mass and energy have an equivalence. They are two forms of the same thing: energy is liberated matter; matter is energy waiting to happen. Since c2 {the speed of light times itself} is a truly enormous number, what the equation is saying is that there is a huge amount-a really huge amount-of energy bound up in every material thing.4 You may not feel outstandingly robust, but if you are an average-sized adult you will contain within your modest frame no less than 7 × 1018 joules of potential energy-enough to explode with the force of thirty very large hydrogen bombs, assuming you knew how to liberate it and really wished to make a point.
( Bill Bryson )
[ A Short History of Nearly ]
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