Slashdot Mirror
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."
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...
This, of course, is only true under the assumption that it's the neutrinos that are really causing the increase in radioactive decay. The article does mention that there were many unknowns in the measurements. It may be something else that causes this increase, or even a combination of two. It may also be the case that more neutrinos, the rate at which they're emitted, or other interacting fields alter the effect.
You are right, they are purposely avoiding using the same isotopes to avoid observing the phenomenon that caused them to perform this research. "Truly, you have a dizzying intellect." :)
Call me naive, but maybe they had better reasons not to use the same material. I am not a physicist, so I don't know if it's correct, but here are some reasons I thought of, of the top of my head:
1) Gold may have more neutrino activity, so there was a better chance to observe said phenomenon.
2) The scientists involved have more experience working with gold, so they preferred using a material they are experienced with.
3) Gold may be easier to work with and this it is easier to construct thin foils.
4) They had a pile of unused gold and didn't know what to do with it
Again, I don't know if these are valid/correct reasons, but I'm somehow convinced there is a better reason than the one you stated.
Whenever in an argument, remember this.