# Why does E=mc^2?

**URL:** <https://boards.straightdope.com/t/why-does-e-mc-2/922984>\
**Category:** Factual Questions\
**Created:** [October 15, 2020, 5:10am UTC](https://boards.straightdope.com/t/why-does-e-mc-2/922984 "2020-10-15T05:10:29Z")\
**Posts on this page:** 1\
**Showing post:** 13

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**Author:** ![Pasta](https://avatars.discourse-cdn.com/v4/letter/p/ecccb3/32.png) [@Pasta](https://boards.straightdope.com/u/Pasta)\
**Post date:** [October 15, 2020, 5:52pm UTC](https://boards.straightdope.com/t/why-does-e-mc-2/922984/13 "2020-10-15T17:52:56Z")

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> [@Northern\_Piper](#):
>
> But what does the speed of light (squared) have to do with the relationship between mass and energy?

[This thread is a place to start](https://boards.straightdope.com/t/speed-of-light-revisited-permeability-and-permittivity/842167). In it, there are a number of posts talking about why _c_ shows up in so many places, such as _E_=_mc_2). (Unfortunately the old vBulletin markup gets in the way in a few parts.)

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