E=mc^2<p>You may be thinking &quot;Oh, you fool--E=mc^2 is for fission and fusion, and certainly doesn&#x27;t apply to things like the energy in the heat of an object&quot;.  But weirdly, it does. <a href="https:&#x2F;&#x2F;physics.stackexchange.com&#x2F;questions&#x2F;87259&#x2F;does-decrease-in-temperature-affect-mass-e-mc2" rel="nofollow">https:&#x2F;&#x2F;physics.stackexchange.com&#x2F;questions&#x2F;87259&#x2F;does-decre...</a>