As a member of the vast universe, the earth, whether revolving or rotating, will be affected by interstellar forces and will be adjusted in constant acceleration and deceleration. At present, the acceleration of the earth's rotation means that the days are getting shorter and shorter. ? Professional data show that time has passed faster than at any time in the past half century. This is because the earth's rotation speed is the fastest in 50 years. ? Dou Zhong, secretary of the Party Committee of the National Time Service Center of the Chinese Academy of Sciences and a popular science expert, said that relevant scientific research found that the earth's rotation rate was accelerating from mid-2020. The earth rotates faster than before, which means that the year will pass faster? This starts with the measurement of time. The basic unit of time measurement is seconds, and there are milliseconds, microseconds, nanoseconds and so on.

Nowadays, the high-precision atomic clock used to measure time has reached the attosecond level, which is 10 minus 18 seconds. In short, it is very short and the human body can't feel it. The high-precision atomic clock has been recording the length of each day with ultra-high precision since the 1960s. By observing the atomic clock, the researchers found that in the past 50 years, it took only 24 hours for the earth to complete one rotation, which is 86,400 seconds. Today, the time per day is only 86,400 seconds. According to British media reports recently, researchers found that July 19, 2020 was shortened by 1.4602 milliseconds, which was the shortest day ever. Although this subtle difference is not fundamentally reflected in people's daily life, it will have a great impact in the fields of communication, electricity and navigation.

So, what is the reason for the rapid change of the earth? This may be related to the change of surface morphology. Just like a figure skater or ballet dancer, the faster the body rotates, the more concentrated it becomes. The more matter is concentrated in the center, the faster the earth turns. Take global warming as an example. When glaciers and ice sheets melt and flow into the ocean, the mass of the earth is redistributed and the matter is closer to the center of the earth than before, then the rotation of the earth will accelerate. A team from tokyo institute of technology, Japan, published a paper in the American journal Science, saying that minerals in the deep mantle have higher conductivity than other parts of the lower mantle, which may be an important reason for the periodic change of the earth's rotation rate. The rotation time of the earth is 23 hours and 56 minutes, about once every 10 year, and the rotation period will increase or decrease by three thousandths to four thousandths of a second. But scientists still don't know why the rotation period changes like this.

There is a mineral layer about 200 kilometers thick in the deepest part of the mantle near the core. They named this mineral post-perovskite. In the study, the researchers simulated the post-perovskite environment in the laboratory, that is, about 6.5438+0.3 million standard atmospheric pressure and 2,500 degrees Celsius, and measured the conductivity of the post-perovskite in this state. They found that the conductivity of the post-perovskite layer is 10 to 1000 times that of the rest of the lower mantle. Researchers believe that the current flowing through the perovskite layer is very strong, which strengthens the electromagnetic coupling between the solid mantle and the liquid outer core, resulting in periodic slight changes in the earth's rotation.