure of time and distance, higher or lower than our selected standard? used in our day to day living. We cannot if 72 pulses occur in one minute, then the "feel" the measure of outer space. So we average number of standard pulses per must use mathematical models to help us second is 72/60 or 1.2 pulses in one second. describe measures that are beyond our Twenty seconds of clock time would be senses, our "feelings." equal to 20 x 1.2, or 24 pulses of "heart Let's begin with some measurements we time." know and can feel. Then use these to de- If we were to keep time in "standard velop ways to describe the measure of things heart time," we could develop a scale as we may never feel and distances which we follows: may never travel. Everyday we are using measurements Clock Time Heart Time which we know by feeling. Some are the 1 second 1.2 pulses result of simple observations such as the 1 minute 72.0 pulses height of a step as we approach a stairway, In space science, however, we need a the time of day when we are hungry or way to describe very long periods of time sleepy, or the speed of an approaching car and very short periods. Sometimes we are as we cross the street. Simple procedures able to use smaller numbers by introducing for measuring distance are estimating by larger units. For example, instead of saying eye, ear, or by using a rule or tape measure. 365 days, we describe this period of time Obviously we cannot use these to measure as one year. We also say one mile instead the distance to an orbiting satellite or the of 5,280 feet. It is more convenient to use speed of Earth as it orbits the sun. Today the larger unit and the smaller number. we have to describe very large and very If we introduce larger units into standard smallmeasures suchas one angstrom heart time, we may describe 1,000 pulses (0.00000001 (10-8) centimeters), the time as 1 kilopulse. The word "kilo" comes to of one nanosecond (0.000000001 (10-9) us from the Greek language and is trans- seconds), or the speed of light (186,000 lated as "one thousand."We may sub- miles per second). stitute1 megapulse for 1,000 kilopulses, Rememberalsothatmeasurement simply supplies information to help a sci- "mega" from the Greek meaning great. entist or you to answer a question or Summarizing we may saY: to solve a problem. Measurement is subject 1,000 pulses = 1 kilopulse to error.So we must develop precise 1,000 kilopulses = 1 megapulse instruments and use them carefully. What appears to be a correct answer may turn out to be incorrect if more precise measur- ing instruments and techniques are used to collect the information. Now let's attempt to make some meas- urements which we can "feel" to help us to understand the more precise instruments used by our space age scientists today. Take your pulse: Count the pulsations in a minute of time. What is your pulse rate in pulses per minute? Have sortie of your friends take their pulse counts. Do pulse counts vary?Some of the factors that effect pulse counts include activity, rest, age, and emotion. Clock Time Read as: Heart Time Scientific Notation 1.0 second one second 1.2 pulses 1.2 pulses 0.1 seconds one tenth 0.12 pulses 1.2 x 10-1 pulses 0.01 seconds one hundredth 0.012 pulses 1.2 x 10-2 pulses 0.001 seconds or one Jiousandth 0.0012 pulses or 1.2 x 10-3 pulses 1 millisecond 1.2 millipulses 0.000001 seconds or one millionth 0.0000012 pulses or 1.2 x 10-6 pulses 1 microsecond 1 micropulse 0.000000001 seconds one billionth 0.0000000012 pulses1.2 x 10-9 pulses 1 nanosecond or 1.2 nanopulses 0.000000000001 secondsone trillionth 0.0000000000012 1.2 x 10-1 2 pulses or 1 picosecond pulses or 1 picopulse Table II- 1
How many pulses are in a megapulse? Converting our table to standard heart time, we have: 1 rmgapulse = 1,000 kilopulses 0.001 pulses 1 millipulse 1 megapulse1000 x 1000 pulses = 10-3 pulses pulses 0.001 millipulses = 1 micropulse 1 megapulse = 1,000,000 or I million = 10-6 pulses Now we can add these to our table. 0.001 micropulses1 nanopulse = 10-9 pulses lthour 4,320.0 pulses or 0.001 nanopulses = 1 picopulse 4.32 "kilopulses" = 10-1 2 pulses Our heart time is based on an imaginary standard heart, . pulsating at a rateof 72 1 year 37,842 "megapulses" pulses per minute.If we were to keep We could describe the five hourdrive time in standard heart time, ourstandard from New York to Washington, D. C.in heart would be placed in theNational standard hearttime,as taking 21,600 Bureau of Standards at Washington,D.C. pulses or 21 kilopulses, plus 600 .pulses. It might be placed next to the standard Mariner IV'stripto Mars took seven meter and standard kilogram (Figure11-3). months. Seven months equals 3 mega- pulses, plus 1 kilopulse, plus 104pulses of standard heart time. An exceptional high school sprinter can run the 100 yarddash in 9.8' seconds. From Table II-1 we. standardized 1second as 1.2 pulses.So we are able to express this in "standard" heart time' as 100yards in 9.8 x 1.2, or 11.76 pulses. Heis able to averag61 yard per 11.76/100, or 0.1176 pulses over the 100 yard distance.The Ranger IX's pictures of the moon were recorded to the thousandth of a second (0.001 seconds).This would be equal to. 12 ten-thousandths of a pulse, or 0.0012 of a pulse. Prior to the invention of our familiar The answers for the exercises in this mechanical and electrical clocks, the pulse Chapter will be found at the end of this was used as one of man's timing methods. Chapter. You know how Galileo discovered the principle of the pendulum by timing the Exercises: swing of a cathedral chandelier with his
Figure 11-5 1.a.With a pin, punch a small hole in the bottom of a paper cup.Fill the cup with water. Placethe cup over another cup, so that the water drips into the second cup. Suggestion: Make the hole large enough so that you have 50 to 80 drops per minute. Count the number of drops of water in one minute of time.Record the drops in a minute. Repeat, counting the number of drops in a minute. Repeattheprocedure three more times. Record your results in a table like the one below: Test 1 ? drops in 1 minute pulse beat. Huygens (Hi gens) used Galileo's Test 2 9 drops in I minute discovery of the principle of the pendulum to regulate the first mechanical clock. Test 3 ? drops in 1 minute Run in place for 15 seconds. Now take Test 4 drops in 1 minute your pulse rate in pulses per minute. Com- Test 5 ? drops in 1 minute pare this rate to your rate when you were Total ? drops in 5 minutes at rest. Pulse rate at rest Table 11-2 Pulse rate after running Compute the average number of drops Your heart speeds up and slows down. per minute. We will consider this number Our standard heart also would vary with as the standard in Drop Time. changes in conditions such as pressure, b. Copy and complete the following oxygen supply, temperature, food supply, using your standard drop time: and activity.Consider, for example, what would happen to our methods of measuring Clock Time Drop Time if the foot became longer or shorter, or if (1)1 second ?drops the pound became heavier or lighter.Al- (2)1 minute drops (standard) though standard heart time is a possibility (3)1 hour .L drops or and was useful in the past, it is obvious that scientists have attempted to find other ?kilodrops timekeepers which show less vadation. The (4)1 day ?kilodrops following exercises will help you understand (5)1 year kilodrops or another historical timekeepMg method. megadrops Remember: 1,000 drops = 1 kilodrop 1,000 kilodrops = 1 megadrop Table 11-3 c. How many drops in a megadrop? 2.A'satellite orbits the earth in 90 minutes. How long is this in Drop Time? WIDTH OF A PALM 3.Mariner IV took 22 pictures of the planet Mars in 25 minutes. a. How long did it take Mariner IV to take 22 pictures in Drop Time? b. How long did it take in Drop Time to take 1 picture? 4.What are some of the problems in keep- ca- ing time with drops of water? The measures we use effect our under- 1 ARMS WIDTH standing of modern space science and tech- nology. The development of measurement VOilOw and the instruments needed have grown as 14.--"ti 401 a matter of convenience.As the need 1 PACE arose for man to better understand the Figure 11-6 world and to make measurements of "non- ordinary" distances, as in the solar system, man produced more precise instruments to Let us investigate the instruments and obtain more accUrate measurements. techniques used to determine distance, Long ago man was able to describe scale, and time.A few thousand years distance by his arms' width, a step or ago, man's abilityto measure was de- pace, or the width of his palm.When termined by the precision of his eye. What there was little communication, the length he could see, he could estimate and there- of the measuring unit was' of little conse- fore measure. quence:a trip along a trapping line, one or two days; and winter, one or two months away. It would not make much difference. When families grouped into-tribes, tribes into nations, and as nations came into con- tact with each other, communication of measures was needed.With the railroad, automobile, airplane, radio, telephone, tele- vision, and satellitenetworks, man has found that it was necessary to standardize his methods of measure. No longer could he pace off a distance, spread"' his arms, or measure the height of a wall with his hand; people of different sizes yielded various results. ti The method of defining these ancient units has disappeared from daily use and in their place have come other methods. As detailed earlier, man's observations and Figure 11-7 ability to .observe, have resulted in a sys- tem of units and standards used throughout a. The Sun is brighter than the star, Polaris. the world. b. The pyramid is taller than the tree.
, 22 2 4 Early instruments were developed so He now could measure the mile to the that man could measure more accurately. yard, foot, inch, and fraction of an inch. Light could be measured in terms of the brightness of the sun, candle, or color. Time could be determined in units of the year, month, day, hour, minute, second, or fraction of a second. More precise instruments enabled sci- entists to make observations that had not been possible before.Ancient theories gave way as new ideas were supported by mon accurate measurements. By 1600, scientists began to specialize and to consider themselves primarily as physicists, astronomers, biologists, chem- Sextant Hour Glass Knotted Rope ists, and engineers.Each of the new sci- (ANGLE) (TIME) (DISTANCE) ences required special measurement tech- niques, and measurement became more' Figure 11-8 accurate.
LIPPERSHEY - TELESCOPE VERNIER - VERNIER SCALE TORRICELLI - BAROMETER GALILEO - THERMOMETER OERSTED - ELECTROMAGNET NEWTON - SPECTROSCOPE Scientists could measure positions onEartli, distances between cities, and thediameter of Earth.
LOS ANGELES
NEW YORK
DIAMETER OF LONGITUDE DISTANCE FROM THE EARTH LATITUDE NEW YORK 70 LOS ANCMLES
They could "Reach Out" into spaceand nr.r.-asure the diameter ofthe moon, the brightness of the sun, and the tremendousdistances tarrlhe stars.
235,000 MILES
itAADON
Figure II-11 time of day, or the time He could more accuratelydetermine the length of a year, the it "took" for a ball_ to drop from atower.
SPRING NOON
SUMMER WINTER EAST slWEST SUNRISE SUNSET
FALL
Figure II-12
Old ideas and concepts gave way tothe new theories brought about bythese approaches.
Ancient Theory Modern Theory Earth Flat Round, pear shaped, Fixed Moving Planets Orbit the Earth Orbit the Sun Oxygen, nitrogen, CO2 , H2 0 Atmosphere "4 ethers" Table 1I-4
In order to describe the measureof Because instruments are subject to error, objects which cannot be seen orfelt, the scientist, as we do, mustrecognize the today's scientists do not always thinkin limits of_his own ability.and of his measur- terms of the mile or the foot,the sun's ing devices. One of the primary concernsof brightness or the candle, the year orthe the scientist is to reduce experimental error. second, but deal in fractionsof units. Errors are reduced by bettertechnique and Many scientists are concerned withdistances more precise instruments. such as of 0.00000001 centimeters(one We will riow see how scientistshave re- angstrom), light measured in termsof fined their techniques and instrumentsin 0.0001 candles (one ten-thousandthof a the measurement of time, distance,and candle) and time in terms of the nano- scale. second (0.000000001 seconds)one bil- Time measurement must havehad its origin in the mind of man as hewatched lionth of a second. So, Even with modern procedures,man's day follow night and the seasons nas& ability to measure depends upon the pre- it is not surprising ,that man finallychose cision of his instruments and hisskill in the sun as the basis formeasuring time. reading or inteipreting these instrument& (Figure 11-13). MIDNIGHT-M NNOON S.:UN
Figure 11-13 From koollo driving the sun acrow the Our day begins at midnight and ends at sky, to tire sun revolving around Earth, midnight.Figure 1144 compares Earth to and to filially Earth revolving around the a giant 24 hour clock. sun, man has utilized the periodic motion Point A, Figure 14, rotatms around the of Earth as an almost perfect "standare of center of Earth,. C, and at -due end of 24 time. The basic units of time betcarre the hours it would have compled one rota- day, the tnonth, and the year. tion, or a circle.. For our punaoses, we will We accept the fact that Earth rotze=s on assume 360 degrees in a circle and noon.as itsaxis once a day and Earth revolves our 00 and 24 hour pointThe mathe- around the sun once a year. But, what is matical symbol, for the wadi degree is ° a day? What is a year? We are able to ielate hours of time to de- hi Figure 11-13, Earth makes one rota- grees of a circile, lust as we -related heart tion from M to N to M every 24 hours. time to clock time as in Table II-1. For a
MIDNIGHT 12 0 or 24 NOON SUN more detailed discussion ofhours of time of 0 hours, then 6 hours later at 6P.M.., and degrees of a circle, reference is made to the sun is at an angle of 90° (or 6 hours. another book of this series, Shapesof 1 holm. = 150_ 6 tours = 90° Tomorrow, Chapter 3, pp. 61-64. At 12:010 midnight, the sun is at anangle Do Ind confuse the termsminutes and of 180° -or 12 hours. At 6 A.M., the sun seconds of is at an angle of 270° or LS Itours. At12 seconds of arc with minutes and We time. Noon, the sun is back at 0' -or0 hours. When speaking of angles, we saydegree have completed 24 hours or 360° . of arc, or: We use the sun's posi6cm as seemfrom 10 (one degree) of arc = 60' Earth ari a reference for our :time.There- (sixty minutes) of arc fore, When we give our loPal time, we are l' (one minute) of arc = 60" actually speaking of the angle of the (sixty seconds) ef arc sun_ This term is usedby a=onorners and space scientists todescribe 'dime. Notice the symbol for minutes of arcis ', Consider Figure 11-16.Wa., are looking and the symbol used for secondsof arc down at Eaxth from above tireNorth Pole, is " Earth Time Angle in degrees of arc 1 revolution 1-zircle 24 hours 360 degrees 1 hour 15 degrees of arc 4 minutes 1 degree of arc 1 minute 15 minutes of arc 4 seconds 1 minute of arc Table II-S N. Points A, B, C, D, and E representsatel- Trace the protractor at the endof the The hour angle of chapter.Cut it out and use it to measure lite tracking stations. Record your the sun from position A is 0 hours.There- the angles in Figure II-15. fore, the time is 11:00 N-Oon.Conipare the answers. Compare your answerswith those four How accurately do you measure? hour angle of the sun from the other given. points.What dme is it at each position, What can you say about your- instrument Position A? See (the protractor)? when it is 12:00-Noon at We an actually speak of time in termsof Table 11-6. an angle, Figure11-14. If we use the position of the sun at 12:00 noon as a startingpoint
S UN
Figure II-16 Position Time Angle of the Sun Hour Angle A 12:00 0° 0' ohours 0 minutes 2:16 PM 34° 0' 2 hours 16 minutes 7:24 PM 111° 0' 7 hours 24 neinutes 195° 0' 13 hours 0 minutes 1;13, 1:00 AM 10:30 AM 337" 30' 22 hours 30 minutes Table 11-6
5.a. Trace and carefully cut out the card- 18 hours. Make a table like the one boamd earth, Figure 11-18. Center the below and record the time now at: =din over the circle below in Figure Time Angle of the Sun E-1.9. Push a straight pin or small paper fastener through point N on the earth New York anak-through the center of the circle as Greenwich imlicated, so that the earth freely ro- Moscow tates around the pin. Align the arrow Tokyo marked New York, at 0 hours or Los Angeles 12:00 Noon. Table 11-7 b. Whac time is it at New York? 12:00 Note to student: We have been concerned Noon. with only the hour angle ot the sun, there- When is it 12:00 Noon at New York. fore, local time. We have not taken up the (1) What time is it in Greenwich? change from one day to another, Monday (2) What time is it in Moscow? to Tuesday, etc., or standard time. (3) What time is it in Tokyo? (4) What time is it in Los Angeles? c. Rotate New Yorkcounter-clockwise 90° or 6 hours. (1) What time is it now in New York? (2) What is the hour angle of the sun from this position? With New York at this position, what time is it now at: (3) Greenwich, England (4) Moscow, Russia (5) Tokyo, Japan (6) Los Angeles, California d. (1) How many hours difference was represented by rotating New York 0° to 90°? As you rotated New York from 00 to 90°, how many hours did: Figure IP! 7 (2) Greenwich, England rotate? (3) Moscow, Russia rotate? (4) Tokyo, Japan rotate? As instruments improved and the ac- (5) Los Angeles, California rotate? curacy of measurements increased, manbe- e. Rotate New York in the samedirec- gan to doubt the simple motionof his tion, counter-clockwise, to 270° or planet. As we found the pulse could not be used as a standard for time, man found that The Earth does not move at a uniform Earth was no longer an acceptable time. speed as it revolves around the sun. At its standard. closest approach to the sun, perihelion, Observations of the stars created the Earth is at a distance of about 91,500,000 first doubt of Earth's simple motion. The miles from the sun. At its greatest distance stars appear to move i° farther to the west from the sun, aphelion, Earth is about each night. This is the same as saying a star 94,500,000 miles from the sun. rises four minutes earlier each night. Re- Aphelion 94,500,000 miles member from Table 11-5, we are able to Perihelion 91,500,000 miles show that an angle of 10 is equal to four Average distance 93,000,000 miles minutes of time. We are able to explain this observation by taking into account Table 11-8 Earth's revolution around the sun. The Earth is at perihelion in winter and at aphelion in summer. For purposes of illustration, Figure 11-21 was constructed with a greatly exaggerated elliptical orbit of Earth.One of the laws concerning planetary motion states that a planet will move faster in its orbit when it isclosest to the sun and slower when it is farthest from the sun.As shown in Figure 11-21, Figure 11-20 again exaggerated, Earth moves from A to B in one day in January.It will move a When Earth is at position A, Figure 11-20, smaller distance, C to D, in one day in July, the sun and a distant star are in a line as As previously shown, Figure 11-20, the seen from M on Earth. Notethat scale and difference between the solar and sidereal angles are exaggerated for clarity.After day is due to the distance that Earth re- one Earth rotation the star would appear volves in its orbit. Althoughexaggerated,thedistance to have returned to position M. However, traveled from A to 13 in January is greater Earth ha3 moved to position B due to its than C to D in July. Due to this difference, revolution around the sun. The Earth must the solar day is somewhat shorter in July rotate about one degree or four minutes and longer in January. If we were keeping before the sun appears to return to position time with a watch, we would find the M2.Therefore it takes 23 hours and 56 sun would be about eight minutesbe- minutes for Earth to complete a star day, hind the watch in spring and about eight sidereal day, and 24 hours to complete a minutes ahead of the watch in fall.Our sun day, solar day. watch time does not speed up in July or A sidereal day = 23 hours 56 minutes slow down in January. We keep time as A solar day = 24 hours Another observatica which cast doubt on Earth as an accurate timekeeper was that Earth's revolution around the sun did not take 365 days but about 36514 days. Every four years a day is gained. This does not seem to be very important, but over hundreds of years we would find that the seasons would be confuse& Spring would begin in the summer, summer in the fall, fall in the winter and winter in the spring. Further it was finally discovered that Earth'sorbitaround the sun was not circular but a nearly circular ellipse as in Figure 11-21. an average, or we speak of the average or mean solar day as 24 hours.Our clocks and watches which run at a uniform rate SUN during the year, actually keep average or mean time. Another reason that solar days are not uniform in length of time is due to the fact NEW MOON that the axis on which Earth rotates is not perpendicular to the plane of Earth's orbit. This produces some interesting observa- tions in the sky. For the present it will be sufficient to say that this phenomenon alone would cause the sun to be ten minutes behind a watch in February and FIRST LAST August and ten minutes ahead in May and QUARTER November. QUARTER By adding the effects of Earth's orbit and the axis of Earth, we arrive at truly complicated observations as in Table 11-9: Month Minutes FULL MOON February 15 minutes, watch behind the sun May 4 minutes, watch behind the sun Figure II-22 July 6 minutes, watch behind the sun October 16 minutes, watch ahead of the sun 360° 12° in one day Table 11-9 30 days If the moon is at position 1, Figure 11-22, seven and one-half days later it would be at Apparent solar time was accurate enough position 2. The moon would have moved for our ancestors.It is not nearly accurate 7% days at 12° per day or 90° in 7% days. enough for the aerospace age.With our From position 2 it would move to position precise instruments we have turned from 3, and it would be 90° from position 2, or Earth's rotation, to a calculated average 180° from position 1.At position 3, the or mean time. moon would have orbited 270° in 22% Another early timekeeper was our near- days.Returning to position 1, the moon est neighbor in space, the Moon. Man was has completed a 360° orbit in 30 days. able to estimate the time of night from Each day the moon would appear to have the appearance of the moon and its posi- moved 12° in the sky. tion in the sky. More recently, scientists Look again at Figure 11-22.When the have investigated the moon not as a time- moon is at position 1, the moon is between keeper, but as a landing place for Man's the sun and Earth. As the moon passes be- first venture into outer space. tween the sun and Earth, one of three As you know, the moon orbits Earth at things occurs as shown in Figure 11-23. an averagedistance of about 240,000 Throughout the year, as the moon orbits miles. Earth (Figure 11-23) it can appear to pass As illustrated in Figure 11-22, the moon above the sun, a; below the sun, c; or di- passes from position 1, to 2, to 3, to 4, and rectly between the sun and Earth, b. Posi- returns to position 1 as it orbits Earth. One tionsa and c occur most frequently. lunar orbit takes about 30 days.Notice Position b infrequently occurs.What do the orbit of the moon is approximated as a we call the phenomena when the moon circle.Remember a circle has 360°.If passes directly across the disc or face of the moon completes one orbit or 3600 in the sun as in position b?In any event, 30 days, then it moves 12° in one day! position a, b, and c, m Figure 11-23 could NEW MOON
