does e really equal mc squared?

Question: does e really equal mc squared?
- Keywords:
  energy,
  history,
  maths,
  properties
Asked by chalier to Helen on 21 Nov 2014.
- Helen Johnson answered on 21 Nov 2014:
  
  It really does (but it changes when you get close to the speed of light)! It means mass is a way to store energy. c is the symbol for the speed of light. In a nuclear reactor there is change in mass of the particles, and this is converted to energy.

Question: does e really equal mc squared?