Eideard

Daylife/AP Photo used by permission

The story begins, in a sense, in classrooms around the world, where students are taught that the rate of decay of a specific radioactive material is a constant. This concept is relied upon, for example, when anthropologists use carbon-14 to date ancient artifacts and when doctors determine the proper dose of radioactivity to treat a cancer patient…

But that assumption was challenged in an unexpected way by a group of researchers from Purdue University who at the time were more interested in random numbers than nuclear decay. Ephraim Fischbach, a physics professor at Purdue, was looking into the rate of radioactive decay of several isotopes as a possible source of random numbers generated without any human input.

As the researchers pored through published data on specific isotopes, they found disagreement in the measured decay rates – odd for supposed physical constants.

Checking data collected at Brookhaven National Laboratory on Long Island and the Federal Physical and Technical Institute in Germany, they came across something even more surprising: long-term observation of the decay rate of silicon-32 and radium-226 seemed to show a small seasonal variation. The decay rate was ever so slightly faster in winter than in summer…

On Dec 13, 2006, the sun itself provided a crucial clue, when a solar flare sent a stream of particles and radiation toward Earth. Purdue nuclear engineer Jere Jenkins, while measuring the decay rate of manganese-54, a short-lived isotope used in medical diagnostics, noticed that the rate dropped slightly during the flare, a decrease that started about a day and a half before the flare.

If this apparent relationship between flares and decay rates proves true, it could lead to a method of predicting solar flares prior to their occurrence, which could help prevent damage to satellites and electric grids, as well as save the lives of astronauts in space…

Jenkins and Fischbach guessed that the culprits in this bit of decay-rate mischief were probably solar neutrinos, the almost weightless particles famous for flying at almost the speed of light through the physical world – humans, rocks, oceans or planets – with virtually no interaction with anything…

Their findings strengthened the argument that the strange swings in decay rates were caused by neutrinos from the sun. The swings seemed to be in synch with the Earth’s elliptical orbit, with the decay rates oscillating as the Earth came closer to the sun (where it would be exposed to more neutrinos) and then moving away…

Enter Peter Sturrock, Stanford professor emeritus of applied physics and an expert on the inner workings of the sun. Sturrock knew from long experience that the intensity of the barrage of neutrinos the sun continuously sends racing toward Earth varies on a regular basis as the sun itself revolves and shows a different face, like a slower version of the revolving light on a police car. His advice to Purdue: Look for evidence that the changes in radioactive decay on Earth vary with the rotation of the sun…

But there’s one rather large question left unanswered. No one knows how neutrinos could interact with radioactive materials to change their rate of decay.

“It doesn’t make sense according to conventional ideas,” Fischbach said. Jenkins whimsically added, “What we’re suggesting is that something that doesn’t really interact with anything is changing something that can’t be changed.”

“It’s an effect that no one yet understands,” agreed Sturrock. “Theorists are starting to say, ‘What’s going on?’ But that’s what the evidence points to. It’s a challenge for the physicists and a challenge for the solar people too.”

If the mystery particle is not a neutrino, “It would have to be something we don’t know about, an unknown particle that is also emitted by the sun and has this effect, and that would be even more remarkable,” Sturrock said.

“Common sense” pundits may believe that once a question is answered, search and examination, further learning is unneeded. But, one of the delights of scientific methods is that more questions always arise from solutions.

RTFA. Longer, detailed tale of the search for an answer.