But you haven't created or destroyed anything - just changed it, which is what I was taught. There is no something from nothing. Prior to Einstein, it was believed that the following were two independent absolutes:
- Matter can be neither created nor destroyed.
- Energy can be neither created nor destroyed.
The conversion of matter into energy would thus have been thought impossible since it would destroy matter and create energy. Nowadays, there's a new rule, that says that the total amount of (matter+energy) is constant, but matter and energy can be converted into each other.