The magnetic fingerprint

Back in 1963, Frederick Vine and Drummond Matthews came up with a groundbreaking idea (pun very much intended); that the Earth's crust is divided into a bunch of chunks called plates that are all moving relative to each other, and that this is what causes virtually all earthquakes and volcanoes.

The main evidence for this dramatic paradigm shift in our understanding of how geology works came from the discovery on the ocean floor of regions of hardened lava that have opposite magnetic signatures.  When molten rock freezes, tiny magnetic particles that were free to move when they were in a liquid become locked into place, acting like billions of little compass needles recording the direction of the Earth's magnetic field at the time.  As you undoubtedly know, the positions of the magnetic poles flip, on average every three hundred thousand years (although the actual intervals vary greatly, for reasons that are still unknown).  So the rocks Vine and Matthews studied, on either side of the Mid-Atlantic Ridge, which showed symmetrically-arranged parallel stripes of magnetic signatures, showed that new oceanic crust was being formed all the time at the ridge, driving the plates apart and gradually widening the Atlantic Ocean.

Well, it turns out that lava isn't the only thing that can record what the magnetic field is doing.  According to a study last week in Proceedings of the National Academy of Sciences, so can pottery.

When clay is fired, its chemical structure changes, fusing into ceramic.  Different clays fire to different temperatures; in our kiln we fire our work to 1220 C (2232 F), which works for the clays classified as stonewares and mid-fire porcelains.  If we were to fire a high-fire porcelain to that temperature, it would still be brittle and not water-tight; fire an earthenware clay to that temperature, and it (literally) would melt.  (The difference is in the formulation of the clay, which is a complex subject about which I am still learning.)

But when you fire any clay to the correct temperature for that type, it effectively turns to stone.  The particles fuse together, giving it strength and resistance to breaking.  And this has the effect of locking into place any magnetic particles the clay may contain -- same as with Vine and Matthews's solidified lava on the ocean floor.

White stoneware vase with a cobalt splatter glaze

The reason this topic comes up is the discovery by a research team out of University College London of the fact that some earthenware bricks dating to the reign of Nebuchadnezzar II of Babylon (605-562 B.C.E.) show a magnetic particle pattern indicating a strange and sudden surge in the strength of the magnetic field -- something that has been nicknamed the Levantine Iron Age Geomagnetic Anomaly.

"It is really exciting that ancient artifacts from Mesopotamia help to explain and record key events in Earth history such as fluctuations in the magnetic field," said study co-author Mark Altaweel.  "It shows why preserving Mesopotamia’s ancient heritage is important for science and humanity more broadly."

Noting this odd magnetic fingerprint -- the cause of which is as yet unexplained -- has another added benefit; once they've identified it in items of known age (as with the bricks, that had an identifying stamp), it can be used to date ceramic items that have no such marks.

It makes me wonder what kind of record I'm creating in my own pottery.  When we have pieces with too many flaws to be worth keeping, we shatter them against the cement wall along the back of our house (there's now a pile of pottery shards at the base of the wall).  We think of it as our ongoing effort to confuse future archaeologists.  But supposing they do piece together some of our failed attempts at bowls and mugs and various sculptures, maybe they'll find out something more than our dubious skill at making pottery -- but what the Earth itself was doing in 2023.

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The heart of the world

One of the biggest mysteries in science lies literally beneath our feet; the structure and composition of the interior of the Earth.

We have direct access only to the barest fraction of it.  The deepest borehole ever created is the Kola Superdeep Borehole, on the Kola Peninsula in Russia near the border of Norway.  It's 12.26 kilometers deep, which is pretty impressive, but when you realize that the mean radius of the Earth is just under 6,400 kilometers, it kind of puts things in perspective.

What we know is that the crust is principally silicate rock -- lower-density felsic rocks (like granite) forming the majority of the continental crust, and denser mafic rocks (like basalt) comprising the thinner oceanic crust.  Beneath that is the semisolid mantle, which makes up two-thirds of the Earth's mass.  Inside that is the outer core, thought (primarily from estimates of density) to be made up of liquid iron and nickel, and within that the inner core, a solid ball of red-hot iron and nickel.

At least that's what we thought.  All of this was determined through inference from evidence like the relative speed of different kinds of seismic waves; despite what Jules Verne would have you believe, no one has been to the center of the Earth (nor is likely to).  But figuring all this out is important not just from the standpoint of adding to our knowledge of the planet we live on, but in comprehending phenomena like magnetic field reversals -- something that would have obvious impacts on our own lives, and which are still poorly understood at best.

