Our planet's center may need to be updated.
According to new evidence, the solid inner core changes direction every six years, instead of rotating faster.
This not only has implications for our understanding of the inner workings of our home world, but it can also explain a mystery that has perplexed scientists for some time: an intermittent variation in the length of Earth's day.
"From our findings, we can see the Earth's surface shifts compared to its inner core, as people have claimed for 20 years," said John E. Vidale of the University of Southern California.
The inner core spun slightly slower from 1969 to 1971 and then moved the other way from 1971 to 1974. The length of a day was predicted to grow and shrink. It's likely that the two observations are the same.
There's still a lot we don't know despite the fact that our understanding of Earth's core has improved. We can't just go there and look at it; everything we know, we have gleaned from indirect observations.
This is an effective tool. Scientists have been able to determine that Earth's inner core is a hot, dense ball of solid iron, which is a little larger than the size of the dwarf planet. The evidence shows that it rotates faster than Earth.
The phenomenon was first described in 1996 with an estimated super rotation rate. The rate was revised to 0.29 degrees per year using data from underground nuclear tests conducted in the 1970s.
They added two tests from 1971 and 1969 to the new research. That showed something strange. According to the data, Earth's inner core was sub rotating at a slower rate than Earth's.
There is a diagram showing a model. Edward Sotelo is a USC faculty member.
The researchers said this was consistent with what they had previously said. The inner core slows down when it is in the full swing of its spin.
The community has been split on the viability of the inner core model.
We expected to see the same rotation direction and rate in the earlier atomic tests, but we didn't see it. It was moving in the other direction.
We don't have a confirmed explanation for the six year periodicity of the oscillation.
Earth's days go through time variations of plus or minus 0.2 seconds every six years or so, as well as the Earth's magnetic field going through a six-year period. They match the periodicity of the model for the inner core of Earth.
It will require more data to be untangled. The facility that recorded the data from the nuclear tests is no longer open and underground nuclear testing is not as frequent.
The results so far suggest that Earth's insides are a bit more complex than we knew, and further advances in sensor technology could mean that the detailed data needed to probe Earth's inner core isn't so far into the future.
The inner core is moving under our feet and it seems to be going back and forth a few times a year.
Is the inner core locked compared to everything else in the long term or is it moving? It's important that we understand how the inner core formed and how it moves over time.
The research was published in a journal.
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