The Nature of Science in Science Education Rationales and Strategies edited by WILLIAM F. McCOMAS University of Southern California, Los Angeles, California, U.S.A . ... '' KLUWER ACADEMIC PUBLISHERS DORDRECHT I BOSTON I LONDON NAHUM KIPNIS 10. A HISTORY OF SCIENCE APPROACH TO THE NATURE OF SCIENCE: LEARNING SCIENCE BY REDISCOVERING IT My interest in teaching the nature of science came from attempts to integrate history into physics courses for teachers at the Bakken Library and Museum beginning in 1985. My background in the history of science and in teaching physics appeared ideal for helping teachers transform the science offacts and equations they typically teach into science as a human activity. Michael Matthews labels this a distinction between "technical" and "liberal" science. The trouble was that many course participants had degrees in biology or chemistry, and were unfamiliar even with "technical physics." Having no foundation to build on, I choose to teach both, and the question was how to do it. By that time, I had already been convinced that physics could be taught to all students by shifting the emphasis from the memorization of facts to developing skills of thinking, reasoning, and systematic purposeful work by students. I decided to try investigative laboratory experiments as one of the main vehicles for achieving this purpose. Teachers conducted experiments in groups and individually. When they brought the new labs to their schools, they appealed to the majority of students and raised their interest in learning science. The peculiar feature of these laboratory activities was that many of them recreated historical experiments. The idea of reproducing historical experiments in the classroom came from Devons and Hartmann ( 1970). I could have achieved my goal with other experiments as well, but I wanted to use history as much as possible, and the historical experiments did have an advantage over the "real-life investigations" practiced by some teachers, such as finding the cause of the clogged classroom sink or determining which paper towel is most absorbent. First, with the historical approach, the result is always known to the instructor, which is not the case with the sink and towels. Second, a historical experiment can be chosen so as to help teach a narrow scientific topic, while most real-life phenomena are too complex and complicated for students' study. Third, for the first two reasons, the students' chances to succeed are higher with the historical experiments than with the other ones. Finally, a success in repeating a historical scientific discovery may boost students' self-confidence much more than in fixing the plumbing. It is not that technological problems are unusable; if carefully chosen, they are. However, it is easier to learn the necessary investigative skills in historical scientific experiments and then use them to tackle the frequently more complicated problems in technology. 177 W. F. McComas (ed.) The Nature of Science in Science Education, 177-196. C 1998 Kluwer Academic Publishers. Printed in the Netherlands. I78 N. KIPMS Soon, it became clear that with all its advantages, the historical approach brings to the forefront very difficult questions of science usually suppressed in textbooks, such as the changeability of theories, the meaning of experimental support and its application in selecting one of several competing theories, and others. Some teachers came up with such questions on their own, while others recalled similar challenges from their brighter students, who having found out from popular science books and television programs that theories come and go concluded that scientific knowledge is of no real value. Teachers realized a necessity in answering those questions, but they did not know how to do so. Thus, I realized tlnt in the environment that emphasizes thinking and usage of history, teachers had no choice but to address basic issues of the nature of science, and they must be taught how to do it. Teachers certainly could have benefitted from proper philosophy of science courses (Matthews, 1990; McComas, 1995), but I expected them to obtain such training elsew[ere. On my part, I tried a more practical approach tlnt could be complementary to theoretical courses: to bring up the issues of the nature of science from within the science, in particular when engaging teachers into "doing science." This chapter will give an example of such an activity and the way it addressed the questions related to the scientific methodt. TIIE NATURE OF SCIENCE: A HISTORICAL APPROACH The historical approach in science teaching has had several periods ofpopularity. In the late 1950s, James Conant suggested that all necessary knowledge of the nature of science could be gained from studying a few historical cases. The cases must come from the "old" science (usually, this means scientific ideas from the l7-l9h centuries), for only the old science can allow a nonspecialist azuffrciently good grasp of the subject matter (Conant, 1959). While Conant's cases were written for universities, several authors incorporated his idea into the secondary school curriculurn, some explicitly and others implicitly. At one extreme, the nature of science was advocated as a separate instructional element, the understanding of which is emphasized more strongly than that of the science content involved (Klopfer, 1961, 1992). In Klopfer?s scheme, student booklets, prepared for each case, contain excerpts from primary sources alternated with the author's narrative, and also questions directing students' attention to various aspects of science as described