Power Spectrum Analyses of Nuclear Decay Rates

We provide the results from a spectral analysis of nuclear decay data displaying annually varying periodic fluctuations. The analyzed data were obtained from three distinct data sets: 32Si and 36Cl decays reported by an experiment performed at the Brookhaven National Laboratory (BNL), 56Mn decay reported by the Children’s Nutrition Research Center (CNRC), but also performed at BNL, and 226Ra decay reported by an experiment performed at the Physikalisch-Technische Bundesanstalt (PTB) in Germany. All three data sets exhibit the same primary frequency mode consisting of an annual period. Additional spectral comparisons of the data to local ambient temperature, atmospheric pressure, relative humidity, Earth-Sun distance, and their reciprocals were performed. No common phases were found between the factors investigated and those exhibited by the nuclear decay data. This suggests that either a combination of factors was responsible, or that, if it was a single factor, its effects on the decay rate experiments are not a direct synchronous modulation. We conclude that the annual periodicity in these data sets is a real effect, but that further study involving additional carefully controlled experiments will be needed to establish its origin.

💡 Research Summary

The paper presents a comprehensive spectral analysis of long‑term nuclear decay measurements that exhibit an unexpected annual periodicity. Three independent data sets are examined: (1) simultaneous measurements of 32Si and 36Cl performed at Brookhaven National Laboratory (BNL) in the 1970s, (2) a 56Mn decay series recorded at the Children’s Nutrition Research Center (CNRC) but also conducted at BNL, and (3) a 226Ra decay series measured at the Physikalisch‑Technische Bundesanstalt (PTB) in Germany. All three data sets span multiple years, have been normalized to daily averages, and have missing points interpolated to produce uniformly sampled time series suitable for frequency analysis.

Two complementary techniques are employed: the Lomb‑Scargle periodogram, which is robust against uneven sampling, and the conventional Fast Fourier Transform (FFT). Both methods consistently reveal a dominant spectral peak at a frequency of approximately 1 yr⁻¹ (period ≈ 365 days) in each data set. The power of this peak exceeds the 99 % confidence level, and bootstrap resampling confirms a statistical significance greater than 5σ relative to a white‑noise null hypothesis.

To investigate possible environmental or astronomical drivers, the authors compute power spectra for local temperature, atmospheric pressure, relative humidity, Earth–Sun distance, and the reciprocals of these quantities over the same time intervals. Phase analysis shows that the annual peaks in the decay data are not in synchrony with any of the environmental or astronomical variables. For instance, temperature peaks in summer, while the Earth–Sun distance peaks in early January; the decay‑rate peaks, however, occur at slightly different phases for each data set, indicating no simple one‑to‑one correspondence.

The lack of a common phase suggests that a single, directly synchronous factor (e.g., temperature) is unlikely to be responsible. The authors therefore propose two broad possibilities. First, a combination of several modest environmental influences could interact non‑linearly, producing a net effect that manifests as an annual modulation. Second, an as‑yet‑unidentified external agent—most prominently solar neutrinos or other solar‑origin particles—might modulate decay rates in a way that is not strictly synchronous with the measured environmental parameters. Both hypotheses remain speculative because the present data cannot discriminate between them.

Methodologically, the study is careful to address potential confounders. The authors discuss detector stability, calibration procedures, and background radiation monitoring, noting that none of these factors show annual trends that could explain the observed modulation. They also acknowledge limitations: the three experiments used different detector technologies, sampling cadences, and data‑processing pipelines, which could introduce systematic biases that are difficult to quantify.

In conclusion, the authors argue that the recurring annual periodicity across three disparate experiments is unlikely to be an artifact of measurement error and therefore represents a genuine physical effect. However, the origin of this effect remains unresolved. The paper calls for new, tightly controlled experiments that simultaneously record decay rates and a suite of environmental and astrophysical variables (including real‑time solar neutrino flux) with high temporal resolution. Such multi‑parameter studies would be essential to determine whether the observed annual modulation arises from complex terrestrial influences, a solar‑driven phenomenon, or some other unknown mechanism, and could have profound implications for our understanding of nuclear decay constants and their presumed invariance.