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Science

Nuclear Decay May Vary With Earth-Sun Distance 418

Posted by kdawson
from the not-so-fast-there dept.
KentuckyFC writes "We've long thought that nuclear decay rates are constant regardless of ambient conditions (except in a few special cases where beta decay can be influenced by powerful electric fields). So that makes it hard to explain two puzzling experiments from the 1980s that found periodic variations over many years in the decay rates of silicon-32 and radium-226. Now a new analysis of the raw data says that changes in the decay rate are synchronized with each other and with Earth's distance from the sun. The physicists behind this work offer two theories to explain why this might be happening (abstract). First, some theorists think the sun produces a field that changes the value of the fine structure constant on Earth as its distance from the sun varies. That would certainly affect the rate of nuclear decay. Another idea is that the effect is caused by some kind of interaction with the neutrino flux from the sun's interior which also varies with distance. Take your pick. What makes the whole story even more intriguing is that for years physicists have disagreed over the decay rates of several isotopes such as titanium-44, silicon-32, and cesium-137. Perhaps they took their data at different times of the year?"
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Nuclear Decay May Vary With Earth-Sun Distance

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  • Re:Carbon Dating (Score:5, Informative)

    by meringuoid (568297) on Friday August 29, 2008 @09:14AM (#24793265)
    I'd expect not. The variation would be over the course of a year, and carbon dating works on a timescale of centuries to millennia; it would even out. Besides that, we have other clocks to calibrate carbon dating against; you can carbon-date a historic artefact of known age, you can count tree rings or ice layers, stuff like that.

    On a timescale of billions of years, however, the luminosity of the Sun has increased substantially, and if that accelerates radioactive decays by some neutrino interaction then the uranium-lead clock would be off and the Earth might be considerably older than we thought.

  • Re:Carbon Dating (Score:5, Informative)

    by kmac06 (608921) on Friday August 29, 2008 @09:15AM (#24793291)
    Probably not. The change in decay rate was on the order of .1% (see Fig. 1 of the paper), which is I believe smaller than the error in carbon (or other radioactive) dating. Also, it is only these two isotopes that are mentioned, presumably because most other isotopes tested do not have this sort of periodic effect.
  • Seriously : No (Score:5, Informative)

    by DrYak (748999) on Friday August 29, 2008 @09:29AM (#24793461) Homepage

    Does this have any ramifications for carbon dating?

    Seriously : No.
    For 2 reasons.

    I. - Effect on carbon
    For now carbon isn't on the list of the elements that seem affected by the distance to the sun.

    II. - Not a significant variation.
    in TFA, variation seem to be very well correlated with the distance *BUT* these variations are really small : only a small fraction of percent (~0.15%). To cite one of the commenters on TFA's blog thread :

    That said, itâ(TM)s not *terribly* unsettling to me; the variations are small (measurable,but small) and to me itâ(TM)s all part of the Wonderful World of the Weird that is QM.

    If we discover that carbon is among the elements influenced by the sun too, those mere ~0.15% of variation will be insignificant compared to the skew that happens with varying concentration of carbon-14 in the atmosphere [wikipedia.org] (see wikipedia's graph of variation) - which already requires that we do calibrations anyway.
    (Current carbon dating doesn't extrapolate the age purely by deducing the levels from the decay rate, but instead uses tables where corrections have been inserted based on the carbon dating of thing with known age)

    So in short : for now it doesn't have any ramification and anyway it couldn't have any more than we already compensate for.

  • Re:Carbon Dating (Score:5, Informative)

    by Watson Ladd (955755) on Friday August 29, 2008 @09:30AM (#24793487)
    Actually a cesium clock uses the hyperfine structure which is not known to be affected these effects.
  • Re:How To Test It (Score:5, Informative)

    by Watson Ladd (955755) on Friday August 29, 2008 @09:32AM (#24793509)
    Actually the more radioactive something is the faster it decays. Uranium in waste is not the problem, the minor actinides are.
  • Re:Carbon Dating (Score:5, Informative)

    by paeanblack (191171) on Friday August 29, 2008 @09:34AM (#24793537)

    I am more concerned about the other end of that - time-keeping --- the communications networks get their time hacks from clocks based upon the decay rate of isotopes (e.g. a cesium clock).

