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Earth moves far under our feet: Study shows Earth’s inner core oscillates

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Re: Earth moves far under our feet: Study shows Earth’s inner core oscillates

#11

Post by thaumasiotes »

andrewflnr wrote: post #7

This article seems like it's trying to imply that the core changes position relative to the earth, when all the actual details, and the linked journal article [0] only talk about changes in rotation speed relative to the surface. This appears to be a uniquely and bafflingly bad case of science journalism. Anyway, it would be cool if this led us to understand where mantle plumes come from. I don't know how likey that…

> This appears to be a uniquely and bafflingly bad case of science journalism.

No, it's all like that.

Though I should note that the model of "the core is shifting position relative to the surface" is fully justified here. Here's the statement:

> “The inner core is not fixed — it’s moving under our feet, and it seems to going back and forth a couple of kilometers every six years,” Vidale said.

And here's the concept:

> Research published in 1996 was the first to propose the inner core rotates faster than the rest of the planet — also known as super-rotation — at roughly 1 degree per year.

But rotating at a speed that is so slightly different means exactly that the location on the surface of the core that is directly below a particular point on the surface shifts -- slightly -- over time. Positional change relative to the surface is what's happening.

Re: Earth moves far under our feet: Study shows Earth’s inner core oscillates

#12

Post by peterlk »

dragonwriter wrote: post #10
peterlk wrote: post #8

> The scientists say their model of inner core movement also explains the variation in the length of day, which has been shown to oscillate persistently for the past several decades. How do we measure persistent changes to the length of a day on Earth? This seems like a maddeningly slippery problem. - Geosynchronous sattelites? What if they're slightly off? - Star readings? Can we measure that precisely enough from t…

> wobble (the motion that gives us seasons) Axial inclination plus revolving around the sun gives seasons, wobble is a separate effect (and internal forces—mantle convection is the one I’ve mostly seen cited but core movement would also be in this category—are a source of wobble.)

Ah yes, of course. Thanks for the clarification!

Re: Earth moves far under our feet: Study shows Earth’s inner core oscillates

#13

Post by BluSyn »

It's fascinating to think there's so little we really know of our own planet. Our knowledge about the inner workings of Earth's core are all from indirect measurements, and there's a fundamental limit to the resolution of our models using these methods. I'm sure there's so much more to learn, and many more surprises, if we discover novel new ways to inspect deep underground.

Re: Earth moves far under our feet: Study shows Earth’s inner core oscillates

#14

Post by wongarsu »

peterlk wrote: post #8

> The scientists say their model of inner core movement also explains the variation in the length of day, which has been shown to oscillate persistently for the past several decades. How do we measure persistent changes to the length of a day on Earth? This seems like a maddeningly slippery problem. - Geosynchronous sattelites? What if they're slightly off? - Star readings? Can we measure that precisely enough from t…

Observing quasars and the like [1]. We measure it to figure out when we need leap seconds (to keep UTC within 0.9 seconds of UT1, the time given by earth's position and rotation in the solar system)

1: https://en.m.wikipedia.org/wiki/Very-long-baseline_interfero...

Re: Earth moves far under our feet: Study shows Earth’s inner core oscillates

#15

Post by mc32 »

Wait... is it then actually possible it's not the whole Earth, as suspected by Dzhanibekov at one point, but just the inner core that might flip axis due to having an intermediate axis of inertia if the metals/density are not evenly distributed?

Re: Earth moves far under our feet: Study shows Earth’s inner core oscillates

#16

Post by andrewflnr »

thaumasiotes wrote: post #11
andrewflnr wrote: post #7

This article seems like it's trying to imply that the core changes position relative to the earth, when all the actual details, and the linked journal article [0] only talk about changes in rotation speed relative to the surface. This appears to be a uniquely and bafflingly bad case of science journalism. Anyway, it would be cool if this led us to understand where mantle plumes come from. I don't know how likey that…

> This appears to be a uniquely and bafflingly bad case of science journalism. No, it's all like that. Though I should note that the model of "the core is shifting position relative to the surface" is fully justified here. Here's the statement: > “The inner core is not fixed — it’s moving under our feet, and it seems to going back and forth a couple of kilometers every six years,” Vidale said. And here's the concept:…

I mean, I've noticed most science journalism is bad, but this one made me feel like I was having a stroke.

And the perspective of positions on the core and surface moving relative to each other in some cylindrical coordinates may well be what the article meant, but they sure didn't make it clear, and it's ultimately ill-defined: the correct unit for that change is still an angle. A particular linear distance can only accurately describe it given a particular latitude, which is expressed in, guess what, an angle. This is of course an overly technical way if explaining how the "moving" terminology just obfuscates a pretty simple and accessible underlying concept. They went out of their way to make it less clear.

Re: Earth moves far under our feet: Study shows Earth’s inner core oscillates

#17

Post by [deleted] »

andrewflnr wrote: post #16
thaumasiotes wrote: post #11

Earlier quoted context omitted.

> This appears to be a uniquely and bafflingly bad case of science journalism. No, it's all like that. Though I should note that the model of "the core is shifting position relative to the surface" is fully justified here. Here's the statement: > “The inner core is not fixed — it’s moving under our feet, and it seems to going back and forth a couple of kilometers every six years,” Vidale said. And here's the concept:…

I mean, I've noticed most science journalism is bad, but this one made me feel like I was having a stroke. And the perspective of positions on the core and surface moving relative to each other in some cylindrical coordinates may well be what the article meant, but they sure didn't make it clear, and it's ultimately ill-defined: the correct unit for that change is still an angle. A particular linear distance can only…

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