# Length contraction

Objects moving fast are shorter along the direction of motion, by the factor 1/gamma.

Physics (university) · Part 10: Relativity and quantum physics · Card 3 of 11 · Last updated 2026-10-19

## Analogy

A moving ruler looks squashed along its length.

## Example

**Ship length**

gamma = 1.25
L = 100 / 1.25
L = 80 m

## In practice

A 100 m spaceship moving at 0.6c is measured as 80 m long.

## Questions people ask

### Does the ship really get shorter?

Observers measuring the ship moving at speed find a shorter length along the motion, and that is a real measurement in their frame. People on the ship measure it at normal length. Space and time depend on motion, so length is not one fixed number.

### Does length contraction happen sideways?

No. Only the dimension along the direction of motion shrinks. Height and width are unchanged. A fast moving sphere would measure as a flattened disc in the direction of travel. The effect is only noticeable above about ten percent of light speed.

## Related concepts

- [Postulates of relativity](https://studyvisually.com/learn/science/physics-university/physics-university-part-10/physics-university-part-10-concept-1)
- [Time dilation](https://studyvisually.com/learn/science/physics-university/physics-university-part-10/physics-university-part-10-concept-2)
- [Mass-energy equivalence](https://studyvisually.com/learn/science/physics-university/physics-university-part-10/physics-university-part-10-concept-4)

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