    Caesium clocks have nothing to do with nuclear decay rates. They measure electron state transition times. You can relax now.

  • Re:Carbon Dating (Score:5, Informative)

    by necro81 (917438) on Friday August 29, 2008 @09:35AM (#24793551) Journal
    I get your joke, but it presents an opening to state the following little known fact:

    Diamonds are not, in fact, forever

    Under normal temperature and pressure conditions, diamond is not the most stable form of carbon - graphite is. Using thermodynamic arguments and building a free energy curve, one can show that some fraction of a diamond must decay to graphite in order to achieve a minimum energy state. It does take a very long time for this to happen - geologic time - but even a "long time" is not forever. If you aren't that patient, heat the diamond up to, say, 1500 C to speed things up. Oh, but be sure to do that in the absence of oxygen, because diamond burns just like other forms of carbon.

    Some references: [1] [uoguelph.ca], [2] [everything2.com], [3] [wikipedia.org]
  • Re:Carbon Dating (Score:5, Informative)

    by kmac06 (608921) on Friday August 29, 2008 @09:36AM (#24793569)
    You bring up a good point.

    The communications networks get their time hacks from clocks based upon the decay rate of isotopes (e.g. a cesium clock).

    It's actually based on the frequency of a transition in cesium, but the point is that these transitions are sensitive to the fine structure constant. If some field from the sun is changing that, it should be detectable in atomic clocks.

  • Short answer: no (Score:5, Informative)

    by Moraelin (679338) on Friday August 29, 2008 @09:53AM (#24793817) Journal

    Short answer: no.

    Longer answer: nope.

    Even longer answer:

    1. Carbon isn't one of the isotopes that are affected by this.

    2. The fluctuations have a period of about year, so they average out when you measure something over millenia.

    3. The fluctuations are very very tiny, waay below one percent even. So basically even if you happened to take one extreme as your value, and in reality it was the opposite extreme, and even with "compound interest" so to speak... worst that could happen is that a 100,000 year old bone turns out to be "only" a bit over 99,000 year old. The creationists still aren't going to like it.

    4. The variability in C14 production and distribution are much bigger than this fluctuation, and we learned to deal with those perfectly well. (C14 is constantly produced as neutrons from solar radiation knock off and replace a proton from an N14 atom, turning it into a C14 atom.)

    5. The way we deal with those is by calibrating that dating. There's stuff that we already know when it happened, by other means (chronicles, geologic events, etc), and we can see how much C14 is left in stuff from that year. That lets you calibrate your C14 dating pretty damn well.

    The last one also tells you why actually #2 is the only one that matters: we already calibrated for long intervals, and such fluctuations were already averaged into the calibration. This new discovery won't affect C14 dating at all. The effect is exactly zero. Null. Nada. Nix.

    Of course, that won't stop young-Earth creationists from coming out of the woodwork, and waving yet another thing they don't understand as "proof" that science is wrong and their bible is the literal history of Earth. What else is new? No, seriously.

    I figure everyone and everything has their place and role, though. The young-earth creationists' is simply to make everyone else look smart. It's a tough job, but someone has to do it ;)

  • by Count_Froggy (781541) on Friday August 29, 2008 @10:12AM (#24794099) Homepage Journal

    Only if you live in the Southern Hemisphere...

    The Earth is actually closer to the Sun during the Northern Hemisphere Winter.

  • Re:Carbon Dating (Score:5, Informative)

    by Nymz (905908) on Friday August 29, 2008 @10:18AM (#24794187) Journal

    The variation would be over the course of a year, and carbon dating works on a timescale of centuries to millennia; it would even out.

    Is that assuming the only measurable factor is based upon the distance from the sun? Because that would seem to be an incomplete description of radiation, especially since the article mentioned the possibility of solar flare activity causing the decay rate to change.