in the text. Blank spaces are provided for student to write answers to these questions. Sorne of the questions refer to various aspects ofthe nature of science (Klopfer, 1964). The idea of using original historical materials tThe term "scientific method" used here mears lhe corzrnan features ofreseardr Srategies applied by scientists in modern times that we want students to leam. HISTORY OF SCIENCE APPROACH I79 together with questions to answer was appealing, however, I found its practical realization unsatisfactory. While some historical experiments were included, their purpose uas largely illustrative. Most important, I did not believe tlnt "nature of science" can survive in the secondary school as a separate subject. At the other extreme, history was used solely to aid in learning scientific concepts, and if students were expected to draw conclusions about science and scientists, they had to do this on their own, using historical examples incorporated in the text @utherford et al., 1964). There were also attempts to provide a middle groundbetrveen these two extr€mes by balancing the study of nature of science with that ofscientific oonc€ptsr or using inquiry as a vehicle for learning science (Schwab, 1964). The general approach is appealing, but the role of a historical element in it is rather limited. In general, Schwab's approach appears sound, but the historical element in it plays only a casual role, if any. For instance, although Galileo's name is mentioned, students' experiments with pendulums have nothing to do with the historical ones. After a period of neglect, historical approaches reappeared in the I 980s, with the emphasis on evaluating case studies, role playing and doing historical reading. Some issues of the nature of science come up when students discuss historical accounts in the class (Lochhead & Dufresne, 1989). Unfortunately, while the roleplayng activities will be of some interest to all students, only those few who are actively involved as panelists or actors will get the full intellectual benefit from these activities, because only they had done all the reading. For the majority of students, a better way to integpte the historical element would be to recreate history in action rather than on stage. Some historical experiments have already found their way into teachers'education @evons & Ilartmann, 1970; Teichmann, 1986). My intention was to do it on a more comprehensive basis and to make history an organic component of science. Learning the Nature of Science llhile Learning Science Although teachers report that they like learning about the hiSory ofscience, they fell ttnt it is unlikely that they will pass much of that knowledge on their students, because they have no time for any "extra" units, zuch as those devoted specifically to the history and nature of science. For this reason, I zubordinated the discussion of historical and philosophical issues of science to learning scientific concepts superimposing them so as to make them inseparable. The topics of units are the same as in regular science courses, zuch as "electrical conductors and nonconductors," and the goal is the same: to fonnulate the laws of phenomena. The difrerence is in the ways the unit is taught. History and the nature of science are involved in three areas. The first concerns the way a new scientific concept is introduced. I have found that understanding of I8O N. KIPNIS a concept imprwes if it is "rediscovered" with active participation on the part of the learner. Usually, it begins with the instructor's demonstration of a relevant historical experiment, for instance, the first experiment of Stephen Gray2. After a short discussion, students begin repeating and modifying this experiment following a certain plan (see Table I). The instructor stops students wery 10-15 minutes to discuss the intermediate results. If some groups difrer in their rezults, this particular experiment is repeated until a consen$rs is established. After the final conclusion is formed, the instructor informs students of Gray's subsequent procedures and results, and the participants can compare how closely they came to the scientist. Although technically the experiments are simple, it is not easy to draw a conclusion from them, because it involves introducing a new con@pt of conductivity (Kipnis, 1996). Thus, students get a lesson about a possibility of various interpretations of experimental rcsults (including the erroneous ones) and a diffrculty of making the best general conclusion (it was not Gray who introduced the general concept of "@nductors and "nonconductors"). If pedagogically advisable, the chain of "rediscoveries" follows historical events. This is the case with static electricity, for instance, which led some teachers to replace their whole static electriciff unit with the one developed at The Bakken @akken, 1995). However, occasionally, history defies what we call "common sense," as with the case of interference of water waves being discovered after interference of light. In such cases, I prefer to sequence instruction in ways that students will find easier to grasp. Later, we discuss that scientific developments are not always "logical" and may be very convoluted. The second area concerns the type of experiment used. I emphasize investigative experiments which require students to imitate scientists rather than use artificial or contrived experiments. In another lesson from history we see that since much of physics remained a qualitative science up to the middle ofthe nineteenth century, an obsession with measurements in high-school physics app€ars unjustified. Thus, I