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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."
So, there still is a chance that there is a deviation.
I think the proper phrasing should be "No evidence for inconsistency of nuclear decay found". It seems pedantic, but proper scientific methodology works this way. There
can still be inconsistency in nuclear decay, just not in this test scenario. You cannot prove consistency, you con only be very, very sure this is how nuclear decay works because you performed many studies that have failed to show something else. (Not that I despute their findings).
Whenever in an argument, remember this.
From TFA:“There are always more unknowns in your measurements than you can think of,” Lindstrom says.
How big were the foil and spherical samples? Neutrinos interact very weakly, so much so that neutrino detectors need to be on the order of 1 km^3.
Heck, if I had that much gold (whatever isotope) I'd have better ways to spend my time.
Set your phasers on "funky"!
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.
I love talking with such people. :3
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.
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)
That's crazy talk. Everyone knows that the answer to all astrophysics problems is "11-dimensional dark matter particles".
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.
A Gold-198 foil hat, to keep the neutrinos out...
This is not the sig you're looking for.
I hate to be THAT person, but what does this mean for us normal humans? Does it mean anything at all?
How can they invalidate the orginal experimenter's experiment unless they try to replicate the original experiment?
They weren't trying to invalidate the findings of the original experiment. That was just something Slashdot made up for the heading (I've no idea why). They were investigating whether a particular mechanism could account for the findings of the original experiment.
well, he's not the life of the party...he's the HALF-life!
rewriting history since 2109
Dark matter particles?
Only at night.
Undetectable Steganography? Yep, there's an app fo
The variation in decay rates is said to have two cycles; a yearly fluctuation, and a 33-day cycle (proposed first because that's the rotation of the sun's core, THEN found in the data). These experiments should have been run for at least 66 days, preferably for more than two years, before making claims that this has anything at all to do with the effects that have been observed so far. They can't even say that gold-198 displays evidence of the phenomenon they are trying to measure. This experiment cannot provide any useful information for investigating the possible connection between nuclear decay rates and distance to the sun. Nothing to see here but some attention grabbing with no real substance, gold-198 or not. Yawn.
On the one hand you take life too seriously, and on the other, you do not take playful existence seriously enough. Seth
Yes, they're not replicating the original experiment, but they are testing the proposed, more general, mechanism -- i.e. that seasonal variations in neutrino flux from the Sun cause variation in decay rates. That's what the original experimenters were wondering about -- does this affect everything? I suppose followup studies could do the same experiment for every element in the period table and every radioactive isotope, including the ones used in the prior experiment, but the fact remains that the new experiment with gold has narrowed the possibilities for what might be going on, and they used a rather elegant experiment to do it. Is there an effect on all isotopes? Well, apparently not within measurement uncertainties for gold-198, although a smaller variation remains possible.
You can also turn the argument around: if the first experimenters found a real effect for Mg-54, Si-32, and Rn-226, then so what? That doesn't mean there's any effect at all on the decay rates for any other isotope, including the ones used for radiometric dating and other techniques where the observed variation (if taken at face value) would have a small effect. Maybe the process doesn't work for potassium, uranium, or rubidium, and until people test the specific isotopes in those methods, who cares if they find something odd in Mg, Si, or Rn?
In other words, you can't fault the followup study for not testing the same isotopes if you are simultaneously claiming that the original experiment has grand implications for the decay rates of all isotopes. Well, you can, but it wouldn't be particularly consistent.
3) Gold may be easier to work with and this it is easier to construct thin foils.
This. Gold is a phenomenally ductile metal -- ideal for making the thin foils typically used in preparing radioactive sources. If you want a radioactive source, the easiest thing to try (broadly speaking) is electroplating your nuclide of interest on a gold substrate. Then all your measurements require you to take the shielding properties of gold into account, but that's not usually too big a deal.
I am a nuclear physicist (grad student), and one of the key issues we have to deal with is sample preparation. The bleeding-edge is thin carbon foils, but that's expensive and tricky and takes a long time. If you want a sample quick, you use a gold substrate. No conspiracy here, folks.
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.