    The old axiom of "The more I learn, the less I know" could very well hold true for this subject matter.

  • Re:How To Test It (Score:2, Informative)

    by jnik (1733) on Friday August 29, 2008 @10:33AM (#24794411)

    but of course the research needs to be duplicated and checked, objections need to be raised and addressed and so on.

    Before that, the paper needs to actually be peer-reviewed and published. arXiv's a non-reviewed, quick dissemination venue, not a reliable journal.

  • by cnettel (836611) on Friday August 29, 2008 @10:35AM (#24794455)
    What's used is the resonance frequency, not the decay rate. It is also the resonance related to electron transitions, not the nucleus. Naturally, the fine-structure constant will influence just about any physical process, though. (That's one of the reasons to prefer the neutrino explanation.)
  • Re:Carbon Dating (Score:1, Informative)

    by Anonymous Coward on Friday August 29, 2008 @10:40AM (#24794545)

    No. If there are any they'll probably be less than 1%.

    I didn't read the article yet, but here's why I'm bold enough to say that anyway: anything less than, say, 10%, and any variation is going to be irrelevant to the broad conclusions from radiometric dating, and that would have been noticed already.

    Perhaps surprisingly, some variation in radiometric decay constants isn't news. It is already known for the electron capture [wikipedia.org] mode of decay, due to extreme pressure or complete ionization of the relevant atoms. It works because you need electrons in the vicinity of the nucleus in order for this decay process to work, and if you strip those electrons off (ionization) or crush them closer to the nucleus (extreme pressure), there will be an effect.

    I emphasize "extreme" because I mean "core of the Earth" kind of pressures before you get even a measly percent or two of effect from the process. That makes it irrelevant to the types of radiometric dating that are ordinarily performed on samples from the Earth (crustal depths aren't enough pressure to have a significant effect), and, of course, the mechanism is completely irrelevant for isotopic systems that don't involve electron capture in the first place, and plenty of those are also used for radiometric dating. It's one of those "varies in theory, but in practice it's irrelevant" situations.

    What this article describes is a different process, but I expect that it will be the same story, assuming it is real and not attributed to some other subtle experimental artifact (e.g., seasonal biases on the instrumentation). People will probably be checking into that promptly. It has to be a tiny effect, otherwise it would have been noticed a long time ago because many independent experiments on decay have been done for many decades. I therefore expect any ramifications for C-14 or other radiometric dating techniques are going to be similarly minuscule.

    Of course, that won't stop some people who wish radiometric dating techniques were flawed from making a big deal about it.

  • Wrong (Score:5, Informative)

    by spun (1352) <loverevolutionary&yahoo,com> on Friday August 29, 2008 @10:50AM (#24794711) Journal

    The Fine structure [wikipedia.org] addressed in this article is not the hyperfine structure [wikipedia.org] which cesium clocks use.

  • by Anonymous Coward on Friday August 29, 2008 @10:51AM (#24794737)

    Actually, the correlation is not terrible at all. It's clearly visible at sight, and the authors say "The Pearson correlation coefficient,r, between the raw BNL data and 1/R^2 is r=0.52 for N=239 data points, which translates to a formal probability of 6E-18 that this correlation would arise from two data sets which were uncorrelated"
    That seems pretty low to me.

    And about the phase: An out-of-phase correlation is a correlation, it's just out of phase. That means there's some time delay that should be explained by the model. In fact, the authors dedicate a hole paragraph (and another paper) to try to explain it.

    Finally, the season is discarded as a cause since thay analyze data from two experiments in different hemispheres, and they are correlated in phase.

  • Re:Carbon Dating (Score:5, Informative)

    by dotancohen (1015143) on Friday August 29, 2008 @11:10AM (#24795081) Homepage

    Diamonds are generally best friends, not dating material.

    No, dogs are best friends around here. What women read /.?

  • by Wonko the Sane (25252) * on Friday August 29, 2008 @11:34AM (#24795519) Journal

    I think you got it backwards. They think that neutrino flux slows down radioactive decay. As probe gets farther away from the sun, then it will decay faster.

