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.
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.
The first unquestionable proofs of the transformation of elements into different chemical elements have been provided by the study of the phenomena of radioactivity.
