Hacker News new | past | comments | ask | show | jobs | submit login
Earth’s magnetic field is acting up (nature.com)
191 points by evo_9 6 months ago | hide | past | web | favorite | 79 comments

"Pottery jugs from between the eighth and second centuries B.C. bear administrative stamps that changed with the political situation. Unbeknown to the people firing these jugs, the act of heating locked information about the Earth's geomagnetic field into minerals present in the clay. Because the stamps provide precise information about when the pots were fired, the study allows a detailed look at geomagnetic changes over 600 years."


This is one of the most amazing things about humans to me. I marvel at how it's possible to get so much information about our universe by observing so little. Astronomy is another field that I'm really impressed with. It's possible to infer things about galaxies, stars, planets, etc. just buy observing some light coming from them to our little blue planet. Absolutely crazy.

How many such techniques we haven't even discovered or technology is not there to observe such things?

I really enjoyed reading Our Mathematical Universe by Max Tegmark that explores such things.

I always love reading the crazy new techniques for extracting text from rotten old paper and papyrus. I distinctly remember reading a few months back an article about someone detecting trace chemicals from an old pocket bible or something, and deduced the owner had liver disease or something equally insane. wish I could find that article!

I was just about to post the link to this New Yorker article in response to GP's question. I believe this is the one you're referring to:


Under the right conditions, proteins can survive for millions of years. In recent years, proteomic studies of art works and archeological remains have yielded biological information of startling clarity, revealing gossamer-thin layers of fish glue on seventeenth-century religious sculptures and identifying children’s milk teeth from pits of previously unrecognizable Neolithic bones.

Yes! Thank you, it was somehow impossible to Google this.

Sherlock Holmes would be envious of such abilities.

I also really liked Our Mathematical Universe.

You’d probably like this short story which is about exactly what you’re describing: https://www.lesswrong.com/posts/5wMcKNAwB6X4mp9og/that-alien...

Regarding astronomy, the more amazing things are what we've been able to predict by mathematical inference before we had the technology to validate the predictions.

on similar lines, imho, mendleev’s periodic table is also quite amazing. it is now close to 150 years old !!!

from a random page on the web


Mendeleev realized that the physical and chemical properties of elements were related to their atomic mass in a 'periodic' way, and arranged them so that groups of elements with similar properties fell into vertical columns in his table.

Gaps and predictions Sometimes this method of arranging elements meant there were gaps in his horizontal rows or 'periods'. But instead of seeing this as a problem, Mendeleev thought it simply meant that the elements which belonged in the gaps had not yet been discovered. He was also able to work out the atomic mass of the missing elements, and so predict their properties. And when they were discovered, Mendeleev turned out to be right. For example, he predicted the properties of an undiscovered element that should fit below aluminum in his table. When this element, called gallium, was discovered in 1875 its properties were found to be close to Mendeleev's predictions. Two other predicted elements were later discovered, lending further credit to Mendeleev's table.


> what we've been able to predict by mathematical inference

Or purely mathematical intuition.

Double pottery awesomeness today between that and this post https://news.ycombinator.com/item?id=18869653

>"Pottery jugs from between the eighth and second centuries B.C. bear administrative stam ... the stamps provide precise information about when the pots were fired"

How do they know the dates are correct? Carbon dating doesn't work for those years: https://en.wikipedia.org/wiki/Hallstatt_plateau

Because of the stamps - they can relate them to texts to figure out when those administrations were in power.

Right, but since when are ancient texts reliable sources for historical dates?

... because they wrote down the dates?

Calendars are not a recent invention. People have been dating texts for as long as there have been texts. Especially texts related to trade and accounting.

If the pot says "made in the 4th year of king such-and-such", all you have to do is find out when that king took office, which is probably on a monument somewhere, if not in dozens of other texts, since a new administration is a pretty big deal that lots of people would write about.

Different civilizations had different calendars at different times, the calendar would often restart with each new king, some kings would be erased from history because they lost a war, etc. I doubt it is as easy as you say.

Eh, but some of the texts are pretty good at pointing out both useless as well as well liked rulers, and contains long lists of "Z, son of Y was king of X for K years, he did not fear $deity and was useless and died and his son was king after him", in between all the success stories.

Correlating them to other historic texts, filling in the missing parts, removing thing one doesn't care about etc is the job for historians.

I don't understand the high regard historians are being held given here. It is like just because they have extremely messy/biased data to deal with their conclusions are held in an even higher regard than that of science.

There's a whole discipline of experts who spend their whole lives studying this stuff. It's awful arrogant for an amateur to assume they're all full of shit.

