Saltmarsh and Shapira did not check the tritium observations. "Those look like they were handled correctly," Shapira says. He can offer no explanation for the apparent increase in tritium levels. So that is one mystery.

A second mystery, Shapira reports, is that "right after the neutrons hit the acetone, there are light flashes as the bubbles collapse, then there is a quiet period, and then thousands of flashes¿90 percent of the light¿comes out after about a millisecond. Why that happens I don¿t know."

Shapira does know what he would do differently to answer the question more clearly. "For starters I would not use neutrons to create the bubbles¿I would use a laser or even a charged particle beam, something you can really control. You cannot guide neutrons." And it would be better, he suggests, not to set the acetone flask on a steel table, which can reflect neutrons back toward the detector. Finally, he advises, use a more advanced detector that uses boron or an ionization chamber. That will filter out gamma rays, which confounded both his and Taleyarkhan¿s measurements.

With stakes so high and so many reputations on the line, the debate over this discovery is certain to produce lots of sound and heat¿but perhaps also a flash of illumination.

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