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The '''speed of light in vacuum''' (symbol: '''''c'''''<sub>0</sub>), often just referred to as the '''speed of light''', is a [[physical constant]] which appears in several different contexts. As the name suggests, it is the speed of [[electromagnetic radiation]] in [[vacuum]], and is the maximum speed at which matter, energy or information can travel; it also links [[space]] and [[time]] in [[Theory of relativity|relativistic]] contexts, and appears in the famous equation of [[mass–energy equivalence]] ''E''&nbsp;= ''mc''<sup>2</sup>. In the [[International System of Units]] (SI), it has the defined value of {{nowrap|299 792 458 metres}} per second.

==Notes and references==
===Notes===
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===References===
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==External links==
{{wikipedia|Speed of light}}

[[Category:Physical constants]]

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