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Nuclear Decay May Vary With Earth-Sun Distance
Posted by
kdawson
on Fri Aug 29, 2008 08:03 AM
from the not-so-fast-there dept.
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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Carbon Dating (Score:5, Interesting)
Does this have any ramifications for carbon dating?
Re:Carbon Dating (Score:5, Funny)
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Re:Carbon Dating (Score:5, Funny)
I dated graphite once, she wasnt very original, kinda flaky, and left dark marks on me... Diamonds, is still playing hard to get though...
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Re:Carbon Dating (Score:5, Funny)
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Re:Carbon Dating (Score:5, Funny)
Diamonds are generally best friends, not dating material.
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Re:Carbon Dating (Score:5, Informative)
Diamonds are generally best friends, not dating material.
No, dogs are best friends around here. What women read /.?
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Re:Carbon Dating (Score:5, Funny)
Dogs read Slashdot?!
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Re:Carbon Dating (Score:5, Informative)
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]
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openings for little known facts (Score:5, Funny)
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Re:Carbon Dating (Score:5, Funny)
Diamond: When you only want the best for your grill.
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Re:Carbon Dating (Score:5, Interesting)
The idea that a diamond will decay into graphite in geologic time is a popular fiction. The activation energy barrier for the diamond-graphite transition is high enough that substantial decay at STP will take far longer than the Earth will last, and the time scale is therefore not geologic. Several samples of diamond have been found that crystallized before the formation of the solar system, and some carbonados [wikipedia.org] exhibit Xenon isotope concentrations in inclusions that suggest that they formed in distant supernovas and fell to earth.
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Re:Carbon Dating (Score:5, Funny)
Hi honey, I got you this fabulous graphite ring. It lasts longer than a diamond! Will you marry me?
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Diamonds are Forever... (Score:5, Funny)
...only if they maintain the correct Bond.
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Re:Carbon Dating (Score:5, Informative)
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.
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Re:Carbon Dating (Score:5, Informative)
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.
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Re:Carbon Dating (Score:5, Informative)
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.
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Re:Carbon Dating (Score:5, Informative)
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Re:Carbon Dating (Score:5, Interesting)
Also, it is only these two isotopes that are mentioned, presumably because most other isotopes tested do not have this sort of periodic effect.
I stand corrected! From the paper:
Although there are hundreds of potentially useful nuclides whose half-lives have been measured, the data from many of the experiments we examined were generally not useful, most often because data were not acquired continuously over sufficiently long time periods.
So the possible ramifications of this increase!
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Re:Carbon Dating (Score:5, Interesting)
Also, it is only these two isotopes that are mentioned, presumably because most other isotopes tested do not have this sort of periodic effect.
I wouldn't presume that. The very thing that makes this so interesting is that "the modulations are synchronised with each other and with Earth's distance from the sun." To me, that makes it likely to be a general effect on all radioactive materials. I don't know if this will lead to anything that supports a young earth theory, but it'll be interesting to see what comes from it. The article also mentions:
It turns out, that the notion of that nuclear decay rates are constant has been under attack for some time. In 2006, Jenkins says the decay rate of manganese-54 in their lab decreased dramtically during a solar flare on 13 December.
This is a good example of how many holes there might be in our theories about the universe. We have been making measurements for a few 1000 years in one solar system (mostly just on one planet) and things that we don't see changing, like radioactive decay rates, we consider constant. It's exciting to think how much more there may still be to discover.
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Engineering Ramifications? (Score:5, Interesting)
This is a good example of how many holes there might be in our theories about the universe. We have been making measurements for a few 1000 years in one solar system (mostly just on one planet) and things that we don't see changing, like radioactive decay rates, we consider constant. It's exciting to think how much more there may still be to discover.
This makes me wonder about the http://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator [wikipedia.org]power sources on board the Voyager spacecraft, as they are based on the decay of radioactive material. Has our earth-centric understanding of the universe led us to build probes designed to push the boundaries of the solar system and continue into interstellar space, that will gradually lose power the further they get from the sun?
Whoops.
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Re:Engineering Ramifications? (Score:5, Insightful)
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Re:Engineering Ramifications? (Score:5, Interesting)
Sorry, doesn't wash. The probes are not in powered flight, they're simple ballistic projectiles. No ion engines at work, which might show the effects you suggest.
It would clearly be interesting to construct a probe to test this effect using a greater distance that the difference between the Earth's perihelion and apihelion
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Re:Engineering Ramifications? (Score:5, Insightful)
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Re:Engineering Ramifications? (Score:5, Insightful)
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. If we see a .1% variation over that relatively small distance, how different would the rate be at 100AU, or half-way to the nearest star? How do we know that radioactive isotopes decay at all if you get them far enough away from a star?
It's also not simply a matter of how long the power supply will last. Those generators work by converting the heat from each decay event into electricity, and if the rate of decay is less than it should be, then it will not produce continuous power.
I'm not saying that it's definitely a problem, I just think this raises interesting questions.
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Re:Engineering Ramifications? (Score:5, Informative)
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%.
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Re:Carbon Dating (Score:5, Funny)
Yes - but not enough to account for the difference between Joan Rivers' apparent and actual age.
