Radioactivity

Mysterious from the start, radioactivity attracted researchers who struggled to understand it. What caused certain atoms to give off invisible, penetrating rays? Where did the energy come from? These questions became increasingly pressing when researchers realized the process seemed to continue indefinitely, producing huge quantities of energy. Investigators found cases where radioactivity did change, forcing them to the startling conclusion that radioactive bodies were transmuting into other substances. Chemical elements were not immutable after all. Radioactivity produced traces of matter so minuscule and evanescent that researchers had to devise new techniques and instruments to investigate them.