# Definition:Time/Fourth Dimension

## Definition

In the Theory of Relativity, it is convenient to consider time as another dimension in addition to, and treated similarly to, the $3$ dimensions of ordinary space.

## Historical Note

The treatment of **time** as **the $4$th dimension** originates with Albert Einstein.

While introduced as a mathematical convenience, the concept took hold in popular culture as a pseudo-scientific backing for an entire subgenre of science fiction: the time-travel story.

## Sources

- 1986: David Wells:
*Curious and Interesting Numbers*... (previous) ... (next): $3$ - 1997: David Wells:
*Curious and Interesting Numbers*(2nd ed.) ... (previous) ... (next): $3$