INTRODUCTION to Physics
Without the science of physics and the work of physicists, our modern ways of living would not exist. Instead of having brilliant, steady electric light, we would have to read by the light of candles, oil lamps, or at best, flickering gaslight. We might have buildings several stories high, but there could be no hope of erecting an Empire State Building. We could not possibly bridge the Hudson River or the Golden Gate much less build a jet plane, use a cell phone, or watch a television show. The personal computer would be unimaginable.
All other natural sciences depend upon physics for the foundations of their knowledge. Physics holds this key position because it is concerned with the most fundamental aspects of matter and energy and how they interact to make the physical universe work. For example, modern physics has discovered how atoms are made up of smaller particles. It has also revealed how these particles interact to join atoms into molecules and larger masses of matter. Chemists use this knowledge to guide them in their work in studying all existing chemical compounds and in making new ones.
Biologists and medical researchers in turn use both physics and chemistry in studying living tissues and in developing new drugs and treatments. Furthermore their electrical equipment, microscopes, X-rays, and many other aids and the use of radioactivity were developed originally by physicists.
Physicists have also led in bringing people to think in scientific ways. What we call the scientific method had its real beginnings some four centuries ago in many fields of knowledge. The most impressive of the early triumphs came in physics and in its application to astronomy for studying the motions of the Sun, Moon, planets, and stars.
Galileo made the first real contributions, in the late 16th and early 17th century. He discovered the natural laws that govern falling bodies and the swinging of the pendulum. Shortly after this, Johannes Kepler established the three laws that explain all the motions of the planets. Finally, in the late 17th century Isaac Newton explained these results by establishing the law of gravitation. This law applies invariably to all matter in the universe—whether it is as small as a grain of sand or as large as the Sun. This triumph of explaining a vast range of phenomena with a single law inspired workers in all fields of knowledge to trust scientific methods.
This revolution in understanding was greatly aided by concurrent advances in technology. Instruments such as clocks, barometers (which measure the pressure of the atmosphere), and telescopes were invented and improved. For example, Galileo, Kepler, and Newton made contributions to the development of telescopes and thus gave astronomy a powerful instrument with which to work.
There is no exact distinction between physics and other natural sciences because all sciences overlap. In general, however, physics deals with phenomena that pertain to all classes of matter and energy. Physicists try to discover the most basic laws of nature, which underlie and often explain those of other fields of science.
One major branch of physics, mechanics, deals with the states of matter—solids, liquids, and gases—and with their motions. The pioneer achievements of Galileo, Kepler, and Newton dealt with solid masses of matter in motion. Such studies are a part of the subdivision of mechanics called dynamics, the study of matter in motion. This wide-ranging topic includes not only the motions of stars and baseballs but also those of gyroscopes, of the water pumped by a fire engine (hydrodynamics), and of the air passing over the wings and through the jet engine of an airplane (aerodynamics).
The other great subdivision of mechanics is statics, the study of matter at rest. Statics deals with the balancing of forces with appropriate resistances to keep matter at rest. The design of buildings and of bridges are examples of problems in statics.
Other divisions of physics are based on the different kinds of energy that interact with matter. They deal with electricity and magnetism, heat, light, and sound. From these branches of physics have come clues that have revealed how atoms are constructed and how they react to various kinds of energy. This knowledge is often called the basis of modern physics. Among the many subdivisions of modern physics are electronics and nuclear physics.
Physics is closely related to engineering. A person who uses physical principles in solving everyday problems is often called an engineer. For example, electricity is one of the subdivisions of physics; one who uses the natural laws of electricity to help in designing an electric generator is an electrical engineer.
