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Earth Government Science Technology

Iron Age Potters Accidentally Recorded the Strength of Earth's Magnetic Field (npr.org) 118

Posted by BeauHD from the stamped-with-a-royal-seal dept.
Solandri writes: We've only been able to measure the Earth's magnetic field strength for about two centuries. During this time, there has been a gradual decline in the field strength. In recent years, the rate of decline seems to be accelerating, leading to some speculation that the Earth may be losing its magnetic field -- a catastrophic possibility since the magnetic field is what protects life on Earth from dangerous solar radiation. Ferromagnetic particles in rocks provide a long-term history which tells us the poles have flipped numerous times. But uncertainties in dating the rocks prevents their use in understanding decade-scale magnetic field fluctuations.

Now a group of archeologists and geophysicists have come up with a novel way to produce decade-scale temporal measurements of the Earth's magnetic field strength from before the invention of the magnetometer. When iron-age potters fired their pottery in a kiln to harden it, it loosened tiny ferromagnetic particles in the clay. As the pottery cooled and these particles hardened, it captured a snapshot of the Earth's magnetic field. Crucially, the governments of that time required pottery used to collect taxed goods (e.g. a portion of olive oil sold) to be stamped with a royal seal. These seals changed over time as new kings ascended, or governments were completely replaced after invasion. Thus by cross-referencing the magnetic particles in the pottery with the seals, researchers were able to piece together a history of the Earth's magnetic field strength spanning from the 8th century BCE to the 2nd century BCE. Their findings show that large fluctuations in the strength of the magnetic field over a span of decades are normal. The study has been published in the journal PNAS.
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Iron Age Potters Accidentally Recorded the Strength of Earth's Magnetic Field More

Iron Age Potters Accidentally Recorded the Strength of Earth's Magnetic Field

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  • Ingenuity ftw (Score:4, Interesting)

    by Virtual_Raider ( 52165 ) on Wednesday February 15, 2017 @05:11AM (#53872073)
    From TFA: ''' "When dealing with such large-scale phenomena, we don't usually think it can occur within a few decades. We usually think it would take thousands or tens of thousands of years," Forman says. The finding, he adds, "opens up a big can of worms" because researchers just don't know how or why that would happen. So there's something missing about scientists' concept of goings on in the Earth's core.''' But hey, at least now we know we don't know :)

    • Can we get the same data from lavas? Lava has flowed in any given year of Earth's history.

      • Re:Ingenuity ftw (Score:4, Insightful)

        by NoNonAlphaCharsHere ( 2201864 ) on Wednesday February 15, 2017 @06:05AM (#53872195)
        Sure, but how do you date when it cooled?
        • Comment removed based on user account deletion

          • Rocks are dated by radiometry, looking at combinations of unstable isotopes that are appropriate to the type of rock.

            • Rocks are dated by radiometry

              There's at least one professional geologist in this conversation. That geologist thinks that almost always, rocks are dated by correlation of either fossil content, or stratigraphical arguments to rocks that have better fossil suites than your target rocks.

              Sure, radiometric dating may give you an answer - to which question : the age of the sediment grains (as if they might not differ by a couple of billion years between the quartz and the feldspars) ; or the age of the minerals

          • Re: (Score:2)

            by bondsbw ( 888959 )

            If nothing else, doing so could help confirm that the fluctuations found in the clay are due to the earth's magnetic field.

        • Come on, it is just one day after the Valentine's Day and already your date has cooled and has become undatable?

          Buy some more candy, flowers and keep at it man. Don't give up so easily. Nothing is cooled permanently and nothing ever reaches absolute zero.

      • Can we get the same data from lavas? Lava has flowed in any given year of Earth's history.

        You can and geologists have done this (like along the Mid-Atlantic Ridge). But radiometric dating is not precise enough to give "decade-scale" data. The purpose of this study is to see how much fluctuation occurs on short time scales (as opposed to thousands or millions of years).

