Buzz
And the reason for this remains an enigma.
According to scientific observations, backed by precise astronomical observations and atomic clocks, it's been noted that the length of a day has suddenly extended. And notably, scientists are yet to discern why!
This has significant implications for technologies like GPS and other precise systems that govern our modern lives.
Source: NASA / JPL-Caltech
WHAT EXACTLY IS THE ISSUE?
Earth's rotation around its axis has been accelerating over the past few decades. As this determines the length of a day, this trend has made our days shorter. In fact, on June 29, 2022, Earth set a record for the shortest day since humans began using atomic clocks to measure the planet's rotation speed - On that Wednesday, a day was 1.59 milliseconds shorter than 86,400 seconds, or 24 hours.
However, despite this record, since 2020, that stable pace has strangely shifted to deceleration. Days are now getting longer, and the reason remains a mystery. This change is unprecedented in the last 50 years.
Accurate measurements show that Earth's rotation has mysteriously slowed down since 2020, making days longer. Image: Scitechdaily
Although our phone clocks tell us there are precisely 24 hours in a day, the actual time for Earth to complete one rotation may vary slightly. These changes sometimes occur over millions of years. This indicates that a day rarely extends exactly to the magical number of 86,400 seconds.
According to scientists, the Earth's rotation speed is not constant, and the blue planet is increasingly slowing down, making the length of a day longer. Estimates suggest that a few billion years ago, an Earth day was only about 19 hours long; about 200 million years ago, a day on Earth was only about 23 hours long. With an average speed of about 0.002 seconds longer every 100 years, it is predicted that in about 200 million years, a day on the blue planet could be 25 hours long. VTV
THE EVER-CHANGING EARTH
Earth's rotation around its axis has slowed down over millions of years due to tidal friction caused by the Moon's influence.
Over the past 20,000 years, another process has been operating in the opposite direction, accelerating Earth's rotation. As the last ice age ended, ice sheets at both poles melted, reducing surface pressure, and Earth's mantle began to shift steadily towards the poles.
Like a ballet dancer, our planet's rotation speed increases as this mantle shifts closer to Earth's axis. This process has shortened each day by about 0.6 milliseconds per century.
Over many decades and longer, the relationship between Earth's core and surface also comes into play. Major earthquakes can alter the length of the day, although usually by small amounts. For example, the large 2011 Tōhoku earthquake in Japan, with a magnitude of 8.9 on the Richter scale, is believed to have increased Earth's rotation speed by an additional 1.8 microseconds.
In addition to these large-scale changes, short-term weather and climate also have significant impacts on Earth's rotation, causing variations in both directions.
Bi-weekly and monthly tidal cycles move masses around the planet, causing changes in the length of the day by up to a thousandth of a second in either direction. We can observe tidal variations in day length records over periods of up to 18.6 years.
Our atmosphere's movement has a particularly strong impact, and ocean currents also play some role. Seasonal snowfall and rainfall, or groundwater extraction, further alter everything.
WHY DOES EARTH SUDDENLY SLOW DOWN?
Since the 1960s, when operators of radio telescopes orbiting Earth began inventing techniques to simultaneously observe celestial objects such as standard stars, we've had very accurate estimates of Earth's rotation speed.
Comparing these measurements with atomic clocks has shown that the length of the day has hardly ever shortened in recent years.
But there's a surprising revelation when we eliminate speed fluctuations we know occur due to tides and seasonal effects. Although Earth reached its shortest day on June 29, 2022, the long-term orbit seems to have shifted from shortening to lengthening since 2020.
The reason for this change is unclear. Scientists have proposed several possibilities:
On June 29, 2022, Earth set a record for the shortest day since humans began using atomic clocks to measure the planet's rotation speed - That day, a Wednesday, was 1.59 milliseconds shorter than 86,400 seconds, or 24 hours. Image: Internet
Firstly, it could be due to changes in the weather system, with consecutive La Niña events, although these events have occurred before. It may increase the melting of ice sheets, although they have not deviated much from their stable melting rate in recent years;
Next, it could be related to the massive volcanic eruption in Tonga pumping a huge amount of water into the atmosphere? Perhaps not, as that occurred in January 2022.
Scientists have speculated that the recent mysterious change in the planet's rotation speed is related to a phenomenon called 'Chandler wobble' - a slight wobble in Earth's axis with a cycle of about 430 days.
Leonid Zotov, a Russian mathematician, believes Earth may be spinning faster due to a cyclic motion called the 'Chandler wobble'. The wobble was first detected in the late 1880s, when American astronomer Seth Carlo Chandler (1846-1913) noticed pole oscillations over a period of 14 months.
This oscillation began to slow down in the early 2000s, reaching its minimum level in history since 2017. And from 2017 to 2020, 'it vanished' - Professor Leonid Zotov noted.
Observations from radio telescopes also show that the oscillation has gradually decreased in recent years.
One final possibility, which scientists consider plausible, is that nothing specific has changed inside or around Earth. It may only be long-term tidal effects operating in parallel with other cyclic processes to temporarily alter Earth's rotation speed.
DO WE NEED A 'LEAP SECOND'?
Accurately understanding Earth's rotation speed is crucial for a range of applications - positioning systems like GPS wouldn't function without it. Additionally, every few years, clocks insert leap seconds into our official time scale to ensure they don't drift out of sync with our planet.
If Earth shifts towards even longer days, we may need to implement a 'leap second' - something unprecedented and potentially wreak havoc on the entire global Internet system!
This leap second is a necessary adjustment to synchronize the world's most accurate atomic clocks with Earth's rotation speed.
However, the need for a leap second is considered unlikely to happen anytime soon. Currently, we can welcome the news that - at least for a while - we all have a few extra milliseconds each day.
Although Earth's rotation speed doesn't change much for our daily lives, it's crucial to monitor it so that atomic clocks can maintain accuracy to coordinate precisely with GPS and Earth observation satellites.
Article sources: Scitech Daily, Business Insider
