Definition:Relativity Theory

Definition

Relativity theory is the branch of physics concerned with:

the behaviour of matter travelling at speeds that are an appreciable fraction of the speed of light

the structure of spacetime

the theory of gravitation.

The theory was developed in two stages:

Special Theory of Relativity

The special theory of relativity is concerned with the phenomena of physics as experience by two observers moving relative to one another at constant velocity.

Hence it is restricted to inertial frames of reference.

General Theory of Relativity

The general theory of relativity extends the special theory of relativity by considering observers in non-inertial frames of reference.

Also see

• Results about relativity theory can be found here.

Historical Note

Relativity theory was conceived by Albert Einstein in the early $20$th century.

The two theories that it comprises led to a re-analysis of the concepts of space and time, and of the interrelationship between measurement and observer.

Sources

• 1998: David Nelson: The Penguin Dictionary of Mathematics (2nd ed.) ... (previous) ... (next): relativity
• 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): relativity