FIRST THIRD QUARTER QUARTER
Figure 11-23 represent the moon at position 1 inFigure 11-22. Therefore once each month the moon FULL MOON aoes appear to pass "between"the sun and Figure 11-25 Earth. Why don't we notice this whenit occurs? We only "see" it occur when the When the moon, sun and Earth arein moon is at pOsition b(Figure 11-23). position as illustrated by Figure11-24, the Again refer to Figure 11-22.If we are lighted side of the moon is the side toward looking from Earth at the moon, position the sun. Besides being in the daytime sky, 1, we are looking directly into the sun. we are looking at the darkside of the Can you see any object in the skyin the moon. Can we see the moon asillustrated daytime except for the sun? _in Figure 11-24? No It wouldbe in the sky, but we could not see it. When the moon is at position I, (Figure II-25) we refer to the moon as a new moon. Seven and one-half days later, whenthe moon is at position 2, the moonis referred to as the first quarter.The 15 day old moon at position 3, is calledthe full moon. At position 4, 221/2 days after new moon, the moon is called the third quarter.71/2 days after third quarter or. 30 daysafter new moon, the moon isback at position 1 and is again referred to as the new moon. When speaking of the moon, useful terminology is illustrated in Figure 11-26. As the lighted side of the moonvisible from Earth becomes larger, new moon to full moon, the moon is said to be waxing. N ORT H PO LE As the lighted side-as seen from Earthbe- Figure 11-24 comes smaller, full moon to newmoon, C WANING NEW WAXING WAXING WAXING FULL WANING WANING NEW 3rd QUARTER CRESCENT CRESCENT1st QUARTER GIBBOUS GIBBOUS Figure11-26
33 ta4 the moon is said to be waning.If the member when the moon is at this position moon's lighted side as seen from Earth is in its orbit, the moon is passing "between" larger than a quarter and smaller than full, the sun and Earth. Figure 11-27 illustrates the moon is said to be gibbous.If the the moon passing below the sun's position lighted side of the moon as seen from as seen from Earth.Read the following Earth isless than a quarter but greater questionslowly. Rereadit. Ifthe than when at new moon the moon is said sunisdirectly south at12:00 noon, to be a crescent. andthenew moon isdirectly south Why is the quarter moon called quarter? when the sun is directly s--Outh, what time- How much of the moon is always lighted is it when the new moon is in the south? by the sun? 1/2. How much of that lighted 12:00 Noon. Remember we tell time by half do we see at the quarter phase? 1/2. the position of the sun! , If the new moon 1/2 - 1/2 =1/4, or we see 1/4 of the moon's surface is directly south at 12:00 noon, what time at the quarter phases. Using the vocabulary was it when the new moon rose in theeast? previously described, let us attempt to de- 6:00 AM. If the new moon rises at 6:00 scribe where the moon "goes" in the AM, is directly south at 12:00 noon, what daytime. time does it set? 6:00 PM. Or we say the To better understand the "wanderings" new moon sets when the sun Sets. of the Moon and to use the moon as a time- Do you see the new moon set? No. The keeper we will make two assumptions. new moon sets in the fading light ofthe First, we will tell time by the position of sun. The new moon rises at 6:00 AM and the sun, and second, we will assume that sets at 6:00 PM. How many hours is the the sun rises into the eastern sky at 6:00 AM, new moon in the sky?12 hours. How is directly south in the sky at 12:00 noon, many hours do you see it on this day? You don't.It is only in the sky when an-cl-sets in the west at 6:00 PM (Figure the sun is in the sky.Also recall that it 11-27). new moon we are observing the dark side 1200 NOON of the moon. The lighted side is toward the sun. (Figure 11-24). Therefore the new moon phase is the phase of the moon that we cannot see. It is not visible to the unaided eye. The new moon is only in the sky in the day- time.It has already set in the west before darkness and is not seen in the nighttime EAST WEST sky. 6:00 AM 6:00 PM New Moon Rises 6:00 AM You are facing south in Figure-rH-27. Se ts 6:00 PM East is to the left and west-is-to the right. Hours in the sky 12 hours The sun is high in the sky, directly south. Is seen 0 hours What time is it in Figure II-27? 12:00 Noon. What time did the Sun rise on this day? 6:00 AM. What time does the sun set on . this day?6:00 PM.If the sun rises at 6:00 AM and sets at 6:00 PM, how many hours does the sun spend in the sky on this day? 12 hours. How many hours do we see the sun this day? 12 hours. We see the sun all day unless, of course, it's cloudy or raining. We will assume clear days and nights. In Figure 11-27, we observe the moon at the phase we described as new moon. Re-
34 :40 Figure 11-28, represents the moon three days after new moon. The moon has moved 3 days or 36° in its orbit around Earth. What time is represented by Figure 11-28? 12:00 Noon. The sun is due south. If the sun rises at 6:00 AM and sets at 6:00 PM, what time did the moon rise in Figure 11-28? 9:00 AM. The moon is about three EAST WEST hours "behind" the sun. Did you see the Figure 11-30 moon of Figure 11-28 when it rose in the. east?No.It is daylight at 9:00 AM. If In Figure 11-30 the sun is setting in the you are outside looking at the moon in west. What time is it? 6:00 PM. The 71/2 Figure 11-28, could you see it?No. The day old first quarter moon is directly south time is 12:00 Noon. in the sky at sunset. What time is the first quarter in the south?6:00 PM.If the first quarter moon is in the south at 6:00 PM, what time did it rise?12:00 Noon. Did you see it when it rose in the east? No. The sun was high in the sky. What timewillthefirstauarter moon set? 12:00 Midnight. Will you see it as it sets? Yes.It is night.If the first quarter moon risesat 12:00 noon and sets at 12:00 Figure 11-29 midnight, how many hours is the first quarter moon in the sky?12. hours. How Figure 11-29 represents the ,3 day old many hours do you see it? 6 hours. The moon at sunset, 6:00 PM. Do you see the first quarter moon is observed from sunset 3 day old moon at sunset? Yes. The moon has moved out of the glare of the sun. until it sets about midnight. What time will the 3 day old moon set? Waxing First Quarter 9:00 PM.If the 3 day old moon rose at 9:00 AM and sets at 9:00 PM, how many Rises 12:00 Noon hours is it in the sky?12 hours. How Sets 12:00 Midnight many hours do you see it?3 hours.It is Hours in the sky. .. 12 hours observed from 6:00 PM until 9:00 PM when it sets in the west. Could you observe the Is seen 6 hours, 6:00 PM to 3 day old moon at 12:00 midnight? No. 12: 00 Midnight It has already set. The three day old moon is considered a crescent as it is between the quarter moon and the new, moon phase. The three day old crescent moon is said to be waxing. The lighted side is becoming larger as the moon is moving from the new mo6n to full moon phase. The moon at this position in its orbit is then described as a 3 day old EAST WEST waxing crescent moon. Figure 11-31 3 Day, Waxing, Crescent Moon Figure 11-31 represents the 10 day old waxing gibbous moon.The ten day old Rises 9:00 AM gibbous moon is about 9 hours "behind" Sets 9:00 PM the sun. The sun is setting in Figure 11-31 Hours in the sky. . 12 hours and the gibbous moon is toward the south- Is seen 3 hours, 6:00 PM to east.What time did the waxing gibbous 9:00 PM rni:Jon rise?3:00 PM. Did you see it rise?
35 No.What time will it be in the south? 9:00 PM. What time will it set? 3:00 AM. Do you see it as it sets?Yes. If it rises at 3:00 PM and sets at- 3:00 AM, how n. ?my hours is it in the sky? 12 hour How many hours is it visible? 9 hours. 10 Day, Waxing Gibbous Moon Figure 11-33 Rises 3:00 PM Sets 3:00 AM south? 3:00 AM. What time did it rise in Hours in the sky. 12 hours the east?9:00 FM. Do you see it as it rises? Yes. If the 18 day old waning Is seen 9 hours, 6:00 PM to gibbous moon rises at 9:00 PM, what time 3:00 AM will it set?9:00 AM.Will you see it when it sets?No. It will disappear from view in the southwest as 'the sun rises in the east, setting three hours later. 15 Day, Waning Gibbous Moon Rises 9:00 PM Sets 6:00 AM EAST Hours in the sky. .. 12:00 hours Figure 11-32 It is seen 9 hours, 9:00 PM to In Figure 11-32 the full moon :Is rising 6:00 AM as the sun is setting.Notice that the full moon is opposite the sun in the sky, tw,.:Ive hours "1$0.1ind" the sun.What time is illusirated :cry Figure II-32? 6:00 PM.. The sun is setting. If the full 15 day moon rises at 6:00 PM, do you see it as it rises? Yes.The sun is setting.The full moon rises as the sun sets. What time will the full moon be directly south? 12 Midnight. Figure 11-34 What time will the full moon set? 6:00 AM. The full moon sets as the sun rises. How many hours is the full nloon in the sky? Figure 11-34 represents the waning third 12 hours. How many hours do you see it? quarter moon. 12 hours.The full moon is seen all night from sunset to sunrise. Exercises:See if you can answer these questions without looking back Full Moon at the various figures. 6.a. The sun is rising in the east, therefore Rises 6.00 PM the time indicated in Figure 11-34 is ...... 6:00 AM Hours in the sky 12 hours b.The third quarter moon is directly Is seen 12 hours, sunset to south at or sunrise C.The third quarter moon rises at d.Do you see the third quarter moon Notice in Figure 11-33 that the sun is rise? rising.What time is it? 6:00 AM. If the e.The third quarter moon sets at 18 day old waning gibbous moon is in the f.Do you see the third quarter moon southwest at sunrise,, what time was it due set?
36 g. How many hours is the third quarter 8.a. Identify the following phases and the moon in the sky? approximate time.In all cases you h. How many hours do you see it? are looking south. i.The third quarter moon is seen from to j.If a quarter moon is observed in the (1) (2) sky at 10:30 PM, is this the waning third quarter? k. 22 day old, waning third quarter? (1) Rises (2) Sets (3) Hours in the sky (4) It is seen hours, from to FULL MOON PHASE_ TJME- 9:00 PM
(3)
EAST WEST Figure 11-35 Figure 11-35 represents the 27 day old waning crescent moon. 7.a. What time is indicated by Figure II-35? WAXING GIBBOUS b. In what direction is the crescent moon in Figure 11-35? c. What time did the waning crescent moon rise? d. Did you see it when it rose? Figure 11-36 e. What time is the waning crescentin b. the south? f. What time does the waning crescent set? IDENTIFY PHASE, TIME OR DIRECTION g. Do we observe the waning crescent moon setting? h. How many hours is the waning crescent (2) moon in the sky? i. How many hours do we see it? j.27 day old, waning crescent moon: (1) Rises (2) Sets . .. (3) Hours in the sky (4) Is seen hours, from to WANING CRESCENT PHASE - The m-Oon continues in its orbit. As the TIME _ 6:00 PM moon again passes "between" the sunand SOUTHEAST SOUTHWEST Earth, the moon returns to the new moon phase and the lunar cycle is repeated. Figure 11-37
37
k.:5":, 38r Caution: In the previous section, we have You could estimate that the line was stated that you cannot "see" the moonin less than a foot, a few inches, or between the daytime sky. However, there aretimes 3 and 4 inches. You could do-this by basic when you can see the moon when the sunis observation, and if this served our purposes,. still in the sky. This occurs when the moon this is an acceptable answer. However, to is near the full phase. This is due to thesun's make a more accurate measurement than light being bent, refracted, as it passes this, we would use a standard ruler.(At through Earth's atmosphere. At this time, this point, you should copy and cut out the tile brilliant moon stands out against the standard rule7inches; and metric ruler, deep blue of the early evening orearly centiineters, found atthe end of the chaptel.)Measure the length of the line morning sky. with the standard ruler in inches.The result of your measurement indeed shows that the line is less than a foot, it is a few inches in length, and is in fact between 3 and 4 inches. With the ruler, you can de- scribe the length of the line more ac- curately than with your eye. You are now able to describe the line as being between 3%2 and 4 inches. You could also say more accurately that the length of the line was between 3 3/4 and 4 inches. A table of your measurement steps could be asfol- lows: Measurement Step Greater than Less than
1 3 inches 4 inches 2 3 1 /2 inches 4 inches 3 3 3/4 inches 4 inches Repeating your measurement with a centimeter ruler the following information could be obtained: Figure II-38 Measurement Step Greater than Less than In the precedhig sections, we have seen the development of the measurementof 1 9 centimeters 10 centimeters time.We will now apply the same basic 2 9.5 centimeters 10 centimeters principles and procedures to the direct 3 9.7 centimeters9.8 centimeters measurement .of distance, and later t6 indirect measurement of distance with a or 97 millimeters or 98 millimeters Scale. Current methods of measuring ordinary Table II-10 distances are fainiliar to all of us.How- ever, with recent advances in the spacesci- To attempt to read our measurements as ences, the need to measureaccurately be- 3 7/8 inches or 97.5 millimeters, would be comes exceedingly important. Let us to exceed the precision of our instrument. consider the line below, Figure 11-39. in this case, the ruler.Errors to be con-
Figure 11-39
38 sidered in a measurement experiment such VERN IER SCALE as this would include: a. The width of the printed line on the 0 12 3 4 5 ruler 'V1111111III I b. The angle from our eye to the ruler o 2 3 4 5 6 7 8 9 10 c. Texture of the paper PRIMARY SCALE d. Placement of the ruler on the printed page. Figure 11-42 If it were necessary to make a more In reading the vernier measurement of accurate measurement, we would turn to a the penny in Figure 11-40 two readings must more precise instrument, for example, a be taken. The first reading is to determine vernier scale. This device enables us to de- the position of the vernier 0 on the primary termine the length of the line with a greater scale. Prior to the measurement, the vernier degree of accuracy. 0 is at primary 6, (Figure 11-42). Then to read the diameter of the penny, Figure 11-40, the vernier 0 is between 2 and 3 units VERNIER SCALE on the priinary scale. This tells us that the 0 12 3 4 5 diameter of the penny is between 2 and 3 'it e `1- '1 I units.The second reading will determine 0r1 2 3 4 5 6 7 8 9 10 the fraction of the scale unit. In this read- PRIMARY SCALE ing, we must determine which vernier divi- sion coincides most directly with a primary Figure 11-40 _scale division.Upon inspection of Figure The vernier scale is a common attachment H-40, we- see that the vernier scaleis to measuring instruments, such as the ruler, arranged as follows: micrometer, or protractor. The vernier is Vernier Scale Primary Scale used to determine a fraction of division on the main scale that is the primary scale as 0 falls between 2 and 3 in Figure-II:40.Vernier graduations are 1 falls between 3 and 4 different from the primary scale, but bear 3 coincides with 5 a simple relation to it.For example, the 4 falls between 5 and 6 vernier represented by Figure 11-40 is so 6 and 7 arranged that it reads 0.2 or 1/5 of a divi- 5 falls between sion on the primary scale. In order to make Vernier 3 coincides with a primary scale a reading like this, five divisions on the division, and therefore, is the division which vernier scale must equal four diviNions on represents the fraction of a primary scale the primary scale (Figure 11-41). Each vernier scale division is equal to 4/5 of a division.If one vernier division is equalto primary scale division.The difference in 0.2 of a scale division, then three vernier the length of the divisions is ealled the divisions equal 0.6 of a primary scale divi- "least count" of the vernier. By using the sion.Our actual reading is obtained by prinbiple of "least count," we could con- adding the vernier reading to the primary struct a vernier to read 1/32 or 1/64 scale reading. inches, or 0.5 millimeters, 0.1 millimeters, Primary Reading 2.0. units and so on. Vernier Reading O. 6 units VERNIER SCALE Diameter of penny 2.6 units
0 1 2 3 4 In this manner, we are able to directly
1 measure the diameter of the penny with a 1 I high degree of accuracy by making use of 0 1 2 4 an instrument of greater precision than a standard rule. PRIMARY SCALE At this time, the student should care- ,F4gure 11-41 fully read the directions below and then
39 copy and cut out the vernier at theend of nomical unit. The astronomical unit,A.U., is the average distance bitween the centerof this chapter. the sun and the center of Earth. Astrono- Directions: mers have spent hundreds of yearsin ob- Carefully: serving and calculating to refine this basic (1) Copy and cut out the vernier measurement. (2) Cut along Line C to A Figure 11-43 represents Earth's orbit of (3) Cut along Line B to A the sun.It is drawn to scale, I" equals The vernier scale should slide freelyand 48 million miles.To simple inspection, evenly along the primary scale. The smallest the orbit of Earth appears as a circle. unit on the main scale is 14" or 8/32inches. If we were to carefully measure Figure The vernier scale is read in 1/32inches. 11-43, we would fmd that Earth'sorbit This vernier is read the same way asout- is not a circle, but elliptical, slightly oval. lined above. The primary scale is read to the If we were to report our measurement nearest 1/4 or 8/32 iziches plus thevernier of the astronomical unit to a groupof reading up to 7/32 inches. scientists, we would include in our report: Example:Place the vernier over the line 1. Aphelion in Figure 11-39. We are able to see thatthe 2. Perihelion vernier 0 is between 3 3/4, that is3_24132, 3. Average distance from the sun and 4 inches. The vernier 3 coincides most 4. Eccentricity of Earth's orbit closely with a primary scale division.The The above four characteristics are reterred line then measures 3 24/32 inches +3/32 to as the primary orbital elementspertain- inches or 3 27/32 inches. ing to the shape of Earth's orbit. From It should be noted that this measurement these four elements, a scientist could is more accurate than the measurement ob- produce our drawing of Earth's orbit. tained with the standard ruler or vernier primary scale because the vernier is more Aphelion miles precise than the ruler.However, it again should be noted that the same kinds of Perihelion miles errors involved with the ruler measurement are included with the verniermeasurement. Average Distance miles In this case, the errors are more critical be- miles cause of the accuracy of themeasurement. Eccentricity In actual practice, vernier scales have been designed to measure to the nevrest 0.001 inches (one-thousandth of an inch). To determine Earth's farthest point from Let us approximate one of the funda- the sun, aphelion, we would measurethe mental distances of astronomy, the astro- distance from the sun, (s) to El (Figure
S. SUN
Figure 11-43
40 11-43). This_distance is 1 31/32 inches. If. 1 inchequals 48 million miles, then 1-31/32 inches equals 94,500,000 miles. At E1, aphelion, Earthis94,500,000 miles from the sun. To determine Earth's closest point to the sun, perihelion, we would measure the distance from the sun (s) to E2. This distance is 1 29/32 inches. With a scale of 1 inch equals 48 million miles,1 29/32 inches equals 91,500,000 miles. At E, , perihelion, Earth is 91,500,- 000 miles from the sun. To determine the average of Earth's distancefrom the sun, we could add the apheliondistance to the perihelion distance and divide the sum by two.This would give us Earth's average distance as 93,000,000 miles.However, to reduce the possibility of errordue to measurement, we could take a number of Figure 11-44 measurements around Earth's orbit. If we made the indicated measurements At this point we have in Figure 11-44, we would tabulatethe re- sults in a table as follows: Aphelion 94.5 x 106 miles Measurement Altitude Scale In che s Perihelion 91.5 x 106 miles
1 a-s 1 31/32 Average distance 93.0 x 106 miles 2 b-s 1 31/32 1 A.U. = 93 mi:iion miles, 93.0 x 106 miles c-s 1 30/32 3 Table II- 12 4 d-s 1 31/32 5 f-s 1 29./32 The eccentricity of Earth's orbit is a meas- 6 E2-s k 28/32 ure of the "roundness" ofthe orbit or ellipse. If Earth's orbit was a perfect '7 g-s 1 29/32 circle, the eccentricity would be 0.The 8 h-s 1 29/32 eccentricity of an ellipse is always less than 9 i-s 1 29/32 1.The closer the eccentricity to 1, the more elliptical the orbit. 10 j-s 1 31/32 11 k-s 1 31/32 12 E1 -s 1 31/32 Sum = 23 8/32
Table II-11
If we were to sum the 12 measurements, and divide by 12, we would have an average, or mean Earth-sundistance of: 23 8/32/12 = 1 30/32 = 1 15/16 inches. From the scale, one inch equal to 48 million miles, 1_15/16 inches equals 93 million miles. Figure.11-45
4 1 For purposes of illustration, the elliptical orbital elements of Earth would now appear orbit of Earth has been exaggerated in as: Figure 11-45.Notice that the sun is not at the center of the ellipse, C. The Earth at Aphelion 94.5 x 106 ± 7.50 x 103 position Ei is at aphelion at a distance from Average Distance 93.0 x 106 ± 7.50 x 103 the center of the sun of A. The Earth in position E, is at perihelion at a distance of Perihelion 91.5 x 106 ± 7.50 x 103 P from the center of the sun. We are able Eccentricity 0.016 to express the eccentricity of Earth's orbit The astronomical unit, A.U., would have in terms of the aphelion (A) and perihelion a value of 93 x 106 miles plus or tninus (P) distances. 7.50 x 103 miles. With today's standards, A - P our measurements of Earth's orbit are not Eccentricity, e = very realistic and are subject to error. A + P With the advent of the space age, man has continued to refine this basic measure- 94,500,000 - 91,500,000 e ment.Table 11-13 illustrates some recent 94,500,000 +91,500,000 history of the measurement of the astro- nomical unit. 3,000,000 3 1 e If we were to report the orbital elements 186,000,000 18663 of a satellite, we would report the same four primary characteristics as we did for e = 0.016 Earth's orbit.For satellites which orbit Earth, we refer to the highest point in orbit Since the eccentricity is small, 0.016, as apogee and the low point as perigee. as compared to 1, we know Earth's orbit Apogee and perigee are measured from the is nearly circular. center of Earth, but generally are reported To interpret these results, consider the from the surface of Earth. accuracy of our measurement. Your vernier Although scientists measure and make is able to measure to the nearest 1/32 of their calculations based on the satellite's an_ inch.Therefore, each measurement is distance from the center of Earth, the subject to an error of 1/32 inches (1/64 altitude of a satellite is reported to the inches below the value and 1/64 inches general public as the average distance of the above the value).Thus, the measure- satellite from the surface of Earth. ment, in the case of average Earth-sun That is to say, altitude of Echo I is distance 1 15/16 inches, should be written reported as 1,000 miles and not as 4,960 1 15/16 ± 1/64 inches. If we were to con- miles. vert this number to mile's,1 inch equals Si is a satellite at apogee at a distance A 48,000,000 miles, we would show that the from the center of Earth. S2 represents the average Earth-sun distance to be 93,000,000 perigee of the satellite at a distance of P ± 750,000 miles. Our report of the primary from the center of -Earth, Figure 11-46.
