Most of the atoms in the world are either hydrogen or helium. Hydrogen, of course, is the simplest of atoms. One electron circling one proton. The Ockham's razor of atoms. Helium is what you get when a lot of hydrogen atoms are tightly compressed together in a star. It is the consequence of the process of fusion in that context. What about all the other elements? Most of them can be explained as themselves also the products of nuclear fusion in the stars, increasingly rare as they get heavier. But there are a few elements that scientists think require a more complicated explanation, and gold is one of these. These problem elements are neutron heavy and they could only have come into existence in an environment that allows rapid neutron capture, known as "the r process." The usual theory has been, for decades now, that the r-process is created when neutron stars merge with each other, since a dense soup of neutrons, is the most plausible source for gold and ...