This unusual article recently appeared in Nature: a team funded by Google (and involving researchers from a number of very well-respected research institutions) has spent some substantial effort revisiting the various reports of “cold fusion” (commentary pieces here and here). That might seem like an odd way to spend one’s money and time, but I was actually pleased to hear about the work. As I’ve mentioned here before, I vividly remember the announcement by Pons and Fleischmann in 1989 – I was amazed and elated, and bitterly disappointed when the work failed to replicate over the following months. I agree with the people at Google that the potential rewards (scientific and economic, etc.) of replicating something real in this area are so huge that it was worth another rigorous follow-up. They knew full well that it might end by finding nothing.
That’s what they found. None of the major experimental conditions that have been reported to produce anomalous nuclear reactions could be replicated in the hands of this team: metal electrodes loaded with large amounts of hydrogen, metal powders heated in a hydrogen atmosphere, and pulsed plasma discharge conditions. It’s not like they got to all of the reported experiments, but they did a thorough job of investigating these ones that had produced the most hints of something, and, well, there was nothing there. Here are the authors:
So far, we have found no evidence of anomalous effects claimed by proponents of cold fusion that cannot otherwise be explained prosaically. However, our work illuminates the difficulties of producing the conditions under which cold fusion is hypothesized to exist. This result leaves open the possibility that the debunking of cold fusion in 1989 was perhaps premature because the relevant physical and material conditions had not (and indeed have not yet) been credibly realized and thoroughly investigated. Should the phenomenon happen to be real (itself an open question), there may be good technical reasons why proponents of cold fusion have struggled to detect anomalous effects reliably and reproducibly. Continued scepticism of cold fusion is justified, but we contend that additional investigation of the relevant conditions is required before the phenomenon can be ruled out entirely.
There’s a danger in thinking like this, though, because you run the risk of assuming the conclusions. If the conditions for these phenomena are so difficult to achieve, what are the odds that Pons and Fleischmann themselves achieved them? One of the reasons the work made such headlines was the simplicity of the experimental apparatus. The earlier failures to reproduce things, along with scattered reports of partial or intermittent effects, showed pretty quickly that even if there was something going on, it was clearly not as simple as it had first appeared. Now with this latest investigation, we can turn the “clearly not as simple” dial even further up than ever before. You can chase anything, forever, if you’re willing to keep thinking that the negative results mean that it’s just getting trickier. And the question is, at what point do you stop staying “Well, if it’s there, it’s really complicated” and start saying “Actually, if it’s that complicated it might as well not be there at all”.
Most researchers in this field reached that point some time ago, and this new paper will make it easier than ever to write the whole thing off. But the Google team still has some experiments that they’re apparently conducting, especially in the plasma-discharge area, mostly to work out some unexplored parameter space with relevance to more conventionally explicable low-energy nuclear reactions whose rates are expected to be heavily modified by screening effects. This work should produce data that will be of interest to people beyond the remaining cold-fusion believers, and similarly, the team’s work on heated metal powders and hydrogen required them to make advances in calorimetry that could also prove useful. And the hydrogen-saturated palladium electrode work led to new data about the effects of such high loading on the metal structure, and how to measure these reliably.
So they’ve produced useful work – just no cold-fusion breakthroughs. If anyone is going to claim one after this, they’ll have to explain how it lies outside this space that has (from what I can see) been pretty well tamed by the Google team – and it had better be good. I’m not expecting one. It’s now been just over 30 years since Pons and Fleischmann, and I think that this particular dream is pretty well laid to rest. Personally, though, I’ll never forget those first few weeks in the spring of 1989, when it looked like the world had suddenly reordered itself and physics had turned upside down. The good news, though, is that such discoveries do happen from time to time, in physics and in other fields of science as well, and they still can. Live in hope.