Something deep within the Earth is "stretching" the length of the day.

(NLĐO) - "Underground forces" are constantly stretching or shrinking the length of a day on Earth according to different cycles.

A new study from the Swiss Federal Institute of Technology (ETH Zürich) indicates that something hidden in the Earth's core is altering the length of the day.

Scientists have long pointed out that a day is not actually 24 hours long, but is constantly stretched and contracted by various "hidden forces," and they have identified three cycles.

Something deep inside the Earth, right at the boundary between the core and the mantle, is stretching or shrinking the length of the day - AI illustration: Thu Anh

According to Science Alert, the first fluctuation is an increase/decrease of approximately 1.72 milliseconds per century, due to a combination of the bulging of the Earth's crust as the thick ice layer that compressed it since ancient times thins, plus the influence of the Moon.

On a decade-by-decade scale, 2-3 millisecond oscillations are associated with large-scale flows in the Earth's liquid core.

But there is another fluctuation of about 3-4 milliseconds each day, and its cause remains a mystery.

The timing of the fluctuations coincides with movement at the core-mantle boundary. Therefore, the Swiss research team developed a model combining "artificial neural network" technology with paleomagnetic measurements on ancient rocks, as well as modern magnetic field measurements.

They also used available documentation on the Earth's rotation based on data from solar eclipses and lunar eclipses—when the Moon obscures a planet or star from Earth's view—dating back to 720 BC.

The results show that the impact of changes in Earth's ice and water mass is much smaller than previously thought.

Furthermore, the fluctuations on the millennium timescale are consistent with a simplified model of the magnetohydrodynamics of the Earth's outer core.

Generally speaking, this means there is a "third force" existing in the boundary region between the Earth's core and mantle.

Writing in Geophysical Research Letters , the researchers said they couldn't yet definitively prove what it was, but the results highlight the importance of internal planetary geodynamics for the day cycle.

To find the ultimate answer, the existing model of the Earth's core needs to be improved.

Source: https://nld.com.vn/thu-gi-do-trong-long-trai-dat-dang-keo-gian-do-dai-ngay-196241223095511686.htm