        • Actually, there have been a couple of cases where the decades-to-centuries cooling duration of lava intrusions (less variable than lava flows ; more accurately modelled) has suggested that reversals can take place in the decades or so time scale ... but they were single dat points. This method looks considerably more scalable.

    • Re: (Score:2)

      by tsa ( 15680 )

      It's now a known unknown.

    • Re: (Score:2)

      by rcamans ( 252182 )

      Uh, we always knew we didn't know. But PhD's must profess absolute certainty in their publication and pronouncements, or they lose funding and standing.
      So they always communicate like they know.

      • They know what they did and what it means. Scientific papers (at least the ones I've seen) tend to be fairly explicit about what is and what is not known, often listing the latter under a heading like future research possibilities or some such.

  • How do we boost the strength far enough to eliminate cancer?

    • Re: (Score:2, Troll)

      by dwywit ( 1109409 )

      *Raises the question

    • Re:Begs the question... (Score:5, Informative)

      by quantumghost ( 1052586 ) on Wednesday February 15, 2017 @07:37AM (#53872399) Journal

      How do we boost the strength far enough to eliminate cancer?

      In short: you can't. Cosmic radiation is just a small part of the complex system that can trigger cancer. Other aspects include: genetic make-up, environment (carcinogens) and the inherent error rate in the DNA copying machinery [nature.com] (missense, frameshifts, slippage, etc) [to name a few off the top of my head - I don't treat cancer]. And before you go down there....those imperfect copies are what leads to genetic variation (important to fend off predators both macro and microscopic) and evolution [berkeley.edu]. Cancer is just about inevitable in any DNA based system

      • Okay, fair point but I just meant "how can we eliminate that source of cancer?" As a follow-up question, would it retard photosynthesis or any other critical biological processes?

        • Actually, this is backwards. Cancer risk decreases for the first low dosage radiation exposure.

          This is because the radiation "turns on" your body's natural radiation fighting responses. Those responses are actually pretty good, so turning them on decreases cancer risk initially. But if the radiation exposure gets higher, the body's system can't keep up.

          So for optimal cancer risk mitigation, you want slightly higher radiation than Earth currently puts out.

          • Re: (Score:1)

            by Anonymous Coward

            This is still highly debated with data giving mixed results, and pretty much every metastudy trying to look at it suggesting more study is needed before a statement can be made about extremely low radiation levels (e.g. still a need for a very low background biology lab...).

            So for optimal cancer risk mitigation, you want slightly higher radiation than Earth currently puts out.

            Even if there is an optimal level, I haven't seen anything to suggest a level higher than current background levels are the optimal level, considering there is over an order of magnitude variation in background levels on Earth.

          • Animals/humans have no 'natural radiation fighting response'.
            Facepalm

        • how can we eliminate that source of cancer

          To be clear are you suggesting there is a measurable amount of cancer caused by radiation from space?

          *and before anyone is smart, we're talking the type of radiation deflected by magnetic shield, not UV-C from the sun.

          • To be clear are you suggesting there is a measurable amount of cancer caused by radiation from space?

            This has been known for decades - since the start of regular flying at high altitude (above much of the atmosphere's protection) and over the pole (away from a lot of magnetic shielding) on routes like London-Tokyo. Crews have noticeable health deficits, including cancers, and it became a workplace hazard their employers must manage. Which they do by rota-ing, moving people between routes, etc.

            There's a dos

      • Re: (Score:2)

        by Kjella ( 173770 )

        And before you go down there....those imperfect copies are what leads to genetic variation (important to fend off predators both macro and microscopic) and evolution. Cancer is just about inevitable in any DNA based system

        Past child-bearing age it's also wholly unnecessary. So if we invented individualized drugs or gene therapy or nanobots or whatever to kill off all non-conforming cells it'd be great.

      • I know you weren't making a complete list, but an additional factor is we have linear DNA. The enzyme that copies our DNA sticks to the DNA being copied by grabbing on to a few base pairs before and after the copy site. Since we have linear DNA, the enzyme falls off before reaching the end. So each time our cells replicate, the DNA inside them gets a little shorter. And eventually, that "little shorter" is going to run into something important.

