Jakarta – The Earth rotates on its axis, completing this cycle in roughly 24 hours. But did you know that Earth’s rotation isn’t always consistent and precise? Is it true that Earth’s rotation is actually less than 24 hours?
Typically, Earth’s rotation creates the day-night cycle. However, this rotation isn’t exactly 24 hours but rather 23 hours and 56 minutes.
Fluctuations in the length of Earth’s day have piqued the curiosity of scientists, who are keen to uncover the factors behind these variations.
Influence of Earth’s Core
Researchers from ETH Zürich in Switzerland recently identified another factor causing minor changes in Earth’s rotation: the Earth’s core.
A study titled “Length of Day Variations Explained in a Bayesian Framework,” published in Advancing Earth and Space Sciences on November 26, 2024, by Mostafa Kiani Shahvandi and colleagues, reveals that Earth experiences various fluctuations in its daily cycle.
Geophysicist Mostafa Kiani Shahvandi explains that these fluctuations occur because Earth orbits the Sun at a high velocity of about 107,000 kilometers per hour.
This speed, combined with gravitational forces, causes variations in Earth’s daily rotational duration.
The study employed theoretical modeling and observations to measure these fluctuations, considering factors like ice volume changes, water mass distribution, and the elastic properties of Earth’s crust.
Researchers used neural network technology (a type of artificial intelligence) combined with magnetic field data for accuracy. They also referenced earlier studies that provided a comprehensive history of Earth’s rotation using data from lunar eclipses and occultations dating back to 720 BCE.
The findings indicate that the impact of shifting ice and water masses on Earth is smaller than previously estimated. Moreover, fluctuations over millennial timescales align with simplified magnetohydrodynamic models of the Earth’s fluid outer core.
The research highlights that variations in Earth’s daily rotation stem from multiple factors, including the Moon’s gravitational pull, slow elastic movements of Earth’s crust, and changes in water volume affecting mass distribution and rotation.
The study also discovered fluctuations caused by large-scale flows within Earth’s fluid core, which occur over decades, resulting in changes of two to three milliseconds. Additionally, fluctuations of about three to four milliseconds every thousand years were identified.
Causes of Long-Term Fluctuations Remain Unclear
Thus, Earth’s rotation inconsistency is partly due to minor changes in its core, especially over decadal scales.
However, the causes of long-term fluctuations remain elusive, though their periodicity appears more consistent compared to those influenced by the core or other factors.
“Our findings emphasize the importance of internal geodynamics in long-term day-length fluctuations, particularly due to fluid motion in Earth’s outer core,” Shahvandi said, as quoted by Science Alert.
“However, with current gaps, including the lack of comprehensive physical models accounting for various core dynamics components, there’s a strong motivation to improve existing Earth core models,” he added.