You probably don’t feel it while you’re sipping your morning coffee or stuck in gridlock on the way to work, but the ground beneath your feet is technically screaming along at about 1,000 miles per hour at the equator. It feels solid. It feels permanent. But the reality is that planet earth turns slowly compared to its own history, and it’s getting even slower with every passing century.
It’s a bit weird to think about.
We measure our lives in 24-hour cycles because that’s the rhythm we were born into, yet that rhythm is actually a long-term fluke of celestial mechanics. If you could hop in a time machine and head back to the Precambrian era, about 1.4 billion years ago, your day would be over in just 18 hours. You’d be constantly resetting your watch. The Earth has been pulling a long, slow brake job for billions of years, and honestly, the reasons why are both fascinating and a little bit haunting.
The Moon is Stealing Our Momentum
The biggest culprit in this planetary slowdown is that glowing rock in the sky. We love the moon for the tides and the romantic lighting, but it’s essentially a gravitational vampire.
Through a process called tidal friction, the moon’s gravity pulls on Earth’s oceans, creating a "tidal bulge." Because the Earth rotates faster than the moon orbits us, this bulge actually sits slightly ahead of the moon’s position. This creates a constant tug-of-war. The moon pulls back on that bulge, which acts like a literal brake on the Earth’s rotation. It’s tiny. We’re talking about the length of a day increasing by roughly 1.8 milliseconds every century.
That sounds like nothing, right?
But over geological time, those milliseconds stack up like loose change in a jar. Research led by Stephen Meyers at the University of Wisconsin-Madison has shown that this "milankovitch cycle" interaction is a primary driver of how our planet’s orientation and rotation have shifted over deep time. As the Earth loses its rotational energy, that energy has to go somewhere. Physics doesn't just let it vanish. Instead, it gets pushed into the moon’s orbit, which is why the moon is slowly drifting away from us at a rate of about 1.5 inches per year.
We’re losing speed, and we’re losing our neighbor.
When Planet Earth Turns Slowly, Everything Changes
It’s easy to dismiss a few milliseconds as a "science person problem," but the physical consequences of a slowing Earth are actually baked into our infrastructure and our biology.
Take the leap second, for instance.
Since the 1970s, the International Earth Rotation and Reference Systems Service (IERS) has had to manually add seconds to our atomic clocks to keep them in sync with the Earth’s actual rotation. Our computers are incredibly precise, but the planet is "wobbly" and unpredictable. If we didn't add these seconds, our GPS systems would eventually start spitting out wrong directions, and financial markets—which rely on nanosecond precision—would descend into absolute chaos.
Interestingly, there has been a recent debate among scientists because, for a brief window around 2020-2022, the Earth actually sped up slightly. It was a weird anomaly. Some researchers pointed to changes in the Earth’s core or the "Chandler wobble," which is a small deviation in the Earth's axis of rotation. But even with those short-term hiccups, the long-term trend remains undeniable: the planet earth turns slowly and will continue to do so until the sun eventually expands and consumes us both.
The Impact on Earth's Shape
Earth isn't a perfect sphere. It’s an "oblate spheroid." Basically, it’s got a bit of a belly at the equator because the centrifugal force of its rotation flings the mass outward.
As the rotation slows down, that force weakens. Over millions of years, the planet will technically become more "round" as the equatorial bulge subsides. This has massive implications for the oceans. If the Earth stopped spinning entirely (which won't happen for billions of years, so don't panic), the water currently held at the equator by centrifugal force would migrate toward the poles. You’d end up with two massive polar oceans and a giant ring of dry land around the middle.
Glaciers, Earthquakes, and the Core
Believe it or not, climate change is actually messing with how fast the Earth spins, too.
As polar ice caps melt, the water is redistributed from the poles toward the equator. Think of a figure skater spinning in a circle. When they pull their arms in, they spin faster. When they throw their arms out, they slow down. By moving mass from the poles (the "axis") toward the equator (the "arms"), we are effectively slowing the planet down even further.
Geophysicists like Jerry Mitrovica at Harvard have spent years modeling how "glacial isostatic adjustment"—the way the crust bounces back after ice melts—affects rotation. It’s a feedback loop.
- Melting ice changes the planet's mass distribution.
- This shifts the axis slightly.
- The rotation rate reacts to the shift.
- The planet earth turns slowly as a direct result of these surface-level changes.
Some studies even suggest a link between the Earth’s rotation speed and seismic activity. A 2017 study by Roger Bilham and Rebecca Bendick hypothesized that even slight decreases in rotation speed could trigger more intense earthquakes. The idea is that as the Earth’s shape slightly adjusts to a slower spin, the tectonic plates feel the squeeze. While this remains a debated topic in the geophysics community, it highlights just how interconnected the planet's "clock" is with its physical stability.
A History Written in Coral and Mud
How do we even know all this? We didn't have atomic clocks a billion years ago.
The evidence is actually hidden in the fossil record. Certain types of coral, like those from the Devonian period (about 400 million years ago), grow in daily and annual layers, much like tree rings. By counting these microscopic lines, paleontologists discovered that back then, there were about 410 days in a year.
Since the time it takes for Earth to go around the sun doesn't really change, the only way to have 410 days in a year is if the days themselves were shorter—about 21 hours long.
We can see the same thing in "tidal rhythmites," which are sedimentary rocks that preserve the ebb and flow of ancient tides. These rocks act like a prehistoric tape recorder, confirming that the moon was closer and the Earth was spinning like a top in the distant past. It’s a sobering thought: the very definition of a "day" is a sliding scale.
Why We Can't Just Ignore the Slowdown
For the average person, the fact that planet earth turns slowly is a trivia fact. For the tech industry, it’s a nightmare.
In 2012, a leap second caused Reddit, Gawker, and Qantas Airways to experience massive server crashes. Computers hate it when time doesn't move in a straight, predictable line. Because of this, many tech giants like Meta and Google are pushing to abolish the leap second entirely, preferring to let our clocks drift slightly rather than risk crashing the internet. In late 2022, international timekeepers actually voted to stop adding leap seconds by 2035.
We are literally choosing to let our "clock time" stay wrong because the planet’s "natural time" is too inconvenient for our software.
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Actionable Insights for the Chronologically Curious
While you can't speed the planet back up, understanding this phenomenon changes how you look at our place in the universe. Here is what you should keep in mind about our slowing world:
Accept the Drift
Recognize that our 24-hour day is a social construct based on a temporary planetary state. If you feel like there aren't enough hours in the day, you’re technically right—but you’re also lucky you didn't live in the 18-hour-day era of the Precambrian.
Watch the Tech Shifts
Keep an eye on news regarding "Universal Coordinated Time" (UTC). Between now and 2035, the way your devices handle time is going to change as we phase out leap seconds. This might cause minor glitches in older hardware, so keep your systems updated.
Support Climate Science
Since mass redistribution from melting glaciers is a contributing factor to rotational changes, supporting polar conservation is, in a very literal sense, helping to stabilize the Earth’s "rhythm."
Observe the Moon Differently
Next time you look at a full moon, remember that it is actively pushing us away. It is the primary reason the planet earth turns slowly. That silver orb is a gravitational brake that has shaped the history of life by giving us longer, cooler days and more stable environments.
The Earth will keep slowing down. Eventually, millions of years from now, a day might last 25 or 26 hours. We won't be around to see it, but the record of our 24-hour world will be written in the rocks and corals for whatever comes next to find. It’s a reminder that nothing, not even the rotation of a planet, is truly permanent.