began to emphasize qualitative experiments where students study a certain phenomenon to find a qualitative empirical law to describe it (Kipnis, 1995). The result is considered "true" if obtained by all groups. These experiments are preceded and followed with theoretical discussions in such a \ilay as to "r@reate" an infioduction into science ofa new physical concept (potential, for instance) or a law (zuch as the relationship between potential and capacitance) (Kipnis, 1992,1996). The investigation is, to a certain extent, guided by the teacher. However, since shdents have some freedom of action, we can consider this imitation of the work of '? ln I 73 I , tlE Engli$ ph)6icis Stepheo Gray observd white rubbing a glass tube corked at the ends" thal not only glass attracted a feather, but so did the cort. Gray srppced that electricity produced in glass by rubbing somehow moved to lhe cork. When he iruerted a nail in the cort, eleoricity reac{red the nail too. Through his worft with long "communicating lineq" Gray discovered lhe concept of"conductors" and "non-conductors." HISTORYOF SCIENCEAPPROACH I8I scientists suffrcient to give students a taste of the problems scientists face. By making students "discoverers" we achiwe two objectives. First, we remove some of the "mystery" from science by showing it to be a professional activity that requires certain skills, and that everyone with necessary skills and motivation can discover something narandusefirl. Involving history has additional advantages. Seeingthat they are capable of repeating on their own certain important steps of famous scientists or deciding who was right in a scientilic dispute (Lawrenz & Kipnis, 1990) gives students a tremendous boost to their selfrconfidence. Second, they will see how easy it is to choose an incorrect direction ofresearch, how difficult it is to invent a good procedure, and how easy it is to reach a false conclusion. Studens will realize that while not everyone can become Newton or Volta everyone can discover something. This will teach them a proper appreciation of great discoveries of the past, on the one hand, and a habit of critically analyzing information about modern discoveries. on the other. The third area deals with the stnrtery of experimenting. The one discussed here is distilled from scientific treatises of the past (table I). The strategy consists oftwo stages: Preliminary and Main Parts. The Preliminary Part is the one with which teachers are least familiar. It comprises the origin of the problem and initial experiments, which do not follow any plan but aim at discovering a few plausible variables and a reliable experimental procedure. The problem with the widely spread method of doing openended experiments is that usually a teacher solicits students' suggestions about the variables to study after they observe a single demonstration. Having received a considerable number of ideas, the teacher asks each group to investigate a different variable, with the idea that all these partial results can be combined at the end into a general one. One problem with this approach is that bringing variables "out ofthe blue" is inefficient. In our case, students do a sufficient number of modifications of the original experiments until they can say which changes appear to affect the result, and select the oonesponding parameters as variables. Also, only the most obvious two or three variables are selected for the further examination in the Main Part which allows all groups to study all variables eliminating a possibility of false results due to poor statistics. The Main Part is the planned stage of an investigation (fable I). Each variable is examined while keeping the rest constant, and this examination follows a certain plan identical for all variables. We start with preliminary experiments which result in a certain hypothesis about the way this variable affecs the phenomenon. Although students may have some idea of this hypothesis from the Preliminary Part, this knowledge is not definite, for in some initial experiments several variables are changed at a time. Unlike those, the preliminary experiments are "clean," for everything but one variable remains constant. To advance a hypothesis even two experiments may be enough. But to test it more experiments are needed, and they must be difrerent from the preliminary ones. If the test shows that the hypothesis is false, we do additional experiments and suggest another hypothesis. Finally, we 182 N. KIPNIS summarize all conclusions about separate variables and formulate a law or a nrle. While studying each subsequent variable we use the rcsults about the variables previously examined. Thus, it makes sense to insist ttnt all groups investigate the variables in the same order, at least" during the period when students learn how to investigate and need more assistance. It must be noted that teachers cannot have too many firll-scale investigations with 2-3 variables, similar to the one in the example, because they take from one to tluee hours and require a carefrrl preparation on the teachers' part. For this reason, teachers supplement them with a gr€ter number of shorter experiments (10-20 minutes each), which deal only with a single variable. TABLE I A strategy for investigation I. PRELIMINARYPART l. Background (origin ofthe problan) 2. Initial observations and experiments 3. Formulating a problem 4. Selecting variables 5. Selecting a procedure II.lv{AINPART Variable I a. Preliminary experiments b. Hypothesis c. Test d. Conclusion Variable 2 a. heliminary experiments b. Hlpothesis c. Test d. Conclusion Additional Variables