We just got another piece of the puzzle in the form of a paper last week in Nature that suggests our picture of the Earth's inner core as a homogeneous ball of solid iron and nickel may not be right.  Using data from seismic waves, scientists at the Australian National University in Canberra have concluded that the inner core itself has two layers.  The exact difference between the two isn't certain -- as I said before, we're limited by what information we can get long-distance -- but the best guess is that it's a difference in crystal structure, probably caused by the immense pressures at the center.

[Image courtesy of Drew Whitehouse, Hrvoje Tkalčić, and Thanh-Son Phạm]

In general, whenever a wave crosses a boundary from one medium to another, it refracts (changes angle); this is why a straw leaning in a glass of water looks like it's bent.  If the angle is shallow enough, some of the wave's energy can also reflect off the interface.  When that happens to seismic waves inside the Earth, those reflected waves bounce around inside the core; when they finally make it back out and are measured by scientists on the Earth's surface, features such as the energy, wavelength, and angle can provide a lot of information about the materials it passed through on its journey.

The authors write:

Earth’s inner core (IC), which accounts for less than 1% of the Earth’s volume, is a time capsule of our planet’s history.  As the IC grows, the latent heat and light elements released by the solidification process drive the convection of the liquid outer core, which, in turn, maintains the geodynamo.  Although the geomagnetic field might have preceded the IC’s birth5, detectable changes in the IC’s structures with depth could signify shifts in the geomagnetic field’s operation, which could have profoundly influenced the Earth’s evolution and its eco-system.  Therefore, probing the innermost part of the IC is critical to further disentangling the time capsule and understanding Earth’s evolution in the distant past.

The discovery of the Earth's hitherto-unknown center could help us to understand one of the most fundamental questions in geology; the structure of the inside of the Earth.  We still have a very long way to go, of course.  As I said, even understanding how exactly the core generates the Earth's protective magnetic field is far from achieved.  But the new research gives us a deeper comprehension of the structure of the inner core -- the red-hot heart hidden beneath the deceptively tranquil surface of our home planet. 

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Flipping out

There's been a lot of buzz lately about the Earth's impending magnetic field reversal.

Well, the alleged impending magnetic field reversal.  We don't know for sure that one is imminent; it's the same sort of thing as when you hear that the Yellowstone Supervolcano is "overdue for an eruption."  Neither of these is on some kind of timetable.  You rarely hear volcanoes say, "Well, I'd love to visit, but I'm supposed to erupt at 3:34 PM today, and I can't afford to be late."

The magnetic field flip is even more irregular than supervolcano eruptions, at least to judge by the geological record.  We know reversals have happened by looking at (relatively) new igneous rock formations near the Mid-Atlantic Ridge; as the lava cools, magnetic particles in the molten rock freeze into place, locking in a magnetic signature that tells you what the Earth's magnetic field was doing at the time.  And if you do a scan across the Mid-Atlantic Ridge you find mirror-image parallel stripes along the ridge, progressively older as you move away, documenting 183 reversals over the past 83 million years.  The timing of those reversals, however -- and therefore the width of the stripes -- varies tremendously, from about 25,000 years to about ten million years (the longest stable interval discovered so far).

[Image is in the Public Domain courtesy of NOAA]

As a quick aside, you may know that these magnetic stripes were one of the most persuasive arguments for the developing theory of plate tectonics, back in the late 1950s and early 1960s.  The mid-ocean ridges were identified as divergent zones -- places where the plates were moving apart, and new rock upwelling to fill the space in between.

In any case, we don't know for sure if the Earth's field is ready to flip, but it certainly seems to be wandering around a bit.  The last full reversal was about 780,000 years ago, but there was what seems to have been an abortive flip -- the Laschamps Event -- about 41,400 years ago, which only lasted about five hundred years before flipping back to its original polarity.  (Because of the speed of the switch, geologists don't consider this to be a full geomagnetic reversal, but a "geomagnetic excursion," where the poles didn't make a long-term move but just kind of went on walkabout.)

In fact, the Laschamps Event is why the whole topic comes up.  Recently a paper was published in Science describing what scientists have learned from an unexpected source -- the sixty-ton trunk of a kauri tree (Agathis australis) that was accidentally unearthed in New Zealand by some workers breaking ground for a new power plant.  The tree trunk had been submerged in a bog and preserved, and as luck would have it, the tree's 1,700 year life span was right across the Laschamps Event.

Specifically, they looked at the content of carbon-14 in the wood; C-14 is a radioactive form of carbon that is best-known for its role in the dating of preserved organic matter, but also is a good indicator of the level of cosmic ray bombardment (because it's formed when stratospheric carbon dioxide is hit by ionizing radiation).  

