Length contraction is a phenomenon predicted by the theory of special relativity, formulated by Albert Einstein. It states that objects moving at high speeds will appear shorter in the direction of their motion when observed from a stationary frame of reference. This effect becomes significant as the object's speed approaches the speed of light. For example, if a spaceship travels close to the speed of light, an observer on Earth would measure its length to be less than its length at rest. However, the astronauts inside the spaceship would not notice any change in their own measurements, as they are in the same moving frame of reference.