Gereral Conclusion Formation HISTORY OF SCIENCE APPROACH I83 An ExamPle of the Strateg in Action: Does Light Trm'el Along a Straight Line? Some features of this technique are iltustrated in the following example. In this contexl ..student" can refer to any learner, while "teacher" can be either a university instructor or a secondary school teacher who knows this stratery. The description of the experiinent is a hypothetical student report which follows the plan illustrated in Table I, in which several possibte answers imitate results from different gfoups' In an actual experimental report, a student can use the same format writing in the the blank space under relevant headings. The law of rectilinear propagation of light is one of many that may be "rediscovered" during a unit on optics and vision. This example is based on the book for teachers Rediscovering Optics (Kipnis, 1992), and the following discussion includes excerpts from it. This study is recommended for secondary students ( 1218 years of age), although its modified version is quite applicable for those in upper pri-"ry grades (9-l2years of age). If students have not had geometry, the teacher ihould-farniliarize thern with the concept of similar figures using models and drawings. The teacher begins the unit on light with the question: "what conditions ztre necessary to see a certain object?" Students provide a variety of answers, including: "a healthy eye," "a suffrcient amount of light," "the requirement lnt the line of vision should not be blocked," etc. Subsequently these answers serve to introduce a variety of topics to study, beginning with the eye and the meaning.of "vision." During this fiist lesson the teacher describes ome early theories of vision using a combination of lecture and discussion. In particular, in the "extromission" th@ry, the eye sends out a "fire" which touches an object and receives information of its shaf, size, and color (something similar to a radar). According to the "intromission' theory, something (a "mask" or an "image" of the object) detaches itself from its surface and moves toward the eye. When students {art smiling at zuch "naive" ideas, it is useful to challenge them to refute any of these notions' Students will quickly realize that the matter is not as obvious as it may have appealed at first' and the teacher may use this case as an example of an important maxim of science that "obvious is something you have nwer thought about'" The teacher summarizes that ancient philosophers finally realized they could not resolve the problern of vision in full, and began focusing on some part of it that could be resolved. That was done by Euclid (ca. 300 BC) who ignored what agent is moving between the eye and the object, which directiorl and how it interacts with ft. "yi and paying attention only to the trajectory of the agent's motion' That is how -the concept of a ray was hrn. While Euclid was thinking of t visual rty coming from the eye, to Ibn al-tlaytham (ca. 965-1039 AD) it was a /igtt t ray amdng from the object. lVhatever the case, they agreed that the trajectory must be a straight line. The teacher challenges students to prove this experimentally. As illustrated I84 N. KIPNIS by the following interaction, students will probably come up with the following idea that many teachers use to study reflection and refraction. Mary. I would use three pins and a nrler. First, draw a straight line on paper using a nrler and place two pins at its ends. Second, move a third pin between the two until all three appear to coincide. Finally, check whether the third pin is on the same straight line with the others. Teacher. This sounds like an easy experiment. Let us do it following Mary's instructions. . . . we'll repeat the experiment hree times. What are the results? John. It's true, and all the pins make the same straight line. Teacher. Incidentally, do you take it for granted tlnt a nrler's edge is straight? John. No, I can prove it. For instance, if I look along the edge of a ruler and see all its points on a straight line, the edge is straight. David. Wait a second! We've just proved experimentally that light moves rectilinearly on the basis of the coincidence of the line of vision with the line drawn with a ruler. Now, you are saylng tlxat the ruler's edge is straight because it coincides with the line of vision. This is circular reasoning! Indeed, it appears that the proof is irnpossible. For this reason, Euclid simply postulated tlnt a ray is a straight line. Howwer, to al-Haytham that was not good enough, and he tried to find a physical demonstration. To test whether the light of a flame spreads rectilinearly, Ibn al-Haytham employed a tube with a pinhole. To extend his proof to the light scattered in the atmosphere, he let light into a room through a one-foot hole into the outerwall and trpo identical holes in the inner wall. He found that a luminous spot C (Figure l) on the floor appeared only when this spot and the holes B and A on both walls were on the same straight line as verified by a stretched thread. Students may say that because the holes are big, points A and B have a large range of movement within each hole, which implies many different lines connecting them and producing different projections C on the floor. Then the teacher suggests another test based on comparing the shape of an object and of its shadow. The idea came from Aristotle (384-322 BC), who claimed to deduce from it that light rays cannot be straight lines. Students may look surprised at this conclusion, and the teacher suggests to investigate whether Aristotle was right. The following excerpt