Based on observations and analysis, they formulate theories and laws to describe the forces of nature, such as gravity, electromagnetism, and nuclear interactions. They also devise ways to apply the laws and theories to problems in nuclear energy, electronics, materials, communications, aerospace technology, and medical instrumentation. Astronomy is sometimes considered a subfield of physics. Astronomers use the principles of physics and mathematics to answer questions about the fundamental nature of the universe, and about celestial bodies such as the sun, moon, plants, and stars. They may apply their knowledge to problems in navigation and space flight.
Most physicists work in research and development.
Some do basic research to increase scientific knowledge. For example, they investigate the structure of the atom or the nature of gravity. Some physicists, conduct applied research and develop new devices, products, and processes. For instance, research in solid-state physics led to the development of transistors and then to integrated circuits used in calculators and computers. They also design research equipment.