<p align="right">Last Update: <font color="#4f81bd">October, 15, 2024</font></p> ## BIG IDEAS - The [[SI units|SI unit]] for length. - A meter is a [[Base Units|base unit]] for the SI system. --- ### Definition The definition of a meter has changed over the years. The internationally agreed upon definition is the distance light travels in a vacuum $1/299 \ 792 \ 458$ of a second. ### Source [Meter | NIST](https://www.nist.gov/si-redefinition/meter) --- Return [[Home|Home]] | [[SI units]] | [[Physical constant|Physical constants]] | [[Base Units]]