Earth Is spinning faster now than it was 50 years ago

Ever feel like there’s just not enough time in the day? Turns out, you might be onto something. Earth is rotating faster than it has in the last half-century, resulting in our days being ever-so-slightly shorter than we’re used to.

Why Earth rotates

Our solar system formed about 4.5 billion years ago, when a dense cloud of interstellar dust and gas collapsed in on itself and began to spin. There are vestiges of this original movement in our planet’s current rotation, thanks to angular momentum 

Thanks to that angular momentum, our planet has been spinning for billions of years and we experience night and day. But it hasn’t always spun at the same rate. Hundreds of millions of years ago, Earth made about 420 rotations in the time it took to orbit the Sun; we can see evidence of how each year was jam-packed with extra days by examining the growth lines on fossil corals.

Although days have gradually grown longer over time, during humanity’s watch, we’ve been holding steady at about 24 hours for a full rotation — which translates to about 365 rotations per trip ’round the Sun. As scientists have improved at observing Earth’s rotation and keeping track of time, however, they've realized that we experience little fluctuations in how long it takes to make a full rotation.

A new way to track time

In the 1950s, scientists developed atomic clocks that kept time based on how electrons in cesium atoms fall from a high-energy, excited state back to their normal ones. Since atomic clocks’ periods are generated by this unchanging atomic behavior, they don’t get thrown off by external changes like temperature shifts the way that traditional clocks can.

Unexpected change

Since the first leap second was added in 1972, scientists have added leap seconds every few years. They’re added irregularly because Earth’s rotation is erratic, with intermittent periods of speeding up and slowing down that interrupt the planet’s millions-of-years-long gradual slowdown.

“The rotation rate of Earth is a complicated business. It has to do with exchange of angular momentum between Earth and the atmosphere and the effects of the ocean and the effect of the moon,” Levine says. “You're not able to predict what's going to happen very far in the future.”

But in the past decade or so, Earth’s rotational slowdown has … well, slowed down. There hasn’t been a leap second added since 2016, and our planet is currently spinning faster than it has in half a century. Scientists aren’t sure why.

The trouble with leap seconds

Depending on how much Earth’s rotations speed up and how long that trend continues, scientists might have to take action. “There is this concern at the moment that if Earth’s rotation rate increases further that we might need to have what's called a negative leap second,” Whibberley says. 

“In other words, instead of inserting an extra second to allow Earth to catch up, we have to take out a second from the atomic timescale to bring it back into state with Earth.”

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