Physical science is the systematic study of the inorganic world, as distinct from the study of the organic world, which is the province of biological science. Physical science consists of four broad areas: physics, chemistry, astronomy and the Earth sciences. Each of these is in turn divided into fields and subfields. This article describes the first two of these areas.
Physics, in its modern sense, was founded in the mid-19th century as a synthesis of several older sciences – namely, those of mechanics, optics, acoustics, electricity, magnetism, heat, and the physical properties of matter. The synthesis was based in large part on the recognition that the different forces of nature are interconvertible and related because they are forms of energy.
The boundary between physics and chemistry is somewhat arbitrary. As it has developed in the 20th century, physics is concerned with the structure and behaviour of individual atoms and their components, while chemistry deals with the properties and reactions of molecules. These latter depend on energy, especially heat, as well as on atoms; hence, there is a strong link between physics and chemistry. Chemists tend to be more interested in the specific properties of different elements and compounds, whereas physicists are concerned with general properties shared by all matter.