Ernest Rutherford, The Man Who Found The Nucleus

He found the nucleus, and in doing so broke the atom so thoroughly that only quantum mechanics could put it back together. In 1909 two men in a darkened room in Manchester spent weeks counting faint flashes of light on a screen. Ernest Marsden, an undergraduate whom Hans Geiger had judged ready for a project of his own, had been set a question by his professor that nobody expected to yield anything. He was firing alpha particles at a metal plate, with the detecting screen on the same side as the source, and looking for particles that came back. Some did. Roughly one in eight thousand bounced off a platinum reflector at ninety degrees or more. Nothing in the accepted picture of the atom could turn a fast alpha particle round, and the man who had set the question spent the better part of two years working out what it meant. That man was Ernest Rutherford. His answer, published in 1911, was that the atom is almost entirely empty, and that its positive charge and nearly all of its mass sit in a core so small it occupies a vanishing fraction of the volume. He had found the atomic nucleus.…