"The switch from natural sources of particles to accelerators would start a new era in the history of science, the era of accelerator physics. ...The two men who actually built the first accelerator were John Cockcroft and Ernest Walton, graduate students working... under the supervision of Rutherford. ...For five years they struggled to create a technology of big machines in a laboratory of tabletop experiments, just as the Wright brothers had struggled to create a technology of flying machines in a bicycle shop ....In April of 1932, they had a machine that produced a steady stream of hydrogen nuclei with an energy of about half a million volts. ...Walton was... ready to do the experiment... to bombard a target made of the light metal lithium. The result was spectacular. The lithium nuclei were split in two and fell apart into pairs of helium nuclei. The helium nuclei came out with thirty times as much energy as the hydrogen nuclei going in. ...Rutherford happily spent the rest of the day serving as Walton's assistant... That day, the era of tabletop nuclear physics ended and the era of big machines and big projects began."