SATELLITE Figure 11-46
42 Source of A.U. in measurement millions Experimenter's Estimate of Number and data of miles A.U. value range - - - - 93.35 1 Newcomb, 1895 93.28 93.20 2 Hinks, 1901 92.83 92.79 - - - - 92.87 3 Noteboorn, 1921 92.91 92.90 92.92 4 Spencer Jones, 1928 92.87 92.82 - - - 92.81 5 Spencer Jones, 1931 93.00 92.99 -- - 93.01 6 Witt, 1933 92.91 92.90 - - - - 91.92 7 Adams, 1941 92.84 92.77 -92.92 8 Brower, 1950 92.977 92.945- - - - 93.008 9 Rabe, 1950 92.9148 92.9107- - - - 92.9190 10 Millstone Hill, 1958 92.874 92.873- - - - 92.875 11 Jodrell Bank, 1959 92.876 92.871- - - - 92.882 12 S. T. L., 1960 92.9251 92.9166- - - 92.9335 13 Jodrell Bank, 1961 92.960 92.958- - 92.962 14 Cal. Tech., 1961 92.956 92.955- - -92.957 15 Soviets, 1961 92.813 92.810- - - - 92.816 Table 11-13
Example: Echo I was orbited in August of satellite launched January 21, 1958, had 1960. Apogee was measured as 5,010 an apogee measured to be 5,533miles miles and perigee as 4,910 miles. What are and a measured perigee of 4,184 miles. the four primary elements as to the shape Report the four primary orbital elements of the orbit?(Use 3,960 miles as the as to the shape of the satellite'sorbit. average Earth radius) a. Apogee miles b. Perigee miles Apogee = 5,010 - 3,960 = 1,050 miles c. Average Distance miles d, Eccentricity Perigee = 4,910 - 3,960 = 950 miles Table II-15 1,050 + 950 Average 1,000 miles 10. Explorer III launched June 28, 1958, Distance 2 had a reported apogee of 1,740 miles and a reported perigee of 118 miles. 5,010 4,910 100 Eccentricity 0.01 What are the four primary orbital ele- ,010 + 4,9109,920 ments as to the shape of the orbit? miles Apogee = 1,050 miles a. Apogee b. Perigee miles Perigee = 950 miles c. Average Distance miles Average Distance = 1,000 miles d. Eccentricity Eccentricity = 0.01 Table II-16 Table 11-14 Thus far we have been concerned with direct measurement of distance and time. Exercises: We can now extend these ideas to indirect 9. Explorer1,thefirstUnited States measurement with a scale.
43 44 e)
Figure 11-47 Earth Based Photograph
_. "1, 10
Figure 11-48 Ranger IX Photograph
Figure 11-47 shows the surface of the diameter to be over 90 miles.Analysis moon as photographed fromEarth. Figure of Ranger's IX picturesdetermined the 11-48 is of the same area of the moon as average diameter to beabout 94 miles. The photographed by Ranger IX on March 24, Earth based picture represented byFigure 1965. 11-47 was taken at a distance of about These photographs are of particular In- 240,000 milesandFigure 11-48 when terest because Earth based measurements Rnnger TX was about 470 miles from the of Ptolernaeus (the large crater at the topof surface of the rrmon. both photographs) estimate the average
44 4
In both instances and usingsimilar actualanalysis of Ranger photographs, methods, scientists were able to conclude there are both north-south..7cl east-west that the diameter of Ptolemaeus was about scales. 90 miles.Although the moon is seen by The scale also changes as we measure the unaided eye at a distance of 234,000 toward the margin of the photograph due miles and wIth a first class telescope at an to the curvature of the moon, the camera equivalent distance of 500 miles, Ranger's angle, and the longitude of the photo- cameraa "see" it at an equivalentdistance graphed region. For our purposes of of 1/2 of a mile. illustration, we will assume a flat surface, The best Earth-based photograph is able make measurements with an average scale to resolve, see clearly, lunar surface features and assume north-south and east-west scales shall com- to he equal. as small as 1,000 feet. Later we Now we will examine in detail two major pare this figure with theresolution of characteristics affecting our use of the Ranger IX photographs. Ranger camera grid system: camera angle You can use Ranger photographs to esti- and satellite altitude.The camera angle mate size and distance on the moon, if you is the view of the moon as seen from a understand the grid system of the Ranger particular camera, such as camera A, of camera. Ranger IX.This instrument was built for a camera angle of 25°. Figure11-51 repre- sents Ranger IX asitapproached the ...r.- siirface of the moon and is drawn to scale, 6z_ 1 inch equals 250 miles. At an altitude of 0 1,300 miles, Camera A with a field of 7:2 view of 25° would "see" a circular area of 0 the moon as in Figure 11-50. SCALE-___ I CENTRAL RETICLE
i
,..L
Figure 11-49 The grid system is superimposed on the camera face.The grid crosses of Figure 11-49 are called reticles, (vet'-i-kels). The center cross mark on the camera face is called the central reticle.Grid north is defined as a straight line drawn from the central reticle to the middle reticle in the north margin. Grid north differs from true Camera A uses a mask on the light lunar north depending upon spacecraft posi- sensitive electronic tube in place of camera tion, camera attitude, and the altitude of film.The resulting image of the moon is Rangel above the moon. the portion of the full 250 view represented Actual distances on the moon can be as the shaded area in FigureI1-50. calculated from the camera scale. The scale The area of the moon's surface seen by is the ratio of the distance between the Camera A's tube would depend upon the central reticle and the reticle immediately altitude of thesatellite. The altitude, to the left and the distance vizible between Figure 11-51, is the distance from the space the two points on the lunar surface. In the craft to the surface directly below. At an altitude of 1,300 miles, Position A. Figure 11-51, Ranger IX viewed a square about 1300 MILES A 492 miles o side, BC. This is a surface area of the moon of 492 miles by 492 miles or 242,064 square miles and could resolve features of 2,600 feet. At an alti- tude of 500 miles, position D, Ranger IX's 25° camera A could photograph a square of about 186.8 miles on a side, EF, or a surface area of 186.8 x 186.8 or 34,394 square miles.At this altitude, Camera A could resolve surface features of 1,000 feet. As the altitude continues to decrease, the area photographed decreases, and the resolution increases.We could compile our data as in Table 11-17. These figures are approximations and will afford us a general understanding of thescientific principles of measurement underlyingthesuccessfulRanger mis- 500 MILES D sions. Remember at an altitude of 1,300 miles, the camera is able to view a square approxi- mately 492 miles on a side.The 492 miles represents the distance from the reticle on the left margin to the reticle at the right margin. The distance represented between two reticles, average scale, would be 492 miles divided by 4 or 123 miles. This distance is represented by 1 5/8 inches. Therefore,1 inch would equal 76 miles. We-may set up a table for scales at various altitudes, Table II-18. Figure II-31
Ranger 9 Camera A Camera Angle 25° Surface area Resolution Altitude (Miles) (Square miles) (feet)
1. 1300 242,064 2,600 2. 500 34,894 1,000 3. 250 10,000 500 4. 100 1,697 200 5. 4.5 4 9 Altitude Length of side Average Scale 1 inch equals (miles) (miles) (neles) (miles)
1300 492.0 123.0 76 475 186.8 46.7 29 250 100.0 25.0 15 100 4L2 10.3 6.4 4.5 2.0 0.5 0.3 Table II-18
Refer to Figures 11-47 and 11-48.The 1 inch 1.4 inches three large craters found in the photo- 65 miles X miles graphs arePtolemaeus(topcenter), Albategnius (lower right), and Alphonsus x = 65 x 1.4 (lower left).The scale for Figure 11-47 is x = 91.0 miles 1 inch equals 80 miles. Use your standard ruler to measure the We repeat the procedure for the craters diameter c,f the crater Ptolemaeus. A close Alphonsus and Albategnius and record the estimate of the diameter from rim to rim measurements in Table 11-19. would be 1.2 inches.To calculate the Comparing the results of the measure- diameter of Ptolemaeus in miles: ments, we find that the diameter of the craters in Figure 11-47 varies from those 1 inch 1.2 inches obtained in Figure 11-48. We can attribute 80 miles X miles the variation in your mzasurement to: x = 80 - 1.2 a. One measimement x = 96 miles b. Irregular shaped craters The scale for Figure 11-48, a Ranger c. Problem in determining the rim of the photograph, is 1 inch equals 65 miles. crater Measure Ptolemaeus in Figure 11-48 with d. Black and white shading your ruler.You will find the diameter to be 1.4 inches. Calculating the diameter in e. Not measuring throug;1 the centerof miles, the crater
Scale Scale 1 inch = Diameter Diameter Earth80 miles 1.2 inches 96.0 miles Ptolernaeus Ranger 65 miles 1.4 inches 91.0 miles Earth80 miles 0.75 inches 60.0 miles Alphonsus Ranger 65 miles 0.9 inches 58.5 miles Earth 80 miles 0.9 inches 72.6 miles Albategnius Ranger 65 miles 1.1 Inches 71.5 miles
Table II-19 Figure 11-52
To reduce the occurrence of experi- the crater.This value would certainly be mental error, we can repeat thy, procedure more representative andbetter understood. we used in determiningthe astronomical Measuring ten random diameters of eacn unit earlier in this chapter. in this manner, of the craters in Figures 11-47 and 11-48, we would speak of the averagediameter of we colledt our data as follox .s,Table 20:
Ftolemaeus Alphonsus Albategnius 'Dial Earth-basedRanger Earth-based Ranger Earth-based Ranger 1.10 1- 1.20 1.30 0.75 0.90 0.90 1.20 2- 1.15 1.40 0.80 0.95 1).85 3- 1.10 1.40 035 1.00 1.00 1.30 1.35 4- 1.00 1.45 0.80 L10 0.95 1.20 5- 1.10 L50 0.85 1.05 1.00 1.15 1.40 0.80 0.95 0.90 1.05 6- 1.15 1.20 1.30 0.80 1.00 1.05 7- 1.10 8- 1.20 1.45 0.70 1.10 1.00 1.10 1.50 0.75 1.05 1.00 1.10 9- 1.20 10- 1.15 1.40 0.80 1.00 0.95 Total 11.35 14.10 7.80 10.10 9.60 11.75 Total 11.35 14.10 7,80 10.1 9.60 11.75 10 No. of Trials 10 10 10 10 10 Average Diameter (Inches) 1.13 1.41 0.78 1.01 0.96 1.17
Average Diameter 6.1 (Miles) 90.4 91.0 62.4 65.'t 76.8 Table 11-20
48 HEIGHT OF MOUNTAIN Ey this procedure, our figures more closely agree with each other.Using this procedure to determine the average diam- LENGTH OF SHADOW eters of the craters, we have tended to reduce the possibility of experimental or random Figure 11-53 error.The greatest possibility of error in our determinations would be a constant The altitude of the central peak of error.To reduce the constant error, we Alphonsus is about 3,400 ft. would go back over our procedures and re- Students familiar with trigonometry may check our determinations of: make more accurate determinations by use a. Calibration and precision of measur- ing instruments of the tangent formula. b. Distance to moon c. Calculation of scale tan 11° d. Determination of the center of the crater CB e. Dennition of rim of tlie crater 0.1944 By continuing to refine our procedures 3.2 and calculations, we continue to increase CB .1944 x 3.2 the accirracy of our measurements. Using the same basic procedure, we are = 0.62 miles able to calculate the approximate altitude of the mount lins on the moon. Turn to 1 mile = 5,280 ft. Figure 11-58. The mountain in the photo- graph is referred to as the central peak of 0.62 miles = 3,273 ft. Alphonsus. The scale on this photograph The altitude of the central peak of is 1" equals 6.4 miles. When the photo- Alphonsus is about 3,300 ft. graph was taken, the sun was at an angle of Using the above methods, astronomers 110 to the surface of the moon. You can have determined from both Ranger and measure the length of the shadow as 0.5 Earth-based photographs craters up to about inches. Our scale drawing would appear ass 180 milesindiameter and mountains Figure 11-53.For purposes of illustration, towering over the surface of the moon more wc magnify our scale 6 times or say, 3". than 25,000 ft. equals 3.2 miles. Many new and striking ideas about From Figure 11-53, you. are able to de- the Moon have resulted from the Ranger, termine La as 110, the angle of the sun. and Surveyor rihotographs.There is still The line AB represents the length of the a greatdeal more tolearnfrom the_ shadowf the mountain, 3 inches or 3.2 Ramer and -Surveyor photographs. In ract, miles.Line CB represents the altitude of c.-_,.*ntists will be studying these pictures the mountain.If you measure CTI, you for years to come. find it is 5/8 inches long. We determiro the approximate ahitude of the mountain as follows: 3 inches 3.2 miles 5/8 inches X miles 5/83.2 X 3 X = 0.66 miles To convert our answer into feet, we con- tinue a- follows: 1 mile = 5,280 ft. 0.66 miles = 3,400 ft. Figures 55, 56, 57, 58 and 59 are Ranger 14. On the enclosed Atlas of the moon, IX photographs of the crater Alphonsus. Figure 11-60, locate and mark the im- You have seen that the scale changes with pactpoint of the following moon the altitude of the satellite.It is necessary satellites.Remember that North is to set up a series of scales to measure to the bottom of. the page, East to the surface features.The scales may be ap- left, and West is to the right. proximated by a number of scale drawings a. Ranger VIIImpacted 7/13/64 as represented by 1 igure 11-51. Lat. 10°S Long. 20°W b. Ranger VIIIImpacted 2/20/65 Lat. 2° N Exercises: Long. 2° E 11. Measure the crater marked II in Figures c. Ranger IX-1mpacted 3/24/65 11-55, 56, 57.Determine its average Lat. 13° S Long. 2° W diameter. d. Surveyor ISoftlanding 6/1/66 Average Lat. 2° S Crater II Scale Diameter Long. 4°W e.Surveyor IIFailed, Impacted a. Figure 11-55 1"=76 miles_miles 9/20/66 b. Figure II-561"=29 miles_miles Seathing Bay area, SE c. Figure II-57 1"=15 miles miles of Copernius _ f. Surveyor IIISoftlanding 4/19/67 12. Determine an approximate diameter Lat. 3°S for the crater marked III, Figures 55 Long. 23°W and 56. g. Surveyor IVImpacted 7/16/67 Average Lat. 0°N Long. 1°W Crater III Scale Diameter h. Surveyor VSoftlanding 9/10/67 1" = 76 miles _ miles Lat. 1°N a. Figure II-55 Long. 23°E 1" b. Figure 11-56 29 miles _ miles i.Surveyor VISoftlanding 11/9/67 13. From Figure 11-59, determine the di- Lat. 0°N ameter of various crateis.Scale 1" = Long. 1°W 0.3 miles. Then, pick out the srmllest . Surveyor VIISoftlanding 1/10/68 structurevisibleto your eye, and Lat. 40° S calculate its size in feet. Long. 11°W
50 pt,141,1tp diviei " , Odit4616 141,1111!11 11 '
Ar' ,.11 I. I _I .1..11171,141. t- e
4 59 56 93. Eichstalt 164. Lambert 237.Proclus Lunar Map 91. Encke 165. Landsberg 238.Protagoras 95. Endyinion 166. Langrenus 239.Ptolemaeus 98. Epigenes 167. Lassell 240.Purbach This map of the moon is based on 97. Eratosthenes 168. Lee 241.Pythagoras the original drawing by Karel Andel, 98. Euclides 169. Lehmann 242.Pytheas 170. Letronne published in 1926 as Mappa Seleno- 99. Eudoxus 243.Rabbi Levi 100, Etiler 171. Levzrrier graphica. 172. Lexell 244.Ramsden /01. Fabriciu. 173. Licetus 245.Regiomontanus MOUNTAINS AND VALLEYS 102. Faraday 174. Lilius 246.Retchenbach 103. Fermat 175, Lindenan 247.Reiner a. Alpine Valley n. Laplace Prom. 104. Fernelius 176. Linne 248.Reinhold b. Alps Mts. o. Leibnitz Mts. 105. Firmicus 177. Littrow Repsold c. Altai Mts. p. Pico 106. Flamsteed 178. Lohrmann 250.khaeticus d. Apennine Mts. q. Piton 179. Lon5ontontanus 251.kheita r. Pyrenees Mts. 107. Fontenelle 252.Riccioli e. Carpathian Mts. 108. Fracastorius 180. Lubiniezky Miner f. Caucasus Mts. s. Rheita Valley 109. Fra Mauro 253. g. D'Alembert Mts. t. kiphaens Mts. 181. Maclear 251.Ross 110. Franklhi 182. Macrobi us 255.Rothmaiiii h. Doerfel Mts. u. Rook Mts. 111. Furnenus i. Haenius Mts. v. Spitzbergen 183. Mddler 256.Sacrobosco j. Harbinger Mts. w. Straight Range !12. Gambart 184. Magelhaens 257.San then k. Heraclides Prom.x. Straight Woll 113. Gassendi 185. Maginus 258.Sasserides 1. Hyginus Cleft y. Taurus Mr. 114. Gauricus 186. Mairan 259.Saussure m. Jura Mts. z. TenerifTe 115. Gauss 187. Manilius Scheiner 118d. Manzinus 260. 116. Gay-Lussac 189. Maraldi 261.Schickard LUNAR CRATERS 117. Oeber 190. Marinus 262.Sch iller 118. Geminus 191. Maskelyne 263.Schröter 1. .Abenezra 48. Bullialdus 119. Gemma Frisius 192. Maupertuis 264.Seieuctis 2. Abulfeda 49. Bu:ckhardt 120. Goclenius 193. Maurolycus 265.Sharp 3. Agatharcbides 50. Burg 121. Godin 194. Mayer, Tobias 266.Simpelius 4. Agrippa 122. Goodacre 195. Menelaus 267.Snellius 51. Calippus 123. Grimaldi 268.Sosigenes 5. Albategnius I 96. Mercator Stailius 6. Alexander 52. Campanus 124. Gruithuisen 197. Mcrsenius 269. 7."Aliacensis 53. Capella 125. Gi,ricke 198. Messala 270.Stevin us 8. Almanon 54. Capuanus 126. ,:nberg 271.Stilfler 199. Messier 272.Strabo 9. Alpetragius 55. Cardanus 127. Hahn 200. Metius la. Alphonsns 56. Casatus 273.Struve 128. Hainzel 201. Melon 274.Struve, Otto 11. Apianus 57. Cassini 129. Halley 202. Milichius 12. Apollonius 58. Catharina 130. Hansteen 203, Miller 275.Tacitus 13. Arago 59.Cavalerius 131. Harpalus 201. Monge 276.Taruntins 14. Archimedes 60.Cavendish 132. Hase 295, Moretus 277.Theaetetus 15. Archytas 61,Celsius 133. Heinsius 206. M6sting 278.Thebit 16. Aristarchus 62.Cepheus 134. Helicon 207, Mutus 279.Theophilus 17. Aristillus 63.Chacornac 135. Hell 280.Timaeus 64.Cichus 208. Nasireddin Timocharis 18. Aristoteles 136. Heraclitus 209. Neander 281. 19. Arzachel 65.Clairaut 137. Hercules 282.Torricelli 20. Asclepi 66.Clausius 210. Nearchus 283.Triesnecker 138. Herigonius 211. Nicolai 21. Atlas 67.Clavius 139. Herodotus 284.Tycho 22. Autolycus 68.Cleomedes 140. Herschel Colombo 212. Oken 285. Men. 23. Azophi 69. 141. Herschel, J. 213. Oron tius 70.Condamine 142. Hesiod us 24. Baco 71.Condorcet 286.Vendelinus 25. Badly 143. Hevelius 214.Palisa 287.Vieta 72.Conon 144. Hippalus 215.Pallas 26. Barocitts Cook 288.Vitello 73. 145. Hipparchus 216.Parrot 289.Vitruvius 27. Bayer 1.Copernicus 28. Beaumont 146. Horrebow 217.Parry 290.Vlacq 75.Criiger 147. Horrocks 218.Peirce 29. Bernouilli 76.Curtius 30. Berzelins 148 Hortansius 219.Petavius 291.Walter 77.Cuvier 149. tlumboldt, W. 220.Philolaus 292.Weiss 31. Bessel Cyrillus 32. Bettinus 150. Hypatia 221.Phocylides 293.Werner 222.Piazzi 294.Wilhelm I 33, Bianchini 151. Isidorus 295.Wilkins 79.DamoiseaLI 223.Picard 34. Ric la 296.Wurzelbauer 35. Billy 80.Daniell 11523: Jaansen 224.Piccolomini 36. Birmingham 81.Davy 225.Pickering, W. H. 154: Julius Caesar 226.Pictet 297.Zach 37. Bin: p?.Dawes 298.Zagut 38. Blancanus Gasparis 227.Pitatus 155. Kepler 228.Pitiscus 299.Zuchius 39. Blanchinus 84.Delambre 156. Kies 300.Zupus 40. Boguslawcky 85.De la Rue 157. Kirch 229,Plana 41. Bohnenberger 86.Delaunay 158. Klaproth 230.Plato 42. Bond, W. C. 37.Delisle 159. Klein 231.Playfair 43. Bonpland 38.Deluc 160. Krafft 232.Plinius 44. Borda 89.Descartes 233.Pontantts 15. Boscovich 90.Diophantus 161. Landsberg C 234.Pontecotdant Dollond 162. Lagrange 255.Posidonins 46. 11..,,q!ter 91. Prinz 47. ::,:ussingar. 92.Doppelmayer 163. Lalande 236.