        (To counteract this, a whole lot of junk base pairs are adde

    • We send aaron eckhart with hillary swank and a small nuke in a giant metal dildo underground to give the core a boost. Haven't you seen the documentary? It's been done before.

  • Loosened? (Score:1)

    by Anonymous Coward

    Pretty nifty.

    I'm a bit miffed about language: "[...] it loosened tiny ferromagnetic particles in the clay. As the pottery cooled and these particles hardened, [...]"
    That's a pretty graphic description, but in a geek site... can't we just say Curie point, or Curie temperature?
    If we don't keep the standards, who will?
    (If you think some jargon is exclusive: insert a link to Wikipedia -- there's, as often, a very nice article on that).

  • The large variation in results for the magnetic fields is the creation stage of the pottery was done in completely uncontrolled circumstances.

    • Duh. I mean the large variation in the result is because the pottery was created in uncontrolled circumstances.

      • Re: (Score:2, Informative)

        by Anonymous Coward

        Then how do you explain the fact that clay with the same seal displays very similar effects, and with different seals display different effects, with the magnitude of the effect lining up with the years indicated by the seals on the pots?

      • Re: (Score:3)

        by pz ( 113803 )

        Multiple samples from independent sources and locations help mitigate those concerns, along with a slowly-varying time course of the field strength.

        What manufacturing circumstances would change the strength of magnetization for ferrous inclusions in cooling pottery that would be present before, say, 0 AD to pick a convenient, arbitrary and approximately relevant threshold?

        • I agree that if they prove a tight correlation it means something. I can't see anything about that in the links though, so is this an article which proceeds from the assumption that the correlation with earth magnetism is very tight(if we assume correlation is tight then we can conclude magnetic field has decreased 30%), or does it prove the tight correlation as well. There is statistics involved and I can't see what kind.
          Testing that correlation can also be done with experiments today with new pottery. Hav

  • Isn't this actually Paleomagnetism/Archaeology 101? I mean, reconstructing the magnetic field in shape and strength from the finds is a substantial endeavor, but the headline itself is no news to anyone in the field. It's been one of the bog-standard methods of how archaeological sites are surveyed.

    • Re:Paleomagnetism (Score:5, Funny)

      by TeknoHog ( 164938 ) on Wednesday February 15, 2017 @07:58AM (#53872457) Homepage Journal

      no news to anyone in the field.

      I see what you did there. Also, thanks to Slashdot's no editing policy, we now have a record of pun field strength for future paleocomedians.

    • Exactly. Back in the '80s my prof at university told us that was one of the ways he used when dating North American aboriginal sites. The idea was you could determine where magnetic north was the last time a fire ring was used (and thereby calculate a fairly accurate date range) since the iron in the rocks/earth in the ring would align to magnetic north when heated to a high temperature.
    • Using magnetostratigraphy (field strength changes compared to a standard - usually ocean core sediments - with a magnetism-independent dating method, such as biostratigraphy or tephra beds) is old hat. The new idea here is that the tax seals provide a date for each sample, and the magnetic traces in the pottery provide an estimator of the field strength at that time, increasing resolution of the variation in the geomagnetic field in the past.

      Clear as mud now?

  • Interesting (Score:3)

    by Big Hairy Ian ( 1155547 ) on Wednesday February 15, 2017 @07:04AM (#53872315)
    This could also be used to prove/disprove theories that some Pharaohs may have ruled concurrently rather than consecutively.

    Just a thought

  • Declining fields and Pole Reversals. . (Score:5, Informative)

    by Salgak1 ( 20136 ) <salgak.speakeasy@net> on Wednesday February 15, 2017 @07:49AM (#53872437) Homepage

    . . . . back in my Geophysics days (early 1980s), we already knew that the current planetary magnetic field was in decline, and we were approaching a pole reversal "real soon now" (in Geologic timeframe, not human timeframe. . ).

