A study in rocks found that, 2.46 billion yearsA day on Earth was only 17 hours The moon was closer by about 60,000 km.
at a slow pace, The moon is moving away from the earth The earth rotates slowly on its axis. To say something about these changes in the distant past, the geologists Use of information stored in rocks and fossils. But the more they go back in time, the more difficult it is to retrieve this information.
In his research, the A team of scientists affiliated with Utrecht University, The University of Geneva and the University of Quebec in Montreal They noticed a very old type of sedimentary rocks in western australia, which is known as Banded iron formations. In these sediments, they find a regular pattern of alternating iron-rich layers with layers containing more clay.
According to the researchers, this characteristic pattern is associated with periodic changes in the shape of the Earth’s orbit and the direction of its axis of rotation. These earlier differences, in turn, affected the distribution of solar radiation received by the Earth (Milankovitch cycles), and thus the climate as well. It is these climatic fluctuations that are subsequently recorded as periodic patterns in the geological record. But the point here is that this distinct cycle pattern has also gradually changed over time.
This slow change is a direct result of the “tidal evolution” of the Earth-Moon system, and thus is also related to the distance between Earth and the Moon in the past, explains Earth scientist Margaret Lantinck of Utrecht University.
Through a detailed analysis of the cycle patterns in the rock layers, scientists have been able to reconstruct the distance between Earth and the Moon at the time of deposition, 2.46 billion years ago.
Today, this distance is about 384,300 km. On average, of course, because the Moon doesn’t make a perfect circle around the Earth; Its orbit is an ellipse. “During the time period we studied, the distance between Earth and the Moon was much shorter: about 200,000 miles,” Lantink said in a statement.
This distance turned out to be consistent with an improved model of the history of the Earth-Moon system recently published by French astronomers. “It is also important to note that our interpretation of patterns in rock layers in terms of Milankovitch cycles was confirmed by dating volcanic minerals in uranium and lead rock samples.”
Over time, the Earth’s rotation around its axis has also slowed down. This has been known for a long time, but Lantink has now found a way to determine how long a day spent on early Earth: 17 hours, instead of the current 24 hours.
In a previous study he and colleagues from Switzerland did, he actually showed that Earth’s climate underwent regular changes 2.5 billion years ago due to periodic changes in the shape of Earth’s orbit. Lantinck explains that the current climate change has no astronomical cause: it happens on much shorter time scales, and humans are responsible for it.