60 " (X) Answers to Chapter II
1.a.The standard number of drops per c. (1)6:00 PM minute is found by dividing the total (2)6 hours number of drops by the number of (3)about 10:45 PM minutes, in this case, 5. (4)about1:15 PM (5)about8:15 AM Standard (6)about2:45 PM 60 d. (1)6 hours Standard (2)6 hours Standard x 60 or (3)6 hours (4)6 hours Standard x 60 (5)6 hours 1,000 5.e. Time Angle of Standard x 60 x 24 the Sun (4) 1,000 New York 6:00 AM 18 hours Standard x 60 x 24 x 365 (5) Greenwich about10:45 AM 22 hours 45' 1,000 Moscow about1:15 AM1 hour 15' Standard x 60 x 24 x 365 8:15 PM 8 hour 15' or Tokyo about 1,000 x 1,000 Los Angeles about2:45 AM 14 hour 45' c. (1) 1,000 x 1,000 = 1,000,000 6.a.6:00 AM = 1 x 106 = 1 million b.6:00 AM oy sunrise 2. Standard x 90 C.12 midnight d.Yes, it is dark when it rises 3.a.Standard x 25 e.12 noon b.Standard x 25 f.No, it is daylight when it sets 22 g.12 hours h.6 nours 4. Some problems encountered when i.12 midnight to 6:00 AM using drop time are as follows: j.No, the waning third quarter does not All drops are not the same size. rise until midnight. The number of drops per minute k.(1) Midnight would vary depending upon how full (2) Noon the cup is. Try this. (3) 12 As the opening became larger after (4) 6 hours, from Midnight to 6:00 continued use, the water would drop AM out faster. .You have to keep filling the cup. 7. a.600 AM e.In cold weather, the water could b.Southeast freeze, and in high temperatures, the C.3:00 AM water could boil. d.Yes, it is still dark at 3:00 AM As early as 1400 BC., the Egyptians C.9:00 AM constructed water clocks and they were f.3:00 PM as time- g.No, it is still light at 3:00 PM used almost 2,000 years 12 hours keepers. h. 1. 3 houis 5.a. Complete as instructed. J.(1) 3:00 AM b. (1) about 4:45 PM (2) 3:00 PM (2) about 7: IPM (3) 12 hours (3) about 2:15 AM (4) 3 hours, from 3:00 AM until 6:00 (4) about 8:45 AM AM 8.a.( 1 )Full Moon 10.a. Apogee1.740 miles Midn4ht b. Perigee 118 miles c. Average (2) 1st Quarter Distance929 miles 9:00 PM d. Eccentricity 0.17 (3) Waxing Gibbous 11. Average Diameter 9:00 PM a. about 24.5 miles b. (1) Waning Crescent b. about 25 miles 6: 00 AM c. about 24.5 miles Southeast 12. Average Diameter (2) Waxing Crescent a. about 52 miles 6:00 PM b. about 51 miles Southwest 13. Smallest features visible in Figure 61 are about 500 feet. 9.a. Apogee1.573miles b. Perigee 224miles 14. Add other satellites and landings, to the c. Average map of the moon as they occur. You Distance898.5 miles can obtain their position from your d. Eccentricity0.14 local newspaper. tf)
to
(I) tr)
te)
cz NOTE:In the printing process the above instru- meats may have become somewhat inaccurate,there- fore you may wish to use your own plastic, metal or wood instruments.
"EMPTY" SPACE
How is IL possible to describe the measure of "empty" space which contains only about 1 particle of material per cubic mile? The content of "empty" space con- tains a wind that travels faster than the speed of sound, strong enough to produce the tail of a comet, a wind which cannot be seen but can be measured (Figure 111-2 and 11I-3).These are the solar winds high temperature electrified gases from the sur- face of the sun.Also throughout space there are fields of gravity, electricity, and magnetism which can be used to describe its measure. Figure 111-2
Radiation belts trap solar wind particles Orbit of IMP satellite one4..::f : turbulence
--.7t....,==""? ..vcc
Moon's waKe detected' December 15, 1963 ,
-17 *11Z,,i:NP.rtg0 4 --,..n"V.4t-9W4V:e:POt\-, ,' cF4A 4. 1 pa+-...-...... --...... -----...._'.*4*...74;i',`,:,&.,,
,,o.4.,,_ ...... _..,_0;,,,.4,..eA, , ..,,,v-..,-.. "... l'rzie47,:s-P,,-4,114f .,;0043. -:-Wkw,,,,-,,..4:S:,,,1,111 W---"P't ..y,.:Alg'i",). -:
Figure 111-3
64/69 II k I. . 14 I . 11 . * * I I I s . o s . I. 1. . . o 1 I tti . . I IS I 411 . I Ii 1 s : I 1_ 0 I I is 1- 6 6 I :.4 I . I I 0 11 . I I 11 4 di I " . I I I I I I . s . 11 . II e /I . I 1 !-1_ I 1 . 4 1 t I . . 5 iI 15 0 . , I 0 A III 0 I I 4 0 0 I. a . 14 I
s II ID 0 I
0 . . lII II
o the train. With sound waves the statement is "velocity equals number of vibrations per second (frequency) times distance from onewavetonext(wavelength),or v f x 2. Nowtomeasurethelengthof a soundwave. Imagine awavelike this and a- second wave identicalto the first But suppose the second wave travels just a wave length behind the first:
What wave will result if they are added together?The "hills" of one wave are added to the "valleys" of the other wave, and the result could be represented iike Figure 111-6 this . These waves cancelled each other when they were added together. Now imagine the two waves are traveling moves back and forth 256 times. This re- exactly together: sults in 256 compressions and rarefactions (sound waves) being sent out into the air every second. This wave will result if they are added When your ear hears the piano note, together: your ear drum also vibrates 256 times a second. At any point within the range of this sound, 256 sound waves go pastevery It will result in a wave with the same fre- second. If we know how far it is from one quency but higher hills and deeper valleys wave to the next, we can soon compute a stronger wave or a louder sound. how fast the waves are traveling.This is If two sound waves cancel each other often compared to a railroad train- passing silenceresults. If two sound waves a crossing. If twenty cars go past in a minute strengthen or re-enforce one another, a and each car is fifty feet long, then 20 cars much louder sound results. The effect of per minute x 50 feet per car equals 1000 sound waves re-enforcing one another is feet per minute which is the velocity of called resonance.
:11
4,1,1Y/4. 4461w:4i /aglii4414140# kl*`
Figure 111-7
71
fr Hold the vibrating fork over the open end of the cylinder. If resonance does not occur with an emptycylinder, slowly, very slowly, add water to the cylinderuntil the volume of sound increases sharply. When resonance occurs, measurethe distance from the top of the cylinder to the surface of the water. Continue to add water slowly to the cylinder while the vibrating fork isheld over the top.If resonance occurs again, measure the distancefrom the top to the surface of the water. The difference be- tween these two measurements is one-half wave length. If resonance does not occur againwith this cylinder, then the distance fromthe Figure 111-8 top to the surface of the water represents one-fourth of a wave length, and should be multiplied by four to give the wave length. Once the wave length has beenmeasured, and with the frequency of thetuning fork We can use resonance to help us measure known, the speed of sound can be calcu- the length of a sound wave. We willneed a lated from vf X P. You should be able to graduated cylinder of at least 100milliliter measure the speed ofsound to be about capacity, a tuning fork with a frequencyof 335 meters per second. 700 cycles per second or higher, ametric If you discover errors in your measure- ruler, and a small amount of water. ment, perhaps you can think of waysof If the vibrating tuning -fork is held over improving your techniques. Does the the open end of the cylinder, Figure111-8, diameter of the cylinder have any effect the compressions and rarefactionstravel on wave length?The longer the wave down tc the closed end of the cylinder, are length you use, the smaller willbe your reflected from the bottom of the cylinder, error of measure,Do you think dif- and travel back out the open endof the ferences m temperature or pressure of the cylinder.A louder sound, or resonance, air could cause errors of measurement? will occur if the cylinder is just theright The speed of sound is dependent upon length so that a compression and rare- Can sound be used to faction travel down it, reflect andarrive air temperature. tuning measure temperature inthe upper atmos- back at the open end while the phere? When rockets became available fork' is completing one-half of its vibration. for scientific use, methods for measuring During the other half-vibration, a compres- in the temperature with sound were devised. One sion and rarefaction are produced technique has proved very valuable. opposite direction, and add to the com- As the rocket soars upward,special pression and rarefaction emerging fromthe grenades are ejected from it oneafter cylinder to make the sound louder. In other words, resonance will occurif n.nother. so they explode with bright flashes the length of the cylinder is exactly one- and loud noises, Figure 111-9. fourth the length of the sound wave. Ground based radar tracking station Resonance can also occur if the lengthof and special photographic trackers areused the cylinderis three-fourths of a wave to pinpoint the location of eachexplosion. length, or one and one-fourth wave length, Meanwhile, sensitive microphones areused or one and three-fourths wavelength, etc. to detect the sounds of the explosionswhen Can you decide why the cylinder cannot be they arrive at the ground, and differences one-half wave length or one wave length between arrival times are computedand long for resonance to occur? recorded electronically.
72 90-4, 1?-312 KILOMETERS /
50 G3 45 G2 SOUND 40 G1 RECORDING
BALLISTIC DOPPLER CAMERA EFFECT TRACKER
Schematic diagramof thegrenade- The tones are the voice of the satellite experiment system. Radar, ballistic camera, What do these tones from spacemean? and Doppler tracking systems are indicated. Whatisthesatellite"saying?" What Each individual system or combinationof languages does the satellite use? The systems suffices for the experiment.Sound satellites transmit their information back recording site is preferably located directly to earth by transmitting a specialkind of under the rocket trajectory. G1 , G2, G3, number called a binary number. We are and G12 indicate various altitudesof gre- all familiar with numbers which contain nade explosions. the numerals 0, 1, 2, 3, 4, 5, 6, 7, 8, and9. A binary number contains only 1 and 0 yet Figure 111-9 can be used to represent anynumber of items. The binary system is based on 2's instead Using the relationshipthatVelocity of 10's like our ordinary numeration sys- (V = tem.Here is a 7 place binary ilumeral equals Distance divided by Time 1(64) + D/T),distancebeing the difference in 1 1 1 1 1 1 1. It means: altitude between successive explosions, and 1(32)+ 1(16)+ 1(8) + 1(4)+ 1(2)+ time, the interval between recorded sounds, 1(1)= 127.Each place in a binary the velocity of sound within tl.k.)altitude numeral contains a digit which is twice the interval can be computed. value of the diet in (he previous place.In We have all heard the "beep-boop-beep" a binary numeral a (I) is used toindicate of Vanguard I, one of America's firstsatel- that the place is filled and a (0) is used to lites, Figure III-10. indicate that it is not. Binary numerals are
73 IX se Eli 1ID e catise any -value can be written 'Thususing onlythe 7 twodigit different binary numeral digits, (1 1010101 arid 0). means: 1(64) -I-0(.3 23 -1-1 (1 6) 1- 0(8) -I- write1 (4-) -1-the 0(2) binary-1(1) numeral = 8 5_ Flow for vv....11.11c1' 36? (Answer: you. 0(100100 2) 1- 0(1 = 1(3 ) = 2)36_ -I- Space 0(16) -vehicles 1- 0(8) 1-utilize1(4-) the 1- anybinary quantity. number Can system you which. write cana binary represent nu- meral7, 8, 9? for e1i of these:0, 1, 2, 3, 4, 5, 6, _Answer: 0 = 0(1) = 0 1=--- 1(1) = 1 10=1(2) -4-0 (1 ) =2 1 1=1(2) 1-1(1 ) =3 100=1(4-) -1-0(2) 0(1) ==4- 101=1(4-) 1-0(2) -i-1(1) =5 1 10=1(4-) -F1(2) -1-0(1) =6 1 1 1=1(4-) -1-1(2) 1 (1) =7 1000=1(8) 1-0(4-) -I-0(2)0(1)=8 1001--=1(8) -1-0(4-) -1-0(2) -I-1(1)=9
A. satellite ccnild send back infox-rnatiori in needed:.the binary system in any way that was transmittingA. satellite back may only transmit two airfeteritany number rtrusi- by cateal notes the digit or tones_ (1) andA. a high low note note could tne digitiiriai- binary(o). Beep, numeral Beep, 1 Boop 1 0 which could means stand for1(4) the represent1 2 0(1 si.,c ) or things 4 2 or 0be = the 6. digit'This 6aould in a eligitsbase ten 5 numeral-and 6 representing Flow could 56 yoii with send beps the aridWhen &coops? Mariner Think IV up passed others_ by Mars it sent lainarypictures numbers.. of the Martian. Mariner. landscape 1V's camera -using saw theferent Martian light landscapeintensities_ in _The'terms electronic of dif- equipmentpreted -various onboard light inteyisities the spacecraft as different inter- backnumbers to Earth. and them On transmittedEarth each each.number number was translatedpicture of backMars towas a light constructed_ intensity and the III-1 1_ Figure ) 1 61,i..., ,, oil f0., i'' 0Mo' 0.10,0**,00,o4iNnik114,', i, , ... .4 4 ,.,,..,6 ,,.....1,4 ...1 ,,, . 10.600146,,,Oliabillthitopoew AI *11,400,006,01,1 04,,,o0.4,61iiii0A0,14004,4,1014., I
1
) MOSAIC OF TIROS PHOTO9RAPHS
+41111.-- -4
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1011 SI
10
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WEATHER MAP, MAY 20, 1960, WITHTIROS CLOUD DATA Figure 111-1 2
helped to- develop models of theworld's weather.Before 1960, Satel blank regions over weather ...ns were limited,and weather Tiaps contained vast sparsely populated areas. oceans, deserts, and other Satellite) Weather Since April 1, 1960, NASA TIROS(Television Infra Red Observation satellites have enabled meteorologists toobtain photographs of large areasof Earth and therefore to deal with weather on ahemispheric or even global basis. TIROS photographs look much likethe cloud cover over Earth, but mustbe transferred to charts to produce a geometricmodel for detailed weather analyr,is. Figure 111-12 shows how TIROS Imade history by yielding datawhich related cloud patterns to weather. The top photographin Figure III-12 is a mosaic ofTIROS photographs covering about one-fourth of Earth'ssurface. The lower picture is of aweather map based on the mosaic. able to identify and locate areasof low pres- From this weather map, meteorologists are high pressure areas, H, with sure, L, indicating cloud coverand possibly precipitation, or clear skies and fair weather. He isalso able to locate weatherfronts, ahAILA4&. , cold fronts and, ilebtailhath , warm fronts.From the position of tlie front,he is able to esti- mate when the weather will changeat a given location.
