The scientist Albert Einstein did not participate in the invention of the atomic bomb and nuclear energy. But he was the key to unlocking the development of nuclear energy and atomic bomb. In 1905, as part of his Special Theory of Relativity, he made a point that a large amount of energy could be released from a small amount of matter. This was development of the equation E=mc2 energy = mass times the speed of light squared. The atomic bomb would clearly this equation worked. But Einstein wasn't thinking of nuclear bombs when he thought up E=mc2. A nuclear chain...
Uranium atoms. It goes on and on if you have millions of dominoes. Then I knocked over the first domino in one of the two straight lines and they all fell. For the second part I took a ruler and held it anywhere between the dominos lined up in the second straight line, then I used my other hand to knock over the first domino. The results were that only some dominos fell because the ruler stopped them from hitting other dominoes. It worked kind of like a control rod used to absorb neutrons in a Nuclear power plant.