is the earth’s core really about to stop spinning? absolutely not.
If you read some science news over the past two week, you were probably informed that in a scenario straight out of an apocalyptic Hollywood blockbuster, the Earth’s core just stopped spinning. Then, when they had your attention, you were told not to worry because changes in the rotation of the planet’s core are normal, probably happen a lot, and are no big deal since we’re still here and none of the oscillations we’ve seen in the geologic record coincided with a mass extinction we couldn’t explain with volcanic activity or asteroid impacts.
Now, the last part is true. There’s absolutely nothing for us to worry about, especially in our modern world, where navigation and mapping is done by satellites, cell towers, and charts based on digital coordinates rather than compasses and migration cycles of animals. But the first part is very much incorrect because it’s physically impossible for the Earth’s core to just stop spinning even if the planet around it was destroyed. The masses and velocities involved are simply too great.
We’re on a mass of mostly molten rock tipping the scales at nearly 6 septillion kilograms and spinning at 1,674 km/h. Since the core, an iron and nickel ball about the size of the Mars that’s hotter than the surface of the sun thanks to residual heat and nuclear decay, is very much a part of our planet, basic inertia dictates that it must rotate as well. Yet there’s a catch. Our core is suspended in a molasses-like layer of molten rock, so its speed is slightly different from that of other layers thanks to drag and oscillations between the planet’s magnetized metals.
so, what’s going on with the earth’s core?
All in all, that difference doesn’t amount to much. Just three to four kilometers per hour is the difference between our rotational speed and that of the outer core. The inner core also has a slightly different velocity as do the layers of the mantle, which is actually terrific news for us as the most visible and powerful manifestation of these differences in rotation is a vast magnetic field that protects us from cosmic rays and, with an assist from our ozone layer, allows life as we know it to safely flourish.
Okay, fine, so the Earth’s core can’t stop. So, what are all these articles talking about? They’re talking about a new study which analyzed data from earthquakes and concluded that the core changes its speed of rotation over a 60-to-70-year cycle by mapping the variations of the sound waves as they traveled though the Earth. It’s not that the core stopped, it’s that it’s currently syncing with the rotational speed of the surface, will slow down a little before speeding back up to turn slightly faster than us, then once again sync up before slowing down, and so on.
From our standpoint, this doesn’t really mean anything, but for geologists, the presence of such a cycle would explain odd seismic readings that appear calmer and more stable when the core’s rotation syncs up with ours, as well as tiny, odd changes in our day, sea levels, and global mean temperatures that also seemed to oscillate every 60 or 70 years. Again, these effects are little more than rounding errors in the grand scheme of things, but scientists always want to know what’s going on when they see a pattern.
why little changes make a big difference
Hold on, you might say, how does a change of a few kilometers per hour here and there affect the entire planet, even if only slightly? Well, it’s because we’re dealing with 6 thousand billion billion tons of rock with continent sized magnetic plumes flowing like fiery molasses spinning at Mach 1.5. Tiny differences in electromagnetic currents, shape and texture of molten rock and metals, and rates of nuclear decay in the inner and outer core reverberate over vast distances and masses, adding up to oscillations powerful enough to manifest on the surface.
Sea floors alter their shapes, affecting the sea levels by just enough to notice when measuring with ultra-precise lasers. Differences in Internal rotation change the day by a matter of seconds. Both change the movement of the storms and jet streams just enough to cause blips on global mean temperature records as the cycle progresses. With this new analysis od decades of data, geologists and climatologists could finally try to confirm the root cause of the stubborn, faint signals linked to the core’s rotation cycle stubbornly emerging from the noise.
While from our perspective, the planet is solid and stationary, it’s actually a giant, hot, gooey, churning ball of energy with a paper thin, often perforated casing that we call home. And this study is a terrific reminder of exactly that. Our world is moving and breathing, almost as if it’s alive. We live at the mercy of forces that make our mightiest nuclear warheads seem like soggy firecrackers by comparison, and we’d do well to remember that, especially since we can take advantage of these forces to secure our own future.
popular science in the shadow of clickbait
Finally, all this leaves us with the problem with which we started. It’s a very interesting study which tells us something very neat and holistic about our planet. What’s with the doomsday evoking clickbait? Yes, the obvious answer is that the writers want you to read the articles so this is a good way to lure you in, but even more insidiously, these clickbait titles are almost a requirement for good SEO so these articles trend in Google searches and will do well on social media, which rewards engagement over literally every other consideration.
Even worse, current SEO standards will often actively penalize attempts at creative titles and writing in a way that isn’t a robotic “golly gosh gee whiz willikers!” style explainer, as quite a few irate bloggers trying to follow SEO playbooks will angrily grouse at you over a beer. But if you work for a major publication and don’t get high social media engagement and first page positioning in search results, the hedge funds who own it will fire a bunch of good writers to replace them with a generative AI content factory, like Buzzfeed.
In short, this story and the clickbait headlines that have social media abuzz with guesses from those who didn’t read beyond them, and the subtitles countered by eyerolls from those who actually read the articles, are perfect examples of the systemic problems we have with how we consume, judge, and deliver news today in general, and science news in particular. But what can we expect from overworked, bored primates living on a giant, mostly molten ball circling a 1.4 million kilometer wide, 4.5 billion year old thermonuclear explosion?
See: Yang, Y., Song, X. (2023) Multidecadal variation of the Earth’s inner-core rotation. Nat. Geosci. DOI: 10.1038/s41561-022-01112-z