.69 .41 STANDARD TIROS =MI /ORIENTATTN
6TH ORBIT
s
10T14 ORBIT =,
IBTH ORBIT
WHEELORIENTATION\
Figure 111-14 Another factor in the improved cover- age by TIROS IX was the position of its TV cameras. Earlier TIROS satellites had cameras on the base of the drum-shaped spacecraft.At times, when the base was turned away from Earth, the cameras looked into space. TIROS IX's cameras were Figure III-1 3 mounted on opposite sides of the drum. Asthesatene slowly"cartwheeled" through space, the cameras photographed To obtain more complete coverage of Earth as it came into view, Figure 111-13. Earth, TIROS IX,Figure111-13,was launched Jantr-4 22, 1965. The ninth in the TIROS series was the first satellite to ORBIT PLANE photograph the entire sunlit portion of PRECESSES EASTERLY WINTER Earth on a daily basis. APPROX 10 PER DAY SOLSTICE Early TIROS satellites were placed in an east-west orbit and were able to photo- graph only 25% of Earth's cloud cover per VERNAL AUTUMN day. TIROS IX was launched into a north- EQUINOX south orbit, Figure 111-1 4, and was able to EQUINOX provide total coverage due to the relation- 1,,SUN ship of the satellite's movement and Earth's 707/\ rotation. As the satellite orbits north- south, Earth rotates east-west under it. Also, TIROS IX was placed in almost a sun- synchronous orbit.That is to say, the normal westward drift of the orbit is the same as Earth's motion around the sun. SUMMER This placed the sun continuously opposite SOLStICE Earth and provided for constant and favor- ablelighting for the photographing of Earth, Figure 111-15. Figure 111-15
76 0 - uS, Ar-o-
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51i . -- , NOW Figure II1-1 6 From analysis of early weather models, meteorologists realized that accurate pre- diction and understanding of weather dy- namics could only result from more com- plete observations of greater areas of the globe which would have to be taken from greater altitudes above Earth-The two major techniques used to provide this in- formation are sounding rockets, Figure III- 1 6, and the TIROS, TOS, Nimbus, and ESSA meteorologicalsatellite programs. (The ESSAServices satellites Administration of the Environmental of the DepartmentScience of Commerce utilize TIROS technology on an operational basis.) Construction of meteorological models and weather charts requires mathematical data on cloud cover, atmospheric pressure, winds at various altitudes, temperature, and As far as exi moisture. mathematical These data can be secured by radiosonde radiosondeol stations which send .balloons aloft several geographical ii times daily. Each balloon carries equipment Eventually toprovide data on atmospheric wind, fined, but no pressure, temperature, and moisture.This servations an balloon technique secures a vertical sampl- ments arep. ing of the atmosphere up to about thirty materials, equ_ kilometers (1 8 miles) above the surface, niquesaret Figure III- 1 7. knowledge of 1
THE MEASURE OF OUR ATMOSPHERE "Explorer Flight Successful" -So read the aloft by these balloons could seldom achieve headlines in November 1935, referring to altitudes greater than about 30 kilometers the then amazing flight in which two men, (18 miles).Sounding rockets have been sealed in a metal gondola, flew a balloon to developed to help fill this void between the the astounding altitude of 72,395 feet _instrument carrying balloons and the orbit- (about 22 kilometers) and returned safely ing satellites, Frgure -Tlie sounding toEarth. In January, 1958, another rockets have been immensely valuable in "Explorer" flew succeisfully, this time 10 collecting information about our upper orbit Earth, at altitudes exceeding 1000 atmosphere. The sounding rockets are simi- miles (over 1,600 kilometers). The mission lar to those vehicles used in the exploration of both "Explorers" included "scientific of space, but are usually smaller.Their exploration of the upper atmosphere." altitude is limited so they do not depart Man's idea of "the upper atmosphere" from the environment of Earth which they changed in those 23 short years.This are designed to explore. chapter illustrates how scientists have de- The Earth and its atmosphere, Figure veloped ways to measure a now very near IV-4, can be thought,of as a "system." At and important part of space the atmos- Earth's surface, gases and other materials phere. are leaving the atmosphere to become part Until the development of powerful rock- of solid Earth.WIlat do you think hap- ets during World War II, almost all research pens to the materials which enter the of the upper atmosphere (Figure IV-2) was lower atmosphere from Earth? Some Will limited to observations which could be work their way into the upper atmosphere, made from the ground or by instruments and some substances in the upper atmos- carried by balloons.Instruments carried phere will move down into lower layers. Considerable "trading" has occurred be- tween the parts of the Earth-atmosphere 400 250 system. EXOSPHERE But what happens at the outer bounda- -riesoftheatmosphere? More trading occurs.Substances which once were part of solid Earth leave.New materials are - 200 captured from space to one day become 300 part of solid Earth, Figure IV-5. Studying the way these "trades" are being made (and have been made from Earth's be- 1.nning) could provide information about 5 Earth both now and at the time of its UJ formation. 200 In order to better, understand Earth today, we need to know when, where, and to what extent changes and events are taking place in the upper atmosphere. To do so requires the ability to 1.r...,ate and de- scribe phenomena as they occur. The concept of a "system" is important in science.Select a group of objects at MIDDLE random.Devise a system in which each -ATMOSPHERE object is an integral part of an operating 30 STRATOSPHERE system. For example a ruler, a protractor, be 1 0 _TROPOSPHERE 6 an art gum eraser, and a pencil could made into a "teeter-totter" lysterif, (Figure IV-6). A glass, some water and a cork Figure IV-2 stopper could produce another; pieces of wire, a socket, a dry cell, a switch, and a In addition to reporting present weather cell holder would be another. When the conditions, the purpose of the measure- various parts act together, we have a sys- ments is to note any trends or patterns tem. In a system, changes in one part, pro- that seem to be developing. When a pattern duce changes throughout the system. intheEarth-atmosphi-:Tesystemisde- Not all scientists carrying out research tected, it is possible to make certain pre- of the upper atmosphere are interestedin dictions as to what the weather is likely the same phenomena. Each experimenter to be in the near future. requires specific data, such as obtained To make these predictions, we must from a particular altitude, or c ciding rely upon the fact that the tropi. There sun, consists of gases which are free to. OW or with special events taking place on com- or tlined with passagesof a satellite over- move within the system under bined effect of all forces acting tux,them. head, Figure IV-7. Upper layers of the atmosphere cc, nsiq of Meteorologists ask: "What factors pres- gases which rest upon thelower '!ayers. ent in the upper atmosphereaffect the Changes taking place in the upper h. 3rs of weather?"In the troposphere, the lowest nearlyall the atmosphere may result in various 1;.rces layerof atmosphere where being exerted upon lower layers. weather is "made,' changes in temperature and pressure, wind speed and direction, The upper atmosphereis,therefore, humidity, precipitation and cloud cover studied because of its unique position with affect the system whic,(i we call our weather. respect to space. We need to know what KM Miles 350 ULTRA V!OL ET MEAN FREE PRESSURE PATH 500 X-RAYS 1012Atm -^300 X = 20 KM ELECTF ONS 0+ (He- H+) 400 250 10-liAtm LU LU 200 DIFFUSIVE 300 < 0 o SEPARATION TEMPERATURE Z 3x10-nAtm 0 150 X = 1 KM 34-(N0+042') 200 AURORAE 2x1010Atm NO+ 010+ 100 NO 0+ 1" Atm X = 10CM 100 41.11111111ralr PRIMARY 50 LYMAN a NIGHT GLOW N0+02+N2+00 NOCT! LUC ENT COSMIC R,1.YS C LOU DS4r4X METEORS (05) (NO5) 1III I Ef 0:N DARY 1500 103 104liI105 106 0 500 1000
EL EC TRONS/CC TEMPERATURE (° K) Figure IV-4
effects are produced by phenomena such as incoming solar radiation, solar wind, meteors and cosmic rays. These data may provide evidence related to phenomena ATMOSPHERE such as aurnra lair storms, and night s of upper atmos- 1 phere are subjected to many external and internal forces. They react to these forces accordingly. The nature and behavüor of gases near EARTH the surface of Earth las occupied the attention of a large nimplicr of scientists Figure IV-5 for a great many years. :Won recently, the necessity of understandimg the behavior of gases andfluidsat -Thealtitudes has occupied the attentionmf Race scientists. On July 17, 1929, Dr. Robert 11. Goddard was the first investigator to successfully launch a, scientific pay1ow3This first pay- load consisted of a barcarater, a thermom- eter and a camera. Figue IV-8 shows Dr. Goddanl, second from-le right, with col- leaves holding the rocl= used in the flight of April 19, 1932. At any given time.,a reasonable de- scription of the state Jok- a gas is provided Figurg by measuring three q-quantities; density,
83 Atomic hydrogen Weather satel I ites 400
Atomic oxygen \\\\ 300
Electron density (electron/cm ) / Auroral displays
200
Rockets
F laer.
02-0 + 0 100 N+0-.+10 N2N + N X15A3ii5c4r1 E layer
60
D layer
50 / 1 ---.= Meteor trolls1 250,000 ft. 1 I 40 200,000 ft. 0>02 I CH4 + +OH 1 Soaurncdeionugs bac kullodosnms 143,000 ft . 1-30 Ozone concentration (ozone/air molecules) edballoons 01,486 ft. 1 L2o 5x10-6 1.420-.-N2+ 03 1
N2 = 78.086/o 0 Everes, 10-7 0 .04% 0220.95% Mt ft: A = 0.93% 29,141
Composition Atmospheric ohenomena chemioe,I reactions and c-bservational tools Figure IV-8 temperature, and pressure.Difficulties in a. Make a mercurialbarometer. Record measuring the volume of the atmosphere a tmospheric pressurereadings in millimeters surrounding Earth are apparent. Since of mercury. density is closely related to volume, the b. Record air temperaturesin different substituted locations around your homeand school. measurement of density can be wood as an indirect methodin the measurement Select open, paved, grassy, shady, or, of volume. areas. Use a centigradescale thermometer. What shall we measure? We mustlearn c. Use an anemometerto record wind to measure (1) density, (2)temperature, speeds. Record data in kilometers perhour. and (3) pressure. Make measurements in differentlocations.. You have probably made many atmos- d. Record vane revolutions perminute of phericmeasurements suchas presscre, a Crookes radiometerplaced in different lo- temperature, cloud formations,precipiia- cations. Devise filter systems for usewhen tion, etc. The data that you have collected revolutions are too rapid to count. is similar to information obtainedfrom e. Take measurementswith a light meter scientific upper atmosphere measurements. and record values in footcandles.Use a Try this: During a one week periodmake solar cell with a voltmeter andrecord values a number of differentmeasurements in re- in millivolts. Compareresults. lation to Earth's atmosphere. Selectspecific Use a geiger counter and recordback- several f. times to make your' measurements ground "noise." hours apart three or four timeseach day. of determining cloud etc.to g. Devise methods Developcharts,graphs,tables, height, speed, and cloud types. record your observations. How manydif- (You h. Launch, helium balloons. Record ferent kinds of data can you gather? altitude will need a physics text and one for geom- direction, speed, rate of ascent and etry and to know how to use theindex.) when last visible. i.Use a radio to determine long-distance Include some of the following inaddition long to others you may devise. radio reception. Compare broadcast,
85 77 wave and short wave,bands. Use maps or a globe to showstation locations and distances in kilometers.List station fre- quency inkilocycles or megacycles per second. j. Determine what gaseousand solid particles are added to theatmosphere by automobile, industry, homes, etc. in your own community. k. Develop means ofdetermining visi- bility distance. 1. Use a simple method, sucnas that shown in Figure IV-9, toestimate air turbulence. Volume is the term used to describe an enclosed space.Stated in another way, volume is the measureof the amount of space enclosed withindefined boundaries. Volume has three dimensions,length, width ^ and depth or height. Units used to express volume are called "cubicunits," such as cubic inches or cubiccentimeters.The development of the measurementof volume from units of length is anintriguing story, and may provide some interestingreading for you. Measuring volumes of gases atthe surface of Earth is practical, for a gas maybe en- closed within containers offixed dimen- sions.Measuring volumes of gases highin the atmosphere presents newproblems. Gases in the atmosphere are notenclosed within containers, and theatmosphere itself may not havemeasurable boundaries. Fig- ures IV-10 and IV-11illustrate some of the difficulties of placing a package of measure- ment instruments into orbit.Figure IV-11 shows Explorer XIX fully inflatedwhereas Figure IV-10 shows the samesatellite packed intoitscanister and extending Figure IV-9 outward from the fourth stageof a Scout launch vehicle. One way to solve this problemis to of material present in a substance is called obtain samples of gases fromthe atmos- its mass, not its weight. phere. When samples are collectedhowever, Weight is often defined as the force of the volumes of the samples areprede- attraction which exists between a mass and termined by the sizes of containersused Earth.Mass remains the same for any for collection. Consequently,if all samples place. Your mass, your number of atoms, have identical volumes, someother unit of will be the same on the moon as on Earth. measurement must be used to compare However, since the moon's gravity is less weight them. than that of Earth, your moon A common method forcomparing one would be less than your Earth weight. sample with another is to measurethe Your weight on Earth will also vary atdif- amount of material in each. The amount ferent Earth loca..ions: the Equator, at the
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I varies directly with mass and inversely with volume. The principle is the same. Density is calculated by dividing the measure of mass by the measure of volume. When density is stated, units of measure must always be included. Thus, the density of the first sample of air would be stated as 0.031 g/m1., read as "zero point zero three one grams per milliliter" or 31 thousandths grams per milliliter."The mass of the second sample would be stated as 0.029 g/ml., read as "zero point zero two nine grams per milliliter,or g- "29 thousandths grams per milliliter." : - - Do you think these two samples of air could have been obtained from the same place at the same time? Give your reasons. If the second sample was obtained from a higher altitude than the first sample, what Fture IV-13 might you hypothesize about the nature of the atmosphere?Remember density de- creases as altitude increases. Defining our problem ab out the atmos- phere in another way, we say "density is a measure of the amount of material present r4- within a given space at a given time. ' Due to this fact we consider both volume and denSity to describe samples from the upper atmosphere.With this in mind, imagine that you are riding at a speed of 20 kilom- eters per hour in a motor boat, and you stick your hand up into the air.Imagine the push of air on your hand. Now imagine that you cautiously place your hand into the water alongside the boat as it continues to move at 20 kilometers per hour, (Figure IV-13). Compare the push on your hand made by water with the push made by air. Figure IV-14 Next imagine that you are an astronaut greater the resistance, the greater the density in a spacecraft orbiting around the earth of the material. at 17,500 mph. As you prepare to leave With your hand you made a crude your spacecraft to take a "walk in space," measurement of the density of air and you open the hatch and cautiously raise water. Your m6asurement was only to de- your hand (Figure IV-14).Imagine the termine which was greater or which was force you would feel on your hand and less. How can we refine this method compare it with the force from the water of measuring so that it will provide accurate and air.Which would you expect to be information about atmospheric density? most dense: Water, air or "empty" space? One group of scientists worked out the Least dense? Give your reasons. following system.Imagine a light hollow Answers to these questions can be made sphere being released from a sounding rocket on the basis of the amount of push or force at the very top of its trajectory, Figure IV- against your, hand due to resistance offered 15. As the sphere falls back to Earth, it must by substances through which your hand is pass through the atmosphere.Since the moving.The greater the density of the falling object is spherical, resistance of the material, the greater the resistance; or the atmosphere will always be directed against experiments above 30 kilometers.Space scientists determine atmospheric density by this method. Figures IV-17 and IV-18 are graphs NOSE CONE showing the results of one such experi- ment.Figure IV-17 shows the radar plots of GLASS CORDS of altitude and the computed rate descent for each altitude.Figure IV-18 gives atmospheric density calculatedfor SPHERE each rate of descent of the sphere. Use these two graphs as sources of in- formation to build a new graph as in Figure IV-19, showing the density of the RUBBER BANDS atmosphere compared to altitude.For SLING SHOT example, at 40 km the rate of descent is 40 mi/sec from Figure IV-17, and a rateof OUTEA CYLINDER descent of 40 m/sec indicates a density of BLASI= r-IP alL4 4.0 pn/m3 from Figure IV-18.So on
INSTRUPIENTT CnMPAIRITMENT Figure IV-19,at altitude 40 km, plot density as 4.0 gm/m3 .Secures graph paper as in Figure IV-19 and continueto plot the Figure IV-I5 other values and then connect your plotted points with a smoothly curved Erie. The completed graph wir show the
,* density of the atmosphere as it was meas- ured to be on a particular day. Many such measurements must be made from a number of different locations before a complete picture of the density of the atmosphere can be well known. Use the graph you have constructed. Figure IV-19 to determine the density of the atmosphere at an altitude of 50km.; 55 km.; 65 km.