What they found is a little alarming.  During the Laschamps Event the magnetic field of the Earth collapsed for something like five centuries, and the tree rings during that time show a significant spike in carbon-14 formation.  The level of bombardment, the researchers say, would have caused auroras in the subtropics -- and would have been sufficient to knock out the power grid.

Right around the same time, there were some significant biological shifts going on.  Large mammals in Australia died out, including the terrifying giant clawed wombat, Palorchestes.

In case you thought I was making this up. This thing got up to three meters from nose to tail and weighed an estimated 1,000 kilograms. [Image licensed under the Creative Commons Nobu Tamura, Palorchestes BW, CC BY 3.0]

At around the same time, Neanderthals disappeared from Europe, and things got a good bit colder -- our ancestors started taking up residence in caves, to judge by the appearance of sophisticated cave art.  Whether any or all of this is connected to the Laschamps Event, however, is unknown.

What seems certain is that if it were to occur today, it would be bad news for technology.  Not only would the flip wreak havoc on our power grid, it would foul up a lot of navigational systems.  (I wonder how birds would be affected, since many of them rely on magnetic field lines to guide their migration twice a year.)

As with all of these sorts of things, there are some people who are Chicken-Littling about the pole reversal spelling the death of humanity, and others who are shrugging and saying we'll be fine because this has happened many times in Earth's history, and here we are.  Well, yeah, giant meteor strikes and flood basalt events and ice ages have also happened many times in Earth's history, but that doesn't mean they're a good thing.

My own response is that we shouldn't panic, but we should try to prepare for it if and when it happens, i.e., listen to the damn scientists.  Which I've said about a million times before, mostly in connection to climate change and the COVID-19 vaccine, but it seems like good advice in general.

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Mathematics tends to sort people into two categories -- those who revel in it and those who detest it.  I lucked out in college to have a phenomenal calculus teacher who instilled in me a love for math that I still have today, and even though I'm far from an expert mathematician, I truly enjoy considering some of the abstruse corners of the theory of numbers.

One of the weirdest of all of the mathematical discoveries is Euler's Equation, which links five of the most important and well-known numbers -- π (the ratio between a circle's circumference and its diameter), e (the root of the natural logarithms), i (the square root of -1, and the foundation of the theory of imaginary and complex numbers), 1, and 0.  

They're related as follows:

Figuring this out took a genius like Leonhard Euler to figure out, and its implications are profound.  Nobel-Prize-winning physicist Richard Feynman called it "the most remarkable formula in mathematics;" nineteenth-century Harvard University professor of mathematics Benjamin Peirce said about Euler's Equation, "it is absolutely paradoxical; we cannot understand it, and we don't know what it means, but we have proved it, and therefore we know it must be the truth."

Since Peirce's time mathematicians have gone a long way into probing the depths of this bizarre equation, and that voyage is the subject of David Stipp's wonderful book A Most Elegant Equation: Euler's Formula and the Beauty of Mathematics.  It's fascinating reading for anyone who, like me, is intrigued by the odd properties of numbers, and Stipp has made the intricacies of Euler's Equation accessible to the layperson.  When I first learned about this strange relationship between five well-known numbers when I was in calculus class, my first reaction was, "How the hell can that be true?"  If you'd like the answer to that question -- and a lot of others along the way -- you'll love Stipp's book.

[Note: if you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]

Jerk analysis

Sometimes there are news stories that I have to feature here simply because they're cool.

This one came from some data collected by a mission called Swarm, consisting of three satellites which were launched in 2013 to study the Earth's magnetic field.  The mission is pretty important -- besides being critical to navigation, the magnetic field of our planet protects us from most of the cosmic particles that strike the upper atmosphere.  And -- somewhat alarmingly -- it appears we may be at the beginning of a geomagnetic pole reversal, when the magnetic field of the Earth flips for reasons still poorly understood.  (We know about 183 such pole reversals in the last 83 million years, which is about as long as we have good data for.  The oddest part is that they are anything but regular.  The shortest duration of a particular polarity was around 400 years -- and we've been in the current one for 780,000 years.)

What the current study looked at is a much more transitory phenomenon called a geomagnetic jerk, which sounds like a derogatory name for a geologist, but isn't.  Actually, it's a sort of hiccup in the magnetic field.  They were first discovered in 1978, when there was a sudden increase in the magnetic field intensity followed by an equally rapid decrease, only lasting a few days.  They can be localized geographically, too; there have been jerks that are measurable in North America and invisible in the magnetic field measured everywhere else.

