Earth, the place we live in, is full of magical landscapes: beautiful beaches, wild forests, hot deserts, and all the species that inhabit it. But have you ever thought of what’s inside of it? The real core of our planet?

3,000 miles beneath your feet, under the crust, beneath the mantle, through layers of hot, molten metal—there’s a solid ball of iron and nickel. About the size of the Moon.

That’s Earth’s inner core. It spins. And for years, scientists thought it was spinning a little faster than the rest of the planet.

But now, they’ve found something strange. The core isn’t speeding ahead anymore. In fact, it’s slowing down.

Like… noticeably. Well, not to you and me. We won’t probably feel it. But it’s enough to show up in 30 years’ worth of earthquake data.

How do we know Earth is spinning slower

Every time there’s a big earthquake, the ground shakes, and those vibrations shoot straight through the planet. Scientists record them using seismograms, which are like the planet’s own medical scans.

A group of researchers at the University of Southern California, led by John Vidale, studied over 100 of these earthquakes—some of them happening in the exact same place again and again, like echoes. The patterns in the seismic waves revealed that the inner core is now rotating more slowly than Earth’s outer layers.

That means the core that was once a little ahead of us, is now a little behind. They call this “backtracking.” And it’s not just a fluke. It’s been happening since around 2010.

The study was published in Nature, and while the shift won’t change our clocks or throw off our calendars, it could technically make our days just a tiny bit longer. A few milliseconds. Almost nothing. But still—that’s wild.

Why is it happening?

No one’s totally sure, yet.

It could be the outer core—the molten metal layer that wraps around the inner core—shifting in some way and dragging the core’s spin.

It could be the mantle, the massive rocky layer above it, pulling at the core through gravity.

And it could also be both. Or something else entirely. That’s the thing about studying the center of the planet. You can’t exactly drill into it. You have to read the signs, follow the waves, guess with math, and wait for the next earthquake.

It doesn’t mean that we won’t get the answer but it will take time.

The core might be more different than we think

The deeper scientists look, the stranger the inner core seems.

It might not be perfectly round, as many thought at first. It might be a little soft. It might even wobble off-center. Some scientists think there’s a second, deeper innermost core inside it—a core within the core.

And it’s all just… happening. Constantly. Right under us. While we drive to work, take naps, scroll our phones, plan our weekends, Earth is turning, the core is slowing, and none of us feel a thing.

“The dance of the inner core might be even more lively than we know.” That is how John Vidale put it.

But it matters. And that’s why scientists have been on it for so long and will continue to be. It has taken years to get to this conclusion, but technology is developing quite faster now than 10 years ago, and the next conclusion may arrive closer than we think.

For the moment, don’t panic; the shift won’t change your day (although some of us will like the day to be longer). This just reminds us that the planet is alive. Not just geologically—emotionally, metaphorically. It’s full of motion and mystery.