Girl holding a Van de Graaf generator, 1998.

UNITED KINGDOM - MAY 22: During his research at Oxford University, American physicist R J Van de Graaff (1901-1967) conceived an improved type of electrostatic generator, in which electric charge could be built up on a hollow metal sphere. Van de Graaff developed this generator for use as a particle accelerator, and it became an important tool of atomic and nuclear physics. It was also adapted to produce high-energy X-rays, and was useful in the treatment of cancer and in the examination of the interior structure of heavy ordnance. The generator shown here was built as a demonstration model for Launch Pad, the children's gallery at the Science Museum, London. (Photo by SSPL/Getty Images)