The new study, released last week in Nature: Geoscience in a paper by Julien Aubert (Université de Paris) and Christopher Finlay (Technical University of Denmark) is called "Geomagnetic Jerks and Rapid Hydromagnetic Waves Focusing at Earth’s Core Surface."  It suggests that what's happening is twofold -- there's a slow convection within our metallic core that, combined with the Earth's rotation, gives rise to the magnetic field on the larger scale; but there are much more rapid, turbulent fluid motions, caused by rising blobs of hot liquid metal.  When those blobs impact the boundary between the outer core and the mantle, it results in shock waves that register on the surface as a jittering of the magnetic flux.

Simulation of the magnetic field within the Earth's core

The weirdest part is that the rising of the blobs (which would make a great title for a horror movie, wouldn't it?) begins a good twenty-five years before it registers on the surface as a jerk.  What process creates the blobs is still not understood, but this is at least a step forward.

"Swarm has made a real contribution to our research, allowing us to make detailed comparisons, in both space and time, with physical theories on the origin of these magnetic jerks," said Christopher Finlay, who co-authored the paper.  "While our findings make fascinating science, there are some real-world benefits of understanding how our magnetic field changes.  Many modern electronic devices such as smart phones, rely on our knowledge of the magnetic field for orientation information.  Being able to better forecast field changes will help with such systems."

All of which makes me wonder, however, how we're going to handle it when the overall magnetic field does its headstand, because the theory is that the field first collapses (or becomes highly erratic) before reforming with the opposite polarity.  I have this strangely hilarious mental image of people with their noses glued to the GPS on their cellphones all heading very efficiently to their destinations, and then suddenly they all start wandering off in random directions, never to be seen again.

Of course, it probably won't be nearly that much fun.

Um, I mean, "catastrophic."  "Catastrophic" is what I meant.

Anyhow, it's nice that we now have another piece of the puzzle as far as what's happening in the core of our planet, which -- as always -- turns out to be far more complex than we realized.  As far as jerks and pole reversals, we'll just have to wait to see what happens and find out if the models hold up under scrutiny.

As always.

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This week's Skeptophilia book recommendation is for any of my readers who, like me, grew up on Star Trek in any of its iterations -- The Physics of Star Trek by Lawrence Krauss.  In this delightful book, Krauss, a physicist at Arizona State University, looks into the feasibility of the canonical Star Trek technology, from the possible (the holodeck, phasers, cloaking devices) to the much less feasible (photon torpedoes, tricorders) to the probably impossible (transporters, replicators, and -- sadly -- warp drive).

Along the way you'll learn some physics, and have a lot of fun revisiting some of your favorite tropes from one of the most successful science fiction franchises ever invented, one that went far beyond the dreams of its creator, Gene Roddenberry -- one that truly went places where no one had gone before.

Flipping out

Coming hard on the heels of claims that Comet ISON is an omen of impending doom to humanity is another claim, to wit: the upcoming reversal of the Sun's magnetic field is...

... you guessed it...

... an omen of impending doom to humanity.

Beginning with a site with the cheerful title, The Warning: New Prophecies Reveal Global Events in the Lead Up to the Second Coming, which describes the pole flip as follows:

The closer the Day of My Great Coming draws, the more people, who say they love God, will withdraw from Me. Even those who say they are holy and exalt themselves within the hierarchy of My Church on Earth, won’t be able to see the Truth. They will not see the Truth because they will be so busy attending to matters and ceremonies, which will be insulting to Me.  The first sign will be that the Earth will spin faster. The second sign concerns the sun, which will loom larger, brighter and begin to spin. Beside it you will see a second sun. Then the weather will cause the world to shake and the changes will mean that many parts of the Earth will be destroyed... 

Wars will spread; earthquakes will shake the four corners of the Earth and famine will grip mankind and every wicked gesture and insult made before God will result in a terrible chastisement. When those who accept My Mercy lead My Church – every demon will curse these children of God. To protect them, God will intervene and woe to those who spit in the Face of their Creator.

The time has come. Those who curse Me will suffer. Those who follow Me will live through this persecution, until the Day when I come to sweep them into My Merciful Arms. And then, only those who remain, because they refused My Hand of Mercy, will be given over to the beast they idolized and to whom they sought pleasure from.

So that sounds pretty cheerful.  Then we have this guy, posting on the apparently well-named site Lunatic Outpost:

The Sun starting flip its magnetic field early in May 2012 as ISON was crossing the Orbit of Saturn.

This was the infamous Quadri-Polar issue last year, which when viewed in the lead up to the end of the Mayan Calendar and Comet Elenin swing in was considered an omen of doom.

