Unless you saw a recent issue of Physical Review Letters or a report based on it you may have missed the prediction by two American physicists that positronic water may exist.
Now, what struck me immediately about this item was that for most people who have come across the word at all, positronic is linked with robots. Think of Data, the android/robot in Star Trek: The Next Generation, who is described from time to time as having a positronic brain. The link with robots is due, as science fiction aficionados know, to the late Isaac Asimov (to whom the Star Trek reference is a small act of homage). He began to write stories about robots in 1940 and quickly took on the status of the SF robotics guru, accidentally inventing the word robotics itself by using it without realising nobody had done so before. He’s usually credited with inventing the Three Laws of Robotics that are supposed to guide the actions of all sentient robots (though he was always more than ready to point out that they were actually suggested to him by his editor, John W Campbell). He needed a scientific-sounding term that would suggest the brains of his intelligent creations to be innovative and futuristic, and so he invented the word positronic to describe matter that was suitable for the construction of an artificial brain with “enforced calculated neuronic paths”. Total nonsense, of course, as Asimov himself was the first to admit.
He based the word on positron, a subatomic particle similar to an electron but with a positive charge instead of a negative one. This had been discovered and named by the American physicist Carl Anderson in 1932. It seems that there is no earlier reference to the adjective before Asimov began to employ it. Indeed, of the four citations for the word positronic in the Oxford English Dictionary, three are from works by him, which seems a touch excessive. Interestingly, all four of them relate to SF sources, none to a scientific context. And even more interestingly, a quick search through half a dozen desk dictionaries finds not one reference to positronic, suggesting either that it is even more of a niche usage than I had thought, or that lexicographers don’t read SF, or that the number of times nuclear physicists need the adjective relating to positron is too small to record.
However, most of these dictionaries do contain an entry for something that hardly exists at all, or at least only fleetingly: a positronium atom. This consists not of a proton and an electron, like a normal hydrogen atom, but a positron and electron pair. Such combinations exist only for a very brief moment before the particles disappear in a small burst of gamma rays. In the article, the physicists say their calculations predict that water in which hydrogen atoms have been replaced by positronium should be stable enough to be observed (though what you do with it having created it is unexplained). Despite being transitory, this pseudo-atom positronium is well known to nuclear physicists, and even has its own chemical symbol, Ps.
But, pleasantly, the article and the reports based on it do use the word positronic several times, which suggests it may be on its way from genre fiction and scientific jargon into the mainstream, perhaps making a small job for lexicographers in the process. Let’s hope when they write the entry they include both senses of the word. Data would be pleased, as would the shade of Asimov.