Once again (and it seems like this happens every couple of years) someone is claiming "success" in a cold fusion experiment. Basically this fellow has made a cell containing some composite of ZrO2 and nanoscale Pd crystals. The claim is that when this cell is filled to moderate pressures (a few bar) with deuterium gas over a couple of days, the cell gets hot (compared to its surroundings) and stays hot for a while (tens of hours), and that 4He is detected afterward. Furthermore, the claim is that control experiments with ordinary hydrogen do not produce the long-term heating or helium, and that control experiments without the Pd/ZrO2 produce no heating at all. People who know next to nothing about nuclear physics argue that the lack of neutrons (from the D+D goes to 3He + n reaction pathway) or gamma rays is fine, since simple p and n counting lets you have D + D goes to 4He, despite the fact that the 3He reaction is vastly more favored in ordinary fusion. There continues to be no credible mechanism for getting the D nuclei close enough to each other to get fusion. Now, it's entirely possible that there is weird chemistry going on here, but how come in twenty years of people trying to do this stuff there has yet to be a clean, well-designed experiment done by physicists that is reproducible and actually shows anything interesting? It's grating on many levels that this, an anecdotal discussion of nonconclusive experiments, gets touted online through slashdot, gizmodo, digg, engadget, etc. Extraordinary claims require extraordinary evidence.