Albert Einstein in 1905.
Courtesy Lotte Jacobi, Hillsboro, New Hampshire
One of Einstein’s predictions had to do with the equivalence of matter and energy. Until 1905 matter had been considered as something that has mass or inertia; energy, on the other hand, had been regarded as the ability to do work. It was believed that the two were as different from each other as, say, a square yard is different from an hour. Einstein’s theory, however, implies that matter and energy are merely two different manifestations of the same fundamental physical reality, and that each may be converted into the other according to the famous equation:
E = MC²
where
E = quantity of energy,
M = quantity of matter, and
C = speed of light in a vacuum.
Nuclei Contain Energy
One more piece of information must be fitted into the story of the atom before it becomes clear why some people began to realize during the 1920s that atomic nuclei contain vast stores of energy that might some day revolutionize civilization. This last item has to do with a nuclear phenomenon known as the packing fraction.