Astronomers sometimes observe that a star of medium magnitude increases suddenly in size; a star invisible to the naked eye may become very brilliant and visible without any telescope - the appearance of a Nova.
Frederic Joliot-Curie
The first unquestionable proofs of the transformation of elements into different chemical elements have been provided by the study of the phenomena of radioactivity.
There is no doubt that radium is transformed spontaneously into an active gas, radon, emitting at the same time alpha particles, or helions.
In England and the United States, where physicists have at their disposal equipment of very high voltages, several new elements were prepared using protons and deuterons as projectiles.