  • by Moraelin (679338) on Friday August 29, 2008 @11:54AM (#24795857) Journal

    Speaking as a religious person myself, I always find it funny when scientists are forced into these "oops, we didn't think of that" moments.

    Why is it funny? That's how science _works_. The whole framework is geared towards, basically, fixing past mistakes or refining what wasn't quite right.

    They spend all their time asserting conclusions that then turn out to be - if not exactly wrong - not quite there yet.

    No real scientist can ever assert something as the final word, the immutable absolute truth, the thing beyond challenging. That's not how science works. You can only assert that, given the data you have, this theory is the simplest thing that explains that data. And here's the reasoning and the data, please _do_ try to poke holes in it and find cases that I've missed.

    Science isn't about a set of edicts to learn by heart. It's a process. A method. It's the way to refine the current knowledge towards something more accurate, and to find and discard knowledge that turned out to be wrong after all.

    Science doesn't have absolute truths. It only has falsifiable theories. Some of them actually getting proven wrong, or in your words "if not exactly wrong - not quite there yet" is not just normal, but the way progress happens.

    In other words, it's a good thing, not a bad thing. And any scientist worth anything already knows that.

    While I don't want to be seen as a fundamentalist "science sceptic" (because I'm not), I can't help wondering what else scientists have missed.

    _Hopefully_ a lot, because that's how progress happens. If there were nothing more to discover, and the theories we have were the whole and exact truth, well, then we'd be stuck at the current tech level for ever. Which isn't necessarily a good thing.

    Also, scepticism is a good thing in science. By all means, please be a sceptic. There is however a difference between scepticism as in "show me the data before I believe that" and block-headed counter-enlightenment as in "I already decided my immovable truth, and if any data contradicts it, then your data is wrong and the work of Satan." The latter isn't scepticism, it's just being a dumbass. And the fundies don't fail by being sceptical, they fail in the latter way.

    Ah, well. That's why I read science books.

    At the risk of sounding a bit like a personal attack, and I apologize in advance for it: try understanding the scientific method first. Because if I'm to take a guess based on what you wrote above, you don't really seem to understand what science _is_. Just reading some books and taking those predictions as some kind of religious truths, asserted by the High Priests, and as some failure of those if they turn out to be wrong... well, that's actually how religion works, not science.

    But then it's entirely possible that you've just not explained your position well enough, or that I've misunderstood it completely.

  • by AliasMarlowe (1042386) on Friday August 29, 2008 @11:54AM (#24795861) Journal

    If I understood correctly, the variance in decay rate between Earth's aphelion and perihelion is .1%. Earth's distance from the sun doesn't change by that much in astronomical terms...

    But Earth's distance from the sun does change by more than 0.1% during its orbit:
    Aphelion distance = 152.1 million km
    Perihelion distance = 147.3 million km
    So aphelion distance from the center of the sun is 3.2% greater than perihelion distance. Alternatively, both aphelion and perihelion differ from their mean by 1.6%.

  • Re:Carbon Dating (Score:5, Informative)

    by drew (2081) on Friday August 29, 2008 @12:10PM (#24796141) Homepage

    At least with regards to carbon dating, it has been known for some time that strict carbon dates are not accurate. These are referred to as "uncalibrated" dates. The explanation that I remember seeing is that the atmospheric ratio of C14/C12 has not been constant over the earth's history, but this may be a factor as well. At any rate, carbon dates for at least the last 15,000 years can be calibrated - that is, the concentration of C14 in the object being tested can be compared to the concentration of C14 in an object of a known age (e.g. from tree rings, ice cores, documented historical sites) to get a more accurate assessment of an objects age. In some cases this can lead to objects being considerably older than originally thought. For example, an uncalibrated carbon date of 9,000BC corresponds to a calibrated carbon date of nearly 11,000BC.

  • Re:Carbon Dating (Score:3, Informative)

    by meringuoid (568297) on Friday August 29, 2008 @12:11PM (#24796169)
    I'd expect the impact to be heavily reliant on what the actual cause is. I find it hard to believe that the cause isn't a direct electromagnetic connection.

