Recently, scientists revealed that the Earth’s rotation tended to accelerate, for an as yet unexplained reason. And for good reason, the axis around which our planet rotates is not fixed and is governed by many factors. However, according to a new scientific article, published in the journal Global and planetary change in September 2022 and spotted by our colleagues at Futura, it would appear that extreme climatic and geodynamic events may have, according to the conclusions, an influence on the forces that govern the rotation and orbit of the Earth.
Precession, a change in the Earth’s axis of rotation under the influence of the Moon and the Sun
To understand how researchers arrived at this hypothesis, we first need to look at what precession is: it is one of the factors that varies the amount of sunlight received by the Earth’s surface. It is therefore a fundamental parameter, as it is partly responsible for the Milankovitch cycles, these changes in orbital characteristics that affect a planet’s climate for hundreds of thousands of years. These cycles are now believed to have rocked the Earth between ice ages and warmer (interglacial) periods.
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Understanding the evolution of precession would allow us to better determine the climatic changes that have occurred over the centuries (and vice versa). However, this is a variable parameter, depending on the forces of attraction of the Moon and the Sun on the Earth, just like the tides. It is therefore unknown over 10 million years. In an effort to understand the different variations, the scientists examined the information contained in the ancient sedimentary deposits. Because the latter still bear the traces of the cyclical fluctuations linked to the climate, like a sort of “natural archive”.
Disturbed tides, changed precession
They then analyzed sediment samples from the early Eocene (55.8 to 40.9 million years). By studying Milankovitch cycles, they were able to calculate “precession rates”, which they compared with theoretical astronomical models. However, if the values seem to agree for the age of 42.5 million years, they diverge for that of 55 million. The experts therefore concluded that some parameters capable of affecting the precession of the Earth’s axis should not have been taken into account in the theoretical models. So they looked at what was happening on our planet at the time.
Because 55 million years ago, our habitat was marked by great upheavals: temperatures were very high and there were no polar caps (optimal climate). Also in this period, India and Asia collide (plate tectonics), while the expansion of the ocean floor is accelerating, says Futura. A global situation that, according to the authors of the study, could have affected the phenomenon of the tides, whose effects would have been weaker than predicted by theoretical models. All this could finally affect the famous precession rate.
The results presented in this study therefore suggest that terrestrial dynamics, be they climate change or tectonic changes (such as the movement of continents), could have some influence on precession. And so, on the rotational motion of the Earth.
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