The riddle of the increase in the Earth-Moon distance is solved

Vue d'artiste de la Terre à l'Hadéen. © Dan Durda, Southwest Research Institute

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[EN VIDÉO] The most beautiful lunar eclipses captured on video Lunar eclipses, like solar eclipses, are rare events. Some lucky astronomers or photographers were able to capture some of them on photo or video. Futura has gathered the best images for you. In 1755, the philosopher Immanuel Kant published a remarkable pamphlet entitled Universal Natural History and Theory of the Heavens: An Essay on the Constitution and Mechanical Origin of the Whole Structure of the Universe Based on Newtonian Principles. He not only laid out what was to become the Kant-Laplace model for the cosmogony of the Solar System, he theorized a cosmos perhaps infinite but mostly full of galaxies similar to the Milky Way, “Islands-Universe” in words of Kant, but he also predicted that the distance between the Moon and the Earth would increase with time. From Kant to Darwin Perfectly master the concepts of Newtonian physics, failing the Newtonian mathematics developed at the same time by Leonhard Euler and d’Alembert , Kant understands that the law of conservation of angular momentum and the frictional existence of the oceans deformed by the tidal forces of the Moon, due to the rotation of the Earth, lead to the dissipation of rotational kinetic energy on her- even from our blue planet. The deceleration of the Earth’s rotation, causing its angular momentum to decrease, must cause an increase in the Moon’s around the Earth to ensure conservation of the total Earth+Moon angular momentum, and thus an increase in distance between the two celestial bodies: on all these basic notions of mechanics, you can consult the physics courses of the two Nobel Prize winners Feynman and Landau. During Kant’s lifetime, but in the following half century, d’Alembert, Lagrange and Laplace intensively developed the theory of tides on mathematical bases and it was also on these bases that the English astronomer and mathematician George Howard Darwin (1845 -1912). ) solidly embodied, around 1880, Kant’s ideas about the deceleration of the Earth’s rotation and the gradual retreat of the Moon. For the record, and as his name suggests, Georges is in fact one of the sons of Charles Darwin (1809-1882), the famous English naturalist and paleontologist, whose work on the evolution of living species revolutionized biology .These works of Darwin accompany his cosmogonic theory. of the Moon, a very interesting theory but the exposition of which would take us too far. We can glimpse it in the treatise on geophysics by the great British astronomer, mathematician and geophysicist Harold Jeffreys who would also contribute to the theory of his compatriot George Darwin to whom the treatise is dedicated. The ideas of Kant and Darwin will finally be solidly verified during the 20th century and a turning point in this matter will come thanks to the lunar program, American and Soviet, which will deposit on the Moon retroreflectors returning laser photons at 180° and which, therefore, will go back and forth from their emission to the Earth. Since 1969, we have therefore had laser telemetry between the Moon and the Earth which has allowed us to demonstrate that the stars were moving away from each other at an estimated speed of 3.83 cm/year. they have some coral fossils that have similar growth rings depending on the length of the day on Earth and also the length of the year. Thus it has been shown that during the Devonian period (more precisely about 380 million years ago) a year had 400 days but that its duration was almost the same as today. It was therefore necessary to deduce that the length of the day was only about 22 hours and therefore that the rotation of the Earth had indeed slowed down, which as we have seen implies that the Moon was closer to the Earth in the past.Fifty years. after Neil Armstrong’s first step, the instruments deployed on the Moon by the Apollo 11 mission are still used by French scientists. Thanks to reflective panels placed on the lunar floor, they measure the distance that separates our planet from its satellite. The key is valuable lessons about the Moon’s rotation or the composition of its core. © CNRSA Moon born 1.4 billion years ago, however, inserting the value measured by laser telemetry into the equations of Darwin’s theory of the movements of the Moon and the Earth, we find that the Moon and the Earth must have been in contact about 1 .4 billion years ago. This result qualitatively agrees with the theory that gives birth to the Moon from a collision between the Earth and a planet the size of Mars, the famous Theia, but quantitatively, it is not at all correct because we know that The Moon is more than 4 billion years old and was born from the Earth-Teia collision about 4.4 billion years ago, so for about 50 years we have been facing a paradox that we have named the Gerstenkorn event, i.e. a contact between the Earth and the Moon 1.4 billion years ago, contact that certainly did not occur at that time A research team from the Paris-PSL Observatory of the Institute of Celestial Mechanics and Ephemeris Calculation (IMCCE) has investigated this problem and has just announced that it has solved it. the puzzle in a paper published in A&A Letters, but an open access version of which can be found on arXiv. Earlier attempts to resolve the contradiction by improving tidal theory, in particular the ocean models of Webb (1982) had represented a fundamental advance by showing the appearance of mechanical resonances (similar to those that swing a seesaw when the frequency of excitation is good) between waves, ocean waves and the forcing of tidal forces, which led to a sharp increase in the dissipation of the Earth’s rotational energy, had not yet taken into account even the speed current tide or the age of the Moon. it is not simple and, until now, there was the risk of circular reasoning. Indeed, regarding the history of the movements of the Earth-Moon system, there are also cyclostratigraphic records in the sediments in relation to deposits associated with tidal rhythms, linked to the variation of tidal deposition between dead tides. and spring tides, as well as Milankovitch’s famous climate cycles. But to interpret these data, it is also necessary to have a modeling of these motions in relation to celestial mechanics to some extent, so that the empirical models of Earth-Moon history that are widely used by geologists today they are problematic. Finally, as explained in a press release from the IMCCE, empirical models do not allow us to deduce physical information about the Earth-Moon system. Tides are mainly the result of the attraction of the moon and the sun and the rotation of the earth upon itself. Satellite measurements allow for animations that visualize sea level variations, represented by gray levels. These level variations are the sum of many components, called tidal waves. The animations highlight the properties of the M2 tide, an effect of the moon’s pull (period, amplitude, wavelength, vibration nodes and propagation speed) and of the K1 tide, an effect of the inclination of the orbit lunar with respect to the equator (phase opposition and critical latitude). © Credits Scientific authors: Le Provost Christian and Lyartd Florent (Legos, UMR CNRS, Toulouse) Director: Ternay Jean-François (CNRS AV) Production: Legos, CNRS AV Distributor: CNRS Images To avoid these difficulties, the astronomers and geophysicists of the IMCCE have refined their modeling taking into account the millions and billions of years of continental drift. The movements of the continental blocks not only modify the Earth’s moment of inertia over time, which influences the rotation of the Earth and the movements of its axis of rotation, but also by changing the shape of the oceans, they give rise to more complexity. tidal propagating waves and energy dissipation than had been originally assumed. Ultimately, the researchers not only eliminated the contradiction represented by the Gerstenkorn event but also achieved a remarkable consistency between the predictions of the new modeling and the history of the evolution of the Earth-Moon distance. , geology, astronomy). It provides the first physical model of the evolution of the Earth-Moon system that perfectly matches current tidal dissipation and the age of the Moon, resolving a fifty-year paradox. Furthermore, this model fits the available geological data very well. Thus, it will probably become the standard reference for geoscientific studies. This study clearly demonstrates that the cyclostratigraphic approach is highly relevant to finding the past state of Earth’s rotation. It even consolidates the entire cyclostratigraphic field. This model differs from previously published ones by allowing resonances of larger amplitudes. This is essential to adjust the current dissipation rate. Therefore, these results will also consolidate the theory of ocean tides, showing the important effect of these ocean resonances. Furthermore, they can be generalized to the ocean tides of extrasolar planets.” Interested in what you just read?
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