    Heck, we were routinely measuring fossilized magnetic remnant fields in far older rocks, not just strength, but orientation as well. And finding the proper orientation of the sample was always difficult, generally required microscopic examination of a thin slice of the sample. The advantage of pottery for recent sampling, is that it is far easier to determine the orientation of the sample. . .

    • Re: (Score:2)

      by pz ( 113803 )

      Hmm ... How are you going to determine field orientation at time of cooling below the Curie temperature for pottery? Wouldn't that require knowing the physical orientation of the item when it was being cooled after firing? Am I missing something, like there's a universal point-to-the-east orientation that all pottery is placed in when cooling?

      I can see making a good guess for geological structures, but pottery?

      • Re: (Score:2)

        by Salgak1 ( 20136 )

        Well, assuming you know the shape of the original pottery, or better still, have a whole piece or enough to reconstruct: simply MEASURE the orientation, then use paleomagnetic detection techniques to measure the remnant field. Then compare the observed field orientation against the physical orientation of the sample

        • Re: (Score:2)

          by pz ( 113803 )

          And you know that the pottery wasn't moved from its original orientation during cooling because .... ?

          • Possibly because it might be a little too hot to move...what would be the purpose of moving pottery before it cools?...well I guess the could have made a kiln on a wagon...or...a spinning kiln...hmmm...

            • Re: (Score:2)

              by pz ( 113803 )

              So the supposition is that kilns have been found with pots inside, we can demonstrate that the pots have been left undisturbed since the start of their last firing many thousands of years ago so you can judge the orientation of the earth's field at the time of cooling, and, moreover, we know the kilns haven't been moved either?

              Color me skeptical.

              Note that the article talks about intensity not orientation. Intensity, I understand. Orientation seems implausible with this method.

            • It's only since (approximately) 1750 CE that people have built kin's out of "fire brick", loaded them with prepared forms (with glazes, etc), spent days firing them up and cooling them down, then carefully emptied the debris and successful product out of the kiln before re-use.

              Before then, the kiln was built around the charge of forms using basically the same clay as the forms, the fire started in the integrated hearth (chimney also integrated to draw the fire), and the charge fired up over several days be

  • "... to some speculation that the Earth may be losing its magnetic field -..."
    Since the data ultimately suggests that fluctuations are completely normal, I submit that this also starts to explain why people are taking scientists less and less seriously.

    I suspect that the cadre of researchers crying that the sky was falling was probably a small percentage, yet because of the synergies of such predictions, commercial media, & natural human histrionics, THIS was the narrative being discussed in the broader

    • Re:What this also proves (Score:5, Insightful)

      by Somebody Is Using My ( 985418 ) on Wednesday February 15, 2017 @09:04AM (#53872705) Homepage

      "... to some speculation that the Earth may be losing its magnetic field -..."
      Since the data ultimately suggests that fluctuations are completely normal, I submit that this also starts to explain why people are taking scientists less and less seriously.

      Don't blame this on the researchers; blame this on the "science writers" (including the author of the summary here on Slashdot). The actual study - at least the abstract and the supplemental material, which was all I could read without a PNAS subscription - says no such thing and that particular wording is just a click-bait addition in order to garner more views. Science journalism - like so much journalism this day - has gone on a real decline over the past twenty years and tries to "spice up" every study rather than simply reporting the science. The end result is that scientists end up sounding inconsistent and hyperbolic ("Coffee Cures cancer!", no wait, "Coffee Causes Cancer"), when they usually are neither; it is the people reporting on their work that are to blame.

      Also see for a more graphic comment [xkcd.com] on the same problem.

      • Let's be clear - I didn't blame it on the scientists.

        I simply said that this is an example of "why people are taking scientists less seriously".

