We all know Einstein's famous equations E=mc^2. It means that energy and mass are two halves of the same variable, and that a little mass makes an enormous amount of energy. We also know its disastrous effects, as evidenced in the US's infamous Manhattan Project.
The first nuclear bomb ever tested was dubbed "The Gadget, " and the test itself was nicknamed the Trinity Test. It was conducted on the morning of July 16, 1945 in the Alamogordo bombing range of New Mexico. The bomb was said to release the energy of about 20 kilotons of TNT, or about 84 terrajoules. Now, if we plug that number into Einstein's equation, we can find exactly how much radioactive plutonium was put towards the actual explosion. Using 3E8 as c and 84E12 as E, we find that the mass of the plutonium reacting was about 9E-4Kg.
However, I assure you much more plutonium was used to create the Gadget than that. So where did all the rest go? Well, into the massive amount of heat and light created, more than enough to blind people and incinerate standing structures for miles. This conversion seems to be the most powerful force we can today harness, and it truly has awe inspiriing results.