Corey S. Powell Profile picture
Jan 24, 2023 7 tweets 5 min read Read on X
If you saw this headline, or one like it, you might reasonably have thought the world has gone mad. The inside of the Earth is spinning backwards?
*But that is not at all what the actual research says.*
[a short thread] #RealityCheck Misleading tweet headline f...
Key point: Earth's core rotates at almost exactly the same rate as the rest of the planet. Did in the past, still does so now. It rotates at the same speed to within 0.001%!
But even the research paper is confusing on that point: #RealityCheck
nature.com/articles/s4156… Schematic of Earth's interi...
What's interesting here is that Earth's inner core rotates *almost* the same as the surface, but not *exactly* the same. It may rotate a tiny bit faster or slower -- and that's not apocalyptic, but it sure is interesting.
sciencenews.org/article/earth-… #Earth #Core Cutaway illustration of Ear...
The first hint that Earth's core goes its own way came in 1996. The core appeared to be turning 1 part in 100,000 faster than the surface. That small difference would case it to drift by 10s of kilometers a year -- a big effect by geophysical standards.
nature.com/articles/38222… Image of earthquake waves t...
Earth's inner core is solid, but the outer core is liquid. That means the inner core is suspended in liquid, like the insides of a chocolate-covered cherry, leaving it weirdly free to move around. #Core #BeFree Cutaway of Earth's interior...Image
Why would Earth's core spin (slightly!) faster or slower than the surface? 1) the gravity of the mantle is pulling on it. 2) magnetic fields from the outer core grab onto it. If we can measure these effects, we learn a lot about the geomagnetic field that keeps us all safe. #Core Image
Bottom line: Earth's core cannot just stop rotating and reverse itself! We're talking *tiny* variations, with the rotation period of the core running less than one second faster or slower than it is up top. Enough to be fascinating, but not enough to do this: #TheCore [fin] Image

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More from @coreyspowell

May 8, 2023
I was a NASA intern in the '80s when I heard that astronomers had discovered a mysterious disk around the nearby star Fomalhaut.
Now JWST has revealed exactly what they are: three enormous, dusty asteroid belts around another star!
webbtelescope.org/contents/news-… ImageImage
In the 18th century, Swedenborg, Kant & Laplace proposed that planets form in discs around stars. It took more than two centuries to see they were correct! But now we can observe discs, asteroids, comets, and even colliding planets around other stars.
en.wikipedia.org/wiki/Nebular_h… Image
There's a lot more to come. JWST will soon zoom in on 17 nearby stars to observe the planets forming around them.
One puzzle: Why are many other planetary systems much bigger than ours? Is there something weird about us?
nasa.gov/feature/goddar… #NASA #JWST Image
Read 4 tweets
Mar 2, 2023
A new seismic study shows that Earth has five inner layers, not four as long believed. Inside Earth's inner core is an *inner-inner* core, a ball of white hot iron 1300 km (800 miles) wide. science.anu.edu.au/news-events/ne… #Geology #earthquakes Schematic showing the newly confirmed inner-inner core of th
Researchers at Australian National University developed a clever way to sense seismic waves reverberating inside the Earth. Those echoes made it possible for them to sense the growing metallic seed at the center of our planet. nature.com/articles/s4146… #Perspective Diagram of the seismic network used to study Earth's complex
The innermost inner core is Earth's fifth layer. Which means it is the perfect setting for a movie sequel that merges The Core with The Fifth Element.
Read 4 tweets
Dec 13, 2022
You're about to hear a lot about #NuclearFusion. I've followed the field for years & can offer context. Top line:
- NIF's "breakeven" does not generate more power than it consumes
- NIF is not a model for a commercial fusion reactor
- This news is a big deal all the same. 1/n Target positioners for the National Ignition Facility.
Fusion researchers measure fusion output in "Q," the ratio of power produced to power needed to maintain the fusion plasma. NIF has exceeded Q=1.
Breakeven, right? Er, the accounting is not so simple, as Charles Seife explains. 2/n theatlantic.com/technology/arc… #fusion #NIF
The power that goes into igniting a fusion pellet is much less than the total amount that NIF consumes. "Breakeven" comes nowhere close to covering all of that consumption! A useful fusion power plant would require anything from Q=5 to Q=100. 3/n
en.wikipedia.org/wiki/Fusion_en… #fusion Photo of the National Ignition Facility.
Read 9 tweets
Aug 1, 2022
Twitter is full of "wonder science" accounts, many of them full of stolen images & misinformation. The recent viral tweet about the alleged void in space offers a good case study in how to spot the fakes. 1/5
Test #1: Who is sending the tweet? Reputable researchers, journalists, and institutions identify themselves. If the account is anonymous and contains no information, you should be suspicious. 2/5
Test #2: What is the source of the information? If there is no source/link (or a generic ID like "NASA"), that's a red flag. It's also a common tactic in bot accounts that scrape or steal images from the actual creators. 3/5
Read 7 tweets
Feb 4, 2022
The true colors of the solar system, a short thread. * First, let's start with the Sun. Can we all agree it's white to the eye?

* inspired by James O’Donoghue & Marina Koren, with some color corrections by me.
Mercury is so gray that it's tough to tell whether you are seeing pictures of it in color or black-and-white. This one is true color, seriously. blogs.agu.org/wildwildscienc…
Venus reflects 70% of the sunlight that hits it, nearly as reflective as freshly fallen snow. So yeah, it is super-white, as you can tell just by looking at it in the sky. nasa.gov/mission_pages/…
Read 13 tweets
Jan 7, 2022
Remember the "mystery hut" spotted by China's Yutu-2 rover on the far side of the Moon? Now we've seen it up close. Behold...a Moon rock. mp.weixin.qq.com/s/VgtehRidYL8-…
Reminder: When you apply a lot of imagination to an image at the very edge of resolution, you're going to "see" all kinds of strange things. The Face on Mars was a classic of this genre.
Fortunately, the universe is full of genuine mysteries. We still don't know for sure whether there is life on Mars!
Read 4 tweets

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