Our planet is a dynamic object susceptible to many changes. For example, as early as 2020, a team of researchers warned that the Earth’s magnetic field was weakening. These changes are not limited only to magnetism, which apart from weakening, changes polarity periodically every 400,000 years approximately, but they can also affect the orbit of the planet as described by the so-called Milankovich cycles. And it is that according to the theory of this Serbian scientist named Milutin, the variations in the Earth’s orbit would be responsible for the succession between the glacial and interglacial periods in which the geological history of our planet is divided.
Regarding this great variability, and due to a qualitative increase in the ability of human beings to measure the constants that govern our world, in recent years a new question has arisen: is the rotation speed of the Earth uniform? Scientists have long known the answer: the speed of rotation of our planet can vary, and it has done so during the 4,500 million years that it has been orbiting around the Sun. In fact, it is known that there was a time on our planet, about 1,400 million years ago, when a day on Earth lasted only about 19 hours .
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However, thanks to the great precision of atomic clocks, in recent years researchers are coming across some puzzling facts. So, just a few weeks ago, on July 19, 2022, scientists recorded what was the shortest day on Earth since measurements began to be taken in this regard, in the 1960s.
Anyone who has ever played with a spinning top, repeón or spinning top, will have been able to observe how its speed varies in small proportions as it rotates on a surface with an irregular texture in which friction changes occur. As in this case, the Earth and its rotation are subject to the laws of physics, and in this sense, despite the record figure for the month of July, the truth is that during the last million years the Earth has been slowing down due to the friction generated by the gravity of the Moon and the generation of the tides.
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However, phenomena are also taking place in the opposite direction. As explained by the Director of the Australian Center for Excellence in Antarctic Sciences at the University of Tasmania, Matt King, and the professor at the School of Geography, Planning and Space Science at the same University, Christopher Watson, in an article published in The Conversation, “when the last ice age ended, the melting of the polar ice caps lowered surface pressure and the Earth’s mantle began to move steadily toward the poles”. This produced that during the last 20,000 years the Earth has accelerated. “Just like a ballet dancer spins faster when he brings his arms in toward his body, the axis around which he spins, our planet’s spin rate increases as this mantle mass approaches Earth’s axis. . And this process shortens the days by about 0.6 milliseconds every century.”
Other factors, such as earthquakes, eruptions like the Tonga Volcano, or weather, can also affect the length of days. “The changes may be due to an effect called chandler wobble, whereby the Earth’s axis of rotation changes in periods of 430 days.” However, King and Watson argue that the length of days on Earth is actually increasing, something for which they still have no explanation, so that scientists postulate that the most plausible is that nothing specific has changed in or around the Earth, and that the phenomenon could simply be due to long-term tidal effects that we mentioned a few lines ago, which work in parallel with other periodic processes to produce a temporary change in the rate of rotation of the Earth.
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