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isolated from their original associations. The current practise of beginning each topic in physics with definitions or statements of laws, instead of with concrete experiences, does violence to the normal processes of acquiring knowledge that is definite and usable.
The prominence given to practical applications is thus one of the best features of the new definition. It is certain that the skilful and successful teacher will begin each topic with a study of such of these applications as are familiar to the pupils in his particular class.
3. Another very important feature of the new definition is the omission of the absolute units. Since the heart and soul of physics is measurement, and since measurement is possible only after units have been defined, the problem of defining units is a very fundamental one in physics. In the development of physics into its present highly complex and abstract form, the definitions of the units used in its measurements have also developed slowly into their present form. When the science was young, the units used were defined in terms of those phenomena which impress human senses most forcibly. Thus weight is a property which impresses the senses in a marked way in most daily experiences. Hence units of weight were established and used long before any one ever thought of defining the unit of weight in terms of the two factors mass and acceleration.
Before steam engines were invented, work was done by horses in treadmills. As a result of this, the work that a horse could do in a certain time was an early unit of work,a unit which still survives in our horse-power-hour. We also reckon work roughly in terms of the work a man can do in a given time, as when we say it requires two days' work for two men to build a chimney. It was a long time before the unit of work was separated into the two factors of weight and distance, and the foot-pound was introduced. This is still the only unit of work used by engineers.
The absolute units have been introduced very recently, having been developed in response to the growing demand of science for greater accuracy by a process of abstraction in which immediate sense impressions and intuition have been pushed into the background to make way for greater rigor and more perfect logic. Teachers are apt to forget that beginners do not appreciate and are incapable of assimilating this refined rigor and logic. The appreciation of these must be developed slowly in the individual as it has been in history. The attempt to make beginners comprehend the absolute units is futile; and experience has shown that high school pupils do not, as a matter of fact, gain clear and usable concepts of these units, notwithstanding the strenuous efforts of the teachers to make them do so. Besides, of what use are they to the great mass of the pupils, even if they did learn to use them in their physics work? These units are used at present only by the professional scientists; and how many of the 125,000 students of physics in the high schools each year become scientists?
Yet quantitative work is necessary in elementary physics, since measurement is the heart and soul of that science. It is, however, perfectly possible to do the necessary quantitative work in terms of the older and more intelligible units with as high a degree of accuracy as the pupils are able to appreciate, and with a great gain in their appreciation of the value of quantitative and definite knowledge. Such quantitative work should be carried on in whole numbers, as it were. It shows far better scientific habits when a student gets as the answer to a problem twenty-two foot-pounds, even if the number is not so very accurate, than when he brings in as his result the number 3.0481723, and is unable to specify clearly the unit in terms of which the result is exprest. In the words of the new definition, " The exercises should be free from the disguise of unintelligible units.”
Thus again the new definition of the physics unit shows that progress is being made. The teachers who framed it have evidently learned from their own experiences that the best results are obtained with beginners if the attempt is not made to teach in the first year the entire science of physics in its present complex form. This is a most important and significant change of front, because it indicates first: That the
course is being framed in the interest of the great mass of students instead of in the interests of the thousandth of one per cent. of them who become physicists annually; and second: That the enthusiasm among teachers for finished science and subject matter is giving way to a desire to have their pupils comprehend and clearly grasp their work, and gain in power and efficiency thru it. Henceforth the teaching of physics will be subordinate to the teaching of boys and girls.
4. Equally commendable with the omission of the absolute units is the omission from the new definition of many of the larger theories of physics; such as the kinetic theory of gases, the theory of ions and electrons, and the electromagnetic theory of light. Theories of this type can be rightly understood by any one only on the basis of a large fund of definite knowledge of concrete facts derived from individual experiences with material things. A pupil must have clear concepts and precise ideas concerning how phenomena take place and what material things will do before he can speculate and form hypotheses successfully.
