Can Radioactive Decay Constants Vary?

Three physicists claim to see cyclical variations in beta decay rates of two elements correlated with solar neutrino flux.

A paper in Solar Physics has one of those long titles that scare people away: “Comparative Analyses of Brookhaven National Laboratory Nuclear Decay Measurements and Super-Kamiokande Solar Neutrino Measurements: Neutrinos and Neutrino-Induced Beta-Decays as Probes of the Deep Solar Interior.” Its potential impact, though, could be paradigm-shaking. Physics World explains:

Further evidence that solar neutrinos affect radioactive decay rates on Earth has been put forth by a trio of physicists in the US. While previous research looked at annual fluctuations in decay rates, the new study presents evidence of oscillations that occur with frequencies around 11 and 12.5 cycles per year. The latter oscillation appears to match patterns in neutrino-detection data from the Super-Kamiokande observatory, in Japan.

Writer Michael Allen is quick to point out that “Other physicists, however, are not convinced by the claim.” It’s easy to understand why; it would call into question what they think they know about radioactive decay rates.

The idea of fluctuating beta-decay rates is very controversial because for more than 80 years, radioactive substances have been thought to follow a fixed exponential decay, under all conditions. The theory of invariable decay constants was set by Ernest Rutherford, James Chadwick and Charles Ellis in Radiations from Radioactive Substances, published in 1930.

The bulk of the article consists of critics doubting the claim. One says it would require “extraordinary new physics, and hence it will require extraordinary proof.” Another reminds readers that “correlation is not causation.” Theoretical physicists will have to explain how neutrinos, long thought to be massless, could influence the decay of much heavier particles. Beta decay involves the transmutation of a proton into a neutron or vice versa with the ejection of an electron and an antineutrino. It’s unlikely that the majority of physicists will be convinced without better evidence and a theoretical foundation to explain the apparent correlation.

The claim in the paper does not appear sufficiently grounded at this time. We’ll have to chalk it up as an anomaly in the current physics, not a scientific revolution. If more anomalies accumulate, the pressure will be on the consensus to account for them within the paradigm of invariable decay constants. It’s a topic to watch. Believing something for decades doesn’t confer truth; look at evolutionary theory.