        I totally agree it's science writing; part of it may be endemic to the democritization of information in the internet age. Formerly, these sorts of fascinating, cutting edge science information would be confined to the pages of discipline-specific journals (who were well able to cover it). If something was really big news, it might show up in the NYT or on the wir

    • Fluctuations in past magnetic field on decade basis was hard as heck to measure on short period basis, because it takes solidifying rock/clay to lock the magnetic particles, and these don't form neat linear progression over time - the stamped pottery was the first that allowed to set samples in chronological order with decade dating precision.

      Past global temperature is much easier to estimate, as its 'records' are 'frozen' as yearly growth of trees; each ring recording how warm and how dry the year was, thr

      • https://upload.wikimedia.org/w... [wikimedia.org]

        So what you're saying is that there haven't been radical near-instant (in geological terms) 'spikes' of warmth about every 120k for the last 3+ million years?

        Funny, that's pretty much what that graph shows to me.

        • "near instant (in geological terms)" means timescales of 1000 years. Not 50. That graph gives resolution of 64 years per pixel at the smallest scale, and even then as NGRIP record might point large changes on 200 years time scale, EPICA follow a much milder change.

    • While the situation may be normal regarding Earth's history, and in past humanity history it would merely mean increased cancer incidence, magnetosphere primarily protects electronics from coronal mass ejections. This has only a history of several decades and was never exposed to diminished Earth magnetic field.

      So, no, life on Earth won't be wiped by the demagnetization, and no enormous natural cataclysm will occur. But you might find electronics fried at nuclear power plants affect our daily life, especial

  • There are a lot of red brick houses in the world. If only the date of the building of the house is known and the bricks are not repurposed from other buildings, similar information can be derived.

    If they can measure the magnetic properties of the mortar you can even get the direction.

    • There are a lot of red brick houses in the world. If only the date of the building of the house is known and the bricks are not repurposed from other buildings, similar information can be derived.

      If they can measure the magnetic properties of the mortar you can even get the direction.

      Yes. But not from 2000 years ago...

  • How does the change in mag field strength jive with warming or cooling of Earth? Does the extra solar radiation heat us any?

  • They may have recorded it inadvertently, not accidentally.

    Accidentally means you were trying to avoid doing it but it happened.
    Inadvertently means you did so without knowing because it was not your focus.

    Alexander Fleming accidentally left out a Staphylococcus plate culture and inadvertently discovered penicillin.

    English is a wonderful language full of very precise words so let's use them accurately!

    • Accidentally is an appropriate word in this context. It refers to something that happened by chance or was fortuitous. You do not specifically have to be trying to avoid something for it to be accidental. English is a wonderful language that has many ways to say the same thing.

    • Well, as other posts have already replied to you, the strict distinction you're trying to make here doesn't really hold in English. Both accidentally and inadvertently can easily apply to something that was trying to be avoided.

      But I sense a problem with the headline too, and I think the real issue is -- why are the POTTERS mentioned at all? There's a kind of implication with the way the headline is worded that the potters "recorded" information, except they had no concept of what such recording might a

  • We need a new protocol that redistributes money from wealthy countries to poor ones who will be most affected by the loss of the magnetic field because the wealthy ones have a lot more electric motors and refrigerator magnets so they're ruining the Earth's field.

  • What the heck is "BCE"? What's wrong with "BC"? (Score:3, Insightful)

    by Bearhouse ( 1034238 ) on Wednesday February 15, 2017 @10:34AM (#53873327)

    Before Common Era? WTF? As opposed to an "uncommon" one?
    OK, I'm a (kinda) scientist, so I should maybe be "against" all the religious stuff, but I have no problem with "Before Christ" just as I have no problem with V for Volt(a) or A for Ampere. (Grant you, these were real people, and real scientists too...)

    FFS, it's not like "BC" is insulting to Muslims or other people who use a different calendar (many also religion-based), since they're not aligned with the same time period.
    If anything, "BCE" seems more insulting, since it implies that their alternative calendars are "not common"... /rant

    • Re: (Score:1)

      by Anonymous Coward

      "Christ" is a title (meaning messiah), not a name. AD is similar in that "D" stands for Domini (Latin for Lord). So both BC and AD express a Christian belief about Jesus.