The study overlooks neutrino oscillations, the neutrinos from the gold have had little chance to oscillate. While it is probable that neutrinos don't affect decay rates, the study isn't as conclusive as the summary makes it out to be.
The decay rate for electron capture is mildly affected by pressure.
A Shadeless room is a brighter room.
you may not be a physicist, but you nailed the scientific methodology exactly. Kudos.
Whenever in an argument, remember this.
Journalism, by the way, is not science. In fact, it is usually the enemy of science.
From scarped cliff or quarried stone she cries "A thousand types are gone, I care for nothing, no not one."
This experiment covered only the decay of Gold-198; The ones that were found to be changing were exhibiting electron capture decays, a completely different mechanism.
For such a limited experiment, the claims are grandiose, IMHO.
Neutrinos also oscillate forms; perhaps the emitted form doesn't interact the same way.
.
Truth isn't Truth - Guliani
IANAphysicist, but everything I've heard about neutrinos is along the lines of "they pass through the entire Earth with a very small chance of hitting anything". This makes me wonder how you can measure any kind of effect involving neutrinos, in a sample that isn't the size of an underground cavern full of water. Certainly they don't have a chunk of gold that big, or does gold have unusually high neutrino-interacting properties? How long does the experiment have to run? How sensitive is the whole setup and how do they isolate it from other neutrino sources, etc.
For all intensive purposes, "whom" is no longer a word. That begs the question, "who cares"?
I didn't know that.
I call bull'... It's turtles, turtles all the way down!!
FAQ: Do rates of nuclear decay depend on environmental factors?
There is one environmental effect that has been scientifically well established for a long time. In the process of electron capture, a proton in the nucleus combines with an inner-shell electron to produce a neutron and a neutrino. This effect does depend on the electronic environment, and in particular, the process cannot happen if the atom is completely ionized.
Other claims of environmental effects on decay rates are crank science, often quoted by creationists in their attempts to discredit evolutionary and geological time scales.
He et al. (He 2007) claim to have detected a change in rates of beta decay of as much as 11% when samples are rotated in a centrifuge, and say that the effect varies asymmetrically with clockwise and counterclockwise rotation. He believes that there is a mysterious energy field that has both biological and nuclear effects, and that it relates to circadian rhythms. The nuclear effects were not observed when the experimental conditions were reproduced by Ding et al.
Jenkins and Fischbach (2008) claim to have observed effects on alpha decay rates at the 10^-3 level, correlated with an influence from the sun. They proposed that their results could be tested more dramatically by looking for changes in the rate of alpha decay in radioisotope thermoelectric generators aboard space probes. Such an effect turned out not to exist (Cooper 2009). Undeterred by their theory's failure to pass their own proposed test, they have gone on to publish even kookier ideas, such as a neutrino-mediated effect from solar flares, even though solar flares are a surface phenomenon, whereas neutrinos come from the sun's core. An independent study found no such link between flares and decay rates (Parkhomov 2010). Jenkins and Fischbach's latest claims, in 2010, are based on experiments done decades ago by other people, so that Jenkins and Fischbach have no first-hand way of investigating possible sources of systematic error. Laboratory experiments[Lindstrom 2010] have also placed limits on the sensitivity of radioactive decay to neutron flux that rule out a neutrino-mediated effect at a level orders of magnitude less than what would be required in order to explain the variations claimed in [Jenkins 2008].
Cardone et al. claim to have observed variations in the rate of alpha decay of thorium induced by 20 kHz ultrasound, and claim that this alpha decay occurs without the emission of gamma rays. Ericsson et al. have pointed out multiple severe problems with Cardone's experiments.
He YuJian et al., Science China 50 (2007) 170.
YouQian Ding et al., Science China 52 (2009) 690.
