4 ms·

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

80 points by lelf 4y ago

layer8 4y ago
Since the change in length-of-day is mentioned, is seems more accurate to say that both the inner core and the crust oscillate with respect to each other.
l33tbro 4y ago
OT - but the insistence on italicized type for this article is rather bizarre. No other USC article I've ever seen follows this formatting.
- anyfoo 4y ago
  Safari here, don't see that?
dontcare007 4y ago
Nikola Tesla is not surprised.
swader999 4y ago
I knew I felt something.
andrewflnr 4y ago
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 is, but it seems that the dynamics between the core and mantle is the right place to look. [0] https://www.science.org/doi/10.1126/sciadv.abm9916 https://www.science.org/doi/10.1126/sciadv.abm9916 <-- Just read the abstract of this instead
- thaumasiotes 4y ago
  > 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.
  - andrewflnr 4y ago
    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.
    - deleted 4y ago
      [deleted]
peterlk 4y ago
> 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 the surface to find tiny fractions of change? - Any surface-based reading also has to deal with the non-spherical nahure of Earth, and its wobble (the motion that gives us seasons) How do they do it?
- shadowgovt 4y ago
  Star readings. We can measure that accurately... In fact, a difference of 0.2 seconds is hugely significant with modern telescopes.
- dragonwriter 4y ago
  > 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.)
  - peterlk 4y ago
    Ah yes, of course. Thanks for the clarification!
- wongarsu 4y ago
  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_interferometry https://en.m.wikipedia.org/wiki/Very-long-baseline_interfero...
BluSyn 4y ago
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.
mc32 4y ago
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?
motbus3 4y ago
interesting. does anyone knows if this affect gravitational forces somehow?

80 points by lelf 4y ago

Since the change in length-of-day is mentioned, is seems more accurate to say that both the inner core and the crust oscillate with respect to each other.

l33tbro 4y ago

OT - but the insistence on italicized type for this article is rather bizarre. No other USC article I've ever seen follows this formatting.

anyfoo 4y ago
Safari here, don't see that?

dontcare007 4y ago

Nikola Tesla is not surprised.

swader999 4y ago

I knew I felt something.

andrewflnr 4y ago

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 is, but it seems that the dynamics between the core and mantle is the right place to look. [0] https://www.science.org/doi/10.1126/sciadv.abm9916 https://www.science.org/doi/10.1126/sciadv.abm9916 <-- Just read the abstract of this instead

thaumasiotes 4y ago
> 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.
- andrewflnr 4y ago
  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.
  - deleted 4y ago
    [deleted]

peterlk 4y ago

> 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 the surface to find tiny fractions of change? - Any surface-based reading also has to deal with the non-spherical nahure of Earth, and its wobble (the motion that gives us seasons) How do they do it?

shadowgovt 4y ago
Star readings. We can measure that accurately... In fact, a difference of 0.2 seconds is hugely significant with modern telescopes.
dragonwriter 4y ago
> 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.)
- peterlk 4y ago
  Ah yes, of course. Thanks for the clarification!
wongarsu 4y ago
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_interferometry https://en.m.wikipedia.org/wiki/Very-long-baseline_interfero...

BluSyn 4y ago

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.

mc32 4y ago

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?

motbus3 4y ago

interesting. does anyone knows if this affect gravitational forces somehow?