90 85 Figure IV-16 80 an equal amount of surface area. The rate 75 at which the sphere falls depends upon the 70 resistance of the air it is falling through. 2, L The amount of resistance depend§ upon = " density of the air. t3'60 Therefore, the rate of descent can be used to indirectly measure air density at 50 various altitudes. Radar measurements pro- < vide continuous information about the rate 45 at which the sphere is descending. Addi- 40 tional data from this method include the sideward motion of the sphere during the free fall which in turn provides information 60 100 140 180 220 260 concerning wind speed and direction in the RATE OF DESCENT M/sec upper levels of the atmosphere.Figure IV-16 illustrates a type of sphere used for Figure IV-17 investigate? How would the lack of ground 8 .0 stations for radar; telemetry; allowances 7.5 for probable mass of Mars; andunknown 7.0 Martian winds influence your thinking? 6 .5 Remember all you have learned about the 6 .0 measurement of gases. by 5 .5 The density of a gas is influenced temperature.Temperature is something 5 .0 all of us have learned about intuitivelyin 4.5 much the same way we have learnedabout 4.0 tAghtness of light, shadings of color,loud- 3.5 nemf sound, or smoothness of texture. 3.0 Altheigh we can "feel" temperature, we ;need o kncot- about its measure. 2.5 If ,mked to describe what is meant_ by 2.0 treammaturc, a common answer is, "rain- 1.5 pera.L1we is tow hot or howcold something 1.0 is."Uhis innnlies that an entire range of temp,-ratures must exist. Cool, warm, icy, .5 5aripor, lukewarm, balmy, hot, Or cold are 0 o 40 80 120 160 200 240 biat Ai few wards used to express tempera- tuses "These words are descriptive -they RATE OF DESCENT Mbec descfite how the temperature of an object Figure IV-18 "eeis." A temperature value could be assigned to =reach term.Using the proper 8.0MINIM 11111111111111111111IIII 7.5 term,itis possible to communicate to 7.0IMMI11111111111111111111111111111111 someone else the description orvalue of 6.5111111111111111111111101111111111111111 the temperature which a certainobject 6.011111111111111111111111111111111111111 possesses. 5.51111111111111I111111111111111=1111111 Use Figure IV-20 to develop a scale of IHNI1111111111111111111=111111111I 5.0 descriptive terms. AA others you know to 0 4.5 prepare similar lists.Compare lists.Par- 4.01111111011111111111111011111111111111111 111111111111111111111111111111 ticularly notice words used within specific 3.5 temperature ranges. If others are asked to 2 3.0111111111111111=111111111111111111111 describe or place a value on this same 2.5 111111110111111111111111111111111111111111 temperature, a major weakness of thescale 2.0 scale is 1.511111111111111111111111111111111111111 becomes apparent. A descriptive 1.0111111111111111111111111111111111111111 subjective - a pers6nal estimate of judg- .5111111111111111111111111111111MMIN ment or opinion is required byeach person using it. Prove this subjectiveness to your- 0 10 20 30 40 50 60 7080 self very quickly. Listen to the comments ALTITUDE IN KM of your classmates as they describethe temperature of outer space, or thesurface Figure IV-19 of the sun, ,or the heat shield of a space- craft as it re-enters.the atmosphere,Figure gm/rn IV-21. Words chosen to describe tempera- You should find 1.1 gm/rn3, 0.60 tures vary from person to person.We soon and 0.21 gm/re . know that we cannot adequatelydescribe Imagine you are a scientist working on a temperatureswithoutusingnumerical project concerned with the study ofthe values to describe the measure of"hot," atmosphere of Mars, and entrusted with designing an experiment to measuredensity "cold," "warm," etc. of the Martian atmosphere. From what you Describing temperature with numerical know about the Martian atmosphere,what values rather than words has interesting changes or modification in the spheredrop possibilities.It is possible to express a metiod of measuring densitymight you _greater sange and variety of temperatures. Each numeral has a fixed value while the turethe fo_ is value of a wolci depends upcm judgment somett of the user.If temperatures can be ex- eter rr: pressed. as numerals, then instead of esti- mornel mates,Temperatures temperatures are can measured be measured. with tiler- merals It may seem that to measure therrnc themometers. temperature of the upper atmosphere, expres mometer,itis only andnecessary the temperature to send up would a ther- be usedmean? ti expressed as a numerical value, Figure IV- atmosl 22_ Unfortunately, all is not that simple. To To understand why, we must find answers to value c scale 1,76 parentfor m overIf 0tl seari ng ofthe theba_ standthe "t hot that
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ba I my
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cool
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cy
_Figure IV-20
OR .1'604044400440g111141010404001K 000.116,01,14, , /,,,,h114,/,11101140,1I10fihilA , , h..011,0.44{1, 1.0,44 N.4000114004404birre41'.1414110004441410010411640MW0041.,
a am . .ill,.Ati ..11111a1) balloon will become partially inflated as shown in Figure IV-24a. The circumference of the balloon can be measured with a piece of string as shown in Figure IV-24b. Finally, if the bottle-balloon system is removed from the pan of warm water and allowed to cool, the balloon will slowly collapse to a position similar to its originalposition as in Figure IV-7.3.Could the air in the bottle change --olume during this activity? What evidence :supports your answer? Sup- pose the bottle-balloon system wereplaced
Figure IV-23
"r/ in the refrigerator c you wedict what might happen? Consider these queons: How can you check the accuracy ,;!. your Trediction? How %Pas a temperatame change converted into al number? Pill a bottle Vo the tri3 with water. Add a ft w drops of food cc.ioring to make the watex easier to observt,. Sellect a one-hole stopper of the ritht sice to fit tightly into the bottle. A piece ot f glass tubing about 12-15 cm long is pushatit throzgh the hole in the stopper so that itiprojects out of the bottom of the stopper ilbout 2 cm (Figure IV-25).Use exttremn care in pushing the glass tubing through law, stopper. To avoid injury or breakage, do mot force the tubing through the stopper. (A small amount of soapy water, or glycerine may be used to lubricate the stopper ansd tubing so that the tubing will slide more ea;sil3r.) The stopper is fitted tightly into the mouth of the bottle.luld forced down slightly so that some wr,ter isJ, displaced up into the glass tubing (Figure IV-26). The poSition of the water in the tubing can be marked With a grease pencil- or a small piece of masking tape. After the bottle has been transferred to a pan of water quite warm to the touch, the system is observed For. changes. 3 to 5
Figure IV-24b
'10
Figura:IV-26 iliinutes later, the position of the liquid in carry out this activity, useextreme care the tube will be higher than the original with open flames.Never allow any part kLosition as illustrated by Figure IV-27. of your body or portion of your clothing This change in position may be measured to come close to a flame.Girls must be Mth a ruler. especially careful with their hair.) 14eXt, the bottle is removed from the pan If the vertical height of the weight is now of warm water and allowed to cool. The measured it shows the weight is lower than Water in the tubing may not return to its its original position.Next heat a larger Qriginal position. portion of the wire by moving the flame jf it should not, could you offer a pos- back and forth along it slowly. Again, the sible explanation?Did the water change height of the weight above the table top is Itolume in this activity?How was the measured. What do you predict about this teoperature change converted into a num- measurement? ber? Remember what we have discussed so If the wire is allowed to cool, and the far about density. height of the weight is measured, how do We can also use a measure of the physical you predict this measurement will compare Droperties of wire to measure temperature. with the original measurement? Be very Take a piece of fine wire (about B & S gauge *24 or #26). About 50 cm of the wire is kisPended horizontally between two firmly fixed supports, but not tightly stretched, i$11re IV-28. A weight, such as a small Jlaice can filled with water or sand is sus- Dended from the wire so -that the weight Swings freely. The vertical distance from the table surface to the bottom of the Weight is measured with a ruler (Figure A portion of the wire is then heated tising a small flame from a candle, alcohol Figure IV-28 lainp or small burner.(Caution:If you
r
Figure IV-27 Rgure IV-29 sion or contraction is related to the amount of temperature change, so not only can temperature changes be detected, but the amount of change can be measured. Per- haps you can think of some ways to use each piece of equipment just described as a thermometer to measure temperature? What advantages or disadvantages will each have? How might these thermometers be improved? Perhaps *the most common therms:it-fie- ters are those constructed of a glass tube filled with a liquid, usually alcohol or mercu- ry, Figure IV-30. Most of the liquid is con- tained in a bulb attached to one end of a long stem. A very fine opening, called a ca-Pillary tube extends down the center of the long stem. When the liquid expands, itis Figure IV-30 "pushed down" the capillary, and_ when cooled it contracts and is "pulled" back careful when you answer the next question. into the bulb.The total volume of the Consider the evidence you have available. capillaryisso small, that a very small Did the wire change volume during this change in the volume of the liquid pro- activity? duces a large displacement in the position Although generalizing from a small num- of the liquid in the capillary. In this way ber of observations can be dangerous, it small changes of temperature can be de- appears that a relationship has been dis- tected, but since the stem is usually long, covered.It appears that matter expands these changes can be detected over a large when warmed and contracts when cooled. range of temperatures. The danger of generalizing from so few Refinement and miniaturization of the observations will become very apparent if instruments you have just investigated en- you substitute a long rubber band for the able scientists of our space age to find out wire, or cool the water down to freezing. a great deal about the upper atmosphere It also appears that the amount of expan- without actually going there.
96 Chapter V WHAT LIGHT CAN TELL US
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(1141041i44° 004 /16i411C)06'M°04 40f7) 0 e iJ004 11(1 tt°14114>10>4°4i 4$ t1)11004"1'40004°Xor-'00t 00(tiorelte:tiPiti) M 1001:1+4 tH00e00m4" m000000m dM Od 4fi 6,40P0 clOczA -Wov oom 0.,04-)1740"4' c114 0000o4 >)1) co,i9414400,-400 nit 4) " 64* :r-iin0 01' cd (el., ,?4>4.4dtio (1:400g40 "w' C4000.,0 t,'14:k004'0 c:1(1441.004A>k') 0,7100,g ,111 1111111111 11 1,11 11 11 1 11 11 1 1 1 1 11' 1 11111111 111 111L111 1111 1 .111 1 1 1 III 1 III 1 IV! VI 111 11 1 i 1 1 11 1 11 1111 1 i 111'11 11 1 11 1 i ;I 11 II 1 1111 11111 111 Ill 11' 1 1 11 11 I II I II 1 III 10,, III hil ' I 11. 1 1'1' 1 ii, '1,1111 I 1111 I 1 .11 I I 1 I 1,11,11111,1 1 1 111111 III I I I 111 I III I 1111 1111 l' 11 1111111111L I . I I 1 11 I 1111 101, I 11 I 1 11111111'1111111,11111 I i 11 11 I 1 111 1111111111ii,"hill'illirllij1111 1 I 11 1,111111111, ill I 111,1111111 111 II' 1 1 II H '. 1 ill li 11111 II 1111 11.1111 1111 I 11 ,,1 11 111,1,,11,111,11 lil 11111,,,,11111111,1 1 11,-111 .111111.111111,111 11 1 1 1 11111 ' 1 1 1 1 1 1 1 1 11 1 II 1 ri 1.111,11 .111 I 111 1 I ,101 1, II 11 I I, 11 1V!,1311 the height of something as tall as Saturn V, Figure V-3. You could climb to the top of -741171 the gantry and measure one tape length at a time until you got down, but this would be Fox difficult. It would probably be better and Asa._ easier to measure this larger distance in- directly. Space science had its start far back in the misty beginnings of human history. Ancient man stood alone under the splen- did twinkling of the night sky and he won- dered. The questions that came to his mind, stirring his curiousity, are similar to the thoughts you would have today. Questions about stars come to mind easily. How far away are they? What are they? Theseand Figure V-5 all the other questions can be answered only if we measure.But what is there about a spectrum. We get nothing elsejust bright- star that you can possibly measure? ness, position, and spectrum, FigureV-5. The invention and development of the The unequal brightness of the stars is telescope has not changed what we can easily seen by anyone who looks at the measure. Even with the 200 inch Mt. night sky.The luminosities have great Palomar light-collector, we still measure the range. Some stars are so brilliant thatthey brightness and position of stars to obtain catch our eye immediately. Others are so the fundamental measurements necessary dim that they are barely spots in the dark- to describe space and its content& In addi- ness, Figure V-6. Between these extremes tion to these two measurements, by 1800, we find all the other possibledegrees of space scientists learned how to make the brightness. light from a star give off a rainbow its About 1800 years ago Claudius Ptolemy organized a book that listed the brightness of every star visible to the ancient astrono- mers. The brightness of a star as seen by the unaided eye was called the magnitude of the star.Long before Ptolemy, it had been accepted that the brightness of a star would be classified as one of 6 different magnitudes. A first magnitude star would be extremely bright. About 20 stars were bright enough to be rated 1st magnitude. A star dimmer than1st magnitude had a higher number such as 2nd, 3rd, 41111 or 5th magnitude.Finally the stars that were barely visible were called 6th magnitude. When telescopes came into common use, the system of magnitudes had to be ex- tended, for now astronomers were able to see many stars dimmer than the6th magnitude. Astronomers however were faced with a problem. They had to figure out jue: what 7th magnitude would be. How much dim- mer than 6th magnitude would a 7th mag- nitude star be?In order to do this, the difference between the brightness of any of the other magnitudes had to be measured. Are all stars of the same brightness? If they are then the apparent differences in brightness are caused by differences in the distance between the stars and Earth. Close stars would be bright and far away stars would be dim. It could also be that all stars are the same distance from Earth, and their dif- ference in brightness is caused by their chemical make-up. For a long time man did not know why some stars appear brighter than others. The answer came by studying the position of the stars, and their spectra. Figure V-6 Stars are moving all the time. If you go out and look at the night sky and then 260 look again an hour later, you will see that the stars have moved. We know that this 240 apparent movement is caused by the rota- tion of Earth. 220 The patterns of the stars, the constella- fze,t tions, appear to stay the same. For this 200 reasonthestarsaresometimes called "fixed."In Ptolemy's book "The Alma- F 180 gest," he had recorded the position of the fixed stars.This was done by measuring 160 vl4 angles. When we look at the night sky it ap- 140 pears that we are standing at the center of Z a black dome which we call the celestial < 120 sphere. Since it does appear to be a sphere
cre we can measure position using angles. Lei 100 In order to use angular measurement you must choose a starting point. In estab- 80 lishing latitudes and longitudes to measure position on Earth, the Equator and the 60 Prime Meridian have been chosen as start- ing points.Similarly, the extension of 40 Earth's equator on to the sky was chosen as one starting point. Any star on this line 20 would be on the celestial equator (Figure V-8). 3 4 The position of any star can be partially MA GN IT UDE described by measuring the angle from the Figure V-7 celestial equator to the star, as seen from Earth.The name given to this measure- In 1856 Pogson determined that this differ- ment is declination. Since declination can ence Was 2.5. So a first magnitude star was be above or below the celestial equator, it about 2.5 times brighter than a second is called North (÷) declination or South () magnitude star. A 1st magnitude star would declination (Figure V-9).But declination be 2.5 X 2.5 or 6.3 times brighter than a does not do the whole job.If a star is 3rd magnitude star. Use Figure V-7 to de- found at25° South () declination, it termine how much brighter than a 7th could be anywhere on the dashed circle magnitude star a 3rd magnitude star is. shown in Figure V-9. NORTH CELESHAL CELESTIAL POLE NORTH POLE SPHERE
HOUR CIRCLE Figure V-8 Figure V-10 450 NORTH CELESTIAL DECLINATION NORTH NORTH POLE CELESTIAL POLE TERRESTR I AL NORTH POLECELESTIAL DECLINATION CIRCLES (NORTH) TERRESTR I AL EQUATOR CELESTIAL EQUATOR CELESTIAL OUR CIRCLE TERRESTR I AL MERIDIANS TERRESTR I AL LATITUDE (SOUTH) Figure V-11 25° SOUTH DECLINATION meridians or lines of longitude. Celestial parallels of declination correspond to ter- Figure V-9 restrial (earth) latitude. If you imagine Figure V-10 sliced in A second reference line is employed to half at the celestial equator, you have space locate star position. This is done by divid- cut up like an orange (Figure V-12). When ing the celestial sphere into hour circles as this is done, we are able to measure angles shown hi Figure V-10. around the celestial equator. But we need Combining these two systems of imagi- a starting pomt for space measurements just nary lines on thk., celestial sphere (Figure as we need the Prime Meridian for terres- V711), the hour circles correspond to earth trial measurement.Astronomers selected the place where the sun appears to cross CELESTIAL EQUATOR the celestial equator OA its trip North. There are two days each year when the sun is directly over the equator.These days are called equinoxes because the hours of daylight (12) and the hours of darkness (12) are equal. The equinox that marks the beginniag of Northern hemisphere Spring occurs when the sun crosses the celestial equator on its way North (Figure V-13). This point is called the vernal equinox and is used as a beginning place in measuring angles eastward along the celestial equator (Figure V-14). These angles are called right ascension and are measured from the vernal equinox to the point where the hem- circle Figure V-12 of a star intersects the celestial equator. Right ascension angles, for convenience in astronomical measurement by clocks, are also expressed by hours, minutes and sec- onds. Thus, a right ascension coordinate of- 15° would be one hour )f time. RIGHT ASCENSION DECLINATION
ALDEBARAN 60.5°(4h 34') 16°26' NORTH ELESTIAO RIGEL 75.2°(5h 13') 8°14' SOUTH BETELGEUSE 75.9°(5h 53') 7°24' NORTH CASTOR 105.5°(7h 32') 31°58' NORTH MERAK 165° (11 h 00')56°34' NORTH
Figure V-.1.5
We find, then, that the position of a star can be described by giving twoangles. These angles are called right' ascension and declination. The position of some well known stars is given in Figure V-15.In 1718 Halley discovered that the positions of the "fixed' stars were not fixed. He found that positions of stars had changed. They oh were not in the places given inPtolemy's Almagest. This opened a new age in astron- omy.Within 20 years, the distance to a star was measured. The light from stars can also tell us much. If we analyze it we have some idea of the composition of a star, what it is made of. When we notice the beauty of a rainbow, sunlight falling on raindrops, we are really seeing light broken into a spec- trum. When light passes through triangular shaped glass, the light is broken up into a Figure V-14 spectrum.Isaac Newton was the first to over two inches.The box can be any depth more than this. The box should also be about twice as long as it is wide. A shoe-box usually does a fine job.
