Physics is closely related I0 the other natural sciences and, in a Sense, cncompasscs themChemistry, for example, deals with lhc inlcmction of atoms to form molecules; much of modem geology is larger a study of the physics of the earth and is known as geophysics; and astronomy deals with the physics of the stars and outer space. Even living systems are made up of fundamental particles and, 11S studied in biophysics and biochemistry, they follow thc same types of laws as the simpler Particles traditionally studied by a physicist. The emphasis on the interaction between particles in modem physics, known as the microscopic approach, must often be supplemented by a macroscopic approach that deals with larger elements or systems of particles. This macroscopic approach is indispensable to the application of physics to much of modern technology. Thermodynamics, for example, a bmnch of physics developed during the 19th century, deals with the elucidatìon and measurement of properties of a system as a whole and remains useful in other fields of physics; it also forms the basis of much of chemical and mechanical engineering. Such propenies as the temperature, pressure, and volume
0f a gas have no meaning for an individual atom or molecule; these thermodynamic concepts can only be applied directly to a very large system of such particles. A bridge exists, however, between the microscopic and macroscopic approach; another branch of physics, known as statistical mechanics,
indicates how pressure and temperature can be related t0 the motion of atoms and molecules on a
statistical basis,
Physics emerged as a separate science only in thc carly l9th century; until that time a physicist