In 1989, the University of Utah announced what seemed to be the scientific discovery of the century: nuclear fusion, producing usable amounts of heat, could take place on a table-top, through the electrolysis of heavy water using electrodes made of palladium and platinum.

The cold fusion story seemed to stand science on its head — not only because it was played out in the popular press without the ritual of peer review, but also because both sides of the debate violated what are generally supposed to be the central canons of scientific logic.

Science in the twentieth century has been much influenced by the ideas of the Austrian philosopher Karl Popper. Popper argued that a scientific idea can never be proved true, because no matter how many observations seem to agree with it, it may still be wrong. On the other hand, a single contrary experiment can prove a theory false forever. Science advances only through demonstrating that theories are false, so that they may be replaced by better ones.

The cold fusion story seemed to stand science on its head.

The proponents of cold fusion took the opposite view. Many experiments, including their own, failed to yield the expected results. These were irrelevant, they argued, incompetently done or lacking some crucial ingredient. Instead, all positive results — the appearance of excess heat or a few neutrons — proved the phenomenon was real. This anti-popperian approach played no small role in cold fusion's downfall, as seasoned experimentalists refused to believe what they couldn't reproduce in their own laboratories: to them, negative results still mattered.

On the other hand, the anti-cold-fusion crowd was equally guilty, if you believe another of the solemn canons: that science must be firmly rooted in experiment or observation, unladen with theoretical preconceptions. On the contrary, the failure of cold fusion was due, above all, to the fact that it was an experiment whose result was contrary to prevailing theory.

In spite of the well-founded scepticism of most scientists, there are still a few serious people around who believe in cold fusion. Let's all hope they're on to something.