Amid all the hustle and bustle of modern life, it may seem that time often “flies”. However, it turns out that this is the case after the Earth recorded the shortest day since the record began in June.
And the 1.59 milliseconds of normal 24-hour rotation on June 29 makes it more likely that a negative leap second will keep the clock aligned—for the first time in history, the global clock has been sped up.
Why is the Earth spinning faster than usual?
Scientists argue that climate change, seismic activity and ocean circulation, as well as the attraction of the Moon and the so-called “Chandler and Bob attraction” – a change in the rotation of the Earth around its axis, can be the cause.
“Chandler and Bobble”
It is defined as the oscillatory motion that occurs when the Earth rotates around its axis. It works like a spinning top vibrates when it slows down.
However, the rotation has become less variable in recent years, which scientists believe may be due to the Earth’s faster rotation, resulting in shorter days.
“The Chandler wobble is a component of the Earth’s instantaneous axial rotational motion, called polar motion, which changes the position of the point on the globe where the axis intersects with the Earth’s surface,” said Dr. Leonid Zotov of the Sternberg Institute. Astronomy, Moscow.
The amplitude of natural vibration is about four meters at the Earth’s surface, but from 2017 to 2020 it disappeared.
And this historical minimum was fully reached with the beginning of the reduction in the length of the day.
However, there are not many explanations for the lack of volatility.
“It’s definitely strange,” said Matt King, a professor at the University of Tasmania who specializes in earth observation. “Obviously something has changed that we haven’t seen since the advent of precision radio astronomy in the 1970s.” “
Changing of the climate
Global warming is also affecting the melting of ice and snow at a faster rate.
Research has shown that as glaciers melt—as a result of atmospheric temperatures rising from the burning of fossil fuels—the redistribution of mass causes the Earth to rotate and rotate around its axis faster.
This is because hundreds of billions of tons of ice are lost to the oceans each year, causing the North and South Poles to move eastward since the mid-1990s.
Previously, only natural factors, such as ocean currents and convection of hot rocks deep underground, contributed to the divergence of the poles.
But since 1980, the location of the poles has shifted 13 feet (4 meters). The Earth’s axis of rotation – an imaginary line passing through the north and south poles – is always moving due to processes that scientists do not fully understand.
But the way water is distributed over the Earth’s surface is one of the factors that causes the axis to shift, and therefore the poles. One example is the melting of the Greenland Glacier as temperatures rise throughout the 20th century.
In fact, about 7,500 gigatonnes of Greenland ice melted into the ocean during this time period. This makes it one of the most important factors in the transfer of mass to the oceans, which causes sea levels to rise and, in turn, destroys the Earth’s axis of rotation.
And while ice melt occurs elsewhere (such as Antarctica), Greenland’s location makes it a more important factor in the movement of the poles, explains NASA’s Eric Evins.
And there is a geometric effect: if you have a mass 45 degrees from the North Pole, i.e. from Greenland, or from the South Pole (like glaciers in Patagonia), this will have a greater effect on the displacement of the Earth’s axis of rotation than the mass.
But if a change in the distribution of water masses and rising sea levels could lead to an acceleration of the Earth’s rotation, then what could have the opposite effect?
NASA says strong winds during El Niño years could slow the planet’s rotation, lengthening the day by milliseconds.
In any case, the impact of climate change on the rotation of the Earth among the scientific community remains relatively small.
Earthquakes and other seismic events can affect our planet’s rotation speed. That’s because it can also move mass towards the center of the Earth – similar to how a spinning person pulls his arms inward – and thus shifts his weight back.
For example, the 2004 Indian Ocean tsunami earthquake moved rocks enough to shorten the length of the day by about three microseconds.
The strong earthquakes in Chile in 2010 and Japan in 2011 also increased the rate of rotation of the Earth and thus shortened the length of the day.
The rotation of the ocean and the pressure on the sea floor also pull the earth’s axis.
In November 2009, events in the Southern Ocean caused the Earth to rotate slightly faster, cutting half of the days of the month off by 0.1 milliseconds each.
And it turned out that the powerful ocean current encircling the continent is to blame for this – the Antarctic current encircling the poles.
Experts from the NASA Jet Propulsion Laboratory (JPL) in California and the Institute of Geophysics in Paris in France noted that it slowed down sharply on November 8, 2009, and accelerated two weeks later.
Then accurate day length data showed that the changes immediately caused the Earth to rotate faster, shortening each day by 0.1 milliseconds before the day length returned to normal on November 20 of that year, in line with the current one.
Mystery at the Earth’s Core
Some experts believe that the explanation lies within the Earth itself, and there is a possibility that something is happening in the core and mantle of the planet.
The speed of rotation of our planet around its axis has changed throughout history. 1.4 billion years ago, a day was less than 19 hours compared to 24 hours today.
Thus, on average, Earth’s days are getting longer, not shorter, by about 74,000 milliseconds per year.
But now the planet is spinning faster than half a century ago.
Sometimes the speed of rotation changes slightly, which affects the universal timekeeper – an atomic clock requiring the addition of leap seconds. Or in the latter case, a negative leap second is likely to occur.
Since the 1970s, a total of 27 leap seconds has been required to maintain the accuracy of atomic time.
The latest happened on New Year’s Eve 2016, when the clock stopped for a second so the Earth could catch up.
But as of 2020, this phenomenon has reversed; The previous fastest day, July 19 of that year, was 1.47 milliseconds shorter than 24 hours.
The change cannot be detected by humans, but it could affect satellites and navigation systems.
Each day on Earth consists of 86,400 seconds, but the rotation is uneven, meaning that over the course of a year, each day contains a fraction of a second more or less. Atomic clocks are very precise and measure time by the movement of electrons in atoms cooled to absolute zero. The International Earth Rotation Service in Paris is responsible for tracking the speed of the Earth’s rotation, and it does this by sending lasers to satellites and using them to measure their motion.
Source: Daily Mail