The word physics comes from a Greek word meaning natural thing. Solid-state physicists developed the transistor and other semiconductor devices. These devises contributed to the enormous growth of electronics industry since World War II. Knowledge obtained from the study of physics is important in other sciences, including astronamy, biology, chemistry, and geology. There is also a close connection between physics and practical developments in engineering, medicine, and technology. For example, engineers design cars and aeroplanes according to certain principle of physics. Laws and theories of physics have enabled engineers and scientists to put satellites into orbit and to receive information from space probes that travel to distant regions of the solar system. Research in physics has lead to the use of radioactive materials in the study, diagnosis, and treatment of certain diseases. In addition, theories and principles of physics explain the operation of many modern home conveniences, from vacuum cleaners to computers.