Just because someone tries as hard as they can and does the best they can doesn't mean they are right. The available info may simply be flawed (GIGO).

Yes but the best people to judge what's garbage and what's not are the experts.

Look I'm done with this thread. I've made my point, and your comment history shows you only post this sort of pseudo-intellectual nonsense. You represent everything that's wrong with this site.

Nah, I just have the proper skepticism. You know, the idea behind science: Nullius in verba

No, that is not how skepticism works. There is a humongous body of knowledge on the topic, and all of it is very well supported with an abundance of of evidence.

Being too lazy to visit a library and educate yourself on a topic is called "willful ignorance", not skepticism.

"nullius in verba" means you don't accept theories on authority alone. It means that you don't formulate a conception of gravity by thinking about elements for a while and then declaring that you figured it out, as Aristotle did, but by considering testable possibilities and performing experiments, as Newton did.

"nullius in verba" does NOT mean you can throw out all of Newton's work as "words words words" because you don't feel like reading it.

> It is like just because they have extremely messy/biased data to deal with their conclusions are held in an even higher regard than that of science.

Yes! If someone can actually make sense of something that was incredibly messy or biased that is a real reason for celebration :-)

Historians are usually pretty good at what they do, and aren't just taking ancient calendars at their word.

On top of that, we also have astronomical records to serve as anchors for other dates. We can figure out when eclipses happened, when each planet was visible, and so on. If ancient texts record an eclipse during the reign of King Foo, and we know when there was an eclipse visible from that area, we can interpret any other events in Foo's time around those definite dates.

They're as reliable as they are, and knowing how much that is is in the purview of an entire academic discipline.

One text is an anecdote. Thousands of independent texts weighed together form our understanding of history.

Are these more accurate than carbon dating? Meaning - if we knew definitively that a pot was baked on a particular date - then use that as the baseline for checking another object, can we build a magnetic timeline and use it to date other things? Like bones?

It sounds like they calibrated the magnetic field data to written history (ie, the bible and other religious texts).

Carbon dating doesn't work for these years because there is a plateau in the reference curve. [1]

The earth must have had a weaker magnetic field (correlates with a low in sunspot activity), or there were lots of solar flares, or a supernova, near the beginning to create more c14 in the atmosphere than usual. Alternatively, the ocean "released" a bunch of old carbon to dilute the atmospheric c14 near the end of the period, thus making those years look older.[2]

[1] https://en.wikipedia.org/wiki/Hallstatt_plateau [2] https://en.wikipedia.org/wiki/Marine_reservoir_effect

Magnetostratigraphy is used to cross-check ages of bones. Similar to how pottery records the Earth's magnetic field in clay, layers of lava containing ferromagnetic minerals (such as magnetite) can provide chronological orders. This dating methodology is called archaeomagnetic dating.


THank you - thats exactly what I was interested in.

Oddly enough, this has a sizable impact to general aviation. Heading is typically measured using a gyro, but the heading values are calibrated to magnetic north (typically via a magnetometer or manually against a compass).

The creep of the magnetic field is noticeable in particular in the numbering of runways - they are numbered according to their heading. Some runways that have existed for a few decades are, accordingly, off by a few degrees. An older runway numbered "35" may have an actual approach heading of 340 (340 degrees from magnetic north). Not a huge problem when flying by eye, but it has the capability of causing some confusion when flying using instruments. Alternately, the runway numbers can even change.

As for GPS, this won't solve the problem either, since GPS can give you a "true" flight path using the movement over time, which with wind will not always match the actual heading of the aircraft due to wind.

That's why runway designations are updated periodically to reflect the magnetic change.

Yup, quite a few were renumbered last year in UK

I’m about 40 hours into Xplane 11, plus another 10 or 20 into reading and watching YouTube tutorials about GA, in particular navigation.

I now know how runways are named. Boy does that clear up a lot. Thanks :)

This is pretty sad. For at least decades, maybe even centuries, there have existed compasses that let you rotate the "north" indicator to match the current local magnetic declination. Adjusting as you travel is no different than the pressure adjustments that pilots make for altimeters. There is no good reason we couldn't have all of the airports using geographic north. That one is far more resistant to change, with continental drift and Earth axis wobble being far slower than magnetic pole movement.

Ease and reproducibility of the measurement is more important than its absolute accuracy. Whisky-ball magnetic compasses are cheap and easy to build, and have been throughout aviation's history, and don't require access to an accurate geomagnetic survey to use.

