text: can someone please explain e=mc^2 in plain simple english to me?   it's a conversion equation. it allows you to convert mass into energy and energy into mass. everything that has mass has energy stored in it. if you were able to convert it completely to pure energy (we can't do that yet), then you'd get the amount of energy shown in the equation. e is energy, m is mass, and c is the speed of light squared.  a raisin if completely converted can power all of new york city for a full day.  >>the faster you go. the more mass you will have. ie if i threw a ball bearing at a piece of wood it would bounce off. if i fired it out of a gun it would go through it.<<  that's not e=mc^2. it's a different postulate by einstein. and the ball gun comparison is completely wrong.