Earth’s inner core paused, then reversed its spin. This is fine

Imagine Earth’s inner core — the dense center of our planet — as a heavy, metal ballerina. This iron-rich dancer is capable of pirouetting at ever-changing speeds.

That core may be on the cusp of a big shift. Seismologists reported Monday in the journal Nature Geoscience that after brief but peculiar pauses, the inner core changes how it spins — relative to the motion of Earth’s surface — perhaps once every few decades. And, right now, one such reversal may be underway.

This may sound like a setup for a world-wrecking, blockbuster movie. But fret not: Precisely nothing apocalyptic will result from this planetary spin cycle, which may have been happening for eons. The researchers who propose this speculative model instead aim to advance understanding of Earth’s innermost sanctum and its relationship with the rest of the world.

The inner core is like “a planet within a planet, so how it moves is obviously very important,” said Xiaodong Song, a seismologist at Peking University in Beijing and an author of the study.

In 1936, Danish seismologist Inge Lehmann discovered that Earth’s liquid outer core envelops a solid metal marble — and it has bamboozled scientists ever since.

“It’s weird that there’s a solid iron ball kind of floating in the middle of the Earth,” said John Vidale, a seismologist at the University of Southern California who was not involved with the study.

Scientists think the core crystallized out of a molten metal soup at some point in Earth’s not-too-distant past, after the planet’s internal inferno had sufficiently cooled.

The inner core cannot be directly sampled, but energetic seismic waves emanating from potent earthquakes and Cold War-era nuclear weapon tests have ventured through the inner core, illuminating some of its properties.

Not very clear from the link summary, but I don’t think the inner core “reverses its spin” what is probably meant is that the mid-depth liquid realm and the metal inner core have always been spinning at slightly different rates and sometimes the inner core is ahead of the liquid realm, at other times (I presume this era since 2009) it spins a bit slower. But they are probably both spinning at similar rates. Whether they both spin at similar rates to the outer crust (where we live) or not, I don’t know. I’ll try to find out more details about all that. It would not seem very stable for the earth if they were not all three layers spinning at similar rates. Perhaps the differentials are quite small as in meters per day.

As to the theory that the outer crust might at various times suddenly stop spinning, that seems very unlikely to me. The earth’s rate of spin is gradually slowing down. The day if measured in modern time units would have been 21 hours long in the dinosaur era. The earth has slowed its rotation very slightly during human history. This was proved by comparing Sumerian eclipse records to what astronomers had calculated should have occurred at constant spin rates. I think the conclusion was that the earth had rotated through about one tenth of a day more than expected going back to 3500 BC so that solar eclipse paths were falling on regions further west than the calculations. If the differential was one tenth of a day, then the eclipse the astronomers had calculated should have been around Tibet or maybe southern China would have been in Sumeria (ancient Iraq) instead.

(That would assume their calculations of the new moon dates were correct, a similar outcome would occur if let’s say the moon was perfectly aligned with the Sun a tenth of a day later than expected)

These changes are not linear and I’ve read that the earth day shortened slightly in recent years (rather than continuing the longer trend of lengthening out). Maybe that has something to do with the other changes going on inside the crust in the liquid outer core and the solid inner core.

I could imagine faster changes in the length of day from some astronomical event on the order of perhaps many seconds or a few minutes per day but a sudden stop in the earth’s rotation seems to require forces that would be so powerful that in all probability the earth would disintegrate entirely.

So, what I discovered in the literature about the rotation of the inner and outer core is this — they are believed to be rotating faster than the mantle by 0.3 to 0.5 degrees of longitude per year. That means that over about 900 years (360/0.4 = 900) the inner and outer core make one more rotation than the mantle. The research being discussed in the linked article says that those two components are not quite rotating in sync, but does not specify the variations, you would have to imagine they are fairly small in relative terms, and the implication is that they average out the same.

In other words, these are fairly small variations, it’s not as though the mantle is rushing quickly over top of the outer edges of the liquid outer core. A difference in rotation of 0.4 deg per year is the equivalent of 30 miles at the equator and perhaps 20 miles in most parts of the United States. So whatever part of the core is beneath your home today was perhaps twenty miles west of there a year ago (since it rotates faster). That is a lot faster than the movement of “hot spots” in the crust like the one that has been moving through southern Idaho and under Yellowstone National Park in geological times. That hot spot is moving at about 0.01% the speed of the core in relative terms. I don’t have any idea if the two things are related in any way.

Selections from the poleshift keyword, sorted (I omitted the Chandler Wobble topics I noticed, check that keyword for those, if interest):

Recordings of the magnetic field from 9,000 years ago teach us about the magnetic field today [12/11/2021]
Is Earth's core lopsided? Strange goings-on in our planet's interior [06/05/2021]
Thousand-Year-Old Furnace in Cambodia Shows How Earth's Magnetic Field Shifts [03/16/2021]
Earth's Magnetic Field Reversal 42,000 Years Ago Triggered a Global Environmental Crisis [02/19/2021]
The Herky-Jerky Weirdness of Earth's Magnetic Field[12/23/2020]
NASA Is Tracking a Vast, Growing Anomaly in Earth's Magnetic Field[08/18/2020]
Weird: Out of Nowhere, Something Just Rocked Earth's Magnetic Field [06/26/2020]
The Mysterious Anomaly Weakening Earth's Magnetic Field Seems to Be Splitting[05/27/2020]
Part of Earth's Magnetic Field is Getting Weaker in 'Vigorously' Developing Anomaly, Scientists Say [05/22/2020]
Modern science reveals ancient secret in Japanese literature [04/06/2020]
Earth Enters Unknown as Magnetic North Pole Continues Push Toward Russia, Crosses Greenwich Meridian [12/13/2019]
Most Recent Reversal of Earth's Magnetic Field Lasted 22,000 Years [08/08/2019]
Ancient Tree With Record of Earth's Magnetic Field Reversal in Its Rings Discovered [07/15/2019]
Check your compass: The magnetic north pole is on the move [02/05/2019]
The northern and southern lights are different. Here's why [01/26/2019]
Earth's magnetic pole is on the move, fast. And we don't know why [01/12/2019]
Shifting North Magnetic Pole Forces Unprecedented Navigation Fix [01/11/2019]
Earth's magnetic field is acting up and geologists don't know why [01/10/2019]
Earth's Magnetic Field Decaying at an Alarming Rate[12/11/2018]
Researchers find fast flip in Earth's magnetic field [08/23/2018]
Why Earth's Magnetic Field Might Not Flip After All [05/01/2018]
Earth's Second Magnetic Field: Satellite Image Reveals Invisible Force From Ocean Currents [04/12/2018]
Africa PHENOMENON threatens to FLIP Earth's magnetic field, taking the poles with it [03/08/2018]
Rediscovering north Local vet's work on magnetism changed maps, textbooks [11/13/2017]
NASA: Earth's Last Full Magnetic-Pole Reversal Occurred 780,000 Years Ago --"We Are Over Due" [02/01/2017]
Earth's magnetic poles are set to swap places - and we're totally unprepared [Isaiah 24] [01/30/2017]
Earth's Magnetic Field is Changing [12/23/2016]
Earth's magnetic poles won't flip any time soon [11/27/2015]
Earth's inner core was formed 1-1.5 billion years ago[10/11/2015]
Earth's Magnetic Shield Is Much Older Than Thought [07/31/2015]
Ice age polarity reversal was global event: [04/06/2015]
NASA's MMS Spacecraft Set for March Blastoff to study Earth's Magnetic Reconnection Events[03/01/2015]
NASA's Magnetospheric Multiscale (MMS) Spacecraft ... to study Earth's Magnetic Reconnection Events [02/28/2015]
Heart of Earth's inner core revealed [02/10/2015]
Earth's Magnetic Field Could Flip in Our Lifetime [10/18/2014]
"Earth's Impending Magnetic Flip" -- Scientific American [10/01/2014]
Forget global warming, worry about the MAGNETOSPHERE: Earth's magnetic field is collapsing ... [01/28/2014]
BREAKING: Scientists say dogs align along earth's north-south axis when pooping [01/04/2014]
Dogs align themselves with Earth's magnetic field when it comes time to poop [01/02/2014]
The sun's magnetic field is about to flip [12/30/2013]
'Will We Soon Find Ourselves Back In The Stone Age?' Why Swarm Is Watching Our Magnetic Field [11/25/2013]
Earth's Pole Has Moved 161 Miles In The Last 6 Months [06/02/2013]
Scientists probe link between magnetic polarity reversal and mantle processes [08/03/2012]
The Enigma 1,800 Miles Below Us [05/30/2012]
Magnetic Pole Reversal Happens All The (Geologic) Time [11/30/2011]
Pole flips tied to plate tectonics [11/26/2011]
Potato Earth: Gravity satellite reveals what our planet REALLY looks like[03/31/2011]
Earth's core rotating faster than rest of the planet but slower than previously believed [02/21/2011]
Magnetic Polar Shifts Causing Massive Global Superstorms[02/09/2011]
Magnetic polar shifts causing massive global superstorms[02/06/2011]
Magnetic Polar Shifts Causing Massive Global Superstorms [02/04/2011]
Signs Of a Different Matter,North Pole Moving [Biff Buffington Reporting From Blizzard Central!!] [01/21/2011]
Earth's magnetic pole shift unleashing poisonous space clouds linked to mysterious bird deaths [01/13/2011]
Earth's magnetic pole shifts, screws up runway at Florida airport[01/08/2011]
Shift of Earth's Magnetic North Pole affects Tampa airport....[01/06/2011]
Tiny 3-D images from Stanford and SLAC shed light on origin of Earth's core [12/16/2010]
First measurement of magnetic field in Earth's core [12/16/2010]
Earth's Core Has Another Layer, Scientists Claim [12/08/2010]
Scientists to Unearth Ice Age Secrets from Preserved Tree Rings [ kauri trees, New Zealand ] [04/07/2010]
Study Peels Back More of the Magnetic Sun[03/12/2010]
Earth Raised Magnetic Shield Earlier than Thought [03/07/2010]
North Magnetic Pole Moving East Due to Core Flux [12/28/2009]
Carolina bays gouged into the ground at a magnetic reversal[07/29/2009]
Runway rename as North Pole moves.... (Pole Shift & Pole Reversal in 2012) [07/12/2009]
Oceans charge up new theory of magnetism [06/16/2009]
The earth's magnetic field impacts climate: Danish study [01/15/2009]
The earth's magnetic field impacts climate: Danish study [01/12/2009]
Earth's Core, Magnetic Field Changing Fast, Study Says [07/10/2008]
Sea floor records ancient Earth [03/23/2007]
Serious Climate Change: Winds Blew in Reverse During Last Ice Age [01/24/2007]
Earth's Inner Fort Knox [Earth's core has 1.6 quadrillion tons of gold] [12/13/2006]
Home and away: Bat uses magnetic compass for long flights [12/07/2006]
Amazon River Once Flowed in Opposite Direction [10/24/2006]
Al Gore warns of pole shift [08/02/2006]
Reversal of Earth's Magnetic Field-(Hey Algore read this) [06/03/2006]
Ships' logs give clues to Earth's magnetic decline [05/13/2006]
Ancient Mariners Reveal Tales From The Earth's Core [05/12/2006]
Ice Ages Blamed On Tilted Earth [04/30/2006]
Global Warming Needs New Look at Mechanisms Involved [01/26/2006]
Earth's Magnetic Pole Drifting Quickly [12/09/2005]
Movement Of Earth's North Magnetic Pole Accelerating Rapidly [No Doubt Bush's Fault!] [12/09/2005]
Earth's magnetic pole shifting; Alaska may lose northern lights [12/08/2005]
Canada: Our North loses the Pole ~~ moving toward Siberia [06/17/2005]
When the compass suddenly points south ( Magnetic Pole Flip, latest SHOCKING news) [01/05/2005]
Magnetic effects seen in water [12/07/2004]
Will Compasses Point South? [07/13/2004]
A clockwise turning low forms in Eastern Pacific!(This is history( [04/18/2004]
Earth Loses Magnetism [01/01/2004]
Earth's magnetic poles on verge of flipping [12/13/2003]
Earth's Magnetic Field Weakens 10 Percent (and some other stuff) [12/12/2003]
Is The Earth Preparing To Flip? [03/27/2003]
Sun's rays to roast Earth as poles flip [11/09/2002]
Earth's magnetic field 'boosts gravity' [09/23/2002]
The Sun: A Great Ball of Iron? [07/17/2002]
Anomalies hint at magnetic pole flip [04/10/2002]
Canada no longer the true north? [03/19/2002]

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