Its interesting that you mention pressure adjustments, because:

* Above 18,000 feet in the US, you don't make pressure adjustments - because its more important to know that your neighbors in the airspace are measuring their altitude the same way you are than it is to know exactly how far off the ground you are. In other parts of the world the threshold is lower, sometimes much lower.

* Airspeed is also measured with a pressure instrument, whose accuracy is affected by the density of the air, which in turn is affected by temperature and altitude. But the speed limits in the regulations, and the speeds ATC might tell you to fly, are all based on the uncorrected output of the pressure instrument - "indicated air speed", as its called. You only try to adjust for altitude and pressure when using the airspeed for navigation.

Sectional charts also display magnetic variation, there's no reason to change the instruments when you can do basic math.

Magnetic declination changes quite a lot as you travel the kind of distances that aircraft travel. Pilots would have to periodically adjust their declination while flying.

Declination is also not linear or varying only by latitude/longitude, but it also varies by area due to magma flows and iron deposits. Take a look at this map of global declinations for reference: https://en.wikipedia.org/wiki/File:World_Magnetic_Declinatio...

There is a good reason. An adjustable compass like that would be much more prone to user-error. Someone may rotate it too much causing very large discrepancies and land on the wrong runway.

Same can be said of altimeter adjustments which would literally cause you to fly into the ground, but that isn't stopping us from allowing manual adjustments.

Barometric pressure can fluctuate every day, and by relatively large amounts causing errors of 500ft+ so there, the 'price' of manual adjustment is worth the gain in accuracy.

I'm not convinced the same can be said for magnetic adjustment.

If you buy maps from the USGS [0], they have the magnetic north and true north indicated on them so you can adjust your compass. I didn't realize how rapidly my maps got out of date.

[0] - https://www.usgs.gov/products/maps/topo-maps

For naviagtion, charts are updated via [0] Notices to Mariners . It is of course the responsibility of the mariner to mark/attach the notice to the chart.

[0] https://en.wikipedia.org/wiki/Notice_to_mariners

I wonder if it will affect animals that use the magnetic field to navigate. There are birds that migrate between Siberia and Australia, for example.

Runway numbers roughly corresponding to heading is really just a numbering convenience and doesn’t even always happen. Many US airports are renumbering their 02/20 runways to something else to avoid pilot confusion, even though those new numbers don’t are even more off the actual heading.

...to avoid pilot confusion.

Out at 57D they had 18/36 and 9/27. A few months ago they changed them all and now it's 19/1 and 10/28. On the radio they are called out by digits so "one", "one nine", and "one zero". Yeah, they should have just left them all off by 10 degrees. Fortunately the wind is usually out of the west.

s/one nine/one niner

Earth's magnetic pole has been known to switch sides in the past. https://en.wikipedia.org/wiki/Geomagnetic_reversal

"183 reversals over the last 83 million years... A brief complete reversal, known as the Laschamp event, occurred only 41,000 years ago during the last glacial period. ... Geologists first noticed that some volcanic rocks were magnetized opposite to the direction of the local Earth's field.".

When this happens, does the magnetism "rotate" around the Earth, or does it fade out and fade back in reversed?

Here's a gif from a 1995 supercomputer simulation of the reversal process - https://imgur.com/a/jgpZZBF "The tubes represent magnetic field lines, blue when the field points towards the center and yellow when away."

Original source: https://www.psc.edu/science/glatzmaier.html It took them a year of computing on a CRAY C90 and 2000 hours of processing.

Closer to fading out and back in.

Does this mean anything for the protection the planet receives from cosmic rays or solar wind?

Indeed. Some people believe these “unshielded” periods might had some influence on the evolution of the species. Without those, the rate of change is just not enough to get to humans...

I'm not contesting but merely interested in references.

I've read a number of pieces over the years that a geomagnetic reversal might be near, and there have been flips as short as a couple of hundred years. Where "near" may be in my lifetime or in the next 500 years.

So we may not know why it's moved more than model, but I don't think we should be unduly surprised.

Here's one recent piece implying a switch could be sooner rather than later: https://www.extremetech.com/extreme/192522-earths-magnetic-f...

So what exactly does that mean? If I'm driving from Chicago to Milwaukee will my compass say I'm heading South?

Fun fact, the earth Northern Magnetic pole (ie the magnetic pole in the northern hemisphere) is actually the south pole of the magnetic dipole. So your compass actually is already telling you that you're heading south.

But yes, the compass you have today will point south instead of north, but this can be solved by repainting which pole of the compass is red :)

The flip can possibly happen in a lifetime, but it probably takes thousands of years. But we have never observed it so we don’t really know how, but we know that it happens.


