what is unification and reduction in physics?
Unification is the attempt to describe all physical forces as a single (unified) set of mathematical relationships. There are 5 forces that cause all observed phenomenon: gravitational force, magnetic force, electric force, weak force, strong force.
Unification has occurred already in two areas:
In the 1860's James Clerk Maxwell showed that magnetism and electricity are described by a single set of equations, and that they are fundamentally the same thing - now known as electromagnetism.
In the 1970's Abdus Salam, Sheldon Glashow and Steven Weinberg did the same thing with the weak nuclear force and electromagnetism . They developed a mathematical model that showed that under the right conditions (high temperatures/energies) the two phenomenon would be the same thing.
Physicists are now working on a "Grand Unified Theory" (GUT) that would also include the strong nuclear force. A more distant goal is the inclusion of gravity to create a truly unified "theory of everything".
Reductionism is a philosophical position which holds that a complex system is nothing but the sum of its parts, and that an account of it can be reduced to accounts of individual constituents. This can be said of objects, phenomena, explanation, theories, and meanings.