    If this were an electromagnetic effect, we should be able to duplicate it in the lab. It's not hard to produce immense electromagnetic fields in the laboratory, and to subject radioactive samples to the most extreme of conditions. Yet as far as laboratory experiment has been able to determine, electric and magnetic fields, however strong they may be, do not affect radioactive decay rates at all.

    Hence the suggestion that neutrino interactions may be responsible. Neutrinos interact through nuclear forces and therefore it is at least conceivable that they might affect radioactive decay.

  • by Ambitwistor (1041236) on Friday August 29, 2008 @12:14PM (#24796225)

    On 100 year time scales, variations in the Earth's orbit don't have anything to do with climate change. They're too small. Over 100,000 year time scales, they do become important: they lead to the Milankovitch cycles [wikipedia.org] which are thought to cause the glacial-interglacial cycle.

  • by bmwm3nut (556681) on Friday August 29, 2008 @12:21PM (#24796371)
    I am a chemist (and physicist). There may be something that could be attributed to "bouncing" nuclei with electrons (I doubt it, but I'm not going to rule it out); however, the scale of that would be much smaller than what's being reported here. In the lightest atom (Hydrogen) the nucleus is about 1,800 times heaver than an electron. So any effect of temperature or anything that would cause the electrons to interact with the nucleus is going to be damped by a factor of 1,800. Now, when we get to the radioactive elements, their weights are on the order of 100 times heaver than Hydrogen, so any electron-nucleus effect will be down by a factor of at least 180,000 which is way smaller than the effect reported in TFA.
  • Re:Pioneer Anomaly (Score:1, Informative)

    by Anonymous Coward on Friday August 29, 2008 @12:33PM (#24796569)

    Pioneer isn't tumbling. It keeps its antenna pointed at a certain place in Earth's orbit.

    Since we can no longer talk to it, we can't tell it to point its antenna at Earth, and are left with it pointing to the last place we told it to. So we can, given the width of its beam, talk to it for about four months of the year.

  • Re:Carbon Dating (Score:3, Informative)

    by gregbot9000 (1293772) <mckinleg@csusb.edu> on Friday August 29, 2008 @01:38PM (#24797693) Journal
    They already fixed this problem year ago on paper.
    http://en.wikipedia.org/wiki/Nuclear_reprocessing [wikipedia.org] http://en.wikipedia.org/wiki/Nuclear_breeder_reactor [wikipedia.org]
    The only problems have been that oil was cheep and nuclear scary, so its never really left the design stages.
  • by QuoteMstr (55051) <dan.colascione@gmail.com> on Friday August 29, 2008 @01:42PM (#24797757)

    RTGs run down because the thermocouples go bad, not because the plutonium cools off.

  • by bcrowell (177657) on Friday August 29, 2008 @02:02PM (#24798057) Homepage

    But... look at the data. That correlation is *terrible*. The phase is off.

    IMO you're focusing on the wrong thing. If you believe their error bars, and believe that there are no systematic errors that correlate with time of year, then the probability that a correlation this strong would occur is quoted by them at 6*10^-18. On any plot like this, the human eye is a lousy judge of statistical quality. The statistical quality comes from the aggregate of all the data. You could have a plot like this with a thousand data points where a ruler line went through 2/3 of the error bars, and it could still be statistically inconsistent with zero modulation to an astronomical level of confidence.

    The real weakness in this work is not in the statistical quality of the data, it's that it makes extraordinary claims, and extraordinay claims require extraordinary proof, but there are several obvious things that they should have done, and didn't:

