I know E=mc2 essentially means energy = mass. One might think why not just say E = m? But I also know that: Every object travels through space and time at the speed of light. So now one might think why not just E=mc? That's essentially where I'm stuck at now. I'm not sure why it's necessary to 2 the c. I know that light waves only travel at right angles, but I don't know if that has any relevance to the formula.