SLIT SCALE
RAZOR BLADES
Figure V-16 REPLICA GRATING investigate this. No matter how this is done, (INSIDE) the spectra are always in the same order: red, orange, yellow, green, blue, and violet. You can investigate this "rainbow" if yon have a glass prism (Figure V-16). Bet- ter still, you can make a simple spectroscope in just a few minutes if you follow the di- rections below. With a spectroscope you can examine spectra of incandescent lights,, VIEWING fluorescent lights, sunlight, or other light HOLE sources. The principle .behind the formation o6 spectra is best explained by imagining that light has properties similar to waves on Figure V-17 water.When waves come from different sources, they interfere with each other. Cut a slit in the far left side of the nar- Sometimes the light waves add together and row end of the box. The position of the make, bright bands. At other locations they slit is shown in Figure V-17. The slit should subtract from each other, producing bands be about 1/8 inch wide and 1 inch high. of darkness.This is what happens when Fasten the razor blades so the slit is very light goes through a replica diffraction narrow, less than 1/32 inch if possible. grating. The two edges must be parallel. It is one thing to read about spectra. It Cut a circular hole about % inch in is far better to see one for yourself. A diameter in the near left corner.Make spectrometer can be made easily.Here is sure that the center of the hole is on a what you need: straight line with the slit at the other end. 1. Replica diffraction gratingThis is Now cover the eye hole with the replica what makes the spectrometer work. diffraction gratMg.Before you tape the If you cannot get one in school, they grating in place be sure you have it posi- can be purchased from scientific tioned properly.The rulings should be supply houses for about 250, or vr,tical. Make sure you can see a spectrum. borrow one from a physics teacher. Put the top on the box. 2. Razor blades. A double-edge blade At this point you have a spectroscope. can be broken in half so that the If you look in the eyehole, and point the two edges can be used. For safety slit at a light source, you will see a spec- reasons you may prefer to use two trum off to the right. But all you can 6) single-edge blades. at this point is look. If you want to be able 3. Cardboard box.It must come with to measure, you need a scale.You can .a removable top. The box has to be make a scale on any piece of white paper. deep enough to hold your diffraction. . Mark the paper at the distances shown in grating. This is probably a little Figure V-18. If your spectrometer is o'T blend into each other. By definition, the colors are divided at the following SLIT places on your scale: t Violet less than 4,500 Blue 4,500 to 5,000 Green 5,000 to 5,700 Yellow 5,700 to 5,900 Orange5,900 to 6,100 A Red more than 6,100 A Place a piece of red cellophane in front of the slit.Notice if any of the colors are absorbed.Try other colors of cellophane, or colored glass. In each case, compare the color of the absorber and the colors trans- mitted. 2. Look at a flourescent light. Notice the bright lines on the spectrum. Notice the scale positiom. LoRk for bright green at about 5,000 A., and yellow about 5,800 A. 3. Burn some salt in a gas flame in a dark room. Look at the spectrum. This time you get no rainbow, in- stead 3r,pu see a bright yellow line at 5,900 A. In Igil4 Joseph Fraunhoffer was using an improved version of the spectrometer. When he looked at sunlight, he discovered that the entire spectrum was marked by hundreds of black lines. Some were darker than others. He made a map of these lines as shown in Figure V-19. If you are inter- estedinspectra and the abbreviations shown below get yourself a good physics book and a chemistry book and read about larger, copy Figure V-18.Cut this out them and extend the lines until they "reach your Did you see these lines when you looked scale.Then mark off ygur scale 4000, atsunlight through your spectroscope? 5000, 6000, and 7000 A. Remember No. Try, this technique. that we measure lightspectra in ang- Take your spectrometer and fasten a stromsthe different wavelengths of light piece of wax paper over the slitlhe pre- give us different colors.One angstrom is cautions given here are necessary.Under 0.00000001 centimeters (Chapter II).It no condition should you point the slit of may be too dark inside the box to see the your spectrometer directly at the sun. scale.If this is true, cut a small rectangular Instead, place a piece of plate glass on top opening, in the top of the box.This of a sheet of black paper.Line up the opening is cut above the scale. Now you glass so that the image of the sun reflects are ready to use your spectrometer. from the surface. Now look at the image 1. Allow light to enter the slit.BE of the sun on the glass. You will probably CAREFUL. DO NOT LOOK AT see two kinds of black lines.Some run THE SUN. DO NOT ALLOW THE horizontally through the entire spectrum. IMAGE OF T.HE SUN TO BE IN These are to be ignored. They are caused THE SLIT. Look at the spectrum on by the uneveness of the razor blades in the your scale. Examine it.Notice the slit.The vertical black lines are the ones order of the colors.Notice if they that made Fraunhofer famous. The darkest HYDROGEN VONIZED Co Hy Fe Hy(4C H) HYDROGEN MAG.+IRON SODIUM IRONI OXYGEN OXYGEN
V OLE.7 BLUE GREEN YELLOW RED ORANIGE Figure V-19
Ftgure V-20 Figure V-21 and clearest should be found in the yellow For example, when sunlight falls on a and in the area where green becomes blue. picket fence, the fence slats absorb light It took50years for human minds to figure from the sun.We say "the slats cast a out what caused These black lines. shadow" (Figure V-21).In a way, the The sun is a sphcrc of hot gases sur- elements in the atmosphere of the sun act rounded by a layer of cookr gases.The like the slats in the fence. They absorb surface of the sun, the part we can see, light and make "shadows."But there is gives off the entire spectrum of light. We something ver- special about the shadows. know that if we blotout the disc of the sun, When light strikes a wood slat, none of the we can see a layer that glows. Thishappens visible light goes through the wood. But naturally during a solar eclipse, Figure V- when the light of the sun passes through 20. This outer layer of gases is part of the the solar atmosphere, the gases only stop sun's atmosphere.It is cooler than the certain regions of the spectrum, causing surface.If it was hotter than the sun's the black lines as in Figure V-19. surface, we would always see the atmos- Why areonlycertaincoloredlines phere, not just during an eclipse. The dif- stopped by the atmosphere of the sun? ferent elements found in the cooler atmos- The answer has to do with the nature of phere of the sun cause ate black lines in the atoms and the arrangement of their protons, solar spectrum by absorbing some of the neutrons, and esnecially the electrons. We colors radiated from the sun's surface. represent atoms with drawings like Figure through your spectromeler you mayob- serve a &it line at 5900A. This time the electrons are absorbing ELECTRON energy- from the light of thebulb,. Sodium IN electrons are gaining energy ..and moving ORBIT away from the nucleus.This miorion is the exact opposite of the fall-in 'ictot gaveoff the yellowlight.It takes in, cr- absorbs. the NUCLEUS yellow 1igh. leaving black limes. Theblack lines in surifight that FraurthoYter first no- 0 ticed are cansed the same way. In 1859 Bunsen (he also iitmented the burner) and Kirchhoff discovered that each different eement gives off its ovn special colors of & spectrum. No two substances have the same absorption. Tley allhave their own set of spectral "shadows." Spec- tra are as good to identify elements as finger prinEs are to identify peaple. They Figure V-22 are all diffezent. By studying the Fraunirnf= lines in sunlight, astronomers have fount. 67 ofthe V-22. This is a model of the hydrogen at- 103 elements we find on Eartii on the sun. om.The electron is in orbit around the But the sun is not the only s5tza. withab- proton in the nucleus. The electronremains sorption lines in its spectrum, . We can use the same distance from the nucleus, just as the same methods to obtain the chemical Earth stays about the same distance from stars which yield a the sun.But what would happen to the coMposition of all size of Earth's orbit if Earth received more spectrum. energy? It would be larger.If an electron We have seen that the only direct received energy, it moves away from th-e- measurements we can make in space are it those that describe the position, thebright- nucleus. If an electron loses energy, of a star. In Shapes moves toward the nucleus.Electrons can ness, and the spectrum giving of Tomorrow of this series, you can see gain or lose energy by absorbing or how we use these direct measurementsto off light. make indirect meaairements describingthe In the experiments with the spectrom- distance to stars and their temperatures. eter, you observed the spectrum givenoff by heated salt. A bright yellow line was present.This line, which isreally two lines close together, is caused by the elec- trons of the sodium atom losing energy and falling closer to the nucleus. The rea- son that sodium when heated has adifferent spectrum than any other substance is that Yellow Orange Red no other atom has the samenumber of electrons in the same orbits as the sodium atom. So only the electrons of sodium can make the moves that give off this array of bright lines shown in Figure V-23. Use the same set-up that producedthe bright yellow sodium line.Burn salt and obsern the bright yellow line at about Figure V-23, A continuous spe4.trum at the top. 5900 A on your scale. Now place a200 A bright line spectrum of sodium below. The watt light one or two feet behind your double line of the sodium atom falls in theyellow burning salt.This time when you look region at about 5,800 A wavelength. TO THE FUTURE A Special Word for the Student
Wait!15k...fore we close, let's pick up and Think of the project group which has dust ei-lf the heart clock we so quickly and worked for 2, 3, or more years in order to catektsdy discardeta. And once more set it bring all the experiments and components upon the table next to the International together for this instant. Standards, which are so unbelieveably.pre- We could also think of the experts of cise they can calibrate our new measuring the world-wide tracking networks ready instruments. Look at it pulsating next to and waiting for the first "beep" of the the gleaming platinum meter so accurate signaling satellite.We may think of the that fit can measuze the wavelength of the stress engineer, who analyzed, reduceo, and orzin-red line of Krypton 86, and next to rebuilt each supporting structure to toler- the mysterious atomic clock whose vibra- ances only the computer could predict; the ting =ystals can measure time to the nano draftsman who designed; the engineer who secorad. (1 CO ) seconds. Take another look tested; the mathematician who calculated; at OUT meart clock that speeds up at times the machinist who drilled and ground; the of stress and slows down during periods of optician who calibrated the lenses; and the rest.Perhaps, in a way, it represents the secretary who filed and typed; these are energy, the work, and the minds of the men the People who made this all possible and and women who created these very accurate whose hearts speed up a little at the ap- instruments for measuring distances and proach of the launch window.Listen times th,..t we cannot ever hope to experi- carefully to the sounds of outer space, ence or "feel." listen to the countdown of Freedom 7, and Next time you sit in front of the tele- the launch of America's first man to orbit vision set and watch the launching of a Earth. In the midst of whirling corn-pullers, Space vehicle, just for a second think of spinning tapes, and crackling intercoms, we our heart clock. As the background voice hear and "feel" the quickening Pulse of the calls out; 5, 4, 3, 2, 1 Ignition Lift human heart. off, "all systems go," and finally "condi- Look up and see Echo, Tiros, Apollo, tions nominal, we have another successful OGO, and many other space explorers as space flight."Instead of thinking only brilliant points in the starry field, announc- about the flash of flame, the billowing ing the achievements and hopes of the clouds of smoke, and the arching beauty of human mind. the gleaming rocket soaring across the sky, No, our International Heart Clock is not give a thought to the people who have a worthless standard._ It represents Man in worked years to make this launch a success. the Space Agenow ending its first decade.
The material as presented in this publication is representative of the judgments of the authors and does not express the official policy of the Department of Health, Education andWelfare. GLOSSARY OF SPACE RELATED TERMS A Atomic Clock A precision clock that de- pends for its operation on an electrical AbsorptionThe process in which incident oscillator (as a quartz crustal) regulated electromagnetic radiation is retained by a by the natural vibration frequencies of an substance. atomic system (as a beam of cesium atoms Absorption Lines The pattern of dark or ammonia molecules). spectral lines against the background of a Axis (pl. axes) 1. A straight line about bright continuous spectrum: produced by which a body rotates, or around which a a cooler gas absorbing energy ftom a plane figure may rotate to produce a hotter source behind it. solid; a line of symmetry.2. One of a Altitude The height of a position or set of reference lines for certain systems object above sea level:(of a star) the of coordinates. angle from the horizon to a star measured along a vertical circle. Anemometer A weather instrument used to measure wind speed. Babylonia An ancient empire in SW Angle The intersection of two lines with Asia, in the lower Euphrates valley. The a common end point. period of greatness, 2800 BC to 1750 Anjstrom (A) .1. unit of length, used BC. chiefly in expressing short wavelengths, Barometer A common instrument used 10-8 centimeters. to measure the pressure exerted by the Aphelion That orbital point farthest earth's atmosphere. Includes the mercury from the sun when the sun is the center and aneroid barometers. of attraction. That point nearest the sun Brightness A measure of the luminosity is called "perihelion. 'The aphelion of of a body. the earth is 1.520 x 10" cm from the Bunsen, Robert Wilhelm 1811 - 99. A sun. German chemist. Apogee In an orbit about the earth, the point at which the satellite is farthest from theearth; thehighestaltitude Camera AngleA major characteristic of a reached by a sounding rocket. camera that limits the view of a particular Astronomical Unit (abbr AU) In the camera by a predetermined setting. astronomical system of measures, a unit of length usually defined as the distance Celestial Equator The great circle on the from the Earth to the Sun, approximately celestialsphere midway between the 92,900,000 statute miles or 14,960,000 celestial poles. kilometers.It is more precisely defmed Clepsydra A device for measuring time as the unit of distance in terms of which, by the regulated flow of water or mercury in Kepler's Third Law, n2 a3 = k2 (1 + m), through a small.opening. the semimajor axis a of an elliptical orbit CompressionThe half of a sound wave in must be expressed in, order that the mi- which air or medium is compressed to merical value of thc...-Gaussian constant, greater than its normal density. k, may be exactly 0.01720209895 when the unit of time is the ephemeris day. In astronomical units, the mean dis- tance of the Earth from the Sun, calcu- Declination The angular distance of an lated from the observed mean motion n object north or south of the celestial and adopted mass m is 1.00000003. equator and measured in degrees along Atmosphere The envelope of air sur- the object's hour circle. rounding the earth; also the body of gases Degree A unit on a suggested scale of surrounding or comprising any planet or measurement. Used to describe the other celestial body. measurement of temperature, time, dis- AtomThe smallest particle of an element tance, and angles. that exhibits the properties of the ele- Density The mass of a substance per ment. unit volume. Diffraction Grating A metal or plastic plate containing ruled parallel lines used Foucault, Jean Bernard Leon 1819 - 68, to bend or spread light wavesafter the French Physicist. light has passed through a narrow slit in Fraunhofer, Joseph von 1787 - 1826, an opaque body. German optician and physicist. Fraunhofer Lines Dark lines crossing the continuous spectrum of the sun or simila: source. The lines result fromthe absorp- Eccentricity The amount by which a tion of some wavelengths by layersof figure deviates from a circularform, as an cooler gases. orbit. Freedom 7 The first American manned Echo-I A large plastic balloon with a space flight. Piloted by AlanB. Shepard diameter of 100 feet launched on August on May 5, 1961. Thissuborbital mission 12, 1960 by the United States andin- lasted 19 minutes and reached an altitude flated in orbit. It was launched as a pas- of 116 miles. sive communications satellite, toreflect Frequency The number of waves leaving microwaves from a transmitter to a re- or arriving at a position perunit of time. ceiver beyond the horizon. Friction The force that resists the sliding or motion of one objectin contact with Ecliptic The apparent annual path of the sun among the stars; theintersection of another. the plane of the earth's orbit withthe celestial sphere. This is a great circle of thecelestial sphere inclined at an angle ofabout Galileo1564 - 1642, Italian physicist and 23°27' to the celestial equator. a stronomer. Geiger Counter An instrument for de- Electromagnetic Radiation Energy prop- tecting and counfing ionizing particles, agated through space or through material used to determine the degree ofradio- media in the form of an advancing dis- turbance in electrical and magnetic fields activity. Gnomon A vertical shaft or stick used existing in space or in the media. Also for determining the altitude of the sun or called simply "radiation." the position of a place bynoting the Electron The subatomic particle that length of a shadow.Used as part of a possible electric possesses the smallest sundial. - charge. Gravity The force imparted by the earth The term "electron" is usually reversed to a mass on, or close tothe earth. for the orbital particle whereas the term Since the earth is rotating, the forceob- "beta particle" refers to -a particle of the served as gravity is the resultantof the same electric charge insidethe nucleus of force of gravitation and the centrifugal the atom. force arising from this rotation. Ellipse A plane curve constituting, the Grid System A system of lines used to locus of all points the sum of whose dis- determine dimension or direction by tances from two fixed point called"foci" means of a scale. is constant; an elongated circle. The orbits of planets, satellites, plane- toids, and comets are ellipses; center of attraction is at one focus. Halley, Edmund 1656 - 1742, British Astronomer. EquinoxesThe two points orA the celestial Hour Angle The angle between the sphere where the celestial equator inter- celestial meridian and the hourcircle sects with the ecliptic. of a celestial object. 95, Dutch Explorer A series -of scientific satellites Huygens, Christian 1629 designed to explore outer space. mathematician, physicist, and astronomer.
