Concept preview

What you will be able to do

1. 01Use E = mc² to relate mass and energy
2. 02Describe relativistic energy and why nothing reaches the speed of light
3. 03Link mass–energy equivalence to nuclear energy

Einstein's relativity delivers one final bombshell: mass and energy are the same thing, related by $E = mc^2$. Because $c^2$ is enormous ($9\times10^{16}$), even a tiny mass hides a colossal amount of energy. The mass locked in a single paperclip, fully converted, could power a town for days. Mass is simply frozen energy.