ftom Rediscovering Optics (Kipnis, 1992) describes a hypothetical student's investigation. The discussion is dramatized to present difrerent possible views or results achieved by different groups. HISTORY OF SCIENCE APPROACH co Figure l. Alhazen's demonstration f the rectilinear propagation of light As discussed with reference to Table I, the actual investigation consists of two elements, the preliminary part and the main part. Each of these elements has subsections. The lesson begins with a short overview of the previous lesson on vision and a short demonstration by which the teacher introduces the zubject for an investigation connecting it with Aristotle's problem -what should the shadow resemble: the object or the sun? Teacher. Here I have two holes cut in an index card, one cirorlar and the other rectangular. I will shine light on them from a desk lamp, and you watch their images on a white screen. What do you see? John: Both images are round. But this is impossible! Teacher: What would you expect? John: A circle and a rectangle. Teacher: That was what Aristotle thought too. He asked: Why is it that when the sun passes through quadrilaterals [a rectangular gndl, as for instance in wickenvork, it does not produce a rectangularly-shaped figure, but one that is circular? Is it because the sun's rays fall in the form of a cone and the base of a cone is a circle, so that no matter what object they fall upon, the rays of the sun must appear circular? For if the rays were straight the figure formed by the zun would necessarily be bounded by straight lines. For when the rays fall straight onto a sfaight line they do produce a rectilinear figure (Aristotle, Problems,334-5). 185 IE6 N. KIPNIS Here Aristotle is referring to the geometrical theorem that if the straight lines originating from a single point touch the extremities of a figure, its projection on a parallel plane must be similar to the original @gure 2). Figure 2. An illustration of Aristotle's argument. Honcver, having seen a round image instead of a rectangularone made him suggest hat perhaps the sun's rays are cones with their apexes on the sun rather than straight lines. While observing a solar eclipse, Aristotle discovered again that the sun's image resembled the sun rather than the opening in a screen: Why is it that in an eclipse of the sun, if one looks at it through a sieve, or through the leaves ofa broad-leaved tree, or ifonejoins the fingers ofone hand over the fingers ofthe other, the rays are crescent-shaped where they reach the earth? Is it for the sarne reason as that wlren light shines through a rectangular peephole that it appears circular and cone-like? (Aristotle, Problems,341). The problem raised by Aristotle of why the image rnade by sunlight passing through an opening is similar to the luminous body and not to the opening, had baffled scientists for almost two thousand years. Let us investigate this problem with the following simple zupplies: index cards, masking tape, razor blade or scissors, paper or cardboard white screen. In each index card make two round holes with a paper-punch and.several square holes of different size using a razor blade or by cutting pieces with scissors and pasting them together. The teacher should explain the significance of each step of this procedure. The Preliminary Part (fable I) begins witlr background, which slrows the origin of the problem, in this case a chance observation by Aristotle. The teacher should emphasize that although scientists do not rely on chance, sometimes they benefit from it. An accidental observation becomes a discovery only when a scientist recognizes something new and unusual. S * ' /--HISTORY OF SCIENCE APPROACH TABLE II An illustration of the strategy in action PRELIMINARY PART OF TI{E INVESTIGATION Background Teacher. We begin this investigation with a problem suggested by Aristotle. The problem is that a rectangular hole produces a round image of the zun? We can repeat Aristotle's experiment by observing an image produced by sunlight passing through a square hole in a cardboard sheet. Incidentally, some l6h century astronomers also became interested in this problem, but their curiosity came not from reading Aristotle but from the needs of their science. Initial experiments Ruth. Our group disoovered that Aristotle's conclusion is correct only when the screan is far away from the index card. He probably never tried to bring the screen close to the hole, for if he di4 he would have seen a square image instead ofa round one. John. Distance is not the only thing that rnatters. We've found that at the same distance between the screen and the card a large square opening produced a squre image, and a small square hole projected a circle. Formulating a problem Teacher. We see that Aristotle was only partially right. This finding suggests that we examine a more general problem than his: why does the image produced by sunlight coming through the same opening at some circumstances resemble the zun and at others, the opening? Selecting variables Mary. We found that two factors affect the shape of the image: l) the distance from the hole to the screen, and 2) the size ofthe hole. These could be our variables. 