Embed Notice

@NeonPurpleStar @jccpalmer
Also, they, and almost everyone else, use the formula that only works for a mass at rest. The full one:

E^2 = (pc)^2 + (m_0 c^2)^2

Th popular one should be more correctly written as:

E = m_{rel} c^2

to emphasise that it is the relativistic mass that is meant here.