Jenkins and Fischbach (2008), http://arxiv.org/abs/0808.3283v1
Jenkins and Fischbach (2009), http://arxiv.org/abs/0808.3156
Jenkins and Fischbach (2010), http://arxiv.org/abs/1007.3318
Parkhomov, http://arxiv.org/abs/1006.2295
Cooper (2009), http://arxiv.org/abs/0809.4248
F. Cardone, R. Mignani, A. Petrucci, Phys. Lett. A 373 (2009) 1956
Ericsson et al., Comment on "Piezonuclear decay of thorium," Phys. Lett. A 373 (2009) 1956, http://arxiv4.library.cornell.edu/abs/0907.0623
Ericsson et al., http://arxiv.org/abs/0909.2141
Lindstrom et al. (2010), http://arxiv.org/abs/1006.5071
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...while the Sun, through proton-proton fusion, emits neutrinos. If solar neutrinos do affect radioactive decay, maybe it's because of the difference between neutrinos and antineutrinos?
Ignoring the noted discrepancies (which may mean the experiments don't confirm anything), the experiment as designed confirms only that neutrino flux -- of the type of neutrinos emitted by Au-198 decay -- does not affect the decay rate of Au-198.
One could generalize this further to say that (Au-198) neutrino flux doesn't affect beta decay, but that's only one type of decay ... and one flavor of neutrino. (Neutrinos come in three flavors, plus their antiparticles. Beta decay actually produces electron antineutrinos, and while some observations suggest than neutrinos can oscillate between different flavors, the time scale for that is too long for it to occur in these small gold samples.) In fact, one (controversial, of course) proposed explanation for the decay-rate oscillations (in Pr-140 and Pm-142) observed at Darmstadt relates to neutrino oscillation.
Even with this generalization, they've only covered 1/9th of the possible combinations of decay type and neutrino flavor (or 1/18th counting antineutrinos). So it's an interesting experiment, but doesn't confirm what the summary says it does -- except for Au-198 beta decay and electron antineutrinos.
I'm not saying that there is a real effect seen in the long-term experiments that seem to suggest it, but considering that measurements of decay rates of different isotopes seem to have shown a different phase vs the position of Earth's orbit, and that some isotopes (eg plutonium in deep space RTGs) may not be showing an affect at all (hard to tell because the decay rate is inferred from a measurement about three levels of indirection removed from the actual decay rate), it leaves open the possiblity that the mechanism (if there is one) varies with the type of nucleus involved.
If there is such a decay rate change, it may have nothing to do with Earth's distance from the Sun, but rather Earth's distance from something else (eg galactic core) in which case interplanetary RTG decay rates wouldn't vary nearly as much as if distance from the Sun were a factor.
(Also, I note that observed decay rate changes so far seem to occur in isotopes of lighter elements (Pr, Pm and Si) and not in isotopes of heavier elements (Au, Pu) so perhaps the more complex nuclear structure of heavy elements masks or cancels the effect.)
So, interesting experiment, and it narrows down the places to look for a possible cause, but it doesn't prove that there's no effect.
-- Alastair
And with the short half life of gold 198, it's hard to believe they even proved that. I work with it on a daily basis, as an integrating neutron detector for my fusor (normal gold 197 picks up a neutron in a moderated neutron oven and becomes radioactive). It's fairly numb compared to say, Silver or Indium, but a little longer lived so the error due to the time it takes to stop a run and start the activity count is less. To make enough gold hot enough to do a statistically valid test, they must have had one heck of an intense source of medium-low energy neutrons. Gold picks them up best at a resonance energy somewhat above "thermal" which is what is found in most reactors -- it's more complex than that, of course, as reactors have a spectrum of neutron energies available if designed for that.
As another poster (calidoscope) pointed out, neutrinos seem to oscillate, and another poster (scruffie) also pointed out that there are also antineutrinos.
So this test was pretty limited in terms of what was actually tested, and how well it could be tested over the pretty short half life of radioactive gold.
Better than not testing at all, but just barely, it doesn't cover many of the bases at all.
Why guess when you can know? Measure!
The experiment doesn't address the larger question of variable decay rate, nor was it designed to. Instead, it indicates that if there is a variability, it probably isn't caused by neutrino flux. That is, in itself, a useful (non)result.
...4) They had a pile of unused gold and didn't know what to do with it :)...
You may have been trying to be funny, but perhaps it is simply the cheapest material to work with.
Slowly waving my hand - "This is not the sig you are looking for."