It was then explained away as the beginning of the solar magnetic field flip which was due in May 2013 the mechanism being that the north pole splits first into a positive end at the north pole and two negative poles at the equator which the link to the positive south pole to form a quadri-polar structure...

While I can't speculate on what this means in terms of major doom it does indicate that ISON has a strong magnetic field with a spherical iron core with a potential for a major electro-magnetic event with the Sun at perihelion...

An interesting number appears if we take Immanuel Velikovsky's rough orbit of Nibiru of 3600 years and round it up to the closest whole number multiple of the 11 year cycle of 3663 years and assuming ISON is Nibiru, it means we are in the 333rd Sunspot cycle which is really a half cycle as the Sun returns to its original polarity configuration every 22 years.

Looking at the quarter cycle of 5.5 years this is the 666th cycle!

Then we have this rather alarming post, on the amazingly wacky David Icke Forum:

Solar flairs [sic], the north pole moving, the weak magnetosphere allows more solar wind into the atmosphere, the tectonic plates are moving much more, we have the earth tilting and springing back on its axis as we can see from the sunset being out of place and its timing. All of these things have a profound effect on our psyche...  are you feeling off lately?

So put the first post, with all the devils and demons and so on, together with the second, with Nibiru and the number 666, and the third, with "out-of-place sunsets," and you have a trifecta of evil that just makes me want to hide in bed under my down comforter.  But of course, given that it's currently 19 F outside, I felt like that already, so maybe that's not all that significant.

Let's put this in perspective, why don't we?  Maybe look at some facts?  Crazy idea, I know, but it might just work!  Space.com did a nice job of explaining the pole reversal, as follows:

Every 11 years or so, the two hemispheres of the sun reverse their polarity, creating a ripple effect that can be felt throughout the far reaches of the solar system. The sun is currently going through one of those flips in its cycle, said scientists working at Stanford University's Wilcox Solar Observatory, which has monitored the sun's magnetic field since 1975.

"The sun's poles are reversing, and this is a large-scale process that takes place over a few months, but it happens once every 11 years," Todd Hoeksema, a solar physicist at Stanford said in a video about the polarity reversal. "What we're looking at is really a reversal of the whole heliosphere, everything from the sun out past the planets."

The polarity reversal probably won't harmfully impact Earth, in fact, it could even protect the planet in some ways, scientists have said.
The sun's huge "current sheet" — a surface extending out from the sun's equator — becomes wavier as the poles reverse. The sheet's crinkles can create a better barrier against the cosmic rays that can damage satellites, other spacecraft and people in orbit, scientists said.

So, the whole thing happens every eleven years?  Meaning I have so far lived through four of these pole flips already, and have yet to be eaten by demons, gone through a "major doom," or observed a sunset that didn't happen exactly when it was supposed to?

Well, that's kind of anticlimactic.

If, like me, pictures help you to understand, take a look at Karl Tate's lucid explanation of the whole thing, where along with great diagrams he tells us the following:

Electric currents inside the sun generate a magnetic field that spreads throughout the solar system. The field causes activity at the surface of the sun, surging and ebbing in a regular cycle. At the peak of the cycle, the polarity of the field flips, during a time of maximum sunspot activity...  The sun is not a solid ball, but rather like a fluid. It exhibits differential rotation, meaning the surface moves at different speeds depending on latitude. This results in the magnetic field lines getting wound up. When the winding gets extreme, the magnetic field lines "snap," causing solar flares at those locations on the surface.

So there you have it.  The Sun is undergoing a field reversal, an event that would only have been noticed by astronomy nerds if it hadn't been for the rather odd subset of humanity who seems to like to look around for Portents of Doom.  The pole flip isn't going to do much to us here on Earth, so you don't need to worry about your refrigerator magnets all falling off, your GPS malfunctioning, or the Second Coming of Christ.

You know what I wish?  I wish that once, just once, we'd go through one of these Omens of Evil Where Nothing Happens, and all of the nutty apocalyptoids would get together and publish a retraction.  "Hey, guys," the retraction would say.  "We were wrong!  The Earth didn't end, after all.  I guess we better go sign up for some science classes!"  But of course, that will never happen.  They take what they do, and each other, way too seriously for that.

It's the deadly serious aspect of it that is honestly what amuses me the most -- because people have been foretelling the future for millennia, and have almost always gotten it wrong, and yet they keep trying.  And people keep believing them.  Myself, I'm more like the Roman philosopher and writer Cicero, who quipped, "I do not understand how two augurs can pass each other on the street without laughing."