Although scientists assert that the length of the day is increasing, they have not discovered a clear cause for the phenomena. The observation was unexpected because June 2022 marked the shortest day in almost 50 years. The days were intended to get shorter as time went on due to the acceleration of the Earth's rotation around its axis in recent decades. Scientists noticed a continuous increase in day length beginning in 2020, indicating that the trend appears to have reversed once more.
The Earth's rotation around its axis, which defines how long a day is and has been steadily lengthening over the past few decades, has been accelerating, although the cause of this is yet unknown. Atomic clocks and exact astronomical measurements have shown that days are suddenly growing longer, but scientists are unsure of the cause.
This has a significant impact on our ability to keep accurate time as well as other modern technologies like GPS. The length of a day is determined by the Earth's rotation around its axis, which has been accelerating during the past few decades. Our days have been getting shorter due to this tendency; in fact, in June 2022, we established a record for the shortest day in the last 50 years or so.
Despite this achievement, the continuous acceleration has strangely slowed down after 2020; the cause of this is yet unknown. Days are once again growing longer.
The time it takes for Earth to complete one spin varies very slightly, despite the fact that the clocks on our phones show there are exactly 24 hours in a day. Even earthquakes and storm events can contribute to these changes, which can take place over timescales ranging from millions of years to virtually quickly.
It turns out that a day rarely has exactly 86,400 seconds.
Earth's rotation has slowed down over millions of years as a result of friction brought on by the Moon's tides. Each day is lengthened by this mechanism by around 2.3 milliseconds every century. A day on Earth was just approximately 19 hours long a few billion years ago.
Another process, which has been operating in the opposite direction for the last 20,000 years, has sped up the rotation of the Earth. Earth's mantle began gradually sliding toward the poles as the last ice age ended as a result of the polar ice sheets melting, which decreased surface pressure.
Our planet's spin rate increases when this mass of mantle moves closer to Earth's axis, just as a ballet dancer spins faster when they draw their arms toward their body — the axis around which they spin. And over the course of a century, this technique cuts each day by around 0.6 milliseconds.
The relationship between the interior and surface of the Earth is also important over decades and longer. The duration of the day can be altered by powerful earthquakes, but usually only slightly. For instance, the magnitude 8.9 Great Thoku Earthquake in Japan in 2011 is thought to have accelerated Earth's rotation by only 1.8 microseconds.
In addition to these significant shifts on a larger scale, weather and climate also have significant effects on Earth's rotation over shorter timescales, resulting in changes in both directions.
The duration of the day can shift by up to a millisecond in either direction as a result of the biweekly and monthly tidal cycles, which move mass around the planet. In length-of-day records for durations as long as 18.6 years, we can observe tidal changes. A significant influence comes from the motion of our atmosphere, and ocean currents also have an impact. Additional changes result from seasonal snow cover, rainfall, or groundwater extraction.
Why is Earth suddenly slowing down?
We have had extremely accurate estimates of Earth's rate of rotation since the 1960s when operators of radio telescopes around the planet began to develop methods to simultaneously examine cosmic objects like quasars.
These estimates and an atomic clock were compared, and the results showed that the length of the day had been decreasing recently.
Once we eliminate the rotation speed variations caused by the tides and seasonal impacts, a startling revelation emerges. Despite the fact that Earth's shortest day will occur on June 29 of 2022, the long-term trend appears to have changed since 2020 from shortening to extending. Over the past 50 years, there has never been a change like this.
It's unclear why this alteration occurred. Even though back-to-back La Nia incidents have happened before, it might be caused by weather system changes. Although the ice sheets' steady rate of melting hasn't changed significantly in recent years, there's a chance that it has risen. Could it be connected to the massive Tonga volcanic explosion that released a great deal of water into the atmosphere? Given that it happened in January 2022, probably not.
The "Chandler wobble," a little variation in the Earth's rotating axis with a period of around 430 days, is thought by scientists to be responsible for the planet's recent, enigmatic change in rotational speed. The wobble has decreased recently, and radio telescope observations reveal that it has as well; the two may be related.
The option that nothing specific has changed on or around Earth is the final one we consider likely. It may simply be that periodic processes and long-term tidal effects are interacting to temporarily alter the Earth's rotation rate.
Numerous applications require a precise grasp of the Earth's rotation rate; without it, navigation systems like GPS would not function. Additionally, to keep our official timelines in step with our globe, timekeepers add leap seconds every few years.
We may need to adopt a "negative leap second" if Earth were to change to even longer days; this would be unprecedented and might crash the internet.
The requirement for negative leap seconds is now thought to be rare. We may now rejoice in the knowledge that we all have a few extra milliseconds each day, at least for the time being.
This article has been directly published from a wire service feed without any text changes. The only change is to the headline.
What does the unexpected acceleration of Earth's rotation mean for us?
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