Solar Neutrinos May Be Affecting Radioactive Decay Rates On Earth

The rate of decay of radioactive material on Earth may be affected by neutrinos emitted by the sun, according to a study published in the November edition of the journal Solar Physics. The controversial findings suggest that radioactive decay rates — long considered physical constants — may be more variable than previously thought.

Solar neutrinos are produced by nuclear reactions in the central core of the sun. It is estimated that up to 100 billion solar neutrinos — nearly massless particles that travel almost at the speed of light — pass through the tip of your finger every second.

For this particular study, researchers measured decay rates of silicon-32 and chlorine-36 at Brookhaven National Laboratory (BNL) in New York. Doing so revealed on unexplained fluctuations in the decay rates — ones that the researchers said were caused by the rotation of Sun's radiative zone, which is the region between the core and the convective zone, and of the solar core.

Analysis of 5 years of measurements by the Super-Kamiokande observatory in Japan also revealed similar patterns in the decay and neutrino data.

"I speculate that neutrinos interact with the W-boson that is believed to mediate beta decay," lead author Peter Sturrock from Stanford University told Physics World. "But I am hoping that some theoretical physicists will take up this problem."

W-bosons, along with Z-bosons, are elementary particles that carry the weak nuclear force — one of the four known fundamental forces of nature.

However, given the fact the neutrinos barely interact with normal matter, not everyone is convinced these ghostly particles can affect the decay of radioactive isotopes.

Hamish Robertson, director of the Center for Experimental Nuclear Physics and Astrophysics at the University of Washington, Seattle, told Physics World that evidence for solar neutrinos affecting beta-decay is "not persuasive."

"Evidence that fits the hypothesis has been brought forward, while other evidence that does not fit (for example, long-term studies of the beta decay of tritium), is ignored," Robertson said. "Fitting the fluctuations to one natural phenomenon after another will eventually lead you to reach a spectacular conclusion."