ABSTRACT
German physicist Wilhelm Roentgen was working with a novel lab device, a glass tube pumped free of most of its air, with a metal electrode at each end. When high voltage was applied to the electrodes, a glow appeared between them. Though the tube had an opaque covering, Roentgen noticed that whenever it was turned on, a fluorescent screen three meters away would light up. Roentgen had discovered an unknown kind of penetrating radiation he dubbed “X-rays.” They generated universal wonderment. Computed tomography creates X-ray images of cross sections of the body that a computer then assembles into a detailed image. When this is done from different angles, changes in density can be converted into pictures of soft tissue, along with bones and blood vessels. Positrons are elementary particles first suggested in 1928 when French physicist Paul Dirac predicted that an electron has a kind of fraternal twin, exactly the same but with the opposite electrical charge.
