Um segundo a menos, e não a mais...

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For the entire history of precise timekeeping, we have only ever added time to our clocks. Now, for the first time, we may have to take a second away.

The reason is strange and a little unsettling. Earth is spinning faster than it used to. Our planet has never been a perfect clock. Its rotation naturally wobbles, and for decades the long term trend was a gradual slowing, mostly caused by the Moon's tidal pull. To keep our atomic clocks in sync with the actual turning of the planet, timekeepers occasionally added a leap second. Between the 1970s and 2016, they did this 27 times.

Then something flipped. Around 2016 to 2018, scientists noticed Earth had quietly started speeding up. Movements deep in the planet's molten core appear to be the main driver, subtly changing how fast the whole world turns. The days are now occasionally coming in a hair shorter than 24 hours, by a millisecond or two.

If this continues, our clocks will drift slightly ahead of the planet, and to correct it timekeepers would need to remove a second rather than add one. This is called a negative leap second, and it has never been done. Current estimates point to around 2029 as the possible moment.

There is a fascinating climate twist buried in this. The rapid melting of polar ice is shifting mass from the poles toward the equator, which actually slows the spin a touch, like a skater extending their arms. Researchers calculate that without that ice melt, we might have needed this adjustment as early as 2026. Human driven warming is, in a small way, tugging on the length of our day.

Not everyone agrees it will happen, since the core's behavior is unpredictable. And the effect is tiny for daily life. But for the computers that run banking, power grids, and the internet, subtracting a second is genuinely tricky, because software was only ever built to add.

If Earth can speed up and slow down beneath our feet without us feeling a thing, how much of the world do you think is quietly shifting that we never notice?

Source: Nature, Duncan Agnew, Scripps Institution of Oceanograph