Hypothesis An idea or guess proposed as photographs of Mars and scientific data an explanation for the occurrence of pertaining to the physical characteristics, phenomena. Mariner IV confirmed the original finding of Mariner II relative to interplanetary space. Future flyby missions to both Venus and Mars are planned. The tendency of an object, as a Inertia Mass The measure of the amount of result of its mass, to continue in motion matter in a body, thus its inertia.The at a constant speed or to remain at rest. weight of a body is the force with which it is attracted by the earth. Mega A prefix meaning multiplied by one million as in "megacycles." Meridian A great circle which passes Kilo A prefix meaning "thousand" used through the zenith directly north and in the metric or other scientific systems south. of measurement. Micro 1. A prefix meaning divided by Kirchoff, Gustav Robert 1824 - 87, one million.2. A prefix meaning very German physicist. small as in "micrometeorite." Micrometeorite A very small meteorite or meteoritic particle with a diameter in Latitude The angle from earth's equator general less than a millimeter. to a point on Earth as measured along a terrestial meridian. Light Year The distance light travels in one year at rate of 186,000 miles per Nanosecond (Abbr nsec) 10 second. second (300,000 kilometers per second). Also called `millimicrosecond."' Equal to 5.9 x 10" miles. NASA (Abbr) National Aeronautics and Longitude The angle between the Prime Space Administration. meridianandtheterrestialmeridian Neutron A subatomic particle with no through a point on earth. electric charge, and with a mass slightly Luminosity The brightness of a star or more than the mass of the proton. object as compared to a standard such as Protons and neutrons comprise atomic the sun. nuclei; and they are both classed as Lunar EclipseThe partial or total obseura- nucleons. tion of the sun's light on the moon, Newton, Sir Isaac 1642 1727, British caused by the passage of the earth be- scientist, mathematician, and philosopher. tween the sun and moon. North Pole The point at which northern end of earth's axis intersects the surface of earth. NucleusThe positively charged core of an MarinerThe initial unmanned exploration atom with which is associated practically of the planets, is being conducted in the the whole mass of the atom but only a United States Under the Mariner program. minute part of its volume. Mariner 2, launched August 26, 1962, A nucleus is composed of one or more passed within 21,000 miles of Venus on protons and an approximately ecwal num- Deeember 14, 1962, and radioed to earth ber of neutrons. information concerning the infrared and microwave emission of the planet, and the 0 strength of the planet's magnetic field. On July 34, 1965, Mariner IV snapped OGO The Orbiting Geophysical Observa- the first close-up pictures ever taken of tories are designed to broaden our knowl- another planet as it sped by Mars at dis- edge of Earth and space and how the sun tances ranging from 10,500 miles to influences and affects both. OGO is de- 7,400 miles.Beside providing close-up signed to carry about 20 different experi- ments. The advantage of OGO is that it Pressure (Abbr p) As measured in a makes possible the observation of nu- vacuum system, the quantity measured merous phenomena simultaneously for at a specified time by a so-called vacuum prolonged periods of time. OGO I was gage, whose sensing element is located in launched September 4, 1964 and OGO II a cavity (gage tube) with an opening October 14, 1965. oriented ina specified direction at a Orbit 1. The path of a body or particle specified point within the system assum- under the influence of a gravitational ing a specified calibration factor. or other force.For instance, the orbit Primary Body The spatial body about of a celestial body is its path relative to which a satellite or other body orbits, another body around which it revolves. or from which it is escaping, or towards 2. To go around the earth or other body which it is falling. in an orbit. The primary body of the moon is the Orbital Elements A set of 7 parameters earth; the primary body of the earth is defining the orbit of a satellite. the sun. Proton A positively-charged subatomic particle having a mass slightly less than that of a neutron but about 1847 times greater than that of an electron. Es- sentially, the proton is the nucleus of the Pendulum An object suspended from a hydrogen isotope 1H1 (ordinary hydro- fixed point able to move back and forth gen stripped of its orbital electron).Its by the action of gravity and momentum. electric charge (+4.8025 x 10° esu) is Perigee That orbital point nearest the numerically equal, but opposite in sign, earth when the earth is the center of to that of the electron. attraction. Protons and neutrons comprise atomic That orbital point farthest from the nuclei;they are bothclassedas earth is called'apogee."Perigee and "nucleons." apogee are used by many writers in re- Protractor An instrument, graduated in ferring to orbits of satellites, especially degrees of arc, for plotting or measuring artificial satellites, around any planets or angles. satellite, thus avoiding coinage of new Proxima Centauri A star in the constella- terms for each planet and moon. tion Centaur at a distance of about 4.3 Perihelion That orbital point nearest the sun when the sun is the center of attrac- light years. tion. Ptolemy, Claudius 127 - 151 AD, Greek That orbital point farthest from the sun mathematician, astronomer, and geogra- is called "aphelion."The term "peri- pher. helion" should not be confused with "parhelion," a form of halo. Period The interval needed to .corriplete a cycle. Often used . in reference to time of complete orbit. Radiometer A device used to measure Pico A prefix meaning divided by one some property of electromagnetic radia- million million. tion. In the visible and ultraviolet regions Precession Change in the direction of the of the spectrum, a photocell or photo- axis of rotation of a spinning body, as a graphic plate may be thought of as a gyroscope, when acted upon by a torque. radiometer.In the infrared, .solid state The direction of motion of the axis is detectors such as photoconductors, lead such that it causes the direction of spin of sulfide cells and thermocouples are used, the gyroscope to tend to coincide with while in the radio and microwave regions, that of the impressed torque. The hc.ri- vacuum tube receivers, often with para- zontal component of precession is called metric or maser preamplifiers, are the "drift," and the vertical component is most sensitive detectors of electromag- called "topple." netic radiation. Radiosonde A balloon-borne instrument In some contexts the terms "revolu- for the simultaneous measurement and tion" and "rotation"are used inter- transmission of meteorological data. changeable; but with reference to the motions of a celestia. 3ody, "revolution" Ranger A program designed to send back refers to the motion in an orbit or about to Earth a number of high-resolution an axisexternal to the body, while pictures of the Moon's surface, and to "rotation" refers to motion about an show features at least one-tenth to one- axis within the body.Thus, the earth hundredth the size of features discernible revolves about the sun annually and ro- from Earth.Ranger VII was successful on July 31, 1964. Ranger VIII was suc- tates about its axis daily. cessful in meeting its objectives on Feb- Right Ascension The angle as measured ruary 20, 1965 and Ranger IX onMarch along thecelestialequator from the 24, 1965. More than 17,000 high resolu- vernal equinox eastward to the hour tion photographs were received from the circle of the celestial object. Rotation Turning of a body about an three satellites. axis within the body, as the daily rota- Rarefaction The half of a sound wave in which the air or medium is expanded to tion of the earth. See Revolution. less than its normal density. Refraction The bending of a beam of light as it passes from one medium into Satellite 1. An attendant body that re- another in which the index of refraction volves about another body, the primary; is different. especially in the solar system, a secondary The (dimen- body, or moon, that revolves about a Relative Humidity (Abbr rh) planet. 2. A man-made object that sionless) ratio of the actual vapor pressure revolves about a spatial body, such as an t' the air to the saturation vapor pressure. Explorer I or a TIROS satellite orbiting Rendezvous The event of two or more about the earth. objects meeting at a preconceived time Saturn A family of launch vehicles de- and place. veloped by the U.S. to ultimately place A rendezvous would be involved, for three men on the moon. example, in servicing or resupplying a Scale A reduction or increase in size or a space station. dimension of an object in proportion Resolving Power The ability of a tele- resulting in a model. scope or lens system to separate ob- Sideral DayThe time or interval between jects which are very close together. two consecutive meridian crossings of a Resonance1. The phenomenon of ampli- star. fication of a free wave or oscillation of a Solar Eclipse The partial, total, or an- system by a forced wave or oscillation of nular obscuration of the sun's light on exactly equal period. The forced wave the earth by the passage of the moon may arise from an impressed force upon between earth and the sun. the system or from a boundary condition. Solar Wind A stream of protons con- The growth of the resonant amplitude is stantly Moving, outward from the sun. characteristically linear in time.2. Of a Synonymous with solar plasma. system in forced oscillation, the condition which exists when any change, however Solar System The group of planets and small, in the frequency of excitation their satellites, and other celestial objects causes a decrease in the response ofthe which are under the gravitational in- system. fluence of the sun. Reticle The crosses located on the grid Sounding Rocket A rocket designed to system of the Ranger cameras. Used to explore the atmosphere within 4,000 determine distance and direction by scale. miles of the earth's surface. Revolution Motion of a celestial body in Space 1. Specifically, the part of the its orbit; circular motion about an axis uniNrerse lying outside the limits of the usually external to the body. `iirth's atmosphere.2. More generally, the volume in which all spatial bodies, including the earth, move. Telescope An optical or radio instrument SpacecraftDevices, manned or unmanned, used to observe celestial objects. which are designed to be place(' into an Temperature A measure of the average orbit about the earth or into a t jectory energy of motion of themolecules of a to another celestial body. substance. SpectrometerAn instrument which meas- Thermometer Any instrument used to ures some characteristics such asintensity, measure the expansionand contraction of electromagnetic radiation as a function of a substance due to changes in the mo- of wavelength or frequency. tion of molecules. Spectrum 1. In physics, any series of energies arranged according to wavelength TIROS (Television Infra Red Observation (or frequency); specifically, the series of Satellite) A series of United States images produced when a beam of radiant meteorological satellites designed to ob- energy, such as sunlight, is dispersedby a serve the cloud coverageof the earth and prism or a refraction grating.2. Short measure the heat radiationemitted by for "electromagnetic spectrum" or for the earth in the infrared. any part of it used for a specific purpose Troposphere That portion of the atmos- as- the 'radio spectrum' (10Ithocycles to phere from the earth's surface to the 300,000 megacycles). tropopause; that is, the lowest 10 to20 Star Transit The passage of a star across km of the atmosphere. The troposphere the celestial meridian. is characterized by decreasing temperature Sundial An instrument for indicating the with height, appreciable vertical wind mo- time of day from the position of a shadow tion, appreciable water vapor content, cast by the sun. and weather.Dynamically, the tropo- Surveyor The United States program for sphere can be divided into the following the scientific exploration of the surface layers:surface boundary layer, Ekman and subsurface of the moon.Surveyor layer, and free atmosphere. was dc,igni;d ":;) soft land on the moonand explorethephysical,chemical,and mineralogical properties at the landing U site.This information was relayed back to Earth by means of extremelyhigh V resolution photographs.These pictures 'Vanguard I Launched in 1958, analysis revealed lunar particles a few centimeters of the orbit this satellite revealed that in size. Earth is not symmetrically oblate, but The Surveyor missions: bulges in the southern hemisphere. Surveyor I June 1, Vernier Scale A movable, graduated 1966 scale, used for the measuring of fractional Surveyor II SeptemberUnsuccessful units of the primary scale. 20, 1966 The size or measure of space or Surveyor III April 19, Volume 1967 matter in three dimensions. Surveyor IV July 16, Unsuccessful 1967 Surveyor. V September Wavelength The distance from one point 10, 1967 on a wave to the correspondingpoint on Surveyor VI November 11, 1967 the next wave. Surveyor VIIJanuary Weight The force with whioh an earth- 10, 1968 bound body is attracted toward the earth. The successful Surveyor missions have re- Weightlessness A condition in which no turned to Earth thousands of photographs acceleration, whether of gravity or other, of the lunar surface as well as classic force, can be detected by an observer photographs of Earth. within the system in question. Any object falling freely in a vacuum is weight1ess, thus an unacceleratedatel- lite orbiting the earth is "weightless" al- though gravity affects its orbit. Weight- lessness can be produced within the atmosphere in aircraft flying a parahoPc flight path. X
Zenith That point on the celestial sphere vertically overhead. The point 180°from the zenith is called the "nadir."
119 107- AN AEROSPACE BIBLIOGRAPHY Ley, Willy, Rockets, Missiles, and Space Travel.New York: Viking Press, 1961. Abell, George, Exploration of the Universe. Longstreth, T. Morris, Understanding the New York: Holt, 1966. Weather. New York: Collier Books, 1962. Adler, Irving, Seeing the Earth from Space. Mehrens, H. E., The Dawning of the Space New York: Day, 1962. Age. Ellington AFB, Texas: Civil Air Asimov, Isaac, The Double Planet. New Patrol, 1963. York: Abe lard-Schuman, 1960. Meitner, John G. editor, Astronautics For ,Satellites in Outer Space. New Science Teachers. New York: Wiley, York: Random, 1964. 1965. Astronauts Themselves, The, We Seven. ,Meteorology for Army Aviation. New York: Simon & Schuster, 1962. Washington:Superintendent of Docu- ,Aviation Weather for Pilots and ments, 1963. Flight Operation Personnel. Washington: Moore, Patrick, Guide to Mars. New York: Superintendent of Documents, 1965. Macmillan, 1961. Bell, Joseph N., Seven Into Space. New ,A Guide to the Planets, New York: Hawthorn, 1960. York: Norton, 1960. Bergaust, Erik, Reaching for the Stars. ,Picture History of Astronomy. New York: Doubleday, 1961. New York: Grosset, 1961. Blair, Thomas A. and Robert G. Fite, The Solar System. New York: Weather Elements. Englewood Cliffs, Criterion, 1961. N.J.: Prentice Hall, 1965. Cantylaar, George, Your Guide to the Newlon, Clarke, Famous Pioneers in Space. Wearher.Cranbury, N.J.: A. S. Barnes New York: Dodd, Mead, 1963 Co., 1964. Pickering, James S., Astronomy for Ama- Chester, Michael, Rockets and Spacecraft teur Observers. New York: Fawcett, of the World. New York: Norton, 1964. 1960. Day, John H., The Science of Weather. Pothecary, LJ.W. The Atmosphere in Ac- Reading, Mass.: Addison-Wesley, 1966. tion. New York: St. Martin's Press, 1965. Egan, Philip, Space for Everyone. Chicago: Richardson, Robert S., Astronorn,y in Ac- Rand McNally, 1961. tion. New York: McGraw-Hill, 1962. Frutkin; 'Arnold W., International Coopera- Riehl, Herbert, Introduction to the Atmos- tion in Space.Englewood Cliffs, N.J.: phere. New York: McGraw-Hill, 1965. Prentice, 1965. ,Space Science Series, 14 books, Gamow, George, Gravit;. New York: New York: Holt, 1965. Doubleday, 1962. Al- endt, Myrl H., The Mathematics of Gat land, K. W. editor, Spaceflight Today. , pace Exploration. Fallbrook, Cal.: Aero, 1964. Emme, Eugene M., A History of Space Glasstone, Samuel, Sourcebook on Space Flight. Science& Princeton, NJ.: VanNostrand, Faget, Max, Manned Space Flight. 1965. Gardner, Marjorie H., Chemistry in the Goddard, Robert H., Rocket& New York: Space Age. American Rocket Society, 1946. (Reprint Goodwin, Harold Leland, The Images of of 1919 and 1935 Smithsonian Reports) Sparo Hawkins, Gerald S., Splendor in the Sky. Henry, James P., Biomedical Aspects of New York: Harper & Row, 1961. Space Flight. Hicks, Clifford B., The World Above. New Hunter II, Maxwell W., Thrust Into Space. York: Holt, 1965. Hymoff, Edward, Guidance and Control Hoyle, Fred, Astronomy: A History of of Spacecraft. Man's Investigation of the Universe. New Jaffe, Leonard, Communications in Space. York: Doubleday, 1962. Naugle, John E.,. Unmanned Space Flight. ,Of Men and Galaxies.Seattle: Stern, Phillip D., Our Space Environment. University of Wh -hington, 1964. Sutton, Richard M., The Physics of Space. Huffer, Charles M. and others, An Introduc- Wedger, Jr., William K., Meteorological tion to Astronomy. New York, 1967. Satellites. Youug, Richard S., Extraterrestrial Bi- PERIODICALS ology. Stine, G. Harry, A Handbook of Model Aviation Week and Technology.Weekly. Rocketry. Chicago: Follett, 1965. cio Fulfillment Manager. PO Box 430, Thompson, Phillip and Robert O'Brien, Highstown, N.J. 08520. $8 per year. Weather. Morristown, N.J.: Silver Bur- Technology Week. Weekly. American dett, 1965. Aviation Publications, 1001 Vermont Trinklein, F. E. and C. M. Huffer, Modern Avenue, N.W., Washington, D.C. 20005. Space Science. New York: Holt, 1961. $5 per year. Vaeth, J. Gordon, Weather Eyes in the Sky. Review of Popular Astronomy. Six times a year.Sky Map Publications, 214 South New York: Ronald, 1965. Bemiston, St. Louis, Missouri 63105. $4 per year. SELECTED REFERENCES Sky and Telescope. Monthly. Sky Publish- ,Aerospace Age Dictionmy, The, ing Corporation, 49-51 Bay State Road, Clarke Newton, complier.New York: Cambridge, Mass. 02138.$6 per year. Watts, 1965. Skylights.9 times a year. National Aero- ,Aerospace Education Bibliogra- space Education Council, 616 Shoreham phy, 3rd Edition, EP-35.Washington: Building, 806 15th Street, N.W., Wash- Superintendent of Documents. ington, D.C. ,La Rousse Encylopedia of As- Spaceflight.6 times a year. Sky Publish- tronomy, Lucien Budaux and G. De- ing Corporation, 49-51 Bay State Road, Vaucouleurs, editors, New York: Putnam, Cambridge, Mass. 02138. $3.50 per year. 1962. Moser, Beta C., Space-Age Acronyms. New OTHER BOOKS OF THIS SERIES York: Plenum, 1964. ,What's Up There. Washington: Superintendent of' Documents, 1964. ,From Here, Where. Washington: Superintendent of Documents, 1965. Shapes of Tomorrow, The. Wash- ington: Superintendent of Documents, 1967.
122 INDEX A Aerobee, 88 declination, 101-103 Galileo, 11, 21 Albategnius, 47 density, 85-96 gases, 83-92 Almagest, 101, 103 diffraction grating, 104, 105 density, 83-96 Alphonsus, 47, 49 direct measurement, 38, 99 pressure, 83-96 anemometer, 85 drop time, 21 temperature, 83-96 angstrom, 19, 25, 105 volume, 83-96 angular degrees, 8 Geiger counter, 85 gibbous moon, 32-37 aphelion, 31, 40-42 Earth, apogee, 42, 43 gnomon, 9 altitude, 12 Goddard, Robert H., 83, 85 Apollo, 26 aphelion, 31, 40-42 apparent motion, 8 gravitational force, 12 axis, 6, 12, 13, 32 Greenwich, England, 28, 29 astronomical unit, 40 density, 12 measurement of, 40, 41 eccentricity, 40-43 Atlas of the Moon, 61 Equator, 13, 101 atmosphere, 84 latitude, 10, 102 Halley, 103 clouds, 85 longitude, 102 hour angle of the sun, 27 Mars, 74 North Pole, 13, 27 hour circle, 102, 103 samples, 82 orbit, 7, 32, 40 Huygens, 21 troposphere, 81 perihelion, 31, 40-42 hypothesis, 7, 70, 89 upper, 81 phases, 7 atmospheric density, 88-91 Prime Meridian, 101, 102 atom, 107 revolution, 7, 31 indirect measurement, 38, 100 electron, 107 rotation, 4, 7, 10 inertia, 12 neutron, 107 seasons, 7 instruments, 85 nucleus, 107 eccentricity, 40-43 anemometer, 85 proton, 107 Echo I, 3, 42 barometer, 83 atomic clock, 109 eclipse, 41 Crookes radiometer, 85 axis, 6 Egypt, 4 Geiger counter, 85 electrical clock, 21 metric ruler, 65 electron, 107 micrometer, 39 Babylonia, 4 ellipse, 31 precision of, 19 barometer, 83, 85 Equator, 13 protractor, 65 binary number, 73, 74 equatorial ring, 9 radiosonde, 77 brightness, 100 equinox, 103 ruler, 65 Bunsen, 107 errors, 19, 38 telescope, 100 experimental, 48, 49 thermometer, 83 measurement, 39, 42, 72 tuning fork, 70-72 vernier scale, 39, 40 calendar, 4 Explorers, 43, 81, 86 lunar, 5 celestial equator, 101-103 clepsydra, 10 first quarter, 32-37 clock, forces, atomic, 107 friction, 12 Kirchhoff, 107 electrical, 21 gravitational, 12 hour glass, 10 Foucault, 12 L. mechanical, 10, 12 pendulum, 12 Fraunhofer, 105, 107 latitude, 10 shadow, 8 launch window, 14 sundial, 8 lines, 105 least count, 39 water, 10, 21 Freedom, 7, 109 frequency, 72 light measurements, 100, 101 clouds, 75-77, 85 light year, 13 compression, 71-73 friction, 12 From Here, Where, 11 longitude, 102 crescent moon, 32-37 luminosity, 100 Crookes radiometer, 85 full-moon, 32-37
123 11 0 Explorer, 43, 81, 86 magnetic radiation, 99 pendulum, 10-13, 21 Mariner IV, 20, 22, 74 Mariner IV, 20, 22, 74 average period, 12 OGO, 4 Martian atmosphere, 91 bob, 10 Ranger IX, 20, 44-61 Mars, 20 Foucault, 12 Surveyor, 50 mass, 86-91 period, 10, 11 Tiros, 75-79 Maya, 5 perigee, 42, 43 Vanguard, 73 measurement, 19 perihelion, 31, 40-42 satellite orbit, 42, 43 angstrom, 19, 25 period of the pendulum, 12 apogee, 42, 43 degrees, 26, 27 Pogson, 101 eccentricity, 40-43 direct, 38, 39 Polaris, 10, 22 mean distance, 42, 43 indirect, 38, 100 precision of instruments, 19 perigee, 42, 43 light, 103, 104 pressure, 77, 85-96 Saturn V, 99, 100 light year, 13 primary scale, 39, 40 scale measurement, 49 nanosecond, 19, 25 Prime Meridian, 8, 101, 102 scientific notation, 13 scale, 49 proton, 107 seasons, 7 standard, 22 protractor, 27, 39, 65 shadows, units, 19 Proxima Centauri, 13 lengths, 6, 49 mechanical clock, 10, 12 Ptolemaeus, 44, 47 Shapes of Tomorrow, 27, 107 meridians, 8 Ptolemy, 100 sideral day, 7, 31 Prime, 8, 101, 102 Alrnagest, 101, 103 solar, terrestrial, 8 day, 7, 31 metric ruler, 65 Q eclipse, 32, 106 micrometer. 39 noon, 8 Moon, 32 system, 22 Atlas, 61 radiation, time, 10 crescent, 32-37 light; 99 wind, 69, 70, 83 first quarter, 32-37 magnetic, 99 solar spectrum, 106, 107 full, 32-37 radiosonde, 77 sounding rockets, 81, 82, 89-91 gibbous, 32-37 Ranger IX, 20, 44-61 sound waves, 70 longitude, 45 altitude, 45 compressions, 70-73 new, 32-37 camera A, 45 frequency, 70-73 third quarter, 32-37 camera angle, 45 rarefactions, 70-73 waning, 32-37 grid north, 45 resonance, 70-73 waxing, 32-37 grid system, 45 wavelength, 70-73 motion of Eart1:, resolution, 45, 46 space, reticle, 45, 46 mathematical model, 70 scales, 45 spacecmft rendezvous, 14 nanosecond, 19, 25 rarefaction, 70-73 spectrum, 103-107 NASA/Goddard Spaze refraction of light, 38 spectroscope, 104-107 Flight Center, 4, 7 rendezvous, 14 diffraction grating, 104, 105 neutron, 107 rocket, 14 model, 104 new mOon, 32-31 spacecraft:14 speed of sound, 72, 73 Newton, 12, resolution, 45 standard heart time, 19, 21 North Pole, 13, 27 resonance, 71, 72 standard of measurement, 72 North Star, 10, 22 revolution, 7, 31 star, NOrthern Hemisphere, 7 right ascension, 103 absorption lines, 105 nucleus, 107 rotation, 10, 31 apparent motion, 101 ruler, 38, 47, 65, 95 brightness, 101 day, 71, 31 0 declination, 101-103 OGO, 4 luminosity, 101 orbits, 40 sand glass, 10 magnitude, 101 Earth, 7, 32, 40 North Star, 10, 22 satellites, 4143 Echo I, 3, 42 Polaris, 10, 22
124 Proxima Centauri, 13 clepsydra, 10 spectrum, 103-107 wavelength, 104-107 sun, waxing moon, 32-37 apparent position, 8, 27 weight, 86-91 hour angle, 27 What's Up There?, 13 sundial, 8-10 equatorial ring, 9 XYZ gnomon., 9 model, 9 Surveyor, 50 system, earth-atmovhere, 81 operating, 81, 82
telescopes, 101 temperature, 83-96 thermometer, 83, 85-96 third quarter moon, 32-37 time, drop, 21 hour circles, 26, 27 hours, 27 kilo, 19-22 local, 28 mean, 32 mega, 19-22 midnight, 26-29 minutes, 27 nanoseconds, 19, 25 shadows, 8, 91 solar, 10 standard heart, 19, 20 TIROS (Television Infra Red Observation Satellite) 75-79 troposphere, 81 tuning fork, 70-72
Units of measurement, 19 upper atmosphere, 81
V Vanguard I, 73 vernier, 49, 40 least count. 39, 40 primary scale, 39, 40 scale, 39, 40 volume, 86-96
waning moon, 32-37 water clock, 10, 21
125 112