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.^{[1]} This can be said of objects, phenomena, explanation, theories, and meanings.^{[2]}