If the more comprehensive theories are presented to a beginner before he has an adequate fund of definite knowledge of concrete facts, not only is his power of framing hypotheses blunted, thereby killing his scientific imagination; but also he soon comes to regard those theories as finalities, and is then unable to distinguish clearly between facts and theories— between knowledge and belief. To be able to frame fruitful hypotheses and to distinguish between facts and theories, is of fundamental importance for scientific,-i.e., clear and definite thinking Without this ability, progress in science would be impossible, because scientific growth depends on the creative power of hypotheses.
The current teaching of this type of theory often leads pupils into habits of what Professor William James calls “ vicious abstractionism,” in his significant article on a very prevalent abuse of abstraction in the Popular science monthly for May, 1909. Samples of this are the following: “An electron is nothing but an electric charge in motion.” “Light is simply waves in the ether.” “An electric current is nothing but an electron current.” Of this form of conclusion Professor W. S. Franklin says (Science, June 11, 1909, page 938): “ As if one could be placed under obligations to understand clearly any physical fact in terms of an extremely vague hypothesis!” To a person with a mind given over to vicious abstractionism, the precise ideas essential to scientific thinking are impossible. Those who treat science in this way are but searching for the pot of gold that lies buried at the end of the rainbow.
5. A final important point in the new definition is the statement which immediately precedes the syllabus of required topics; namely, “ It is expected that the teacher will arrange these topics in such order as to suit his individual needs." It is to be hoped that every teacher will take careful note of this statement before reading the list of topics. If it were not for this statement, it would appear that the syllabus simply stamped into fixt form current unfortunate practises. Because of this statement, teachers will be able to experiment and to make progress along the lines just suggested.
In closing, a few suggestions as to how the order of topics might be changed to make the teaching of the subject more successful will be added. The order of the syllabus is unfortunate wherever definitions and laws come first and experiments and applications after. For example, the first section reads: Metric system, Linear measure, units: meter, centimeter, etc. It is far better for the student to introduce these definitions when a need for making a measurement appears in the process of solving some problem or of settling some questionable point in the discussion. Only thus will the definition be concrete and the concept it embodies clear.
Section II A reads: Pascal's law of fluid pressure. The hydraulic press. For the reasons just given, the order might better be reversed. The law must come out of the experience, and not the reverse. In like manner, the topic: Conservation of energy, occurs in the middle of mechanics; whereas no student can appreciate it as a scientific conclusion until he knows something of heat and electrical energy and their interrelations. Presented early in the course, it becomes to him
a dogma to be accepted on authority instead of being a wellsubstantiated hypothesis of great fertility.
The first topic in heat is: Heat—a form of energy. This conclusion ought not to be reached until the student has drawn from concrete experience a large fund of information about the properties of heat. In light, in like manner, the first section is: Definitions: Light, luminous bodies, etc. A much better order would be: The pin-hole camera, rectilinear propagation of light, the eye, the photographic camera, refraction, etc. If only we teachers could get a realizing sense of how injurious it is to the scientific spirit of our pupils to be forever telling them what is right and what wrong in science, immediate improvement in our work would result. Pupils should gain from their study of science a habit of framing and testing hypotheses for themselves, but we are constantly breaking up this habit by too quickly telling them things they should find out, and correcting their supposed mistakes from the point of view of current scientific theory.
The syllabus also contains some topics which should be treated only qualitatively or else omitted entirely. The teacher may, however, transfer the quantitative treatment of these topics to the end of the course, omit it entirely for those who are not going to college, and cram those who are preparing for an entrance examination on it at the last minute. Since experience has shown that the high school pupils can not assimilate the quantitative treatment of these topics, the order just suggested will meet any quantitative requirement with a minimum of injury to all concerned. Getting over " the quantitative treatment just before examination will also increase the college-bound pupil's chances of passing.
The most important of the topics that may to advantage be handled in this way are: Mass, density, Newton's laws of motion, force (as ma), momentum, uniformly accelerated motion, falling bodies, relation of weight and mass, law of universal gravitation, absolute zero, relation between direction of current and lines of magnetic force, direction and magnitude of induced electromotive force, electrification by induction.