The nature of physical knowledge

  Until the end of eighteenth century , the study of material things was treated as a single feature of human thinking and called natural philosophy . But , as knowledge increased , it was found obligatory to divide the study of nature into two main branches , the physical sciences and biological sciences . The biological sciences deal with living things , while the physical sciences are concerned with the properties and behavior of non- living matter .

     The two main  physical sciences are physics and chemistry . Broadly speaking ,chemistry deals with the action of one kind of substance on another , while physics is concerned mainly with matter in relation to energy .

    For basic purposes , the study of physics may be grouped under such headings as mechanics , properties of matter , heat , wave motion , light , magnetism , and electricity . At higher level we have particle physics , nuclear physics , and plasma physics ….. etc.

     Since it is the most vital of sciences , physics finds several applications in other fields . Thus we have those branches of science known as physical chemistry and biophysics . Physics has also come to play an important responsibility in medical and surgical research .

    In physics, certain properties of matter are measured and the results examined to see if there is any mathematical relationship between them.

It is important to grasp the true meaning of the equations we find an a physics book. They do not tell us what things are in themselves, but are simply a convenient way of expressing the laws governing their behavior.

This is the main purpose of science, to seek out the laws of the universe and, if possible, to express them in precise mathematical form.

     Technologists use this information for such purposes as designing electric dynamos and motors, radio, television and radar installations, artificial satellites and spacecraft, nuclear power generators and so on, all of which have helped to make our material way of life so different from that of our forefathers.

Measurements in physics

   All measurements in physics, even of such things as electric current, are related to the three chosen fundamental quantities of length, mass, and time. Until about the year 1800, workers in various countries used different systems of units. Thus, while an Englishman used inches, a continental scientist would measure lengths in centimeters.

Fortunately, this unsatisfactory situation has now been changed by the efforts of various international committees of scientists who have met for discussion regularly over many years.

International System of Units

   In 1960, the General Conference of Weights and Measures recommended that everyone should use a metric system of measurement called the International System of Units ( abbreviated SI in all languages). The SI units are derived from the earlier MKS system, so called because its first three basic units are the meter ( m ), the kilogram ( kg), and the second ( s ).

Work of national physical laboratories

  Through history man has always realized the need for standard weights and measures, and from time to time these standards have been revised, improved, and established by law.

  In most big countries of the world there are laboratories, supported largely by government funds, in which scientists are at work on problems of industrial and national importance. These institutions are responsible for maintaining and improving the standards of all the important physical quantities. Scientists from the various countries compare their results and regularly meet for discussion, and often they are able to announce new definitions of the basic units.

Coming up : Measurement of length, mass, and time.