The Sciences

Scientist Smackdown: Are Solar Neutrinos Messing With Matter?

80beatsBy Andrew MosemanAug 26, 2010 7:52 PM


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The sun is breaking the known rules of physics—so said headlines that made the rounds of the Web this week. That claim from a release out about a new study by researchers Jere Jenkins and Ephraim Fischbach of Purdue, and Peter Sturrock of Stanford. The work suggests that the rates of radioactive decay in isotopes—thought to be a constant, and used to date archaeological objects—could vary oh-so-slightly, and interaction with neutrinos from the sun could be the cause. Neutrinos are those neutral particles that pass through matter and rarely interact with it; trillions of neutrinos are thought to pass through your body every second. In the release itself, the researchers say that it's a wild idea: "'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.'" Could it possibly be true? I consulted with Gregory Sullivan, professor and associate chair of physics at the University of Maryland who formerly did some of his neutrino research at the Super-Kamiokande detector in Japan, and with physicist Eric Adelberger of the University of Washington. "My gut reaction is one of skepticism," Sullivan told DISCOVER. The idea isn't impossible, he says, but you can't accept a solution as radical as the new study's with just the small data set the researchers have. "Data is data. That's the final arbiter. But the more one has to bend [well-establish physics], the evidence has to be that much more scrutinized." Among the reasons Sullivan cited for his skepticism after reading the papers:

  • Many of the tiny variations that the study authors saw in radioactive decay rates came from labs like Brookhaven National Lab—the researchers didn't take the readings themselves. And, Sullivan says, some are multiple decades old. In their paper, Fischbach's team takes care to try to rule out variations in the equipment or environmental conditions that could have caused the weird changes they saw in decay rates. But, Sullivan says, "they're people 30 years later [studying] equipment they weren't running. I don't think they rule it out."

  • The Purdue-Stanford team cites an example of a 2006 solar flare, saying that they saw a dip in decay rates in a manganese isotope before the occurrence that lasted until after it was gone. Sullivan, however, says he isn't convinced this is experimentally significant, and anyway it doesn't make sense: Solar neutrinos emanate from the interior of the sun—not the surface, where flares emerge. Moreover, he says, other solar events like x-ray flares didn't have the same effect.

  • If it were true, the idea would represent a huge jump in neutrino physics. At the Super-Kamiokande detector, Sullivan says only about 10 neutrinos per day appeared to interact with the 20 kilotons of water. Sullivan says the Purdue-Stanford team is proposing that neutrinos are powerfully interacting with matter in a way that has never before been observed. "They're looking for something with a very much larger effect than the force of neutrinos, but that doesn't show up any other way," he says.

Fischbach and Jenkins, who have published a series of journal articles supporting their theory on neutrinos and radioactive decay, emailed DISCOVER to respond to these criticisms of their work. Regarding the first one, the researchers defended the integrity of the data even though they didn't take it themselves, saying the experiments "were carried out by two well-known and experienced groups. We have published an analysis of these experiments, in Nuclear Instruments and Methods ... showing that the potential impact of known environmental effects is much too small to explain the annual variations." And in response to number two—why would you tie neutrinos to a flare, when they emanate from the sun's interior?—Jenkins and Fischbach write that we know some flares are tied to events deep inside the sun. "We therefore consider it possible that events in the core may influence flares," they write, "but this remains to be established. We have never claimed that all flares are related to events in the core." The big one, though, is number three: are we really seeing some kind of physics never seen before? Fischbach and Jenkins don't back off:

"We agree that, according to current theory of the standard weak interaction, neutrinos should not be influencing decay rates. We also agree that Super-Kamiokande data are not anomalous. Our position is that either neutrinos have properties we do not yet understand, or some other particle or field behaving like neutrinos is influencing decay rates. In slightly more detail, we are not considering neutrino capture as in the case of Super-K. Rather we work in a picture where neutrinos pass through the sample of decaying nuclei, as they pass through everything else, and exchange an energy on the order of 10-100 eV. Given the sensitivity of beta decays and electron capture to the energy available, the exchange of a small amount of energy in this way could be sufficient to explain the observed effects."

But for Adelberger of the University of Washington, that is still a huge jump based on what the studies have seen. Adelberger tells DISCOVER that he thinks the variation in decay that the labs like Brookhaven picked up is real. But he agrees with Sullivan that the effect is much more likely to come from a problem with the instruments than some new physics from the sun. He also points to studies over the last couple years (here

and here

) that show no link between the sun and radioactive decay rates. Both Adelberger and Sullivan agreed that the Purdue-Stanford findings pave the way to some interesting—and more carefully controlled—research to verify or falsify the idea. But for now, neither is a believer. "The scenarios Fischbach et. al. invoke to support their interpretations despite contrary data are getting bizarre," Adelberger tells DISCOVER. "I think it is unlikely to be correct." Related Content: 80beats: Antarctic Particle Detector Buried in Ice Records Cosmic Ray Weirdness

80beats: Physicists Shoot Neutrinos Across Japan to an Experiment in an Abandoned Mine

DISCOVER: Ice Fishing for Neutrinos From the Middle of the Galaxy

DISCOVER: Opening an Icy Eye on the Neutrino Sky

Image: NASA Solar Dynamics Observatory

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