187 I88 N. KIPMS The next stage (initial experiments) consists of reproducing the phenomenon a number of times to be zure it is real and not spurious. Also, by modi$ing the experimental conditions, the scientist tries to determine which factors affect the phenomena: these will be selected for further study as "variables." In addition to this, during the initial experiments, the scientist develops a satisfactory experimental procedure. unlike the Main Part, in the preliminary part the experiments are conducted without any plan, and several factors can be changed simultaneously. For this reason, all conclusions made, for instance, about the choice ofrelevant variables, are tentative. In the Main Part, each variable is studied with other variables kept constant. The study of each variable begins with preliminary experiments, from which students deduce a hypothesis about how this variable changes. This hypothesis is tested by additional experiments. If different groups disagree on the conclusion about a specific variable, they conduct additional experiments untit they reach a consensus. TABLE III The example continued MAINPART OF TTIE INr'ESTIGATION Variable l: Distance between an Opening and a Screen Pre liminary experiments David. I would suggest placing the screen in the shadow and moving the index card to and from it. Ruth. It looks as if all square holes produce square images when close to the screen. Hypothesis John. The closer the hole is to the screen, the more the image resembles the opening. Mary. Why do you call this conclusion a hy,pothesis? Haven,t we just proved ir? Teacher. we compared only two holes of a specific shape (square). Are we sure HISTORYOF SCIENCEAPPROACH I89 that holes of other shapes behave in the same way? Do we know that the result will not change if we make the hole either very large or very small? In both ci$es, the answer is "No." That is why we need additional experim€nts. The preliminary experiments are necessary to advance a hypothesis, but to prove it one has to perform more experiments and of a somewhat difrerent kind. Test Ruth. Irt us see how holes of difrerent shape but about the same size behave at different distances. Instead of cutting additional holes we changed the shape of the original openings by covering them partially with tape. In our experiments the images of triangles and rectangles closely resembled the apertures when the screen was no further than 15 cm from the card. John. We tried parallelognms and trapezoids. In our view, the similarity was preserved for distances up to 20 cm. Conclusion The image resembles a middle size opening only when the latter is close to the screen. Variable 2: The Size of the Opening Pre liminary experiments John. Let us watch the images of two different squares, first, when the card is close to the screen, and then when the card is far from it. Apparently, in both cases the larger square hole makes a sharper square image. Hypothesis Mary. The larger the opening, the closer its picture resembles the original, whatever its distance from the screen. Test John. We can check this in two ways: l) by making the hole much larger and much smaller; 2) by studyng openings of other shape (for instance, triangles of different size). 190 N. KIPNIS Conclusion The hypothesis is true, and the concrusion of the previous part is confirmedagain. Note: if there is a disagreement among different groupr:;i;";; ,=e*,the experiment at the conditions trrat produid the "different'i l. srilt- ' Gene ral C onc lusi o n Forma ti on Sunlight reproduces the shape ofany given opening only when the screen is closeto it' on the other hand, a1a sufficientty rarge aistance -y op""ing p.au"", "Pu-nd1ryce. Perhaps at rarge distances wJobtain ne imagl of tlie'ruminousbody. This hypothesis can be tested by experimenting witi light sources ofdifferent shapes. Again, as in the prelirninary part, the teacher exprains to students the necessityof various steps in the Main part (see Tabre l). In particular, stuaents may iugue*l l*t have already obrained trrc necessary Hypotheses in tir" pr.ii.inary part,and thus no more preliminary Experirnents are necessary. The teacher exprains thatany hypothesis from the preriminary part is tentative, because the experimentsleading to it were conducted without leeping everything but one variable constant.while.the Preriminary Experiments ur" n""""roryiorfoimurating " typotr,.sis, theTest aims at confirming it, which requires experiments different fromthose used tosuggest the hypothesis. .. To extend the importance of sorving Aristotre's problem, the teacher notes thatthe rounding-offof the-shador"', .o*.i, at large distances uas not understood untilthe work of Johannes Kepler (1571-1630). Tile teacher can provide a geometrical lra1ns ynresenting Keprel'f i{*., wtrictr trigtr-schoor students can foilow. Sincethis drawing is based onstraight lines representing light rays, the concrusion is madetl't Aristotre was mistakenabout his phenornenon contradicting the concept of rightrays being geometrical straight lines. Then the teacher discusses with students several points this unit offers about thenature of science. First, we see that even famous scientists .*m err. If studentswonder why they were abre to get better resurts than Aristoti", tr,. t"u"r,", *"yexplain that the scientific method of Greek scientists somewhat differed from themodern one. The ancient Greeks were keen observers of phenomena in nature, buttheir experimentation was sporadic. If instead of limiting his observations to the"natural objects" (the shadow of a fence), erirtou. r".