Though the notion of a simple philosopher's stone of the alchemic sense fell out of scientific conception by at least the 19th century, its metaphors and imagery persisted: man's attempt to discover the essential secret of the universe, redemptively transforming not just lead into gold, but death into life.
In 1901, Ernest Rutherford and Frederick Soddy discovered that radioactivity was a sign of fundamental changes within elements, and it was Soddy who quickly made the connection between this and the ancient search for the philosopher's stone (Soddy had studied alchemy extensively as a hobby). At the moment of realization that their radioactive thorium was converting itself into radium, bit by bit, Soddy later recalled that he shouted out: "Rutherford, this is transmutation!" Rutherford snapped back, "For Christ's sake, Soddy, don't call it transmutation. They'll have our heads off as alchemists." However the term stuck, in part because it drew the new discoveries in nuclear physics into a longer cultural and mystical web.
When it was discovered that radioactivity was also tapping into a latent source of energy bound inside atoms, this furthered the thought that radioactive decay might be the ultimate philosopher's stone. Later, the discovery of nuclear fission would become consciously connected into the same narrative, especially with optimistic hopes of energy "too cheap to meter" and great utopian cities of the future run on nuclear energy.