Peter N. Saeta, an assistant professor of physics at Harvey Mudd College, responds:

Eight years ago researchers Martin Fleischmann and Stanley Pons, then both at the University of Utah, made headlines around the world with their claim to have achieved fusion in a simple tabletop apparatus working at room temperature. Other experimenters failed to replicate their work, however, and most of the scientific community no longer considers cold fusion a real phenomenon. Nevertheless, research continues, and a small but very vocal minority still believes in cold fusion.

Michael J. Schaffer, a senior scientist at one of the major U.S. fusion research laboratories (his employer has requested not to be identified), has provided this historical overview, along with a rather moderate assessment current status of cold fusion:

"Because cold fusion is still an unresolved and controversial subject that generates strong opinions and passionate debate among scientists, I begin by stating up front that I am a mainstream plasma physicist researching fusion energy. I also read many of the papers published on cold fusion, however. I attended the last three International Conferences on Cold Fusion, and I myself ran two sets of cold fusion experiments, both with no clear evidence of excess power release. Overall, I consider myself to be a fairly neutral observer.

"To understand the controversy, it helps to know some basic facts about fusion. Fusion is a nuclear reaction wherein two smaller nuclei join (fuse) to form a new, larger nucleus. When that large nucleus is unstable, it quickly breaks apart and releases energy. The big difficulty is that because the initial nuclei are all positively charged, they are strongly repelled as they approach one another. Therefore, only nuclei having a high kinetic energy approach closely enough to fuse. High-speed nuclei can be made on the earth either by particle accelerators or by extremely high temperatures--on the order of 50 million degrees Celsius or more. In controlled 'magnetic' fusion energy experiments, such as tokamaks and others, a magnetically confined plasma is heated by electromagnetic waves or neutral particle beams. In 'inertial' fusion energy experiments, tiny pellets are compressed and heated by powerful pulsed laser or ion beams.

"Cold fusion claims to release measurable energy from fusion reactions at or near room temperature when deuterium is dissolved in a solid, usually palladium metal. The idea, which has its roots in research going back to the 1920s, is that hydrogen and its isotopes can dissolve to such high concentrations in certain solids that the hydrogen nuclei approach closer to one another than even in solid hydrogen. Furthermore, negative electrical charges from the electrons of the solid host partly cancel the repulsion between the nuclei. Early experiments did not detect any signs of fusion, however. Furthermore, modern theoretical calculations show that the proposed effects, while real, are much too small to produce detectable rates of fusion.

"Electrochemists Martin Fleischmann and Stanley Pons decided to revisit room-temperature fusion. Their technique is to pass current through an electrolytic cell consisting of a palladium (Pd) cathode, platinum (Pt) anode and LiOD (a compound of lithium, oxygen and deuterium, or heavy hydrogen) electrolyte in heavy water (water containing deuterium in place of the ordinary hydrogen). The cathodic reaction liberates unbound atoms of deuterium (D), which enter palladium much more rapidly than do deuterium molecules. Under proper conditions, the concentration can build up to 0.9 or more deuterium atoms per palladium atom, at which point the loss of deuterium balances its rate of implantation. Pons and Fleischmann's cells were part of a calorimeter (heat-measuring device), whose temperature rise on a few occasions indicated on the order of 10 percent excess power, that is, about 10 percent more power leaving the cell than electrical power used to run it. Pons and Fleischmann announced their results at a now famous news conference on March 23, 1989. They also thought they had detected gamma radiation characteristic of neutrons passing through water, but these results later had to be retracted.