[rt"a ut, fh"no*.nonartificially the way we did, he wourd have iiscove.ed the correct resurt. Second, we Y rylg"ing some probrems require a tremendous amount oriirne 1in this caseabout 2000 years!). Third, the case provides an opportunity to tark about the HISTORYOF SCIENCEAPPROACH I9I meaning of an experiment supporting a theory. Perhaps, some students will challenge the teacher's final conclusion that Kepler demonstrated the rectilinearity of light. The teacher answers that a theory is conlirmed when none of the experiments contradicts it. To decide whether there is an agreement or a contradiction, a scientist must make certain assumptions about the phenomenon, which may be true or not. For instance, Aristotle based his conclusion on the idea of a point source of light, while the sun is not one because its angular size is quite large. There may be other more generic questions as well, such as: l) How many experiments are enough to test a hypothesis? 2) What would have happened if we picked a false variable? The teacher explains that repeating an experiment involves varying a parameter to be sure that its quantitative change alters the result. For instance, if an experiment is conducted with only two different sizes of the opening, one would never be certain of the results at much larger or smaller dimensions. If a false variable (the shape ofan opening, for one) is selected, changing it does not affect the result. Since the time invested by a scientist in a given investigation is limite{ an unluclcy choice of a variable may lead to failure. Failure may also occur because ofan inadequate experimental procedure. Aristotle, for instance, could not see a rectangular shadow ifhe never changed the distance between the aperture and tfie "screen." There are otherdiffrculties as well. That is why, although all scientists use a similar research strategy, some of them make great discoveries, while others only minor ones. It is worth noting that the plan of investigation described here was tested with such subjecs as electricity and bioelectricity, optics and vision, acoustics and hearing, waves and vibrations, and graduates ofour programs have applied it to topics in mechanics, chernistry, biology, astronomy, and car troubleshooting. By consulting an appropriate work on the history of science (see Appendix A for suggestions), the general strategy provided here could be used in any science discipline. CONCLUSIONS Teaching aspects ofthe "nature ofscience" through an historical approach appeals to teachers if it is intertwined with teaching science content so that it makes the latter more stimulating without taking additional classroom time. Historical reading combined with investigative experimentation, especially of a historical nature, appears to be a prornising way for students to learn the basics of the scientific method and understand some other issues of the nature of science even when this subject is presented unobtrusively. While reading and a discussion with a teacher may be sufficient for a few motivated and curious students, this will not 192 N. KIPNIS work for the majority of them. Teachers rnay try to appeat to their practical sense, by explaining that theirfuturejob opportunities depend on theirability of systematic and critical thinking, but this is a too far-ferched perspective to many. on the other hand' involving any student on a daily basis in investigative operimentation where they can show their creativity without fear of being punished for errors, can gfadually change their attitude toward science and learning it. However, to teach students how to do investigative experiments, teachers must be trained in a similar way. This requires an investment of time and effort, but the benefits are considerable. This skill is applicable for life and may be used with any science subject and beyond science. Reading without experimentatlon, naturally, takes less preparation on the teacher's part, but its benefits are more limited; an experiment described in a book does not provide as much information as the real one, nor does it create a sense ofparticipation. Taking into account that few e.ducaton have an interest in experimentation and probably even fewer in the history of science, the value of my recommendations s@ms to be very limited. However, it is possible to split a course on the nature of science into two parts, theoretical and experimental, taught by two people. Moreover, the experiments must not necessarity be historical: one can find other experiments for investigations, the results of which are known and comprehensible to tqrchers (two important advantages of historical ones!). .And it is very possible tlut some educators will decide to try the fruit of history and find it interesting, if not delicious. Bakkcn Library and Museum, Minneapolis, Minnesota,USA NOTE Tlre Bakken Library and Museunr, founded by Eart E. Bakkeg inventor oftlre first trarsistorized cardiacpacemaker, is a center for education.and leaming that funhers tbe undentanding ofthe hisrory, cutnrralcon-!ex! and applicatiom of electricity and magnetisrn in tbe life sciences and i.di"in.. It holds a vastcollection of rare books and scic,ntificinsruments relating to ore hisnoricat role of..elec-tricity in life.Inadditiqt to serving as s researcfi.center, The Bakken is a pio-neer in rsing the history ofscience to enhance K-tz $ary^eargalion' through in-service training programs for sciendteacb."., *o*"hopu for students ingrades +12, publicatiors and kits. REFERENCES Arisbrfe-XV,Probbnsl(1970).Inthe L,oeb Ctassical Libaary. Cambridge MA HarvardUnivenityhess. Bekken ubrary and Musetrm (r99s). spark and shock: eqeriments from the golden oge of staticelectricity, Dubuque, Id KendalVtlunt. cqr{t'. J. 8.. (E_d.). (1959). Hamard case histories in qperimental science, canffidge, MA, HarvardUniversity hess. Devqrt S & Hartnanr, L (1920). .A hisoryoFphysics laboratory,, physics today, (\,la9. KiFis, N. (1992). Rediscovering optics, Minneapolis, MN, BENA press. HISTORY OF SCIENCEAPPROACH I93 Kip-c N. (1995). 