Scientists Confirm Nuclear Decay Rate Constancy

As_I_Please writes "Scientists at the US National Institute of Standards and Technology and Purdue University have ruled out neutrino flux as a cause of previously observed fluctuations in nuclear decay rates. From the article: 'Researchers ... tested this by comparing radioactive gold-198 in two shapes, spheres and thin foils, with the same mass and activity. Gold-198 releases neutrinos as it decays. The team reasoned that if neutrinos are affecting the decay rate, the atoms in the spheres should decay more slowly than the atoms in the foil because the neutrinos emitted by the atoms in the spheres would have a greater chance of interacting with their neighboring atoms. The maximum neutrino flux in the sample in their experiments was several times greater than the flux of neutrinos from the sun. The researchers followed the gamma-ray emission rate of each source for several weeks and found no difference between the decay rate of the spheres and the corresponding foils.' The paper can be found here on arXiv. Slashdot has previously covered the original announcement and followed up with the skepticism of other scientists."

Re:How big?

[sFurbo]

The change in neutrino flux due to shape was bigger than the neutrino flux from the sun is, so it must be much bigger than changes in the solar neutrino flux (if I read the summary correctly). If that change in neutrino flux does not induce a measurable change in the rate of decay, then neither will the solar neutrino flux. I think it is a very elegant experiment, testing just what the hypothesis said.

The effect might be different for different decays, so the hypothesis isn't completely dead. Now, if they made an alloy of gold-198 and the isotopes that is claimed to change decay rate...

Re:Semantism

[Kilrah_il]

Well, but our nice editors have used the incorrect phrase "Scientists confirm nuclear decay rate consistancy". Just responding to that.

Variations in time rather than decay?

[timepilot]

Could it be that there are local variations in time during the original solar flare observations rather than fluctuations in the actual decay rate, and that it is not related to neutrinos from the flare but from some other gravitational changes coupled with flares?

I know, my ignorance is showing. Sorry. IANASH (I am not a stephen hawking)

Re:Not a certain conclusion yet

[Anonymous Coward]

"So, there still is a chance that there is a deviation."

Yes, of course. People have been saying that all along. And even with more experiments in the future it will always be the case that a deviation from constancy is possible. However, if there is a deviation, it's vanishingly small and what remains possible is getting smaller as the experiments are refined.

People have been testing the constancy of radiometric decay rates for many decades. Those experiments always have limits in terms of their resolution of decay rates, but there are so many tests by now that we're usually talking about deviations on the order of 1% or less in most cases. It says something that any deviation that might be there is so close to constancy that is difficult to measure experimentally. Variations in decay rate on that scale are certainly a scientifically interesting possibility worth pursuing, but a big "so what?" in terms of their implications for many practical applications such as radiometric dating, where measurement uncertainties are on that order anyway.

Re:Why wouldn't the scientists in this study...

[sFurbo]

It would seem that they started with the simple experiment. If there had been an effect here, no need to go and do the complicated experiment. Now that there weren't an effect, make the same experiment, but with an alloy of gold-198 and manganese-54, and only measure the decay of manganese. Of course, just the proximity of gold-198 should be enough, so perhaps layers of foil of gold and manganese? Anyway, these experiment are more complicated to carry out, so it makes perfect sense to start with the simple experiment.

Re:Variations in time rather than decay?

[maxwell demon]

I'd guess any variation in time so large that you can see it in decay time measurements would have created so many other clearly visible effects that it would not have gone unnoticed.

Radioactive decay variations

[russotto]

This study provides strong evidence against solar neutrino flux being the reason for observed variations in radioactive decay. However, it does not provide evidence against those variations -- nor was it designed to. The measurements still need to be explained; there have been reports of changes in radioactive decay during solar flares, and also seasonal variations; most likely IMO they're some sort of systemic measurement error, but maybe not.

Also note that the idea that decay rates might be affected by particle flux or shape isn't all that farfetched. Fission rates in certain isotopes are, for instance.

Re:Not a certain conclusion yet

[ceoyoyo]

Those are some pretty big deviations to go with the headline "Scientists Confirm Nuclear Decay Rate Constancy." In any field except physics they would be considered significant evidence of a difference.

Re:So really... this means?

[jegerjensen]

The constancy of nuclear decay rates is a fundamental assumption for our understanding of stellar processes, big bang theory and the like. If someone can prove a deviation, it will break just about every cosmological model. If they had found a deviation, the implications could be comparable to what Copernicus did, so I believe this does mean something for the "normal human"...