    • Re:What the heck is "BCE"? What's wrong with "BC"? (Score:4, Interesting)

      by NG-Buddhist ( 958966 ) on Wednesday February 15, 2017 @02:12PM (#53875197)
      BCE/CE has been a standard in discussing historical time periods for a while now. There's nothing impolite about it, just as there's nothing impolite about using Before Christ/Anno Domini, or using a Hebrew calendar, or using a Chinese calendar, or using an Islamic calendar, or a Hindu one, etc.

      • In america!
        Not in the rest of the world.
        It makes no sense to give a certain point in time a different name depending if you refer to it 'before' or 'after'.
        Evereyone, except americans, is saying before _christ_ and after _christ_.
        That means we say AD or AC and BC. The american nomenclature is just confusing :)

        • There's a lot of people in the rest of the world who don't care about anyone named Jesus or Christ, but who have adopted our calendar because it's in very widespread use (the network effect).

          Besides, if Jesus existed, he was born a few (we don't know how many) years BC, which makes no sense. We know when the commonly used calendar started We just go with it.

          • Doesn't change the fact that everyone says AC and BC.
            I really doubt you (yes, you as a person) say in real life CE ... but perhaps you are one of the few non 'english historians' who uses out of political correctness or SJW syndrome 'CE'.
            On the other hand I got already flamed for using the term BC on /. ... rofl.

            Regarding your argument about Christus, well, I would really wonder if he has not lived. But using his 'narrowed' down time of birth for a new calendar and then calling it 'common era' ... erm, I re

            • Doesn't change the fact that everyone says AC and BC.

              This is flat out untrue. It could only be true if you spoke to no-one in your "real life" experience who had any background or interest in one of the historical sciences. It's possible that you have such a benighted existence, but I hope you have a more varied life than you imply.

              I really doubt you (yes, you as a person) say in real life CE

              I do say CE / BCE in real life. Whenever we're talking about historical matters at the pub - e.g. with the digger-d

              • Erm, what point do you want to make?

                Again: except for history freaks! no one is using those terms. And then again: it is only americans, probably on a 'social justice political correctness' trip.

                Just read wikipedia about random events in history, people as in actual people say BC and AC (not AD as most people are not christians or simply don't remember that english/americsns prefer AD over AC)

                In other words: it might be correct english to say BCE, but 90% of the english speakers on the planet don't speak 'c

        • The change from Nicene terminology ("Anno Domini" & "Before Christ") to Common Era terminology is certainly not an American-versus-RestOfTheWorld question, nor even a particularly religious question.

          Hanging a dating system off on specific person's birth date has certain problems for historical work, in particular, some historical facts are needed about this person (call him Cleese, and we can all perform the Parrot Sketch before shuffling off) - such as the day of year that Cleese was born on (not in a

          • I would suggest to simply read stuff about historical events ..
            Everyone is saying BC if it is before 0 and AC if it is after, in rarer cases AD.

            It is only americans and hyper critical /. readers that use CE and BCE.

            I'm 50 and had english in schools. This CE and BCE stuff occured in my life a few years ago. Before that everyone understood what BC is ...

    • Re: (Score:3)

      by imidan ( 559239 )

      The first documented instance of the Vulgaris Aerae (Vulgar Era, meaning “Common Era”) being used interchangeably with Anno Domini was featured in Latin works by Johannes Kepler in 1615, 1616, and 1617. The English version of phrase later appeared in 1635 in an English translation of Kepler’s 1615 work. (In the mid-seventeenth century the English “vulgar” took on a new definition of “coarse,” but it wouldn’t be until this “coarse/unrefined” definit

  • I always find it fascinating when modern science and ancient history collide. There have been a number of stories like this over the years as technology advances. It hits me in both my science and technology spot as well as being a fan of ancient history and trying to piece together things from so long ago.

    That said when I read it I some how saw some bearded ancient historian crying in the corner as scientists take irreplaceable artifacts of the past, smash them, and grind up the remains for magnetic analys

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