In 1903, Rutherford collaborated with Frederick Soddy to write an impor­tant paper, “Radioactive Change.” In this work they offered the first exper­imentally verified calculations of the energy released from an atom due to radioactive decay. The power involved in the transmutation of radioactive elements was astounding. They had found that the energy released by the decay of one gram of radium could not be less than 100,000,000 gram calories. It was probably closer to 10,000,000,000 or 10 billion gram calories.

In 1903, at the University of Kiel in Germany, Philipp Lenard (1862­1947) reached an interesting conclusion regarding atomic structure. Ruth­erford was in accordance with J. J. Thomson’s opinion that the atom was one solid mass, like a plum pudding, with electrons adhering to the out­side, remarking that, “I was brought up to look at the atom as a nice hard fellow, red or gray in color, according to taste.” Thomson was, after all, his thesis adviser for his doctorate, awarded in 1900. A solid object, such as a block of metal, was obviously hard, massive, opaque, continuous, and homogeneous.

Lenard had been working on cathode ray tubes, hoping to accomplish what Roentgen had tried, bringing cathode rays out the end of the glass vacuum tube and into the laboratory. He had devised a metal window thick enough to withstand the air pressure outside the tube but thin enough for

cathode rays to penetrate and flow into the atmosphere. It worked. He was able to detect cathode rays outside the tube using a fluorescent screen, but he noticed that the rays were scattered somewhat when they blew through the metal window. This seemed to contradict the theory that they were