'Quslitalive Phpics in High Sc{rool: A t€ssoi frorn Hi$ory', Proceedings ofthe Third Intemational Hi*ory, Philosophy, and Science Teaching Conference, Minneapolis, MN,Gry.624435). Kiprfs, N. (1996). 'The'Histqical-investigarive'approachtoteaching *iencc',Science and Educanon, (5\ 277-292. Klopfer, L & Cooley, W. (1961). Use ofcase histories in the development of student understanding of science and sciennsrs, Unpublished manuscrip! Harvard University, Cambridge, MA Klopfer, L. (19666). History of science cases, Chicago Il. Science Research Associates. Klopfer, L (1992). Historical perspec.tive on lhe history and nature ofscience on school science programs in BSCS/SSEC, Teachingabant tlre history and noture ofscience and technology: Background papers, Colorado Spring, CO, The Biological Sciences Curriculum Study, 105-129. I-awrenaF.&Kipnis,N.(1990).'Hands-onhistoryofphysics',JournalofScienceTeacherEducation,(l), 54-59. l,octrhea4 J. & Dufresne, R (1989). 'Helping $udarts understand difficuh science concepts through the use ofdialogrres wilh history. History and philosophy ofscieoce in science education (Proceedings ofthe First Intemational Conference), 221 -229 Maihews, M. R. (1990). 'History, philocophy and scierrce teaching Wha! can be done in an undergraduale course?', Studjes in Philosophy and Education, (10), 93-97. McComag W. (1995). 'A thernaric inlroduclion to lhe nature of scierrce', Proceedings of the Third International History, Philosophy, and Science Teaching Conference, Minneapolis, MN, 726-737. Rutherfor4 J. et al. (1970). Harvard project physics, New Yodr, Holt, Rinehan & Winston. Schwab, J. (1954) 'The teaching ofscience as enquiry', in J. Schwab & P. Brandwein (eds.),The Teaching Of Science, Carnbridge, MA Harvard Universiry hess,3l-102. Teichmanq J. ( 1986). 'The hislorical experiments in physics educalion: lheoretical observatiors and praCical examples. Science Education and lhe History ofPhysics', (Proceeding oflhe muhinalional teacher and teacher-trainer conference at lhe DeuGcbes Museunl Munich), 189-221. APPENDIX A This list ofreferences, added by edilor, ad&esses episodes from the history ofscience that may be useful in construcling sccnarios for use with the $ratery described in 0ris chapt€r. This li$ was ab'ridged from one ciginally developed by Robert Lovely and updated by HsingChi Wang The editor sincerely appreciates the willingpess ofthesc two individuals to allow their work to be used here. Teaching the History of Science Conan! J. B. (ed.). (1952). Case studies in experimental science, l-2, Cambridge, Md Harvard University Press. Manhews, M. R. (1994). Science teaching: The role ofhistory and philosophy ofscience, New Yor*, Routledge. Shortlan4 M., & Warwiclq A (eds.), (1989). Teaching the history of science, Ofrorrdn Blackwell. General Studies of the History of Science Boorsti& D. J. (1983). The discoverers, New Yorlq Randorn House. Bronowski, J. (1978). The origins of knowledge and imagination, Lol,;rfur, Yale University Press. Coheru I. B. (1985). Revolulion in science, Cambridge, MA Harvard University Press. Conant J. B. (1951). Onunderstanding science: Anhistoricalapproach NewYorlq Yale University Press. Kuhq T. S. (1977).The essentialtension: Selected sludies in tradition and change, Chicago, Il University ofChicago Press. Harr6, R. (1981). Great scientific experiments, Ot'or4 Phaidon. Lloyd, G. E. R. (1996).ldvrsaries and authorities: Investigation into ancientGreek and Chinese science, New York, Carnbridge University hess. I94 N. KIPNIS RonaqC.A(1982)' Science:Itshistoryanddevelopmentamongthelnonld'scultureq Newyork,Fac.tson File. sanon' G. (1936). The $udy of the history of science. canbndge, Md Harvard University hess. sarton' G. (1952). Horus: A guide to the history of science, watrhanr, Md chronica Bolanica. Thagar4 P. (1992). conceptual revolutions, princetorl NJ, princeton university hess. History of Science: Antiquity through the Renaissance Goldst€in, T. (1995). Dawn ofmodern science: From the ancient Greeks to the renaissance, New yor&, Da Capo Press. Hall, A R. (1984). The rewlution in science I 500-1750, New york, l.ongman tnc. Hafl, M. B. (1994). The scientific renaissance: I 450-l 630, New york, Dover. !1fuC, D. C. (1973). Science in the middle ages, Chicago, IIUniversity ofChicago press. undberg' D. c. (1992). The beginning ofwestern science,-hi"ugq I! univenity of6hicago press. Montgomery, S. L. (1996). The scientifc vorce, New york, Guilford. sobel' D. (1995). Longitude: The true story ofa lone genius who solved the grearest scienti/ic problem of his time, New York, Penguin Book Inc. schrodinger, E. (1996). Naure and the Greeks and science and humanism, New yorlq carnbridge University Press. Toulmirl S', Bush D.' Ackennaru J. S., & Palisca" C. V. (1961). Seve nteenth century science and arts.Rhys, H.H. (ed.), Princetoq New Jersey, princeton Univenity press. The Scientifi c Revolution Boas, M. (1966). The scientific renaissance, 1450-1630, New york, Harper & Row. Buferfiel4 H. (1966). The origins ofmodern science, New york, Free press. Byfebyl' J. (ed.), (1979). I4/illiam Harvey and his age, Balrimore, Johns Hopkins press. coheq I. B. (1985). Revolution in science, cambridge, MA Harvard University press. Drake S. (1957). Discoveries and opinions ofGatileo, GadenCiry, NJ, Doubieday. Hall, A R. (1984). The revolution in science I500-17SL,New yori, t ongman Inc. Koyre' A (1978). Galileo studies, (harc. John Mepham), Atlantic Highlan-ds, Nl Humaniries he*s. History of Science: Nineteenth and Twentieth Centuries Brockman, J. (1995). The third culture, New york, Touchstone. Buchwald' J. Z. (1997). 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