Written by the Fiveable Content Team • Last updated September 2025
Verified for the 2026 exam
Verified for the 2026 exam•Written by the Fiveable Content Team • Last updated September 2025
Definition
Relativity is a theory in physics that describes how the laws of physics are the same for all observers, regardless of their relative motion. It explains how time, space, and mass can change depending on an observer's velocity.
Related terms
Time dilation: Time dilation refers to the slowing down of time for objects that are moving relative to an observer. It means that time passes slower for objects in motion compared to those at rest.
Length contraction: Length contraction is when an object appears shorter when it is moving relative to an observer. This happens because space contracts along the direction of motion.
Mass-energy equivalence: According to Einstein's famous equation E=mc², mass and energy are interchangeable. This means that mass can be converted into energy and vice versa.