During the reversal, it is thought that Earth would have multiple magnetic poles (much like Sol). These would gradually move over the planet resulting in effects as benign as auroras over the equator, or as disastrous as telluric currents powerful enough to ruin electrical infrastructure.

> say I'm heading South

After the reversal is complete, yes. During the reversal your compass could well be rendered useless (pointing toward your closest pole); assuming we're right about how the reversal would happen.

I wonder what effect multiple magnetic poles would have had if they had occurred during the Age of Discovery (15th-18th centuries).

I guess with celestial navigation it would've had less effect that one might think, but it certainly wouldn't have made navigation any easier.

Compasses manufactured for the northern hemisphere have extra weight added to the "south" end of the needle because the "north" end is partially being pulled toward the ground as well as the north magnetic pole. So your compass probably just wouldn't work at all.

My car already gets confused in Chicago. Today, I was driving south towards lower Wacker, and my car thought I was driving alongside Navy Pier in the lake... Wasn't until I got clear onto 290 that it regained its senses.

I'd guess it would cause the mass death of animals that use the poles to navigate.

Wikipedia seems to suggest this is unlikely:

> Hypotheses have also advanced toward linking reversals to mass extinctions.[47] Many such arguments were based on an apparent periodicity in the rate of reversals, but more careful analyses show that the reversal record is not periodic.[17] It may be, however, that the ends of superchrons have caused vigorous convection leading to widespread volcanism, and that the subsequent airborne ash caused extinctions.[48] (https://en.wikipedia.org/wiki/Geomagnetic_reversal)

Mads Faurschou Knudsen and Peter Riisager, Department of Earth Sciences, University of Oxford, Parks Road, Oxford OX1 3PR, UK. Pages 71-74.

Based on an observed correlation between the Earth's magnetic dipole moment and oxygen isotope paleo-precipitation records from caves in Oman and southern China, Knudsen and Riisager suggest that the Earth's magnetic field may have influenced the amount of rainfall in low-latitude regions during the past 5000 years. The physical mechanism that underpins the geomagnetic-climate link is provided by the cosmic-ray-climate theory, which suggests that galactic cosmic ray (GCR) particles entering the atmosphere influence the formation of low-altitude clouds and, in turn, climate. The geomagnetic field shields the Earth from GCR particles and, according to the cosmic-ray-climate theory, it therefore has the potential to influence cloud formation, rainfall, and climate. Since the amount of GCR particles entering the atmosphere is also modulated by the Sun, the cosmic-ray-climate theory is central to the ongoing scientific debate regarding the role of the Sun in climate change. Knudsen and Riisager lend support to the notion that variations in the Earth's magnetic field may influence the climate of our planet. They also deliver independent support for certain aspects of the cosmic-ray-climate theory.


> "On 15 January, they are set to update the World Magnetic Model, which describes the planet’s magnetic field and underlies all modern navigation, from the systems that steer ships at sea to Google Maps on smartphones."

Boggles the mind to think that Mother Nature is the foundation for such significant technology.

If only the Twilight Zone was still around to do an episode on the magnetic north suddenly going MIA. It has gone south (literally) a couple times I believe.

"Boggles the mind to think that Mother Nature is the foundation for such significant technology."

As best I can tell Mother Nature is the foundation of ALL technology...

On the picture, the movement of the pole slightly resembles a pendulum: it is slow at the beginning far from the geographic pole, and it speeding up as it nears it. Makes perfect sense, actually.

Being a son of a geologist, I found it fascinating we could tell from geologic history how many times the earth's magnetic field has flipped. Turns out we're long overdue for a reversal.

> Update, 9 January: The release of the World Magnetic Model has been postponed to 30 January due to the ongoing US government shutdown.

This article isn't much without the accompanying model.

Since the US is on extended winter vacation, maybe China or Russia can maintain the world magnetic model?

>> In 2018, the pole crossed the International Date Line into the Eastern Hemisphere. It is currently making a beeline for Siberia.

I knew Putin was a super villain. Now he's stealing the north pole!

Article linked is truncated, last sentences lifted from here https://www.nature.com/articles/d41586-019-00007-1?utm_sourc...

That's a much better article, free of claims of scientific bafflement. :)

Thanks! We've updated the submission from https://www.newsweek.com/earth-magnetic-field-baffle-scienti..., which points to this.

So it begins

Registration is open for Startup School 2019. Classes start July 22nd.

Guidelines | FAQ | Support | API | Security | Lists | Bookmarklet | Legal | Apply to YC | Contact