Physics: Encyclopedia II - Physics - Overview of physics research

Physics - Overview of physics research

Physics - Central theories

While physics deals with a wide variety of systems, there are certain theories that are used by all physicists. Each of these theories is believed to be basically correct, within a certain domain of validity. For instance, the theory of classical mechanics accurately describes the motion of objects, provided they are much larger than atoms and moving at much less than the speed of light. These theories continue to be areas of active research; for instance, a remarkable aspect of classical mechanics known as chaos was discovered in the 20th century, three centuries after the original formulation of classical mechanics by Isaac Newton (1642—1727). These "central theories" are important tools for research into more specialized topics, and any physicist, regardless of his or her specialization, is expected to be well-versed in them.

Physics - Major fields of physics

Contemporary research in physics is divided into several distinct fields that study different aspects of the material world. Condensed matter physics, by most estimates the largest single field of physics, is concerned with how the properties of bulk matter, such as the ordinary solids and liquids we encounter in everyday life, arise from the properties and mutual interactions of the constituent atoms. The field of atomic, molecular, and optical physics deals with the behavior of individual atoms and molecules, and in particular the ways in which they absorb and emit light. The field of particle physics, also known as "high-energy physics", is concerned with the properties of submicroscopic particles much smaller than atoms, including the elementary particles from which all other units of matter are constructed. Finally, the field of astrophysics applies the laws of physics to explain astronomical phenomena, ranging from the Sun and the other objects in the solar system to the universe as a whole.

Since the 20th century, the individual fields of physics have become increasingly specialized, and nowadays it is not uncommon for physicists to work in a single field for their entire careers. "Universalists" like Albert Einstein (1879—1955) and Lev Landau (1908—1968), who were comfortable working in multiple fields of physics, are now very rare.

Physics - Related fields

There are many areas of research that mix physics with other disciplines. For example, the wide-ranging field of biophysics is devoted to the role that physical principles play in biological systems and the field of quantum chemistry studies how the theory of quantum mechanics gives rise to the chemical behavior of atoms and molecules. Some of these fields are listed below.

Acoustics - Astronomy - Agrophysics - Biophysics - Chemical physics - Computational physics - Econophysics - Electronics - Engineering - Geophysics - Materials science - Mathematical physics - Medical physics - Physical chemistry - Physics of computation - Quantum chemistry - Quantum information science - Vehicle dynamics

Physics - Theoretical and experimental physics

The culture of physics research differs from the other sciences in the separation of theory and experiment. Since the 20th century, most individual physicists have specialized in either theoretical physics or experimental physics. The great Italian physicist Enrico Fermi (1901—1954), who made fundamental contributions to both theory and experiments in nuclear physics, was a notable exception. In contrast, almost all the successful theorists in biology and chemistry have also been experimentalists. However, in the last decades, quantum and computational chemistry became autonomous disciplines straddling the border between theoretical chemistry and theoretical physics. Many quantum chemists or theoretical molecular physicists are therefore often considered as pure theorists.

Roughly speaking, theorists seek to develop theories that can describe and interpret existing experimental results and successfully predict future results through abstractions and mathematical models, while experimentalists devise and perform experiments to explore new phenomena and test theoretical predictions. Although theory and experiment are developed separately, they are strongly dependent on each other. Progress in physics frequently comes about when experimentalists make a discovery that existing theories cannot account for, necessitating the formulation of new theories. Likewise, ideas arising from theory often inspire new experiments. In the absence of experiment, theoretical research can go in the wrong direction; this is one of the criticisms that has been leveled against M-theory, a popular theory in high-energy physics for which no practical experimental test has ever been devised.

Physics - Fringe theories

• Cold fusion
• Dynamic theory of gravity
• Luminiferous aether
• Steady state theory

Adapted from the Wikipedia article "Overview of physics research", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki