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0

shiruken OP t1_j5lq3jx wrote

Direct link to the peer-reviewed study: Y. Yang and X. Song, Multidecadal variation of the Earth’s inner-core rotation, Nature Geoscience (2023)

>Abstract: Differential rotation of Earth’s inner core relative to the mantle is thought to occur under the effects of the geodynamo on core dynamics and gravitational core–mantle coupling. This rotation has been inferred from temporal changes between repeated seismic waves that should traverse the same path through the inner core. Here we analyse repeated seismic waves from the early 1990s and show that all of the paths that previously showed significant temporal changes have exhibited little change over the past decade. This globally consistent pattern suggests that inner-core rotation has recently paused. We compared this recent pattern to the Alaskan seismic records of South Sandwich Islands doublets going back to 1964 and it seems to be associated with a gradual turning-back of the inner core as a part of an approximately seven-decade oscillation, with another turning point in the early 1970s. This multidecadal periodicity coincides with changes in several other geophysical observations, especially the length of day and magnetic field. These observations provide evidence for dynamic interactions between the Earth’s layers, from the deepest interior to the surface, potentially due to gravitational coupling and the exchange of angular momentum from the core and mantle to the surface.

37

Redbeardroe t1_j5lsnu8 wrote

So is the ELI5 on this essentially the earths core stopped rotating and is about to reverse?

20

ramonycajal88 t1_j5lxh6f wrote

Does the effect the earth's magnetic poles? I saw an article last year that the true North has shifted over the last couple years, which appears to also be a part of a normal cycle.

34

justahomeboy t1_j5lxhib wrote

Do you mind explaining how the core and the rest of the planet can have different rotation speeds? I haven’t taken science courses since college so I’m ignorant to the subject matter.

10

KubaKuba t1_j5m0sp9 wrote

I wonder if orbit is a potential cause?

I could imagine rotational artifacts from a non perfectly circular orbital path causing a rotational speed difference between the core and the shell of the earth.

As a matter of fact I would be surprised if it wasn't that.

3

shiruken OP t1_j5m0uqb wrote

Don't really know the specifics, but it has to do with the structure of the Earth where the outer core is liquid while the inner core is solid. Anytime you start spinning layers with liquid, things get complicated.

The New York Time's coverage of this research offers this explanation:

>What’s going on? One idea is that two titanic forces are battling for control over the world’s heart. Earth’s magnetic field, generated by swirling iron currents in the liquid outer core, is pulling at the inner core, causing it to spin. That impulse is countered by the mantle, the mucilaginous layer above the outer core and below Earth’s crust, the immense gravitational field of which grasps the inner core and slows its spin.

27

seamus1982 t1_j5m82pl wrote

Will this cause any problems or issues?

84

coot47 t1_j5mte1b wrote

I would surmise that due to the relative friction, our days will become progressively longer.

−5

NYCmob79 t1_j5n742m wrote

Probably polar reversal. Maybe why we are experiencing no winter in the northern hemisphere. Soon our Winters will be our Summers and our Summers will be our Winters.

−71

NYCmob79 t1_j5n7ckq wrote

Is not a guess. We are over due by several hundred thousand years. The average is 200k years, but the last one was 750k years ago. I'm in the northern hemisphere. We have no winter. I haven't wore a coat this year yet. It should be freezing. I think this is happening now. Soon our winter months will be our summer months and vice versa.

−64

jpipersson t1_j5n9r4m wrote

>So is the ELI5 on this essentially the earths core stopped rotating and is about to reverse?

No. This is not what it says. Reread more carefully. Perhaps also read something about the conservation of angular momentum.

−12

jpipersson t1_j5n9wdy wrote

Seems like this would have an effect on the angular momentum of the rotating globe.

3

MistWeaver80 t1_j5na6ov wrote

Earthquake data hint that the inner core stopped rotating faster than the rest of the planet in 2009, but not all researchers agree.

>In 1996, Song and another researcher reported studying earthquakes that originated in the same region over three decades, and whose energy was detected by the same monitoring station thousands of kilometres away. Since the 1960s, the scientists said, the travel time of seismic waves emanating from those earthquakes had changed, indicating that the inner core rotates faster than the planet’s mantle, the layer just beyond the outer core.

>Later studies refined estimates of the rate of that ‘super-rotation’, to conclude that the inner core rotates faster than the mantle by about one-tenth of a degree per year. But not everyone agrees. Other work has suggested that super-rotation happens mostly in distinct periods, such as in the early 2000s, rather than being a continuous, steady phenomenon. Some scientists even argue that super-rotation does not exist, and that the differences in earthquake travel times are instead caused by physical changes on the surface of the inner core.

>Last June, Vidale and Wei Wang, an Earth scientist also at the University of Southern California, threw another spanner into the works. Using data on seismic waves generated by US nuclear test blasts in 1969 and 1971, they reported that between those years, Earth’s inner core had ‘subrotated’, or rotated more slowly than the mantle5. Only after 1971, they say, did it speed up and begin to super-rotate.

>Now, Yang and Song say that the inner core has halted its spin relative to the mantle. They studied earthquakes mostly from between 1995 and 2021, and found that the inner core’s super-rotation had stopped around 2009. They observed the change at various points around the globe, which the researchers say confirms it is a true planet-wide phenomenon related to core rotation, and not just a local change on the inner core’s surface. The data hint that the inner core might even be in the process of shifting back towards subrotation. If so, something is probably happening to the magnetic and gravitational forces that drive the inner core’s rotation. Such changes might link the inner core to broader geophysical phenomena such as increases or decreases in the length of a day on Earth.

13

SneakyCrouton t1_j5naob7 wrote

First, your math makes no sense, saying it's 550,000 years overdue does make it definite in the next 75 years. And secondly, the seasons are affected by the tilt of the Earth and potentially weather effects such as trade winds which have been affected by the changing sea temperatures due to global warming.

30

ZeroOnline t1_j5nhhm4 wrote

I'm also in the northern hemisphere and when I look out my window I see snow. We had a snow storm a few days ago. Roads are salted. I'v been wearing my winter jacket. Granted it's not as cold as normal, but it's winter. You might also want to be more specific on where exactly in the northern hemisphere you are, because 2 weeks ago most of Midland America was in the freezing temperatures. Chill tf out.

7

Rhaski t1_j5njwbu wrote

No. It's resonance. As it spins, it increases and decreases speed in a periodic fashion. This frequency is a harmonic just like when you flick a wine glass and it rings for a while, but instead of being an inward/outward flexing motion, it's an angular oscillation. This happens in the rotating assembly of some engine configurations too (such as V6 engines), so they have to have a harmonic balancer to smooth out this angular oscillation or it makes everything vibrate horrible when the RPMs match the harmonic frequency of the crankshaft and it can break. It's also observed in shaft couplings like U-joints. This is why the Constant Velocity (CV) shaft was invented, because traditional U-joints operating on an angle (such as in driving a front wheel whilst turning) caused fierce angular vibration to travel down the driveshaft and at the right frequency, it could resonate and lead to failure of the driveshaft or other components. We are seeing this on a much larger system and, consequently, we see a much lower harmonic frequency. In the order of cycles per century rather than cycles per second

6

mrmopper0 t1_j5nkud8 wrote

I have an f150, pop the nuclear device in the back and everyone pile in. It's not technically made to drill to the Earth's core but it has 4wd and I don't mind if it gets dirty.

81

thebiologyguy84 t1_j5nply3 wrote

Earths magnetic field is linked to the cores rotations. I would assume the slowing would cause a decrease in the field that will give less protection to the sun's radiation. I'd also assume the change will be negligible for us normies (non-scientists) to worry about.

63

Bofgrey t1_j5nuek4 wrote

It is simple to understand if you grab an uncooked egg, spin it around on a table, bring it to a sudden stop by putting your hand on top, and then quickly lift your hand again. The rotating insides of the egg will bring it in motion again. (This is also a trick to check if an egg is cooked or not)

4

SLR_ZA t1_j5ny1im wrote

>he last one was 750k years ago. I'm in the northern hemisphere. We have no winter. I

The magnetic north and south pole do not affect the seasons. The earths tilt affects seasons. This does not swap.