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Re:Carbon Dating (Score:5, Funny)
Yes - but not enough to account for the difference between Joan Rivers' apparent and actual age.
When nine-hundred years old you reach, look as good, you will not.
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Seriously : No (Score:5, Informative)
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.
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Re:Carbon Dating (Score:5, Interesting)
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Re:Carbon Dating (Score:5, Interesting)
I.e. no.
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Re:Carbon Dating (Score:5, Informative)
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Re:Carbon Dating (Score:5, Informative)
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.
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Re:Carbon Dating (Score:5, Funny)
They measure electron state transition times. You can relax now.
Why'd you tell him to relax?
Look, he just threw off a bunch of photons all over the place - and it was a forbidden transition!
Ok, so you clean up the mess now! :-)
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Re:Carbon Dating (Score:5, Informative)
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.
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Wrong (Score:5, Informative)
The Fine structure [wikipedia.org] addressed in this article is not the hyperfine structure [wikipedia.org] which cesium clocks use.
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How To Test It (Score:5, Interesting)
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.
You left out the best part of the paper, where they propose how to test these theories:
These conclusions can be tested in a number of ways. In addition to repeating long-term decay measurements on Earth, measurements on radioactive samples carried aboard spacecraft to other planets would be very useful since the sample-Sun distance would then vary over a much wider range. The neutrino flux hypothesis might also be tested using samples placed in the neutrino flux produced by nuclear reactors.
Sounds like we could test the latter relatively easily.
Also, Jeeeeeeeeeeeeeeeeeere H. Jenkins!!!
Re:How To Test It (Score:5, Informative)
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Silicon-32 Decay Variation (Score:4, Funny)
Pioneer Anomaly (Score:4, Interesting)
Cool! (Score:5, Interesting)
Two counter-examples (Score:5, Insightful)
If you count the presence or absence of observation as part of "ambient conditions", there are two cases where nuclear decay rates are affected by ambient conditions: The quantum Zeno effect [wikipedia.org] and the quantum anti-Zeno effect. [wikipedia.org]
It's a trick! (Score:5, Funny)
Phlogiston (Score:5, Funny)
Now if you'll excuse me, I have an appointment with my Phrenologist.
Fine structure constant (Score:5, Interesting)
In their theory, the Sun produces a scalar field which would modulate the terrestrial value of the electromagnetic fine structure constant EM.
The fine structure constant [wikipedia.org] (about 1/137) has been measured to a whopping 10 significant digits, one of the most precisely measure physical constants. If there is a seasonal variation enough to influence decay rates by .1%, wouldn't this show up in different experiments measuring the fine structure constant?
Re:Fine structure constant (Score:5, Interesting)
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But the data is awful (Score:5, Insightful)
Also, note that since the perihelion is right around Jan 1, only about eleven days after solstace-- this data equally well correlates with season.
Synchronized to r^2, not r (Score:5, Interesting)
This graph [arxivblog.com] seems to indicate that the correlation is between the decay rate and the radius of Earth's orbit squared, not just r.
Could it be that the correlation between decay rates is with Earth's orbital velocity [wikipedia.org], acceleration, or dTheta/dT (rate of change of the Earth/Sun vector due to Earth's elliptical orbit)?
Additionally, there seems to be a phase shift between peak r^2 and peak decay rates with the decay rate peak seemingly correlated with our peak acceleration toward the sun.
One possible explanation (Score:5, Interesting)
Everything she touches, / Changes. (Score:5, Interesting)
TFA's frame of reference is the Earth's orbit about the Sun, and reports a small but significant correlation between aphelion - perihelion and decay rates of some radioactive nuclides. TFA suggests that the 4% change between Earth's closest approach to the Sun and its most distant point is a possible cause for the change in decay rates.
When the frame of reference is expanded to galactic distances, we find that Earth's aphelion point is coincidentally very close to a line drawn from the Sun to the center of the galactic core. So it could also be that some shielding or suppressive effect of the Sun's local environment is reducing decay rates when the Earth is behind the Sun relative to the galactic core.
Proposed hypothesis: the changes in radioactive decay rates are related in an unknown fashion to the annual changes in the geometry of the Earth - Sun - galactic core.
This could probably be ruled out with a couple of tests of the existing data:
Aphelion occurs on Jan 4, while Earth's fullest exposure to any presumed galactic core influence occurs on Dec 17. Does the data suggest that increased activity centers around aphelion, or 18 days earlier?
If TFA's heliocentric model is correct, the change in rates of decay from month to month will be a smooth sinusoidal curve over the course of the year. But if the galactic core is involved, the changes in rates of decay will depart from this since the ecliptic does not parallel the galactic plane, and the degree of the Earth's "exposure" to galactic core will vary in a more complex way. Does the data support either of these conjectures?
I'm not going to cite my references here: they would be a distraction. Key words for google: aphelion, perihelion, solstice, galactic core, "plane of the ecliptic", "galactic plane". Um, a quick review of high school trigonometry might be useful, too.
Kudos to all the researchers and lab assistants who contributed to this work. It sounds like years of seemingly mindless drudge data collection went into this database. Yet the results are stunning: something Out There is affecting "constants" that we thought were intrinsic and immutable. That changes things. That changes everything.
Short answer: no (Score:5, Informative)
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 ;)
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