The Earth recorded the shortest day in its history: what is this phenomenon due to?

The truth is you’re right, although yeseitherbe halfway.

But before you look at your calendar, to see if this was one of those days that “got too short”, try to guess how short it was.

It was not for hours, not for minutes, and not for seconds.

According to, a resource website for measuring time and time zones, the earth lasted 1,59 milliseconds less to rotate on its own axis on June 29.

Or better, June 29 lasted 1.59 milliseconds less than 24 hours.

To give you an idea, the blink of an eye lasts 300 milliseconds. In other words, the time he lost that day is the equivalent of just over 300ths of a blink, and can only be perceived with very precise instruments.

Do you see why you are right, but only half right?

But why would the rotation of the Earth be accelerated?

And, if we are seeing shorter and shorter days, does that mean that it can be accelerated more?

amazing precision

The length of days on Earth is measured by rotational motion, or how long it takes for the planet to rotate on its own axis.

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The Earth completes its rotation – one turn around its own axis – in 24 hours.

And thanks to the atomic clockswe can measure those days with a precision that we could not have otherwise.

An Earth day -or a period of rotation- should theoretically take 86,400 seconds, which are the seconds in 1,440 minutes or 24 hours.

But since the year 2020, things have been strange.

The Land of Desire

Until 2020, the “shortest” day on record had occurred on July 5, 2005, with a duration of 1.0516 milliseconds less than 24 hours.

fast spinning globe

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What does it mean that the Earth is spinning faster?

But in 2020, Earth reported the shortest 28 days on record since atomic clocks began to be used in the 1960s.

On July 19 of that year, the planet broke the record it had set in 2005, recording a day 1.47 milliseconds shorter than normal.

The new record, June 29 this year, is 1.59 milliseconds shorter than normal.

But it is something that scientists believe is not a cause for concern.

periodic variations

“We think this has been going on for millions of years. But with very small variations,” Graham Jones, Time and Date astrophysicist, told BBC Mundo.

And Christian Bizouard of the Paris Observatory of the IERS Earth Orientation Center added that the acceleration trend we see today started in the 1990s.

“After an interruption in 2004, with a small slowdown, the acceleration was restored in 2016”, details Bizouard.

But scientists are not sure how long this acceleration will last. “At some point, things will slow down again,” Jones said.

Why is the Earth “rushing”?

“On time scales of decades (between 10 and 100 years), the length of the days presents irregular variations,” Bizouard told BBC Mundo.

Scientists agree that these changes are caused by the interaction of factors such as the activity of the planet’s molten core or the movement of the oceans and the atmosphere.

But in reality the origin of these variations is not understood, says Bizouard.

Jones also acknowledges that experts don’t know “exactly why the Earth speeds up or slows down over long periods of time.”

But, in general, for Jones “it is surprising how precise the Earth is as a ‘stopwatch'”, since “it only misses a few milliseconds”.

What would happen if the Earth went further back or forward?

Even small, changes in Earth’s timing can add up over the years and cause our clocks to gain or lose a second.

core of the earth

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Factors such as the activity of the Earth’s core, oceans, and atmosphere influence the length of days on Earth.

To solve the mismatch, scientists have used the so-called “leap second” since 1973, which can be positive or negative.

That is, this second can be added to our clocks when the Earth is slow, or it can be taken away when the planet finishes its rotations in less time than normal.

Since 1973, the IERS has added 27 leap seconds to the official time of Earth clocks.

“If the shorter days continue, at some point we might need a negative leap second, that is, take a second off our clocks to fit with the faster rotation of the Earth,” says Jones.

“But we may or may not need it. We don’t know if it’s going to happen because we don’t know how long this trend is going to last or if it’s going to last,” she adds.

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