​

And because it happens every 200k years on average and we are beyond that does not mean it will happen in the next 75 years. What about 100 years ago by the same argument?

7

[deleted] t1_j5nzrcp wrote

How does this play with the misshaped inner core that I read about a year or two ago? I remember reading that they assumed that the core was a ball or a sphere but turns out it’s growing crystals or is not smooth?

6

Beanmachine314 t1_j5om4eq wrote

Also, poles do not shift on that kind of time frame. It takes waaay more than 75 years. Maybe they're switching right now, but none of us will be alive to know if the normal pole wandering is a part of pole switching or not.

7

DanYHKim t1_j5p12yu wrote

Does that mean we will be seeing a return of hippies?

>The core’s slowing down isn’t the beginning of the end times. The same thing appears to have happened in the late 1960s and early 1970s, and the study authors at Peking University in China suggest it may represent a 70-year cycle of the core’s spin speeding up and slowing down.

0

Funkytowels t1_j5p9f1w wrote

pole magnetic switch activated.....we're fucked

−1

thulesgold t1_j5plwmb wrote

It doesn't make sense. First of all, there is considerable friction between the core and mantle so having a spin rate difference between them for billions of years is improbable. Second of all, the theory the core spins faster then slows down also makes no sense. It would imply there is an elastic oscillation between the core and mantle as they trade off angular momentum, but this is something we can measure... If the core slowed, then the mantle would speed up making the day shorter. Since I haven't heard news reports of drastic time changes every 70 years Imma gonna call BS on all this recent news on core spin.

0

superradguy t1_j5qsi93 wrote

Better send Hilary Swank down there to investigate

1

Gordomania t1_j5qumwx wrote

A few nukes will restart it. I saw the documentary about it when it happened last time.

8

GeoGeoGeoGeo t1_j5suvl3 wrote

There is a suggested different spin rate between the inner solid core and liquid outer core. The difference, however, is exceptionally small, and they both rotate at the same speed to within 0.001%.

The difference in speed is believed to be a result of two competing forces: The gravitational tug of the surrounding mantle, and the torque induced by the electromagnetic field from the outer core.

So when they report that its stopped spinning they mean relative to the mantle, same as when they say its reversed, and sped up.

1

thulesgold t1_j5sw160 wrote

Sure but slowing down the angular momentum of such a large mass would have noticable effects. For example, since the core is spinning at different velocities relative to the outer core then oscillates back to the original velocity then that energy would need to be banked in a magnetic field or some other means so that the energy is regained. We would see strong changes in Earth's magnetic field. Either way, billions of years of this happening would reduce this oscillation to nothing and affect the rate of the spin of the earth as a whole (beyond slowing due to tidal forces).

It might be interesting to think about the moon forming collision and there was an oscillation billions of years ago but much worse than it is today.

1

tiktock34 t1_j5u6khq wrote

Is there anything that would suggest a shift in this core’s rotation as something that would effect global warming? Would heat radiation in any way change or affect surface temp?

1

sfzombie13 t1_j5yeewy wrote

maybe not, but the magnetic record found in core samples can tell us. from what i've read on the subject, they do know that wandering happens both immediately before and after the shift. last time i checked i think it said it happened in the span of a century or two.

1

Beanmachine314 t1_j5yg9ro wrote

Hello pot, I'm kettle, nice to meet you. Stating you're correct, does not make it so, no matter how little evidence one provides. If that is true, then apparently I'm the correct one as you also provided zero evidence.

1

sfzombie13 t1_j5yizr8 wrote

i was hoping you had something to show me i was wrong. usually that's how it's done when correcting folks. i make the statement, and it's right unless you can show me it's wrong. if it worked as you said, then everybody is always right. hell, even my college professors knew that. i was right and argued with them unless they could show me i was wrong. it happened a lot, and i learned a lot. most important thing i learned was not to change my position unless proven wrong, then accept the error, learn from it, and move on. i'm not concerned with your ideas, unless you can prove them. i have my own ideas, no room for any of yours. facts are always welcome. have a great day.

0

cardinalf1b t1_j69sy1v wrote

How does this play with conservation of angular momentum? If the core slows down or reverses, shouldn't something else speed up or slow down in the opposite direction?

1