Chemical substance can be transmuted into another element through a nuclear reaction. This is so, because all of the atoms in a sample of an element have the same number of protons, though they may be different isotopes, with differing numbers of neutrons. As of 2012, there are 118 known elements, about 80 of which are stable – that is, they do not change by radioactive decay into other elements. Some elements can occur as more than a single chemical substance (allotropes). For instance, oxygen exists as both diatomic oxygen (O) and ozone (O). The majority of elements are classified as metals.
More Than One Universe More Than One Universe More Than One Universe: The Collected Stories of Arthur C. Clarke is a collection of science fiction short stories by Arthur C. Clarke originally published in 1991. The stories originally appeared in the periodicals "Playboy", "Vogue", "Dude", "New Worlds", "The Magazine of Fantasy & Science Fiction", "Dundee Sunday Telegraph", "Analog", "Amazing Stories", "Galaxy Science Fiction", "Infinity Science Fiction", "London Evening News", "Startling Stories", "Venture Science Fiction Magazine", "If", "Boys' Life", "This Week", "Bizarre! Mystery Magazine", "Escapade", "Asimov's Science Fiction", "Astounding", "King's College Review", "Dynamic Science Fiction", "Thrilling Wonder Stories", "Satellite", "Argosy" and "Ten Story Fantasy" as