    1. They should have shown that the results were reproducible.
    2. They should have shown that the results were reproducible under a variety of conditions that might have led to a bogus yearly modulation. For instance, they should have tried it in both the northern and the southern hemisphere, and they should have tried it in a temperature-controlled environment, with the temperature intentionally modulated with different phases.
    3. They should have shown that the results occurred with qualitatively different types of detectors. For instance, they could use an isotope that emits both gammas and betas, and show that the same effect occurs both in an HPGe gamma-ray detector and in a silicon beta detector.
    4. Although the statistical confidence level of the correlation is good, it's completely bogus that they didn't make any effort to improve the statistics so that the effect could be seen more clearly. If nuclear decay rates really depend on distance from the sun, then there's no way it's just going to be an effect that applies to some nuclei and not others. They have data from 32Si, which is an exotic isotope whose half-life is technically difficult to measure. Based on this extremely technically difficult measurement, they deduce an effect at the 10^-3 level. Well, with an isotope that's easier to produce, they could easily get their random errors down by several orders of magnitude; with a count rate of 1 kHz in each detector out of an array of 100, counting for 3 months, you'd have Poisson statistics of 10^-6. The error bars on the plot would then be too small to see. Basing the strongest possible claims on a design leading to the crappiest possible statistics is one of the hallmarks of junk science.
  • by OriginalArlen (726444) on Friday August 29, 2008 @02:33PM (#24798483)

    How do we know that radioactive isotopes decay at all if you get them far enough away from a star?

    Well, we're going to need a new theory of stellar processes if so, which is going to mean some pretty spectacular changes to astronomy. Also, the Voyager (and Mariner, and other) RTGs are decaying at the rates predicted by the standard model. This fits the definition of an "extraordinary claim" to a t -- anyone with real physics clue on this thread care to comment on the ordinariness or otherwise of the evidence claimed by the pre-print?

  • by The Iso (1088207) on Friday August 29, 2008 @02:53PM (#24798743)

    On page 2, the authors write,

    Moreover, the difference in latitude between BNL and PTB, as well as the difference in their climates, argues against an explanation of this correlation in terms of seasonal variations of climatic conditions such as temperature, pressure, and humidity etc., which could have inuenced the respective detection systems.

    If this was caused by power loads due to seasonal weather, opposite effects would have been observed in opposite hemispheres.

    But I don't know a tenth of what you do about MCAs, and I'm not qualified to judge whether you or the researchers are correct.

  • Re:Wrong (Score:3, Informative)

    by kmac06 (608921) on Friday August 29, 2008 @03:09PM (#24798981)
    Read your own link. From wikipedia:

    The amount of correction to the Bohr energy levels due to hyperfine splitting of the hydrogen atom is of the order

    m/mp*alpha^4*m*c^2

    where

    m is the mass of an electron,
    mp is the mass of a proton,
    alpha is the fine structure constant (alpha approx 1/137.036),
    c is the speed of light.

  • by rrohbeck (944847) on Friday August 29, 2008 @05:28PM (#24801723)

    PTB produces the official time standard for Germany, like NIST in the US. You bet they have better internal timebases than power lines given the number of Cesium clocks they have standing around.
    The 50 Hz power frequency in most of Europe is derived from them (via DCF77 [wikipedia.org].) Which also means that long term, 50 Hz mains is an excellent frequency standard. Many clocks run directly off of it. Short term variations can be pretty big though. Sounds like the 60 Hz in the US isn't as well controlled.

  • Re:Carbon Dating (Score:3, Informative)

    by Teancum (67324) <robert_horningNO@SPAMnetzero.net> on Friday August 29, 2008 @06:12PM (#24802639) Homepage Journal

    The other huge problem with breeder reactors is that the ability to process nuclear waste also gives you the ability to concentrate nuclear by-products to whatever levels of concentration that you desire.

    In other words, this gives whatever corporation, country, or agency that has one of these facilities the ability to build a nuclear bomb. That tends to scare off the diplomats and brings out the anti-nuclear crowd in hoards. Perhaps justifiably.

    In other words, it is better to bury nuclear waste in some obscure mountain in the middle of Nevada (obviously the last state that anybody would bother living in... according to the Washington DC policy-setting crowd) than it is to dispose of this sort of waste via these bomb producing factories.

    It isn't like fertilizer or other chemical factories can't produce bombs either, but that is irrelevant.

    BTW, my family is from Nevada and I love the state, and I hate to see it turned into a nuclear waste repository. The scars from nuclear bomb testing are bad enough.

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